scottish universities medical journal volume 3 issue 2
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Scottish Universities Medical Journal Volume 3 Issue 2. Renal Edition. Articles on Acute Kidney Injury, Unilateral nephrectomy and post-transplant immunosuppressionTRANSCRIPT
Lloyd Hughes [Type the abstract of the document here. The abstract is typically a short summary of the contents of the document.]
C o r r e s p o n d e n c e t o : S U M J @ d u n d e e . a c . u k
Scottish Universities Medical Journal‐ Renal Medicine Focus Scottish Universities Medical Journal Volume 3 – Issue 2
Editorial Board
Summer Edition Editor: Lloyd Hughes [5th Year Medical Student; University of Dundee Medical School; Editor‐in‐Chief 2011‐13] Editor in Chief: Laura Fraser [5th year medical student, University of Dundee] Deputy Editor: Kevin Barr [3rd year mental health nursing student, University of Dundee] IT Manager: Naomi McIlvenny [5th year medical student, University of Dundee] Head Reviewer: Rebecca Grant [1st year medical student, University of St Andrews] Features Commissioner: Lauren Copeland [BMSc year medical student, University of Dundee] National PR Representative: James Millar [Academic Foundation Doctor, NHS Grampian]
Associate Editors and Consultant Reviewers for Dundee SUMJ
Dr David Booth ‐ [General Practitioner & Doctors Patients and Communities Facilitator, University of Dundee] Prof Jeremy Hughes ‐ [Consultant Nephrologist NHS Lothian, Reader in Nephrology University of Edinburgh] Dr Hannah Lord ‐ [Consultant Oncologist, Ninewells Hospital and Medical School] Lloyd Hughes ‐ [5th Year Medical Student; University of Dundee Medical School, Editor‐in‐Chief 2011‐13] John Jungpa Park ‐ [Editor‐in‐Chief of Res Medica 2012/13, Medical Student, University of Edinburgh] Dhairya Lakhani ‐ [Vice President, Medical Students' Association of India, 3rd year MBBS Sumandeep Vidyapeeth University]
Table of Contents
Recognition of Acute Kidney Injury [Editorial]...........................................................................p. 4
LD Hughes
Management of Acute Kidney Injury: Advice for the Acute Receiving Unit .............................p. 6‐16
FAI Duthie & J Hughes
Valganciclovir‐Induced Leucopenia in Renal Transplant Recipients treated with Mycophenolate Mofetil ……………………………………………………………………………………………………p.17‐21
MA Waduud, M McMillan & A Jardine
Renal Function After Unilateral Nephrectomy…...........................................................….……p.22‐31
SKD Hamilton, GD Stewart, A McNeill and ACP Riddick & R Phelps
Recognition of Acute Kidney Injury [Editorial] Lloyd D Hughes (5th year MBChB, University of Dundee; Associate Editor, SUMJ) Correspondence to: Lloyd Hughes: [email protected]
EDITORIAL
Acute kidney injury (AKI) is a common clinical syndrome characterised by a rapid (over hours to days) decline in glomerular filtration rate, perturbation of extracellular fluid volume, electrolyte and acid‐base homeostasis, and accumulation of nitrogenous waste products from protein catabolism (blood urea nitrogen and creatinine).1‐2 This is a common clinical syndrome complicates up to 5% of hospital admissions1 and has considerable morbidity and mortality1‐3. Indeed, mortality for community‐acquired AKI ranges between 10‐30%, depending upon patient comorbidities1, and patients requiring renal replacement therapy for AKI have a mortality rate in excess of 50%3. Therefore, this is condition that junior clinicians and students will see regularly and will be required to manage promptly and effectively. However, there is commonly voiced uncertainty about the clinical care of these patients on the general surgical and medical ward. In this edition of the Scottish Universities Medical Journal, Dr Fiona Duthie and Professor Jeremy Hughes provide a framework for the junior clinician or non‐specialist to approach patients with AKI in the Acute Receiving Unit, with consideration of the potential underlying cause and initial investigations and management3.
Within this issue we have two research papers in the speciality of nephrology looking at clinical issues within transplant medicine5 and for patients who had received a unilateral nephrectomy6. Firstly, Dr Mohammed Waduud and colleagues outline some of the complications of newly recommended immunosuppressant regimens to reduce the incidence of cytomegalovirus in the post‐renal transplant patient population. The work found that patients treated with mycophenolate mofetil (MMF) and valganciclovir (VGC) are at a significantly higher risk of leucopenia when compared to patients not treated with MMF and VGC in the first 3 months post‐renal‐transplant. The paper discusses the implications of these findings and how best to manage the risks and benefits of different immunosuppressant regimens. Secondly, Stephen Hamilton and colleagues look at renal function for patients who underwent unilateral nephrectomy. The authors found that there were smaller reductions of GFR after partial versus total unilateral nephrectomy. The authors discuss the importance of these findings in relation to both surgical and medical decisions and make recommendations about follow‐up care of this patient group. As always we welcome comments and suggestions about our publication and welcome submissions for future main issues, online platform and supplements. Finally, as several members of the committee graduate this year, we will be handing over to a new committee who I hope will continue to develop the journal in the coming academic year. References 1) Kieran N & Brady HR. Comprehensive Clinical Nephrology (Editors ‐ RJ Johnson & J Feehally). Acute Renal Failure – Clinical Evaluation, Management, and Outcome of Acute Renal Failure. 2nd Edition. Mosby. 2003; Section 4: Chapter 14. 2) Brady HR, Singer GG (1995). Acute renal failure. Lancet. 346:1533‐40 3) Karsou SA, Jaber BL, Pereira BJ (2000). Impact of intermittent hemodialysis variables on clinical outcomes in acute renal failure. Am J Kidney Dis. 35:980‐91 4) Duthie FAI & Hughes J (2014). Management of Acute Kidney: Advice for the Acute Receiving Unit. Scottish Universities Medical Journal. 3(2):6‐16 5) Waduud MA, McMillan M & Jardine A (2014). Valganciclovir‐Induced Leucopenia in Renal Transplant Recipients treated with Mycophenolate Mofetil. Scottish Universities Medical Journal. 3(2):17‐21 6) Hamilton SKD, Stewart GD, McNeill SA, Riddick ACP & Phelps R (2014). Renal Function After Unilateral Nephrectomy. Scottish Universities Medical Journal. 3(2):22‐31
Management of Acute Kidney Injury: Advice for the Acute Receiving Unit Dr Fiona AI Duthie (MRC Clinical Research Fellow, University of Edinburgh) & Professor Jeremy Hughes (Professor of Experimental Nephrology, University of Edinburgh)
Correspondence to: Fiona Duthie : [email protected]
ABSTRACT
Acute kidney injury (AKI) is a common condition that is associated with significant morbidity and mortality. The term describes a syndrome, formerly known as acute renal failure, which is characterised by a rapid loss of renal excretory function, over hours to days. AKI is can occur in patients under the care of any medical or surgical specialty, and it is important that all clinicians are aware of its prognostic implications and the need for rigorous care. This article aims to provide a framework for approach to the care of patients with AKI in the Acute Receiving Unit, with consideration of the potential underlying cause and initial investigations and management.
Key Words: acute kidney injury; dialysis
Introduction The publication of the National Confidential Enquiry into Patient Outcome and Death (NCEPOD) report in 20091 raised the profile of AKI in the UK and highlighted the need for a change in clinical practice. This retrospective analysis of over 500 inpatient deaths with a diagnosis of AKI revealed that over 50% of cases failed to meet criteria for ‘good’ care. There was inadequate assessment of risk factors for AKI in 29%, and delayed recognition of the diagnosis in 12% of cases. Less than a third of patients had been referred to the Nephrology service, many of which were deemed delayed referrals. Importantly, patients with early senior medical involvement had better outcomes. Although this was a retrospective audit of deaths and not a comprehensive review of all AKI management, it did reveal significant deficiencies in basic patient assessment and treatment and has prompted further research and clinical guidelines in AKI management.
In the UK it is estimated that AKI affects approximately 15‐20% of patients admitted to hospital2,3, although a lack of consensus in diagnosis has previously limited comparison of data. Different study outcome measures have been reported, ranging from variable thresholds of serum creatinine to the requirement for renal replacement therapy. The Acute Dialysis Quality Initiative Risk, Injury, Failure, Loss, ESRD (RIFLE) criteria4 and Acute Kidney Injury Network (AKIN)5 criteria based upon the change in serum creatinine were subsequently developed and validated. The definition agreed in the International Kidney Disease Improving Clinical Outcomes (KDIGO) classification has taken components from both scoring systems and has now been widely adopted6. This takes both serum creatinine and urine output into account, as well as the timing of renal injury. AKI is therefore defined as:
(i) an increase in serum creatinine of at least 26.5μmol/l (0.3mg/dl) within 48 hours,
(ii) an increase in serum creatinine to at least 1.5 times baseline (which is known or presumed to have occurred within the previous 7 days), or
(iii) a urine output of less than 0.5ml/kg/h for at least 6 hours.
The grading of severity of AKI by these criteria is summarised in Table 1, and it is hoped that this definition will provide consistency in both clinical practice and future epidemiological and clinical studies.
The clinical relevance of a relatively modest increase in serum creatinine defined as AKI is based upon evidence that even small rises in creatinine are associated with a significant effect upon patient outcomes including length of inpatient stay, morbidity and mortality7. AKI has been demonstrated to be independently associated with a 4‐fold increased in all‐cause mortality in a large USA study, with increasingly severe AKI by AKIN criteria associated with higher mortality rates8. This 4‐fold increase in mortality was confirmed in a Scottish cohort, which also demonstrated an increased length of inpatient stay in patients with AKI2. In addition to concurrent risks, the risk of developing chronic kidney disease (CKD) in the longer term is increased as the duration and severity of AKI increases9,10. Importantly, elderly patients are more susceptible to AKI, and are more likely to develop CKD following even a single episode of AKI11. The incidence of AKI is increasing, and in light of the ageing population with multiple comorbidities and polypharmacy putting them at increased risk of AKI, this is set to continue in the absence of intervention.
In addition to the effects on patient outcomes, AKI results in a significant cost burden for the NHS. Extrapolating from UK Hospital Episode Statistics (HES) data, it is estimated that the cost of AKI to the NHS was between £434 million and £620 million in England in 2009‐201012, with patients with AKI staying in hospital 4.7 days longer on average than age matched controls. To put this into perspective, this is more than the total combined cost of the treatment of skin and lung cancers over the same period. As up to 20% of AKI is believed to be preventable1,13, this offers an opportunity to intervene to reduce morbidity and mortality, and to minimise utilisation of resource by the NHS.
Table 1: KDIGO AKI Guideline Stage Serum creatinine Urine output 1 1.5‐1.9x baseline creatinine
OR ≥ 26.5μmol/l (≥0.3mg/dl) increase
<0.5ml/kg/h for 6‐12 hours
2 2‐2.9x baseline <0.5ml/kg/h for ≥12 hours 3 3x baseline
OR Increase in serum creatinine to ≥353.6μmol/l (≥4.0mg/dl) OR Initiation of renal replacement therapy OR, in patients <18 years, decrease in eGFR to <35ml/min per 1.73m2
<0.3ml/kg/h for ≥24 hours OR Anuria for ≥12 hours
General Approach and Investigations Risk factors for AKI Clinicians should be aware of the risk factors for developing AKI and be vigilant in managing these patients accordingly on admission to hospital and throughout their inpatient stay. A significant proportion of patients develop AKI while in hospital, and have poorer outcomes compared to those who are admitted with the condition1. Recognised risk factors for AKI are listed in Table 2 and patients with these conditions should have ongoing risk assessment for
AKI including monitoring of renal function. At a minimum, fluid balance should be clinically assessed and charted regularly, drugs should be reviewed and nephrotoxins withheld, and renal function should be monitored at least daily while the patient is unwell. Table 2: Risk factors for AKI Risk factors for AKI3 Age ≥ 75 years
Hypotension SBP<100mmHg or decrease of ≥40mmHg from usual baseline
Sepsis 2 or more criteria of SIRS due to suspected infection
Hypovolaemia Clinical examination
CKD eGFR<60ml/min/1.73m2
Vascular disease History of atherosclerotic vascular disease
Congestive cardiac failure (CCF) History of CCF or current presentation consistent with acute cardiac failure
Diabetes mellitus
Jaundice Clinical or biochemical jaundice
Nephrotoxins Nephrotoxic medications used in the week prior to presentation e.g. ACEI, ARB, NSAIDs
Diagnosis of AKI – the earlier the better! The early diagnosis of AKI is vital, as AKI can be reversible if treated promptly and the duration and severity of AKI correlates with clinical outcomes9. The serum creatinine is widely used as a biomarker for AKI14, and is the key component of the KDIGO criteria. However its limitations must be taken into account when assessing patients in the acute receiving unit. The normal range provided by the laboratory can be misleading, as the creatinine level is affected by factors such as age, sex, muscle mass and dietary intake, and does not show dynamic changes in glomerular filtration rates15. Therefore absolute values must be considered in the clinical context. For example, a creatinine of 110μmol/l would be significantly elevated in an elderly lady who weighs 50kg, but normal in a 100kg young man. The recent NICE guideline on AKI advises a low threshold for suspicion of AKI, recommending that a serum creatinine be checked (and compared with baseline) for all patients with an acute illness, particularly if any of the following conditions are likely or present:
• CKD (eGFR<60ml/min/1.73m2), • heart failure, • liver disease, • diabetes, • history of previous AKI, • oliguria (urine output <0.5ml/kg/h), • neurological or cognitive impairment or disability, • hypovolaemia, • prescribed nephrotoxic medications, • iodinated contrast agents administered in the previous week, • symptoms or history suggestive of urological obstruction (or conditions that may
lead to obstruction), • sepsis,
• deteriorating early warning scores, or • age 65 years or over16.
This comprehensive list may seem to state the obvious, and renal function is performed routinely in acute receiving units and emergency departments. However, despite the identification of AKI, the response can be delayed or inadequate1,3, and this requires further emphasis among clinicians. The aetiology of AKI has long been subdivided into pre‐renal, renal (or intrinsic) and post‐renal causes (Table 3). A thorough history and examination is necessary to detect signs and symptoms, which can often be subtle or gradual in onset and are therefore not readily volunteered. Table 3: Causes of AKI Pre‐renal Renal Post Renal
Hypovolaemia
• Haemorrhagic shock • Fluid losses eg burns,
gastrointestinal losses
Renal hypoperfusion • Drugs eg NSAIDs, ACE
inhibitors • Hepatorenal syndrome • Renal artery stenosis
Hypotension
• Cardiogenic shock • Sepsis • Anaphylaxis • Antihypertensives
Glomerulonephritis Interstitial nephritis Acute tubular injury
• Ischaemia • Drugs eg
aminoglycosides, cisplatin
• Radiocontrast agents • Myoglobin
(rhabdomyolysis)
Obstruction: Extrinsic
• Pelvic malignancy • Retroperitoneal
fibrosis Intrinsic
• Papillary necrosis • bilateral ureteric
stones • malignancy of urinary
tract • urethral stricture
Clues from the Clinical History Given that AKI is a syndrome rather than a specific diagnosis, the underlying aetiology must be found in order to deliver effective treatment and guide prognosis. The history is often a source of diagnostic information, such as a recent diarrhoeal illness suggestive of hypovolaemia as a pre‐renal cause, or prostatic symptoms preceding oliguria and lower abdominal pain suggestive of obstructive nephropathy. However, a detailed history can suggest more challenging diagnoses such as a post‐infectious glomerulonephritis where the timing of recent infective symptoms is key (typically 2 weeks prior to presentation). Also, weight loss and bone pain might suggest multiple myeloma, whereas upper respiratory tract symptoms, fatigue, rash and arthralgia could indicate a small vessel vasculitis. A key component of the history in patients with AKI is an accurate drug history. Drugs such as angiotensin converting enzyme inhibitors (ACEI), angiotensin II receptor antagonists (ARBs) and non‐steroidal anti‐inflammatory drugs (NSAIDs) modulate intrarenal blood flow, rendering the kidneys vulnerable to ischaemia and AKI in the context of intercurrent illness, dehydration or polypharmacy17. Other drugs such as aminoglycosides are directly toxic to renal tubules18. Acute interstitial nephritis (AIN) is a type IV hypersensitivity reaction, and typically occurs 7‐10 days after the first exposure to a drug. The time delay can be shorter than this in cases of repeat drug exposure, or longer in specific medications such as NSAIDs19. AIN can theoretically occur with any drug, but common agents are proton pump
inhibitors (PPIs), NSAIDs, and antibiotics (especially β‐lactam producing agents). AIN may be accompanied by a skin rash but this is usually absent. Therefore a detailed history of both current and recent medications, including duration, is absolutely required. The Clinical Examination It follows on that a thorough examination of all organ systems can aid diagnosis and management in AKI. Clinical signs such as arthropathy, a skin rash, heart murmurs, eye signs (including scleritis and episcleritis) and neuropathies can all provide further diagnostic information. Fluid balance assessment is of particular importance given that it can inform both cause of renal disease and its management. It is often felt to be a challenging skill, particularly when hypoalbuminaemia and/or cardiac failure may be present. Clinical examination should include pulse and blood pressure (including postural changes), jugular venous pressure, peripheral perfusion including capillary refill, skin turgor and the assessment of pulmonary or peripheral oedema20. The need for repeated clinical assessments in AKI is paramount given that fluid balance can change rapidly in the setting of oliguria. The role of central venous pressure monitoring in AKI is controversial, but is often recommended for those in whom fluid balance assessment is difficult or when signs of shock21 are present and Critical Care or Nephrology teams should be involved in such cases at an early stage if appropriate. Investigations Key investigations include blood, urine and radiological tests. Blood tests will be guided by the clinical findings but at a minimum blood should be sent for urea and electrolytes (including serum creatinine), full blood count, bone chemistry including phosphate and corrected calcium, bicarbonate and liver function tests including albumin. A myeloma screen including serum protein electrophoresis and urinary Bence Jones protein should be performed if myeloma is considered a potential diagnosis and in all patients with unexplained AKI. If glomerulonephritis is suspected, then an immunology screen including antinuclear antibodies (ANA), anti‐neutrophil cytoplasmic antibodies (ANCA), anti‐glomerular basement membrane (GBM), and complement levels should be performed, although Nephrology specialist input should not be delayed until these results are available in such circumstances. A urine dipstick is mandatory to assess for blood, protein, leucocytes, nitrites and glucose16. An active urinary sediment is indicated by haematuria and/or proteinuria in the absence of urinary tract infection and can indicate an underlying glomerulonephritis. Although microscopy is no longer used routinely to aid diagnosis of AKI in the UK, a simple bedside dipstick test can inform diagnosis, and the presence of proteinuria also provides prognostic information as albuminuria is associated with an increased risk of AKI22. If present, the amount of proteinuria should be quantified by an albumin:creatinine ratio (ACR) or protein:creatinine ratio (PCR). A renal tract ultrasound is required to investigate potential obstruction16 and, in the absence of clinical suspicion of obstruction, is necessary to confirm a normal anatomy of the urinary tract. Small renal size indicates renal dysplasia or chronic disease such as reflux nephropathy or longstanding ischaemia secondary to renovascular disease. In cases where there is a high clinical suspicion of obstruction such as known pelvic malignancy and oliguria or anuria but the ultrasound does not show dilatation, it is important to consider non‐dilated obstruction23. A Urology opinion should be sought in addition to receiving nephrology input in such circumstances.
Further investigations depend on the history and examination findings. A creatinine kinase (CK) would be required if rhabdomyolysis were suspected as in patients who have had a fall followed by a long period of immobility, or in patients who have had drug overdoses. Inflammatory markers such as C‐reactive protein (CRP) and a septic screen including urine and blood cultures would be required if sepsis thought to be likely. A throat swab for bacteria including Streptococci would be indicated if there were a history of upper respiratory tract infection although the swabs may be negative in patients who present with post‐streptococcal glomerulonephritis. HIV and hepatitis testing should be considered in patients who have risk factors for these conditions or have unexplained AKI. The definitive investigation in unexplained and severe AKI is a renal biopsy. This test may be indicated for diagnostic and/or prognostic purposes, but given that it carries a significant risk of complications such as haemorrhage, it should be undertaken with input from the nephrology team24.
Management of AKI General measures Once abnormal renal function has been discovered, it is important to discern whether this represents AKI, CKD, or an acute renal insult in the context of pre‐existing CKD. It is worth noting that worsening CKD should be considered in the presence of factors such as a gradual onset of non‐specific symptoms, small kidneys on ultrasound, a normocytic anaemia, and high serum phosphate. AKI secondary to pre‐renal factors is the most common form in the UK, particularly in critically ill patients. The diagnosis of AKI, particularly in the context of hypotension or other organ failure, should alert clinicians to the severity of the patient’s illness and the need to consider escalation of care to a high dependency or intensive care environment if appropriate. Patients with AKI should be seen by a Consultant physician within 12 hours of admission16. Treat the underlying cause If AKI is pre‐renal and secondary to a known condition such as haemorrhagic or septic shock or a diarrhoeal illness, then treatment of the underlying condition and supportive measures are required in a critical care setting if indicated. Indications for a urinary catheter include relief of lower urinary tract obstruction, or to monitor hourly urine output in AKI of any cause. Adequate oxygenation and haemoglobin concentration (at least 70g/L) should be achieved25. If upon review there is no clear cause for AKI, an intrinsic renal disease is suspected or there is no response to treatment for presumed pre‐renal AKI, a Nephrology opinion should be sought (see below). Review all medications A review of prescribed medications should be performed and any nephrotoxic medications should be stopped if possible. All drug dosages should be checked as an adjustment may be required in renal impairment. In particular, opiate drugs can accumulate in AKI and can cause opiate toxicity (symptoms and signs of which include hypotension, reduced Glasgow Coma Score (GCS), myoclonic jerks, pruritis, miosis). Antibiotics often require a reduction in dose or frequency of administration.
Fluid balance is key Good management of fluid balance is essential in the management of AKI. If clinical examination reveals hypovolaemia, fluid resuscitation should be initiated quickly to restore cardiac output, systemic blood pressure and organ perfusion. Intravenous fluid should be considered a drug treatment and therefore prescribed with due consideration26. The choice of fluid can be challenging, but recent NICE guidelines have encouraged the distinction of resuscitation and maintenance fluid prescriptions27, with consideration given to the individual patient’s volume status, ongoing fluid losses, and measures of serum sodium, osmolarity and acid‐base status. Maintenance fluid requirements in a 24‐hour period include approximately 25‐30ml/kg/day of water, 1mmol/kg/day of potassium, sodium and chloride, and 50‐100g/day of glucose to prevent ketosis. This does not take into account variation in requirements among patients, such as in oliguria and hyperkalaemia in AKI, or increased fluid and electrolyte losses in conditions such as vomiting and diarrhoea or high output stoma losses, polyuria, or surgical drains and these need to be considered for each patient. The type of fluid prescribed for resuscitation is still an area of ongoing research, but NICE suggest a fluid bolus of 500ml of crystalloid containing sodium in the range of 130‐154mmol/l (such as Normal saline or ‘balanced’ solutions such as Plasmalyte) over 15 minutes, followed by clinical reassessment. A lower volume of 250ml should be used if the patient has a history of cardiac failure. A requirement of more than 2 litres of resuscitation with crystalloid should prompt review by a senior colleague. Due to the high chloride content of Normal saline, patients can become acidotic as well as hypernatraemic if too much is given. ‘Balanced’ solutions such as Plasmalyte are designed to be more physiological, with a lower sodium and chloride concentration and the addition of potassium and magnesium at low concentrations, as well as a physiological pH. Observational data in comparison with Normal saline has proved promising and randomised controlled trials are underway. Their use has been recommended in resuscitation of patients with AKI20, as long as potassium is monitored carefully. Other intravenous fluids available include colloids. The use of colloid solutions has not been shown to improve outcome when compared with crystalloid in resuscitation. Hydroxyethyl starch (HES) solutions (semisynthetic colloids) are associated with a 21% relative increase in the rate of renal replacement therapy (RRT) compared with saline28, and an increase in mortality and RRT compared with Ringer’s acetate29. These studies were performed in the critical care setting but in light of lack of proven clinical benefit, the use of HES in fluid resuscitation is discouraged. Other colloids such as Gelofusine (a bovine gelatin derived colloid) do not seem to carry the same harmful effects but data is lacking. The hypothesis of such fluid remaining in the intravascular space for longer, leading to a lower overall volume of resuscitation fluid required, has not been proven by a recent randomised controlled trial30. Overall, regular reassessment of fluid status is necessary in order to ensure fluid repletion but avoid fluid overload, as this is recognised as a major factor in increased mortality of patients with AKI31. Contrast nephropathy and preventive measures The administration of iodinated contrast in patients with AKI (or at risk of AKI) is often a cause for concern. Iodinated contrast, after causing a brief (minutes) period of vasodilatation, leads to sustained (hours to days) period of intrarenal vasoconstriction and therefore ischaemic injury32. Therefore clinicians need to be aware that an increased risk of contrast nephropathy is associated with factors given in Table 4, and patients should be counseled accordingly.
Table 4: Risk Factors for AKI in adults having iodinated contrast agents16
Key Risk Factors for AKI in adults having iodinated contrast agents16 (16)
CKD (particularly if eGFR<40ml/min/1.73m2)
Diabetes but only with CKD (particularly if eGFR<40ml/min/1.73m2)
Cardiac failure
Renal transplant
Age ≥75 years
Hypovolaemia
Increasing volume of contrast agent
Intra‐arterial administration of contrast agent
In addition, certain medications should be withheld for several days including diuretics, and nephrotoxic drugs especially NSAIDs and ACE inhibitors that are known to reduce GFR. Metformin should be withheld given the risk of lactic acidosis. Patients should be well hydrated prior to contrast imaging studies. NICE guidelines advise that either Normal saline or isotonic sodium bicarbonate should be given intravenously in patients at risk of contrast‐induced AKI16. Suggested rates are 1‐1.5ml/kg/h for 3 to 6 hours pre and 6 to 24 hours post contrast dose32. Although this has been an area of controversy, there is some evidence that sodium bicarbonate may be more effective than saline. However, the priority should be to ensure adequate hydration before and after contrast administration. Another potential protective treatment is acetylcystine although there is no conclusive evidence to recommend routine use33, and randomised controlled trials are underway34. Renal function should continue to be monitored post contrast administration as the prolonged vasoconstriction can lead to a delay in onset of AKI. Haemofiltration can be used as an adjunct to optimise fluid balance and remove uraemic toxins pre‐contrast, and remove iodinated contrast following imaging35. However this has its own associated risks and is generally used only in very high‐risk patients in Critical Care. An important message is that in an emergency setting, the risk assessment of contrast in patients vulnerable to the development of AKI should not delay imaging deemed to be critical for clinical management16. Nephrology colleagues can be consulted if there is a doubt about the risk versus benefit of contrast studies. When to refer to nephrology AKI is a common syndrome and all clinicians should feel confident in its diagnosis, consideration of potential underlying causes and early management. Referrals to nephrology should be made if any of the following conditions are met16:
• Stage 3 AKI6 • AKI in a renal transplant recipient • Background CKD stage 4 or 5 (eGFR<30ml/min/1.73m2) • AKI with no clear cause following standard investigations • Inadequate response to treatment
• Complications associated with AKI such as fluid overload or hyperkalaemia (possibly iatrogenic)
• A potential diagnosis that may need specialist investigations (e.g. renal biopsy) and treatment such as vasculitis, glomerulonephritis, tubulointerstitial nephritis or myeloma.
In general, if in any doubt the nephrology team would rather be involved at an early stage. Renal Replacement Therapy Some patients require supportive treatment for AKI in the form of renal replacement therapy (RRT). The optimal time to start RRT in AKI is an area of controversy but this clinical decision is based upon several factors including serum potassium, urea, fluid and acid‐base balance, and the presence of other complications. The type of RRT for AKI in the UK is divided into two main modalities: intermittent haemodialysis (HD) and continuous veno‐venous haemofiltration (CVVH). Both require central venous access. In short, HD removes solutes by diffusion across a semi‐permeable membrane driven by a concentration gradient whilst CVVH removes solutes by convection under hydrostatic pressure. CVVH is a more gradual, gentler treatment and is therefore used in patients who are haemodynamically unstable. Given the low flow rates it does require anticoagulation with low dose heparin to maintain the blood circuit, which can prove challenging in patients who are coagulopathic or have an increased bleeding risk due to recent surgery or trauma. RRT in general is an invasive treatment, with risks associated with line insertion and with the treatment itself such as cardiovascular instability. Not all patients are suitable for RRT given the risks involved.
Future Developments Biomarkers of AKI The use of urinary biomarkers for AKI is an area of ongoing research. A biomarker is defined as ‘a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention’.36 Urinary biomarkers are of interest and may allow an earlier diagnosis of AKI as they may be present prior to a change in serum creatinine thereby facilitating risk stratification, guiding prognosis and allowing early monitoring and intervention20. Such markers include neutrophil gelatinase‐associated lipocalin (NGAL), kidney injury molecule 1 (KIM‐1), interleukin 18 (IL‐18) and cystatin C37. Much of the evidence comes from small studies in experimental models and the study of surgical patients, so that large scale randomised controlled trials are required to prove their efficacy and utility in AKI diagnosis and management. E‐alerts Another area of research is the potential role of electronic alert systems (e‐alerts) to ensure the early detection, recognition and therefore treatment of AKI. This would involve a computer algorithm that would automatically trigger when a specific absolute change or accelerated rate of change in creatinine was detected by the relevant software38,39. The response to such a change can vary from a ‘passive’ alert, where the result is flagged with a message alerting the clinician user to the problem but leaving them with the responsibility to take action. Other ‘active’ models prompt a telephone call to the responsible clinician, or even a visit from an AKI outreach team. Such schemes have inevitable added costs, and proven improvement in clinical outcome is yet to be seen.
Novel therapies Aside from specific therapies for individual conditions such as AIN (stop drug and consider steroids) and immune‐mediated disorders (immunosuppressive treatment), there is no specific treatment for AKI and the mainstay of treatment is supportive care. Diuretics have not been shown to improve outcome in AKI40 and should be reserved for the management of volume status only. Low dose dopamine, although theoretically beneficial, has not been shown to be effective41 and its use is not recommended. New potential therapies including fenoldopam and atrial natriuretic peptide, with the aim of improving renal perfusion in AKI, are the subject of current research.
Summary In order to move forward and learn from the NCEPOD report, it is important that clinicians in all specialities at all stages in their careers recognise the importance of being aware of risk factors for AKI, as well as the need for diagnosis at an early stage. Initial measures can be put in place, with input from Nephrology and Critical Care colleagues as indicated. All doctors should be able to recognise patients at risk, diagnose AKI at an early stage, and take simple measures such as careful fluid assessment, reviewing medications, initiating investigations and requesting specialist input.
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Valganciclovir‐Induced Leucopenia in Renal Transplant Recipients treated with Mycophenolate Mofetil Mohammed A Waduud (Foundation Year 1 Doctor, MBChB BMedSci (Hons)), Margaret McMillan (Consultant Nephrologist, NHS Greater Glasgow & Clyde) & Professor Alan Jardine (Professor of Renal Medicine & Head of Medicine, University of Glasgow) Correspondence to: Mohammed Abdul Waduud [email protected]
ABSTRACT
Objective Cytomegalovirus (CMV) is a viral infection commonly affecting renal transplant recipients. Current guidelines recommend the prophylactic treatment of patients at risk from CMV with oral Valganciclovir (VGC), however, myelotoxic side effects have been reported. The severity of leucopenia is reported to be increased when used in conjunction with Mycophenolate Mofetil (MMF), although some studies have shown conflicting evidence. Method Retrospective analysis of patient clinical data, post‐renal‐transplant, was performed. Patients included were treated with; MMF and VGC [MMF(+)VGC(+)], MMF but not VGC [MMF(+)VGC(‐)], no MMF but with VGC [MMF(‐)VGC(+)] and, neither MMF or VGC [MMF(‐)VGC(‐)]. Blood results and other relevant data were collected from clinical databases. Results In total, data from 61 patients were analysed. 13 patients were MMF(+)VGC(+), 48 patients were MMF(+)VGC(‐), 5 patients were MMF(‐)VGC(+) and 12 patients were MMF(‐)VGC(‐). Of these, 6 MMF(+)VGC(+) patients and 3 MMF(+)VGC(‐) patients were leucopenic within the first 3 months post‐renal‐transplant (p=0.001). This difference was not apparent in patients that were not treated with a MMF regime. Conclusion Patients treated with MMF and VGC are at a significantly higher risk of leucopenia when compared to patients not treated with MMF and VGC in the first 3 months post‐renal‐transplant. Key Words: Leucopenia, Mycophenolate, Renal, Transplant, Valganciclovir.
Introduction Human cytomegalovirus (CMV) is the most important viral infection in renal transplant recipients, as it is a major cause of morbidity and mortality. [1] Approximately 30‐97% of the general population are thought to be seropostive for CMV, and the prevalence has been shown to increase with age. [2] Solid organ transplant (SOT) is one of the many ways in which CMV may be transmitted to the seronegative patients. Primary infection with the virus is often asymptomatic in an immunocompetent host. However, in an immunocompromised host, primary infection or reactivation of a latent infection can cause CMV disease. This is of particular concern in the first 3 to 6 months post‐SOT when recipients are aggressively immunosuppressed to avoid acute graft rejection. [2]
Several recent studies have shown oral Valganciclovir (VGC) prophylaxis to be superior to pre‐emptive therapy, when CMV infection and disease is a risk following SOT. [3, 4] In prophylactic therapy all patients “at risk” are given Valganciclovir whereas in pre‐emptive therapy patients are monitored for any indications of disease prior to starting therapy. Current guidelines recommend the prophylactic treatment of renal transplant patients at risk from CMV with oral Valganciclovir, 900mg once daily dose, started within 10 days and continued for at least 100 days. [5] Unfortunately, Valganciclovir is known to have myelotoxic effects and studies have reported leucopenia in patients treated with Valganciclovir alone as high as 10‐28%. [6, 7] Mycophenolate Mofetil (MMF) is a commonly used immunosuppressive agent which is often used in combination calcineurin inhibitors as standard practice. However, MMF too can cause leucopenia. The severity of leucopenia has been reported to increase when used in conjunction with VGC.8 Some studies have reported the use of VGC and MMF not to be associated with a greater incidence of leukopenia. [9] It is important to clarify these conflicting results as it could help prevent the establishment and complications of severe neutropenia in this patient group. Consequently, the aim of this study was to investigate whether the use of VGC causes leucopenia in patients treated with a MMF regime post‐renal‐transplant or not.
Methods We retrospectively analysed clinical follow‐up data of renal transplant patients from Glasgow, Scotland, United Kingdom. Ethical approval for the study was deemed unnecessary as patient follow‐up data was being analysed in order to evaluate existing patient care. Caldicott guardian approval was not sort as no patient sensitive data was collected. Study Population Men and women of all ages were included in this study if they had a renal transplant. Patients who were not treated with a MMF regime and those with insufficient data available were excluded from this study. Prophylactic therapy with VGC was indicated in patients if the serum CMV status in the donor was positive and recipient was negative (D+R‐). On occasions VGC therapy was given to patients where the donor was negative and recipient was positive (D‐R+) or both the donor and recipient were positive (D+R+). Data from consecutive patients who had a renal transplant in Glasgow between August 2008 and May 2009 were analysed. This time frame was selected due to limitations in time available to collect data. Collection of data Initially the transplant register was searched to identify suitable patients. Data was then retrieved from two separate databases, namely the “Western Infirmary General (WIG) renal proton” system and NHS greater Glasgow and Clyde Clinical Portal, to verify the search results and collect further data required. The WIG renal proton system contains up‐to‐date and past blood results along with a list of prescribed medications along with their respective doses. Relevant demographic and procedure related data were collected from the NHS greater Glasgow and Clyde Clinical Portal. [10] We collected patient demographic data (age, and gender), the white cell count (WCC) at 3 months, 6 months and 12 months, VGC dose and duration, MMF dose at 1 year, serum creatinine at 1 year, and rejection at 1 year. Furthermore, the presence of leucopenia (i.e. WCC less than 4 x 109/L) with in the first 3 months post‐transplant was also noted.
Primary outcome The primary outcome was leucopenia during the first 3 months. To investigate whether the use of VGC affected the leucocyte count in patients on a MMF regime post‐renal‐transplant, we grouped patients into 4 groups. Patients that were treated with MMF and VCG [MMF(+)VGC(+)], patients treated with MMF and no VGC [MMF(+)VGC(‐)], patients not treated with MMF but with VGC [MMF(‐)VGC(+)] and finally patients not treated with MMF and VGC [VCG(‐)MMF(‐)]. Patients not treatment with MMF were treated with Azathioprine. The use other immunosuppressive agents (i.e. Tacrolimus and Sirolimus etc.) was not evaluated in this study. Secondary outcome We also investigated the mean white cell count (WCC) at 3, 6 and 12 months in the individual groups and renal function at 1 year by measuring the serum creatinine (Cr) levels at 1 year post‐transplant. The relationship between leucopenia and number of infections experienced by patients was not evaluated in this study, as numerous previous studies have reported there to be no association in this patient group. [8] Statistical analysis All analyses were performed using the Statistical Software Minitab 15 (Minitab Inc). A chi‐square test, fisher exact test or 2‐sample t‐test were performed, where possible, to identify any differences between groups. All p‐values less than 0.05 were considered significant. Data which met the assumptions of the normal distribution were presented with the mean and 2‐tailed 95% confidence interval.
Results In total, data from 79 patients had a renal transplant. 1 patient was excluded due to insufficient data. Therefore data from 78 patients were analysed in this study. Baseline characteristics Of the 78 patients analysed, 42 patients were male (53.8%) and 36 patients were female (46.2%). The average age of patients in the study was 45.6 years (95% CI, 42.5 – 48.7 years). 30 patients were seronegative for CMV and 28 were seropositive. The serum CMV status of 20 patients was not commented on. 52 patients received a transplant from cadavers, 17 patients received a transplant from live related donors and 9 patients received transplants from live unrelated donor. The serum CMV status of donors was not obtained. In total 61 patients were treated with MMF and 18 patients treated with VGC (see figure 1). Primary outcome The WIG proton system showed 13 patients to be MMF(+)VGC(+), 48 patients to be MMF(+)VGC(‐), 5 patients to be MMF(‐)VGC(+) and 12 patients to be MMF(‐)VGC(‐) (see figure 1). 6 MMF(+)VGC(+), 3 MMF(+)VGC(‐), 3 MMF(‐)VGC(+) and 4 MMF(‐)VGC(‐) patients were leucopenic at some point within the first 3 months post‐renal‐transplant. The difference between MMF(+)VGC(+) and MMF(+)VGC(‐) patients was statistically significant (p=0.001). The were no significant differences between MMF(‐)VGC(+) and MMF(‐)VGC(‐) groups. The mean dose of MMF at 1 year in patients treated with VGC was significantly lower than patients not treated with VGC (0.87g; 95% CI: 0.53‐1.22g versus 1.27g, 95% CI: 1.07‐1.47g, p‐value=0.046). 15 patients received a single course and 3 patients received multiple courses. In total, 23 courses of Valganciclovir were administered, 5 at 900mg, 17 at 450mg and 1 at 125mg. 16 patients received VGC as prophylaxis. However only 10 patients had treatment
started with 10days of SOT. The mean duration of treatment for all patients treated with prophylactic VGC was 69.2 days (95% CI, 51.8 days to 86.7 days). 2 patients received a prophylactic dose of 900mg, 13 patients received a prophylactic dose of 450mg and 1 patient received a prophylactic dose of 125mg. Secondary outcome No significant differences were observed in MMF(+)VGC(+) and MMF(+)VGC(‐) groups at 3, 6 and 12 months. The average serum creatinine at 1 year was; 123.5µmol/L (95% CI 100.8 – 146.3µmol/L) in the MMF(+)VGC(+) group, 122.5µmol/L (95% CI 84.2 – 160.8µmol/L) in the MMF(+)VGC(‐) group, 413.0µmol/L (95% CI ‐269 – 1096µmol/L) in the MMF(‐)VGC(+) group and 207.5µmol/L (95% CI 63.8 – 351.2µmol/L) in the MMF(‐)VGC(‐) group. The mean serum creatinine at 1 year in patients that were leucopenic in the first 3 months was 135.7µmol/L, 404.0µmol/L, 182.3µmol/L and 113.5µmol/L in MMF(+)VGC(+), MMF(+)VGC(‐), MMF(‐)VGC(+) and MMF(‐)VGC(‐) patients, respectively. No significant differences were observed.
Discussion The use of VGC prophylaxis has a clear evidence based benefit in reducing the rates of CMV viraemia, which can lead to graft rejection, graft loss and death. To the best of our knowledge only two studies have evaluated VGC induced leucopenia in patients treated with a MMF immunosuppressive regime post‐transplant. [8, 9] The study by Brum et al (2008) reported an increased frequency of leucopenia were VGC prophylaxis was given to patients in combination with MMF. [8] However, results from this study were contradicted by Perez et al (2009) who reported no differences in the incidence of leucopenia in patients treated with VGC alone when compared to VGC and MMF, although leucopenia was observed in both groups. Both these studies evaluated similar parameters to those used in our study, with the exception of the analysis of calcineurin inhibitor levels and patient BMI. Our definition of leucopenia also differed, as we defined it as a WCC less than 4x109/L in comparison to a WCC less than 3 x 109/L, which was used in both studies. Outcome measures In this retrospective study, investigating whether the use of VGC affected the leucocyte count in patients treated with a MMF regime post‐renal‐transplant, we found that significantly more patients in the patient group treated with MMF and VGC [MMF(+)VGC(+)] experienced leucopenia when compared patients treated with MMF alone [MMF(+)VGC(‐)] in the first 3 months after renal transplant. However, this difference was not apparent in patients that were not treated with MMF. Consequently, leucopenia was associated with the combined use of MMF and VGC. However the absence of any significant differences in leucopenic episodes between [MMF(+)VGC(+)] and [MMF(‐)VGC(‐)] was surprising and questions the significance of our findings. Insufficient data was recorded to allow for the quantification of the magnitude of leucopenia observed during this period. No significant differences were observed in the different patient groups when analysing the WWC at 3, 6 and 12 months. This may have been due to the cessation of simultaneous VGC and MMF therapy by these time points. As recommended by current guidelines, the most popular dose of MMF prescribed was 2g (twice daily dose of 1g). However, we observed patients treated with VGC to be given significantly lower doses of MMF when compared to patients that were not treated with VGC but on a MMF regime. Consequently the physician may have been guided by patients WCC to adjust the doses of both drugs in an effort to avoid their cumulative side‐effects. Current guidance surrounding the concomitant use of MMF and VGC is sparse and future research is required to improve current guidelines. The most commonly used dosage of VGC
was 450mg, which is half the recommended dosage (900mg). Use of this lower dosage may have been justified by patients having a reduced renal function, physicians experience or literature suggesting 450mg VGC to be non‐inferior to 900mg VGC. [11] We did not observe any significant differences in the number of successful renal transplants at 1 year when comparing the difference groups. Furthermore, no difference in renal function was also observed at 1‐year post‐renal‐transplant. Limitations The low number of patients in this study is an obvious limitation; consequently larger studies are required in order to validate these trends. Several potential confounding factors were not accounted for in this study. The omission of data on other immunosuppressive agents (i.e. sirolimus) used is important to bear in mind as they too can cause myelosuppression. Data relating to CMV viraemia was also not documented, which may be significant as this too can cause leucopenia in patients who did not receive prophylactic VGC. Finally the absence of the CMV status of 20 recipients and all donors in this study makes it impossible to comment on whether VGC was used based on current guidelines.
Conclusion Patients treated with Mycophenolate Mofetil and Valganciclovir [MMF(+)VGC(+)] are at a significantly higher risk of leucopenia when compared to patients treated with Mycophenolate Mofetil and not Valganciclovir [MMF(+)VGC(‐)] in the first 3 months post‐renal‐transplant. However, leucopenia whilst an adverse event is reversible and not associated with long‐term adverse outcomes.
References [1] Weir MR. Medical management of kidney transplantation. Cytomegalovirus in renal transplantation. Philadelphia, PA: Lippincott Williams & Wilkins. 2005; Chapter 28. [2] Keyzer KD, Laecke SV, Peeters P, and Vanholder R. Human Cytomegalovirus and Kidney Transplantation: A Clinician’s Update. Am J Kidney Dis. 2011; 58(1): 118‐126. [3] Witzke O, Hauser IA, Bartels M, et al. Valganciclovir Prophylaxis Versus Preemptive Therapy in Cytomegalovirus‐Positive Renal Allograft Recipients: 1‐Year Results of a Randomised Clinical Trial. Transplantation. 2012; 93: 61‐68. [4] Khoury JA, Storch GA, Bohl DL, et al. Prophylactic Versus Preemptive Oral Valganciclovir for the Management of Cytomegalovirus Infection in Adult Renal Transplant Recipients. American Journal of Transplantation. 2006; 6:2134‐2143. [5] Andrews PA, Emery VC, Newstead C. Summary of the British Transplantation Society Guidelines for the Prevention and Management of CMV Disease After Solid Organ Transplantation. Transplantation. 2011; 92: 1181‐1187. [6] Pescovitz MD, Rabkin J, Merion RM, et al. Valganciclovir results in improved oral absortion of ganciclovir in liver transplant recipients. Antimicrob Agents Chemother. 2000; 44: 2811‐5. [7] Gabardi S, Magee CC, Baroletti SA, et al. Efficacy and safety of low‐dose Valganciclovir for prevention of cytomegalovirus disease in renal transplant patients: a single‐centre, retrospective analysis. Pharmacotherapy. 2004; 24:1323. [8] Brum S, Nolasco J, Sousa J, et al. Leukopenia in Kidney Transplant Patients With the Association of Valganciclovir and Mycophenolate Mofetil. Transplantation Proceedings. 2008; 40:752‐754. [9] Perez JEM, Castroagudin JF, Rios SS, et al. Valganciclovir‐Induced Leukopenia in Liver Transplant Recipients: Influence of Concomitant Use of Mycophenolate Mofetil. Transplantation Proceedings. 2009; 41: 1047‐1049. [10] Kelly C. NHS Scotland eHealth Programme – Clinical Portal: Information for clinicians. The Scottish Government, NHS Scotland. 2009. 1‐12. [11] Kalil AC, Mindru C, Florescu DF. Effectiveness of Valganciclovir 900mg versus 450mg for cytomegalovirus prophylaxis in transplantation: direct and indirect treatment comparison meta‐analysis. Clin Infet Dis. 2011. 52(3): 313‐21.
Renal Function After Unilateral Nephrectomy Stephen KD Hamilton (5th year MBChB, University of Edinburgh), Grant D Stewart (Consultant Urologist, NHS Lothian), Alan McNeill (Consultant Urologist, NHS Lothian), Antony CP Riddick (Consultant Urologist, NHS Lothian) & Richard Phelps (Consultant Nephrologist, NHS Lothian) Correspondence to: Stephen KD Hamilton : [email protected]
ABSTRACT
BACKGROUND: It is clear that Chronic Kidney Disease (GFR <60mls/min) is associated with reduced life expectancy, partly due to an increased risk of cardiovascular disease. To consider the implications for the selection of total versus partial unilateral nephrectomy, we compared retrospectively the renal function of patients undergoing either operation in Lothian. METHODS: Details were collated across NHS Lothian for 1165 patients. Blood results pre‐ and post‐nephrectomy could be retrieved for 334 patients (Group 1). Blood results were also available from at least 6 months post surgery for 194 patients (Group 2). Renal function was estimated using the Abbreviated Modification of Diet in Renal Disease formula. RESULTS: Overall within group 1, total/partial nephrectomy patients’ GFR fell by 14.35ml/min/1.73m2, (95%CI 11.98‐16.72) with post‐nephrectomy GFR <60mls/min in 34.1%. Within group 2, patients’ GFR fell by a mean of 14.09ml/min/1.73m2, (95%CI 10.93‐17.24) with new GFR <60mls/min in 36.1%. Comparing partial versus total nephrectomy, the mean reduction in GFR and occurrence of post‐nephrectomy GFR <60mls/min was 8.13ml/min/1.73m2, 16.7% and 14.73ml/min/1.73m2, 35.4% respectively in group 1. The odds ratio for post‐nephrectomy GFR <60mls/min was 2.7 (95%CI 1.4‐5.3). Group 2 included too few partial nephrectomy patients for comparison. CONCLUSION: Smaller reductions of GFR after partial versus total unilateral nephrectomy are of magnitudes that are significant for overall life expectancy in large cohorts, and possibly relevant for patients with indications for nephrectomy and longer life expectancy. Patients who undergo nephrectomy should have their renal function assessed at least 6 months post‐surgery to detect new GFR <60mls/min and trigger appropriate evaluation. Key Words: chronic kidney disease; nephrectomy; surgical follow‐up
Introduction Background Nephrectomy is by no means a novel surgical intervention having first been introduced for the treatment of localised renal cell carcinoma (RCC) in 1969 (1). Indications for nephrectomy include renal cell or urothelial cancer and benign conditions that lead to a poorly functioning or non‐functioning kidney (2). Nephrectomy is most often performed for RCC. Since Robson et al. first described radical nephrectomy (RN), and from the evolution of laparoscopic techniques in 1990, laparoscopic radical nephrectomy (LRN) has been considered the gold standard curative treatment for stage T2 RCCs (3). With ever‐evolving technology and surgical techniques, there has been a debate over the last decade about the use of partial or total nephrectomy for small renal masses (T1). Issues include whether nephron‐sparing surgery (NSS) gives better oncologic and renal function outcomes than patients having a total nephrectomy.
A collaborative review published in the European Association of Urology found no significant difference in overall survival and cancer‐specific survival between the two techniques. This is further supported by a 2010 review concluding that partial nephrectomy should be the treatment of choice for renal cortical tumours ≤4cm. Nephron‐sparing surgery has been found to be protective against chronic kidney disease whereas radical nephrectomy predisposes to it (4). This is because PN preserves more nephron units (5).
To date, there has been only one randomised control trial comparing the oncologic outcome of nephron‐sparing surgery to radical nephrectomy for small renal tumours. Results from this study somewhat contradict previous literature. They show that both surgical options provide excellent oncologic results. The conclusions (concerning overall survival) find that in the intention to treat population NSS appears to be less effective than RN. However, in the targeted population of RCC patients, outcomes no longer favour RN (6). It is important to note that quality of life and renal functional outcomes of the patients were not addressed in this trial. Although the oncologic outcomes appear to be much the same, Zini et al. demonstrated an overall rise in mortality and non‐cancer related death in patients undergoing RN with RCC T1aN0M0 (7).
In 2006 a paper funded by the U.S. National Institutes of Health sought to challenge radical nephrectomy as the treatment of choice for small renal cortical tumours. The authors concluded that radical nephrectomy is a significant risk factor for the development of chronic kidney disease (11). They go on to suggest that RN might no longer be regarded as the gold standard treatment for the resection of RCC ≤4cm. Arguments for RN come from long‐established renal function outcome data from donor transplant patients that indicate no long‐term decline in estimated GFR. Those against RN highlight that donor patients are a highly selected group, with excellent baseline renal function, whereas those with existing RCCs have lower baseline renal function, which determines their poor prognosis (12). However, in‐depth analysis has shown that RCC does not predispose to CKD (13) whereas many of those facing nephrectomy surgery suffer clinically important adverse renal outcomes (4). Furthermore, renal function (measured as the absence of new‐onset glomerular filtration rates [GFRs] <60ml/ml per 1.73m2) was found to be significantly higher in those undergoing partial nephrectomy (14).
Rationale for Study Chronic kidney disease is raising public health concern worldwide and is now thought to be an independent risk factor in much pathology, including cardiovascular disease (8). A 2004 community‐based study linked declining estimated GFR with risk of death, cardiovascular events and hospitalisation (9). Most literature describes renal insufficiency as an estimated GFR <60ml/min/1.73m2 (stage 3A chronic kidney disease as currently classified by NICE). Go et al. not only show that that there is an increased risk of cardiovascular events at an estimated GFR <60ml/min/1.73m2 but further suggest that cardiovascular events sharply increase again with an estimated GFR <45ml/min/1.73m2 (stage 3B chronic kidney disease). The Framingham Risk Score, which usually predicts cardiovascular risk accurately, often underpredicts cardiovascular disease in CKD patients. However, efforts to alter the equation, by incorporating eGFR, have made negligible improvement (10). For the purpose of this study we are particularly interested in renal function post nephrectomy and the relationship between it and other co‐morbidities – specifically cardiovascular health.
Objectives Projected renal function after nephrectomy is an area of interest that sparks much debate. To date there is little literature accurately documenting the long‐term renal function outcomes post‐nephrectomy. Current literature focuses on oncologic outcomes comparing
radical nephrectomy to nephron‐sparing surgery. Although there is an established link between chronic kidney disease and cardiovascular decline, we sought to identify the rate of CVD in patients undergoing a nephrectomy.
The aim of this study was to determine the effect of removing a kidney on the renal function and cardiovascular system. Further, if we take both radical and nephron‐sparing techniques to be equal in terms of surgical outcome, the aim was to quantify patients’ renal function after either total or partial nephrectomy.
Methods Patient information was collected from three surgical databases across NHS Lothian, TrakCare and Proton. Pre‐op, post‐op and follow‐up blood results were captured from SCI store. Advice was sought from South East Scotland Research Ethics Service and further NHS ethical review was not needed. Caldicott Guardian approval was received for the use of person‐identifiable information. Patients’ corresponding estimated glomerular filtration rates (eGFR) were calculated through the abbreviated Modification of Diet in Renal Disease (MDRD‐eGFR) equation (15). From this, each patient was categorised into their relevant Chronic Kidney Disease (CKD) stage as currently dictated by the National Institute of Clinical Excellence (8). Patients who subsequently started dialysis treatment following surgery were categorised as CKD stage 5. Two groups of patients were identified ‐ all patients who had complete blood results (group 1) and those patients who had pre‐operative and post‐operative follow‐up blood results collected within six months prior to surgery and at least six months following surgery respectively (group 2). Groups were divided into those that had total or partial nephrectomy. Patients excluded from analysis included patients with a baseline serum creatinine >300µmol/l before nephrectomy, patients under eighteen years old as the MDRD‐eGFR equation is not valid for this age group, and patients who had a follow‐up eGFR >300ml/min/1.73m2, which lay outside the boundaries of normality.
At each interval, change in eGFR between groups was compared using t‐test. For frequency distributions that did not meet the assumptions of normality, Wilcoxon ranked‐sign test was used. Incidence of CKD was compared in all groups using contingency tables and χ2 tests. The difference in baseline serum creatinine for those that started dialysis treatment was compared using t‐test. P values of <0.05 were considered statistically significant. Pearon’s correlation coefficient (r) was calculated for each comparison as a measure of effect size to quantify the strength of experimental effect. This is to be used in future work building a multinomial logistic regression model. All analysis was carried out in MS Office Excel 2003 and IBM SPSS Statistics 19.
Results Description of Groups and Patients Of the 1165 patients identified from the surgical databases, SCI store, Proton and TrakCare, 334 patients were included in Group 1 and 194 in Group 2 (Figure 1). There were very few partial nephrectomy patients with complete serum creatinine results (n=24).
The characteristics of the cohort are summarised in Table 1. There are slightly more men in the groups and a similar median age for all. The vast majority of cases are laparoscopic total nephrectomy; 71.4% of the whole cohort were still alive at time of analysis. 5.1% of patients had a history of cardiovascular disease, although past medical history was missing for 73.1% of the whole cohort.
Characteristics Whole cohort
n = 1165
Group 1
n = 334
Group 2
n = 194
p value*
Figure 1. Flowchart showing selection process for patient groups.
Table 1. General characteristics of patients and groups including creatinine follow up time.
Sex (%) M
F
624 (53.6)
541 (46.4)
183 (54.8)
151 (45.2)
105 (54.1)
89 (45.9)
0.89
0.89
Alive/Dead (%) A
D
U
832 (71.4)
296 (25.4)
37 (3.2)
284 (85)
49 (14.7)
1 (0.3)
163 (84)
30 (15.5)
1 (0.5)
0.79
0.79
Age, median 63 66 66 0.64
Total/Parital Nephrectomy (%) T
P
U
1008 (86.5)
61 (5.2)
96 (8.2)
302 (90.4)
24 (7.2)
8 (2.4)
179 (92.3)
13 (6.7)
2 (1)
0.81
Open/Laparoscopic (%) O
L
U
216 (18.5)
880 (75.5)
69 (5.9)
56 (16.8)
275 (82.3)
3 (0.9)
32 (16.5)
162 (83.5)
0.89
0.89
Count of results before operation, mean (SD)
3.43 (4.21) 3.91 (4.64)
Count of results after operation, mean (SD) 10.66 (12.92) 13.42 (14.78)
No. days first creatinine pre‐operation, median
39 26
No. days latest creatinine post‐operation, median
435 791.5
U = unknown. SD = standard deviation.
Corresponding eGFRs for each interval were not distributed normally (Kolmogorov‐Smirnov, p<0.05). However the distributions of difference of means were (K‐S, p>0.05), therefore t‐test was appropriate for comparing these results.
*Comparison of Group 1 and Group 2.
The majority (56.5%) of patients were diagnosed with renal cell carcinoma as shown in Figure 2. RCC accounted for 44.3% of deaths while cardiovascular cause only accounted for 5.4% of total deaths. 22.7% of patients were diagnosed with other non‐functional kidney disease. Diagnosis was missing for 5.2% of the whole cohort while cause of death was missing for 19.9%.
Reduction in eGFR Following Nephrectomy We compared the mean differences in eGFR pre‐operation, immediately post‐operation and at last follow‐up for total versus partial nephrectomy patients within the two groups. On average, patients in Group 1 had a higher eGFR before nephrectomy (Mean=82.90, SE=1.50) compared to their latest follow‐up result (Mean=68.55, SE=1.60). There was a mean drop in eGFR of 14.35ml/min/1.73m2 (95%CI 11.98‐16.72), p<0.001, r=0.54. Therefore baseline eGFR has a large effect on post‐nephrectomy renal function. Patients’ eGFR dropped dramatically post‐surgery (p<0.001) and then rose slightly during the follow up period (p<0.001).
Of particularly interest was the comparison of the mean difference in eGFR at last follow‐up for total and partial nephrectomy patients in Group 1. On average, partial nephrectomy patients had a higher eGFR post‐operatively (Mean=85.22, SE=7.96) compared with total nephrectomy patients (Mean=67.08, SE=1.63. Having had similar baseline eGFRs, partial nephrectomy patients’ latest result is a mean of 18.14ml/min/1.73m2 (95%CI 1.34‐34.95) higher than total nephrectomy patients, p<0.05, r=0.42.
Figure 2. Column chart showing diagnoses of patients. Unknown diagnoses are not included. AML=angiomyolipoma RCC=renal cell carcinoma SCC=squamous cell carcinoma TCC=transitional cell carcinoma
Group 2 displayed a similar pattern of results. However, there were few partial nephrectomy patients with kidney function tests available who had been followed up for six months. Again, patients’ eGFR in Group 2 was higher before nephrectomy (Mean=81.11, SE=1.96) compared to their latest follow‐up (Mean=67.02, SE=2.11). There was a mean drop in eGFR of 14.09ml/min/1.73m2 (95%CI 10.93‐17.24), p<0.001, r=0.28. Baseline eGFR, therefore, has a small effect on post‐nephrectomy renal function. Patients’ eGFR dropped dramatically again post‐surgery (p<0.001) and then rose marginally during the follow‐up period (p<0.01).
Splitting Group 2 into total and partial nephrectomy patients (and then assessing the last follow‐up eGFR result) partial nephrectomy patients had a higher eGFR (M=73.42, SE=11.66) compared with total nephrectomy patients (Mean=66.43, SE=2.14). Given similar baseline eGFRs for both, partial nephrectomy patients’ eGFR was a mean of 7ml/min/1.73m2 (95%CI ‐18.9‐32.87) higher on follow‐up compared with their total nephrectomy counterparts, p>0.05, r=0.17.
Change in Chronic Kidney Disease Stage Total and partial nephrectomy was compared in Group 1, which can be seen in Table 2. There was an association between type of nephrectomy and change in CKD stage, as categorised by new onset eGFR <60ml/min/1.73m2 χ2(1)=2.62, p=0.05. Odds ratio of eGFR <60ml/min/1.73m2 was 2.73 (95%CI 1.4‐5.3) for patients undergoing total nephrectomy.
Table 2. Contigency table showing new onset eGFR <60ml/min/1.73m2 for total and partial nephrectomy.
New onset eGFR <60
N Y Total
Count 157 86 243 Total/Partial T
% within Total/Partial 64.6% 35.4% 100.0%
Count 15 3 18 P
% within Total/Partial 83.3% 16.7% 100.0%
Count 172 89 261 Total
% within Total/Partial 65.9% 34.1% 100.0%
Group 2 could not be compared using chi‐square as a result of patient numbers receiving partial and total nephrectomies.
Dialysis Patients Eleven patients started dialysis treatment following surgery, two (18.2%) of whom have since died. Figure 3 shows a boxplot of baseline serum creatinine before surgery. Average baseline serum creatinine was higher for those who ended on dialysis treatment (Median=199) compared to those who did not (Median=88).
Figure 3. Boxplot showing distribution of mean baseline serum creatinine comparing dialysis patients (n=11) with those that did not require treatment (n=352).
Baseline serum creatinine was higher for those who eventually started dialysis treatment (Mean=205.73, SE=37.83) compared to those who did not (Mean=93.85, SE=1.47. There was a mean difference of 111.88µmol/l (SE=37.86µmol/l), p<0.01, r=0.68.
Discussion The findings of this study show that removing a kidney, whether it is total or partial nephrectomy, results in reduced renal function as measured by estimated GFR. There was a decline in renal function of 14.35ml/min/1.73m2 (p<0.001) and 14.09ml/min/1.73m2 (p<0.001) for Group 1 and 2 respectively. When comparing total and partial nephrectomy, renal function was significantly protected in those who underwent partial nephrectomy. Their eGFR was 18.14ml/min/1.73m2 (p<0.05) higher on follow‐up (Group 1). We showed that this correlated with an increased risk in developing chronic kidney disease. In Group 1, 35.4% of total nephrectomy patients developed new onset eGFR <60ml/min/1.73m2 compared with 16.7% of partial nephrectomy patients, p=0.05. The odds ratio showed that partial nephrectomy patients were 2.73 times less likely to develop new onset eGFR
<60ml/min/1.73m2. Therefore, although p is not significant, we have shown than partial nephrectomy can protect against chronic kidney disease. Further efforts were made to establish why some patients developed renal failure requiring dialysis. Of the 11 patients that subsequently started dialysis their baseline serum creatinine was elevated (Mean=112μmol/L). This suggests that, as one would expect, a risk factor for developing end stage renal failure following nephrectomy is raised baseline serum creatinine. Using Pearson’s correlation coefficients we have shown that baseline eGFR is a strong predictor of post‐nephrectomy renal function (r=0.54, Group 1). Reinforcing that excellent baseline renal function is paramount for a good outcome. There are several weaknesses in this study that limit our ability to comment. Diagnosis was predominately renal cell carcinoma so these patients could have faced adverse renal outcomes regardless of surgical technique. There was inadequate documentation regarding the past medical history, including CVD and associated risk factors, of patients. Therefore, we are unable to comment on the rate of cardiovascular disease in those undergoing nephrectomy. Few complete blood results were collected (n=364) for patients. This limited the sample sizes. Smaller than predicted sample sizes, compounded with few patients undergoing partial nephrectomy, resulted in analyses of Group 2 yielding insignificant results with unacceptable error. Effort could have been made to use Fischer’s exact test to overcome this. The ethnicity of patients was missing which introduced a <1% error into our MDRD‐eGFR calculations. There are several important comparisons to be made with current literature. The findings of this study support the current hypothesis that radical nephrectomy predisposes to poor renal outcome and the rate of CKD is higher in this population (11, 14). Further, our results are mirrored in previous studies that show partial nephrectomy to be protective against this (4, 5). Although we have inadequate documentation to comment on the cardiovascular health of our patients, literature suggests that nephrectomy predisposes to CVD (9). We have shown an increased risk of developing a new independent risk factor for CVD following nephrectomy as represented by new onset eGFR <60ml/min/1.73m2. We are, however, unable to comment on the overall mortality and morbidity of these patients. Ideally, we would have calculated the associated increase in CVD risk percentages. However, others’ attempts at incorporating eGFR into the Framingham Risk Score have so far been unsuccessful (10). We found that raised baseline serum creatinine and poor renal function were strong predictors of adverse outcomes post‐nephrectomy. This is reflected in donor kidney patient research that suggests excellent renal function before surgery protects against adverse outcomes while poorly functioning kidneys pre‐operatively predispose to them (12). Results from this study add to mounting evidence that radical nephrectomy predisposes to chronic kidney disease through a reduction in renal function by removal of an inappropriate number of nephron units. Partial nephrectomy is shown to be protective. Therefore, in surgically appropriate cases, nephron‐sparing surgery could be optimal in order to preserve renal function and prevent an associated increased risk in cardiovascular disease. This study does not go as far as quantifying the risk of developing new onset eGFR <60ml/min/1.73m2 or the chances of starting dialysis treatment. Further work will aim to
build a multinomial logistic regression model to predict these outcomes. Baseline eGFR has a strong influence on post‐nephrectomy renal function and our proposed model aims to quantify the strengths and significance of other variables in renal function outcome post‐nephrectomy.
Conclusion Concerns over detrimental reduction in renal function following radical nephrectomy raised in the literature (4, 7, 11, 12) are reinforced through this study. We have found a significant reduction in renal function with an associated increased risk of chronic kidney disease (and therefore cardiovascular disease) using this technique. Further studies are required to fully qualify these risks. Current findings suggest that, in appropriate cases, partial nephrectomy is optimal in order to protect long‐term renal function. All patients that undergo nephrectomy should have their renal function assessed preoperatively and at least 6 months post‐surgery to detect new GFR <60ml/min/1.73m2 and trigger appropriate evaluation.
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