Mechanisms of hyperuricemia in cyclosporine-treated renal transplanted children

Environmental Triggers of Hyperuricemia and Gout

Gout is the most prevalent type of inflammatory arthritis worldwide and environmental factors contribute to hyperuricemia and risk for gout flare. Causes of hyperuricemia include increased purine consumption from meat, alcohol, and high fructose corn syrup as well as medications such as cyclosporine, low-dose aspirin, or diuretics. Triggers for gout flares include increased purine consumption and medication use such as urate lowering therapy and diuretics. Environmental exposures including lead exposure, particulate matter exposure, temperature fluctuations, and physiologic stress have been found to trigger flares. In the right clinical scenario, these factors should be considered when treating gout patients.

Expert consensus on management of metabolic disease in Chinese liver transplant recipients

Metabolic disease, including diabetes mellitus, hypertension, dyslipidemia, obesity, and hyperuricemia, is a common complication after liver transplantation and a risk factor for cardiovascular disease and death. The development of metabolic disease is closely related to the side effects of immunosuppressants. Therefore, optimization of the immunosuppressive regimen is very important for the prevention and treatment of metabolic disease. The Chinese Society of Organ Transplantation has developed an expert consensus on the management of metabolic diseases in Chinese liver transplant recipients based on recent studies. Emphasis is placed on the risk factors of metabolic diseases, the effect of immunosuppressants on metabolic disease, and the prevention and treatment of metabolic diseases.

The Protective Effect of Febuxostat on Chronic Tacrolimus-Induced Nephrotoxicity in Rats

BACKGROUND

The use of calcineurin inhibitors is a well-known risk factor for hyperuricemia in kidney transplant recipients. We evaluated the effect of febuxostat (Fx), a new uric acid-lowering drug, on hyperuricemia and renal injury in an experimental model of chronic tacrolimus (Tac)-induced nephropathy.

METHODS

Chronic Tac nephropathy was induced by administering Tac (1.5 mg/kg/day) to rats on a low-salt diet (0.05%) with oxonic acid (OA, 2%, 0.2 g/kg/day) for 28 days. Two doses of Fx (5 and 10 mg/kg) were concomitantly administered with Tac or vehicle (Vh). We evaluated the effect of Fx on hyperuricemia by measuring serum uric acid (SUA) levels, fractional excretion of uric acid (FEUA), and urate transporters in Tac-induced nephropathy. The effects of Fx on Tac-induced renal injury were evaluated in terms of renal function and arteriolopathy, tubulointerstitial fibrosis, inflammation, and apoptosis. We evaluated oxidative stress as a protective mechanism via xanthine oxidase (XO) activity, and as a marker of oxidative stress (via evaluation of levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 4-hydroxy-2-hexenal (4-HHE)).

RESULTS

The Tac group showed higher SUA levels and lower FEUA than did the Vh group, but Fx treatment significantly decreased SUA levels in a dose-dependent manner, with an increase of FEUA at a high dose (10 mg/kg). Tac treatment increased urate-anion exchanger 1 and decreased organic anion transporter type 1 expression in renal tubular cells, but Fx treatment reversed the effects on those transporters. Impaired renal function and histological injury (interstitial fibrosis, inflammation, and arteriolopathy) in the Tac group were markedly improved by Fx administration. Increases in apoptotic cell death and activation of proapoptotic caspase-3 by Tac were remarkably decreased by Fx treatment. Tac administration increased the activity of XO in kidney tissue and serum, and the levels of 8-OHdG in urine and 8-OHdG and 4-HHE of kidney tissue, but combined treatment with Fx decreased the levels of these parameters.

CONCLUSIONS

Fx is effective in controlling hyperuricemia and in preventing Tac-induced renal injury, via a reduction of oxidative stress. Therefore, a targeted therapy aimed at inhibiting uric acid by Fx may be a useful approach in the management of the progression of nephropathy in renal transplant patients treated with Tac.

Prevalence and risk factors of hyperuricemia among kidney transplant recipients

Hyperuricemia is common in renal transplant patients (RTRs), especially those on cyclosporine (CsA)-based therapy. We conducted a retrospective study to determine the prevalence of hyperuricemia and its risk factors among RTRs. A total of 17,686 blood samples were obtained from 4,217 RTRs between April 2008 and January 2011. Hyperuricemia was defined as an uric acid level of ≥7.0 mg/dl in men and of ≥6 mg/dl in women that persisted for at least two consecutive tests. Majority (68.2%) of RTRs were normouricemic. Hyperuricemia was more frequent in younger and female RTRs. On multivariate logistic regression, we found high trough level of cyclosporine to be a risk factor for hyperuricemia. In addition, female gender, impaired renal function, and dyslipidemia (hypercholesterolemia, hypertriglyceridemia, and elevated LDL) were also associated with higher probability of hyperuricemia. Hyperuricemia is a common complication after renal transplantation. Risk factors implicated in post-transplant hyperuricemia include high trough level of cyclosporine, female gender, renal allograft dysfunction, and dyslipidemia.

Hyperuricemia beyond 1 year after kidney transplantation in pediatric patients: Prevalence and risk factors

Hyperuricemia is frequent among adult renal transplant recipients; however, data among pediatric kidney recipients are scarce. This study is designed to estimate the prevalence and risk factors of late post-transplant hyperuricemia in pediatric recipients. A retrospective observational multicenter study on 179 pediatric renal recipients (5–18 years) was conducted between April 2008 and January 2011 from five kidney transplant centers of Tehran, Iran. All recipients were followed up for more than 1 year (5.9 ±3.3 years) after transplantation. A total of 17686 blood samples were obtained for serum uric acid (SUA). The normal range of SUA was defined as SUA 1.86–5.93 mg/dl for children between 2 and 15 years in both genders; 2.40–5.70 mg/dl for girls aged >15 years; 3.40–7.0 mg/dl for boys aged >15 and more than 6 and 7 mg/dl in boys and girls older than 15 years old. The median age of the children was 13 years. Male recipients were more popular than female (male/female 59/41%). Hyperuricemia was detected in 50.2% of patients. Mean SUA concentration was 5.9±1.7 mg/dl and mean SUA concentration in hyperuricemic patients was 7.7±1.2 mg/dl. While at multivariate logistic regression elevated serum creatinine concentration (P<0.001) and the time span after renal transplantation (P=0.02) had impact on late post-transplant hyperuricemia. High cyclosporine level (C0 and C2) was not risk factor for huperuricemia. Late post-transplant hyperuricemia was found in about half of pediatric renal recipients, and was associated with impaired renal allograft function.

Uric acid and transplantation

Hyperuricemia is a common complication in organ transplant recipients, with a higher incidence in kidney and heart recipients. Risk factors for post-transplant hyperuricemia include reduced glomerular filtration rate, diuretic use, cyclosporine therapy, increasing age at transplant, obesity, and metabolic syndrome, as well as the presence of pretransplant hyperuricemia. The impact of hyperuricemia in patient and graft survival is unclear because uric acid only recently has been considered a risk factor for cardiovascular disease and graft survival. The effect of uric acid on graft function remains controversial, with studies suggesting that uric acid is an independent risk factor for chronic allograft dysfunction, contrasting with other studies suggesting that hyperuricemia is only a marker of reduced glomerular filtration rate. Strategies to reduce uric acid levels include reduction or avoidance of cyclosporine treatment, adequacy of antihypertension treatment, avoidance of diuretics, nutritional management, and use of uric acid-lowering agents. In this article, we review the incidence and risk factors for the development of post-transplant hyperuricemia, the effect of different immunosuppressive regimens in uric acid handling, and recent results from studies comparing uric acid levels and renal function in organ transplant recipients that try to identify which comes first: hyperuricemia or chronic allograft dysfunction?

Use of uric acid-lowering agents limits experimental cyclosporine nephropathy

BACKGROUND

Hyperuricemia frequently complicates cyclosporine (CsA) therapy. Previous studies have shown that hyperuricemia exacerbates interstitial and vascular lesions in the cyclosporine model. We tested the hypothesis that normalization of uric acid could prevent the development of cyclosporine toxicity.

METHODS

CsA nephropathy was induced by administering CsA (15 mg/kg/day) for 7 weeks to rats on a low salt diet (CsA group). The effect of preventing hyperuricemia was determined by concomitant treatment with a xanthine oxidase inhibitor, allopurinol (CsAALP), or with a uricosuric, benzbromarone (CsABENZ), in drinking water. Control groups included vehicle-treated rats.

RESULTS

CsA-treated rats developed mild hyperuricemia with arteriolar hyalinosis, tubular atrophy, striped interstitial fibrosis, increased cell proliferation and decreased VEGF expression. Treatment with allopurinol or benzbromarone limited renal disease, with reduced interstitial fibrosis, cell proliferation, macrophage infiltration, osteopontin expression and arteriolar hyalinosis, in association with restoration of VEGF expression. Both drugs provided comparable protection.

CONCLUSIONS

An increase in uric acid exacerbates CsA nephropathy in the rat. Concomitant treatment with allopurinol or benzbromarone reduced the severity of renal disease. The similar protection observed with both drugs suggests that the effect is associated more with lowering uric acid levels than the antioxidant effect of allopurinol.

Hyperuricemia after liver transplantation in children

Uric acid may be involved in the development and progression of kidney diseases. Hyperuricemia is a common feature in adult liver transplant recipients but there is limited information in children. In order to estimate the incidence, predictors of hyperuricemia in pediatric liver transplant recipients, and to assess whether hyperuricemia may impact long-term renal function determined by measured GFR, we reviewed data of 70 children who received a first liver transplant between 1991 and 2005 (median follow-up 7.1 yr). Renal function tests performed annually included uric acid concentration, inulin and uric acid clearances. The cumulative incidence of hyperuricemia was 32% at 10-yr post-transplantation, mainly because of decreased urate excretion. The only factor significantly associated with an increased risk of hyperuricemia was older age. After adjustment for donor and recipient age, gender, primary liver disease, immunosuppression, and post-operative acute renal failure, hyperuricemia as time dependent variable tended to predict (p = 0.05) subsequent CRI. The control of serum urate concentration in eight of the 21 hyperuricemic patients either by nutritional management or by allopurinol was not followed by a significant GFR improvement. Hyperuricemia after liver transplantation in children is a frequent problem which needs further investigation.

Hyperuricemia is associated with the development of the composite outcomes of new cardiovascular events and chronic allograft nephropathy

BACKGROUND

To investigate the prevalence and the predictors for the development of hyperuricemia at 6 months after kidney transplantation, and its association with clinical outcomes including patient and graft survival, the development of new cardiovascular events and chronic allograft nephropathy (CAN).

MATERIALS AND METHODS

Adult patients who underwent kidney transplantation at Mount Sinai Medical Center between January 1, 2001 and December 30, 2004 were included in the study. New cardiovascular events and biopsy-proven CAN were investigated.

RESULTS

Of the 307 patients, 163 patients (53%) had normal uric acid levels and 144 patients (47%) had hyperuricemia. After adjustment for age, race, and sex, receiving a cadaveric kidney, having an estimated glomerular filtration rate (eGFR) less than 50 mL/min, and taking diuretics or cyclosporine were associated with hyperuricemia at 6 months after transplantation. Over a mean 4.3 years of follow-up, 83 patients had one, or more, of the events, 4 died, 20 had graft failure, 40 had new cardiovascular events, and 41 developed CAN. Kaplan-Meier survival curves showed that these events occurred more frequently in patients with hyperuricemia (P<0.001). Among transplant recipients with an eGFR less than 50 mL/min, 45% of hyperuricemic and 21% of normouricemic patients had an event (P=0.038). For patients with an eGFR more than 50 mL/min, event rates were similar for patients with and without hyperuricemia, 25.0% vs. 19.4%, respectively.

CONCLUSIONS

These results suggest an important association between hyperuricemia at 6 months after kidney transplantation and new cardiovascular events and CAN in patients with decreased allograft function.

Replacement of Calcineurin-Inhibitors With Sirolimus as Primary Immunosuppression in Stable Cardiac Transplant Recipients

BACKGROUND

Calcineurin-inhibitor (CNI) nephrotoxicity is a major cause of morbidity and mortality after cardiac transplantation. The aim of this study was to assess over 2 years the safety and effect on renal function of withdrawal of CNI immunosuppression and replacement with sirolimus (SRL) in stable cardiac transplant recipients.

METHODS

CNI was substituted with SRL in 78 cardiac transplant recipients (SRL group) of whom 58 (group A) had CNI-induced renal impairment (glomerular filtration rate [GFR] <50 mL/min) and 20 (group B) had preserved renal function (GFR >50 mL/min). Fifty-one patients (CNI group) with renal impairment (GFR < or =50 mL/min) maintained on CNI served as controls. Secondary immunosuppressants were unchanged.

RESULTS

In the SRL group, GFR increased from 47.0+/-18.0 to 61.2+/-22.2 ml/min (P=0.0001) 24 months after SRL initiation. In Group A, GFR increased from 40.5+/-12.7 to 53.9+/-19.8 mL/min (P<0.0001). In Group B, GFR increased marginally from 67.2+/-15.8 to 83.5+/-27.8 mL/min (P=0.10). In the CNI group, GFR declined from 40.5+/-14.0 mL/min to 36.4+/-12.5 mL/min (P=0.23) after 24 months of follow up. There was no significant difference in cardiac rejection or cardiac allograft function. In SRL group, proteinuria increased from 299+/-622 mg/day to 517+/-795 mg/day (P=0.0002) 12 months after SRL initiation and then stabilized; it did not differ from CNI group at 24 months (637+/-806 vs. 514+/-744 mg/day, P=0.39). Uric acid decreased from 7.6+/-2.4 to 6.2+/-1.9 mg/dL (P=0.0007) in the SRL group.

CONCLUSIONS

Graduated substitution of CNI with SRL in cardiac transplant recipients is safe and improves renal function, without cardiac compromise.

Hyperuricemia and gout following pediatric renal transplantation

Hyperuricemia and gout are common complications in adult renal transplant recipients. In pediatric recipients, however, hyperuricemia seems to be rare, but data are scarce. Thirty-two children (21 males, 11 females) were investigated for a median time of 4.8 years (range: 0.4-11.2 years) following renal transplantation. The median age of this pediatric study group was 13.9 years (range: 5.7-20.3 years), and the calculated glomerular filtration rate (GFR) was 61 ml/min per 1.73 m(2) (range:12-88 ml/min per 1.73 m(2)). All patients were given calcineurin inhibitors, with 22 and ten children receiving cyclosporine A (CSA) and tacrolimus (TAC), respectively. The median plasma uric acid was 385 micromol/l (range: 62-929 micromol/l); 15 children (47%) were above the age-related normal range. Only one patient experienced gouty arthritis. There was a significant correlation between plasma uric acid concentration and both time span after transplantation and plasma creatinine, and an inverse correlation to GFR (p<0.05). No significant correlation was found between plasma uric acid and body mass index (BMI). Plasma uric acid concentrations were neither different among CSA- and TAC-treated children, nor did they correlate with drug exposure or blood trough levels of CSA or TAC. Plasma uric acid concentration was not different when compared to children with chronic renal failure (CRF) of a similar degree in native kidneys. We conclude that hyperuricemia is common among pediatric renal transplant recipients and rather a consequence of chronic renal transplant dysfunction than the use of calcineurin inhibitors. Gout, however, is rare.

Frequency of hyperuricemia and effect of calcineurin inhibitors on serum uric acid levels in liver transplanted children

Hyperuricemia is common after renal and cardiac transplantations, but it is rarely reported after liver transplantations. The aim of this study is to determine the frequency of hyperuricemia in children following orthotopic liver transplantation and the effects of calcineurin inhibitors tacrolimus and cyclosporine) on blood uric acid levels. Between September 1997 to January 2004, 76 liver transplantations were performed in 70 children (male/female; 39/31) at Ege University, Organ Transplantation Center (37 deceased donation and 39 live donors). Patients who had been transplanted within the last three months and patients who died within six months after liver transplantation were excluded from the study. Finally 59 patients were included in this study. Uric acid levels were measured before transplantation and after transplantation within six months intervals for two yr. In these series 17 cases had increased uric acid levels after liver transplantation (28.8%). Serum uric acid levels in both groups (tacrolimus or cyclosporine) were detected to be significantly higher than initial values at 12th months (p < 0.05). Hyperuricemia developed in eight patients receiving cyclosporine (eight of 11; 72%) whereas nine patients receiving tacrolimus developed hyperuricemia (nine of 48; 18%). However, the rate of having high uric acid levels was significantly higher in cyclosporine group compared tacrolimus group (p = 0.001, OR: 11.5, CI 95% 2.5-52.4). Uric acid levels were also significantly higher in cyclosporine group in 12th and 18th months (respectively, p = 0.003 and p = 0.003). Serum creatinine levels at 12th, 18th and 24th months were significantly higher in cyclosporine group than tacrolimus group (respectively, p = 0.009, p = 0.04 and p = 0.02). Hyperuricemia is a common complication after liver transplantation in children. Cyclosporine may cause hyperuricemia more often in respect to tacrolimus and this may be related to the impairment of renal functions. Complications developing because of hyperuricemia such as gout disease or renal calculi are quite rare in children.

Gout in renal transplant recipients

AIMS

The aims of the present audit were to determine the prevalence of gout in renal transplant recipients in Canterbury, New Zealand, to identify risk factors for gout, and to assess the range of treatments used, their efficacy and complications. In addition, the authors wished to assess the impact of post-renal transplant gout on the patient.

METHODS

Patients with post-transplantation gout were identified from the Christchurch Hospital Nephrology database. For each patient with gout a post-renal transplantation recipient without gout post transplant was found matched for age, sex and date of transplant. Case notes were audited and patients interviewed.

RESULTS

In total, 47/202 (23%) living renal transplant recipients had gout post transplant. Those patients with gout were more likely to be taking a loop diuretic (68%vs 34%, P < 0.001), to have a higher serum urate and impaired renal function and to have had gout prior to the transplant. Of those patients who developed gout post transplant 70% had an attack at least every 3 months. Of those who returned to work post transplant 48% required time off work because of gout.

CONCLUSION

out is an important problem in the post-transplant population causing significant morbidity and time off work. Diuretics, impaired renal function, gout prior to transplantation and hyperuricaemia are important risk factors. The need for diuretic therapy should be kept under review in these patients. Hypouricaemic therapy should be considered early in those who develop gout post renal transplantation. Further studies are required to determine whether treatment for asymptomatic hyperuricaemia is justified.

Gout in solid organ transplantation: a challenging clinical problem

Hyperuricaemia occurs in 5-84% and gout in 1.7-28% of recipients of solid organ transplants. Gout may be severe and crippling, and may hinder the improved quality of life gained through organ transplantation. Risk factors for gout in the general population include hyperuricaemia, obesity, weight gain, hypertension and diuretic use. In transplant recipients, therapy with ciclosporin (cyclosporin) is an additional risk factor. Hyperuricaemia is recognised as an independent risk factor for cardiovascular disease; however, whether anti-hyperuricaemic therapy reduces cardiovascular events remains to be determined. Dietary advice is important in the management of gout and patients should be educated to partake in a low-calorie diet with moderate carbohydrate restriction and increased proportional intake of protein and unsaturated fat. While gout is curable, its pharmacological management in transplant recipients is complicated by the risk of adverse effects and potentially severe interactions between immunosuppressive and hypouricaemic drugs. NSAIDs, colchicine and corticosteroids may be used to treat acute gouty attacks. NSAIDs have effects on renal haemodynamics, and must be used with caution and with close monitoring of renal function. Colchicine myotoxicty is of particular concern in transplant recipients with renal impairment or when used in combination with ciclosporin. Long-term urate-lowering therapy is required to promote dissolution of uric acid crystals, thereby preventing recurrent attacks of gout. Allopurinol should be used with caution because of its interaction with azathioprine, which results in bone marrow suppression. Substitution of mycophenylate mofetil for azathioprine avoids this interaction. Uricosuric agents, such as probenecid, are ineffective in patients with renal impairment. The exception is benzbromarone, which is effective in those with a creatinine clearance >25 mL/min. Benzbromarone is indicated in allopurinol-intolerant patients with renal failure, solid organ transplant or tophaceous/polyarticular gout. Monitoring for hepatotoxicty is essential for patients taking benzbromarone. Physicians should carefully consider therapeutic options for the management of hypertension and hyperlipidaemia, which are common in transplant recipients. While loop and thiazide diuretics increase serum urate, amlodipine and losartan have the same antihypertensive effect with the additional benefit of lowering serum urate. Atorvastatin, but not simvastatin, may lower uric acid, and while fenofibrate may reduce serum urate it has been associated with a decline in renal function. Gout in solid organ transplantation is an increasing and challenging clinical problem; it impacts adversely on patients' quality of life. Recognition and, if possible, alleviation of risk factors, prompt treatment of acute attacks and early introduction of hypouricaemic therapy with careful monitoring are the keys to successful management.

Uric acid and transplantation

Hyperuricemia is a common complication in organ transplant recipients, and frequently is associated with chronic cyclosporine immunosuppressive therapy. Kidney and heart transplant recipients are prone to develop posttransplant hyperuricemia. Risk factors for hyperuricemia include decreased glomerular filtration rate (GFR), diuretic use, and preexistent history of hyperuricemia. The influence of hyperuricemia in patient and graft survival is unclear because uric acid is not usually considered a common risk factor for cardiovascular disease that affects graft and patient survival. However, there have been small studies that have suggested that control of uric acid levels contributes to recovery of renal function (in heart and liver transplant recipients) and in an improvement in GFR in renal transplant recipients. Despite controversies in the need for hyperuricemia treatment in transplant patients, strategies to decrease uric acid levels includes a decrease or avoidance of cyclosporine treatment, adequacy of antihypertension treatment, avoidance of diuretics, nutritional management, and use of uric acid-decreasing agents. In this article we review the incidence and risk factors for the development of posttransplant hyperuricemia, discuss the influence of different immunosuppressive agents on uric acid metabolism, and suggest some alternative treatments for posttransplant hyperuricemia. We also consider that uric acid should be considered as a potential risk factor for renal allograft nephropathy or for renal dysfunction in nonrenal transplant recipients, as well as a comorbid factor for a decrease in patient and graft survival.

Uric acid stones following hepatic transplantation

We report the case of a 52 year old man with a history of insulin-requiring diabetes and hepatitis B with cirrhosis who received an orthotopic liver transplant. One year later he developed renal colic and was found to have a 3 mm stone at the left ureterovesical junction. Numerous other stones formed and infrared spectroscopy analysis demonstrated all to be composed of 100% uric acid. Urine collections demonstrated a low urine pH of 5.1 without hyperuricosuria. His stones were effectively prevented with potassium citrate therapy. Few incidence data are available for uric acid stone occurrence in solid organ recipients. Calcineurin inhibitors are thought to often cause hyperuricemia on the basis of decreased urate excretion. However, this effect would not be expected to cause hyperuricosuria nor uric acid stones. This class of drugs may also be associated with low urine pH, perhaps on the basis of hypoaldosteronism, but the contribution of such a syndrome to uric acid stone formation is not established.

Hyperuricemia and gout in renal transplant recipients

Hyperuricemia, unlike clinical gout, is extremely common in renal transplant patients. The high prevalence of hyperuricemia is related to prolonged exposure to cyclosporine rather than to its dose or serum concentration. Serum creatinine levels do not show significant correlation with hyperuricemia, behaving more like a surrogate marker for cyclosporine dose and trough level. The low incidence of gout in renal transplant patients, despite the hyperuricemia, may be related to the prolonged immunosuppression effect.

Hyperuricemia exacerbates chronic cyclosporine nephropathy

BACKGROUND

Hyperuricemia frequently complicates cyclosporine (CSA) therapy. The observation that longstanding hyperuricemia is associated with chronic tubulointerstitial disease and intrarenal vasoconstriction raised the hypothesis that hyperuricemia might contribute to chronic CSA nephropathy.

METHODS

CSA nephropathy was induced by the administration of CSA (15 mg/kg/day) for 5 and 7 weeks to rats on a low salt diet (CSA group). The effect of hyperuricemia on CSA nephropathy was determined by blocking the hepatic enzyme uricase with oxonic acid (CSA-OA). Control groups included rats treated with vehicle (VEH) and oxonic acid alone (OA). Histological and functional studies were determined at sacrifice.

RESULTS

CSA treated rats developed mild hyperuricemia with arteriolar hyalinosis, tubular injury and striped interstitial fibrosis. CSA-OA treated rats had higher uric acid levels in association with more severe arteriolar hyalinosis and tubulointerstitial damage. Intrarenal urate crystal deposition was absent in all groups. Both CSA and CSA-OA treated rats had increased renin and decreased NOS1 and NOS3 in their kidneys, and these changes are more evident in CSA-OA treated rats.

CONCLUSION

An increase in uric acid exacerbates CSA nephropathy in the rat. The mechanism does not involve intrarenal uric acid crystal deposition and appears to involve activation of the renin angiotensin system and inhibition of intrarenal nitric oxide production.

Recommendations for the outpatient surveillance of renal transplant recipients. American Society of Transplantation

Many complications after renal transplantation can be prevented if they are detected early. Guidelines have been developed for the prevention of diseases in the general population, but there are no comprehensive guidelines for the prevention of diseases and complications after renal transplantation. Therefore, the Clinical Practice Guidelines Committee of the American Society of Transplantation developed these guidelines to help physicians and other health care workers provide optimal care for renal transplant recipients. The guidelines are also intended to indirectly help patients receive the access to care that they need to ensure long-term allograft survival, by attempting to systematically define what that care encompasses. The guidelines are applicable to all adult and pediatric renal transplant recipients, and they cover the outpatient screening for and prevention of diseases and complications that commonly occur after renal transplantation. They do not cover the diagnosis and treatment of diseases and complications after they become manifest, and they do not cover the pretransplant evaluation of renal transplant candidates. The guidelines are comprehensive, but they do not pretend to cover every aspect of care. As much as possible, the guidelines are evidence-based, and each recommendation has been given a subjective grade to indicate the strength of evidence that supports the recommendation. It is hoped that these guidelines will provide a framework for additional discussion and research that will improve the care of renal transplant recipients.

Difficult gout and new approaches for control of hyperuricemia in the allopurinol-allergic patient

A major obstacle to the treatment of hyperuricemia in patients allergic to allopurinol is the limited availability of suitable, equally effective, alternative, urate-lowering drugs. Conventional uricosuric drugs, including probenecid and sulfinpyrazone, are recommended for allopurinol- intolerant patients with gout and "underexcretion" hyperuricemia who have normal renal function and no history of nephrolithiasis. Therapeutic options in those in whom traditional uricosuric drugs are contraindicated, ineffective, or poorly tolerated include slow oral desensitization to allopurinol and cautious administration of oxipurinol. Allopurinol desensitization is useful particularly in those who have failed other treatment modalities. If available (as in Europe, South Africa, and Japan), benzbromarone may be tried in patients with gout and mild-to-moderate renal insufficiency. Recombinant urate oxidase can be used in the short-term prophylaxis and treatment of chemotherapy- associated hyperuricemia in patients with lymphoproliferative and myeloproliferative disorders. Hyperuricemia and gout occur with increased frequency in cyclosporine-treated allograft transplant recipients. The management of gout in these patients is complicated by two main factors: cyclosporine-induced renal impairment, and interactions with medications used to preserve the allograft.

Sulfinpyrazone reduces cyclosporine levels: a new drug interaction in heart transplant recipients

BACKGROUND

Management of cyclosporine (CsA)-associated hyperuricemia in heart transplantation (HT) is difficult. Because of the myelotoxicity of combined allopurinol and azathioprine, we tested sulfinpyrazone.

METHODS

We studied 120 HT recipients (109 men; mean age at HT, 52+/-10 years). All had received allopurinol for at least 6 months, which was stopped for 1 month before initiation of sulfinpyrazone. Mean follow-up from HT to onset of sulfinpyrazone (200 mg/day) was 59+/-41 months. We stopped the drug after 6+/-2 months. We compared CsA level and daily dose, serum creatinine, blood urea, and uric acid at onset and before interruption of sulfinpyrazone and, as control, in the last 6 months of allopurinol.

RESULTS

Mean uricemia decreased with allopurinol (0.58+/-0.12 vs. 0.41+/-0.07 mmol/liter, p = 0.0001) as well as with sulfinpyrazone (0.51+/-0.13 vs. 0.40+/-0.12 mmol/liter, p = 0.0001). Mean creatinine increased (171+/-42 and 164+/-35 micromol/liter, p = 0.01) with allopurinol, whereas it tended to decrease with sulfinpyrazone (160+/-35 and 154+/-48 micromol/liter, p = NS). Mean urea did not change with allopurinol (14+/-5 vs. 15+/-7 mmol/liter, p = NS), but fell with sulfinpyrazone (14.01+/-5 vs. 12.60 +/-5 mmol/liter, p = 0.0004). Mean CsA levels were constant with allopurinol (193+/-73 vs. 188+/-65 ng/ml, p = NS), although CsA dose was slightly reduced (2.7+/-0.8 vs. 2.6+/-0.8 mg/kg/day, p = 0.007). Conversely, CsA levels dropped with sulfinpyrazone (183+/-89 vs. 121 +/-63 ng/ml, p = 0.0001) despite an increase in CsA daily dose (2.6 +/-0.9 vs. 2.8+/-0.9 mg/kg/day, p = 0.0001). Two subjects were treated for acute rejection. We observed no other side effects. In HT recipients sulfinpyrazone, as an alternative to allopurinol, is effective in achieving metabolic control of hyperuricemia. However, this drug reduced CsA levels, thus the risk of rejection is present.

Course of renal allograft histopathology after transplantation in early childhood

BACKGROUND

We report a long-term prospective follow-up of renal allograft histology in children <5 years of age at transplantation (Tx).

METHODS

Fifty-one kidney allograft recipients were prospectively followed for renal allograft histology and function up to 7 years after Tx. Twenty patients were recipients of kidneys from living related donors, and 31 were cadaveric kidney recipients. All patients received triple immunosuppression. Biopsies were analyzed according to the Banff classification and scored semiquantitatively. The "chronic allograft damage index" (CADI) was calculated.

RESULTS

Five of seven grafts were lost because of nephrosis in patients with congenital nephrotic syndrome of the Finnish type. Most of the biopsies (52-69%) were considered normal (Banff classification), and the proportion with chronic allograft nephropathy did not increase with time. The median CADI score was 2.5 (scale: 0-36) at 1.5 years and 3.5 at 7 years. Recipients with an acute rejection episode had higher CADI scores than recipients without acute rejection episode. Patients with a high CADI score at 3 years had inferior graft function at 5 years. Recipients <2 years of age had CADI scores and numbers of acute rejection episode similar to recipients between 2 and 5 years of age. However, in contrast to the older recipients, the younger recipients did not improve their absolute glomerular filtration rate with time.

CONCLUSIONS

The long-term histopathological findings were mostly mild and stable with time. Acute rejection episode had an impact on these changes and CADI predicted later graft function. Nonimmunological risk factors seem to be more important in the youngest recipients.

Graft function 5-7 years after renal transplantation in early childhood

BACKGROUND

Low recipient age is still a risk factor for graft failure after kidney transplantation (Tx). Detailed prospective reports on long-term graft function in small children after renal Tx are still lacking.

METHODS

Forty-nine kidney allograft recipients who received transplants before the age of 5 years were followed prospectively. The most common disease was congenital nephrotic syndrome of the Finnish type. Twenty patients were recipients of living related donors (LRD), and 29 were cadaveric kidney (CAD) recipients. All patients received triple immunosuppression. Glomerular filtration rate (GFR), effective renal plasma flow (ERPF), sodium, urate, and potassium handling, and concentrating capacity were studied for up to 7 years after Tx.

RESULTS

Patient survival 7 years after Tx was 100% for LRD and 96% for CAD recipients. Graft survival was 94% for LRD and 79% for CAD recipients (P=NS) and 89% and 83% for children >2 years and <2 years of age at Tx, respectively (P=NS). Five years after Tx, GFR was 70 vs. 64 and ERPF was 380 vs. 310 ml/min/1.73 m2 for LRD and CAD recipients, respectively (P=NS). Mean absolute GFR remained stable. GFR was lower in children who received transplants at <2 years than in children who received transplants at >2 years of age, 54 vs. 75 ml/min/1.73 m2 (P=0.02). Sodium handling remained intact, but hyperuricemia was seen in 43-67%; 17-33% showed abnormal handling of potassium; and most patients had a subnormal concentrating capacity.

CONCLUSIONS

Excellent long-term graft survival and good graft function can be achieved with triple immunosuppression, even in young CAD kidney recipients.

Uricosuric effect of the angiotensin II receptor antagonist losartan in heart transplant recipients

BACKGROUND

The angiotensin II receptor antagonist losartan is an effective antihypertensive agent with unique uricosuric properties. This study evaluates the uricosuric effects of losartan in 10 hypertensive heart transplant patients with hyperuricemia.

METHODS

The patients were randomized to receive losartan 50 mg once daily and enalapril 20 mg once daily for 4 weeks according to a double-blind crossover design. Office blood pressure, plasma uric acid levels, and urinary uric acid excretion were monitored throughout the study.

RESULTS

Plasma uric acid levels decreased significantly after 4 weeks of treatment with losartan (P<0.05) but not with enalapril. On day 1 and after 1 month of treatment, a significant increase in uric acid excretion was observed only with losartan. Significant decreases in office systolic and diastolic blood pressures were obtained with enalapril but not with losartan.

CONCLUSIONS

Losartan effectively lowers plasma uric acid levels in hyperuricemic heart transplant patients.

Paediatric kidney transplantation

Renal transplantation is the optimal form of renal replacement therapy leading to substantial improvement in the quality of life. It has rapidly become the standard treatment for end-stage renal disease in children. However, despite impressive short-term results significant long-term problems remain unsolved. Because of the lack of effective treatment for chronic rejection and common recipient noncompliance, allograft half-life has not improved significantly during the last decade. A paediatric recipient is likely to need several retransplantations in adulthood. Moreover, the immunosuppressive drugs used today have potentially serious side-effects including nephrotoxicity and de novo malignancy. These are especially relevant for paediatric recipients who will continue to receive therapy for several decades. Most therapeutic protocols used for children are derived from those used for adults. However, the metabolic differences between an adult and a growing and developing paediatric transplant recipient are not always adequately appreciated before these new therapies are initiated. In the near future, we are likely to see new and more efficient drugs become available. It is important that we try to understand their properties in children and use them and our current arsenal on an individual basis aiming at optimal graft survival but also at avoiding unnecessary adverse effects.