Plasma oxalate concentration and secondary oxalosis in patients with chronic renal failure.

To examine the association between hyperoxalaemia and secondary oxalosis, measurement of plasma oxalate concentration was combined with a search for tissue deposition of calcium oxalate crystals in patients with chronic renal disease. Two groups of patients were studied. In the first, samples of the inferior epigastric artery were taken from 35 patients at the time of renal transplantation. In the second, sections taken at necropsy from 23 patients with chronic renal failure in whom plasma oxalate had been measured before death were examined. Though plasma oxalate concentrations ranged between 6 and 116 mumol/l (four to 78 times greater than the upper limit of the reference range), no extrarenal deposits of oxalate were found in either study. Renal deposition of oxalate was associated with a plasma oxalate concentration of greater than 20 mumol/l. This study gives no support to the suggestion that hyperoxalaemia of the degree seen in patients with the type of chronic renal failure that is not due to primary hyperoxaluria confers an appreciable risk of extrarenal oxalosis.

Renal complications of jejuno-ileal bypass for obesity.

Jejuno-ileal bypass has until recently been an accepted treatment for refractory morbid obesity. Although hyperoxaluria causing renal tract calculi is a well-recognized complication, we describe eight patients who developed significant renal failure attributable to hyperoxaluria resulting from this procedure, three requiring renal replacement therapy. We review the literature, describing 18 other cases with renal failure, the mechanisms of hyperoxaluria and its treatment. Because reversal of the bypass may result in stabilization or partial improvement of renal function, these patients require long-term follow-up of renal function.

Control of varicella-zoster infection on renal and other specialist units.

The introduction of chickenpox onto our renal unit recently raised several issues surrounding the management of patient and staff contracts. This paper describes the action taken and makes various recommendations for future management of similar cases. Guidelines are proposed for the management of patients and staff as well as the role of the infection control team in handling a chickenpox problem. Future developments, including the use of VZ vaccine for patient and staff, are also discussed.

Correction of subclinical ascorbate deficiency in patients receiving dialysis: effects on plasma oxalate, serum cholesterol, and capillary fragility.

Whole blood ascorbate, plasma oxalate, serum cholesterol, and capillary fragility were measured at monthly intervals for 3 mth in 7 patients receiving continuous ambulatory peritoneal dialysis and 4 receiving haemodialysis, to whom ascorbate supplements had not been prescribed for at least 12 mth. Ascorbate supplements, 25 mg/day, were prescribed for the first month and 50 mg/day for the second month; in the final month patients received no supplements. Whole blood ascorbate was below normal in 6/11 patients at the start of the study but was normal in 10/11 patients when taking ascorbate 50 mg/day. No significant changes in plasma oxalate were observed with these doses of ascorbate, and correction of ascorbate deficiency had no effect on serum cholesterol, mean cell volume, or the results of capillary fragility tests. In a supplementary study, ascorbic acid 500 mg/day was administered for 3 wk to 11 patients. This resulted in a significant rise in mean plasma oxalate from 30.3 (SEM 3.5) to 48.4 (SEM 20.3) mumol/l.

The determination of plasma oxalate concentrations using an enzyme/bioluminescent assay. 2. Co-immobilisation of bioluminescent enzymes and studies of in vitro oxalogenesis.

An inexpensive, continuous flow assay for the determination of oxalate in plasma is described. The assay is based on the bioluminescent determination of NADH, a product of the degradation of oxalate by oxalate decarboxylase and formate dehydrogenase, using bioluminescent enzymes immobilized on cyanogen bromide-activated sepharose. The detection limit of the assay is 0.8 mumol/l. Intra-batch CV values of 5.2 and 3.8% were obtained at oxalate concentrations of 18 and 60 mumol/l. Recovery of added oxalate averaged 100.7%. Plasma oxalate ranged from less than 0.8 to 2 mumol/l in 14 healthy subjects, and from 6 to 134 mumol/l in 125 patients with renal disease treated by continuous ambulatory peritoneal dialysis. Ascorbic and dehydroascorbic acid did not directly interfere in the assay. In vitro oxalogenesis was observed in blood from 12 healthy subjects, but only after samples had stood at room temperature for more than 6 h. No significant oxalate generation occurred in blood from 24 patients with impaired renal function, even after standing at room temperature for 24 h. Oxalate generation was inhibited by the addition of oxalate to plasma, but the addition of urea and creatinine was without effect.

Does treated essential hypertension result in renal impairment? A cohort study.

To determine how frequently essential hypertension results in significant renal impairment we undertook a follow-up study of 176 patients with well documented essential hypertension first seen in 1975-1977. Six patients were Asian, two Negro, and the remainder Europid. Follow-up was achieved in 92% of the cohort at five years and in 87% at 12-14 years. At five years 13 (7%) patients had moved away or were lost, and 15 (9%) patients had died (11 cardiovascular deaths). Treated blood pressure was greater than 160/95 mmHg in 60/148 patients and greater than 200/100 mmHg in 16 patients. Despite this, no significant change in serum creatinine was detected in the group as a whole. Increments in serum creatinine of at least 35 mumol/l occurred in six patients. Over the ensuing 6-9 years serum creatinine had returned to normal in three of these patients and stabilized in two; the sixth patient died from myocardial infarction. No patient reached end-stage renal failure. We conclude that progressive deterioration in renal function in essential hypertension is rarely a significant problem in Caucasian patients. A decline in renal function should prompt a search for underlying primary renal disease.

Oxalate retention in chronic renal failure: tubular vs glomerular diseases.

Plasma oxalate concentration was measured using an enzyme/bioluminescent assay in 289 patients (178 males, 111 females) with chronic renal failure (plasma creatinine greater than 200 mumol/l), age (SD) 55.5 (13.8) years. Plasma oxalate ranged between less than 0.8 and 48 mumol/l and showed a positive correlation with plasma creatinine (r = 0.57, p less than 0.0001). The slope of the regression line in 55 patients with glomerulonephritis (GN) was significantly lower than in patients with tubulointerstitial disease (TI); however the intercept was significantly higher in GN than in TI. Analysis of covariance showed no relationship between plasma oxalate concentration and age, duration of renal impairment, or administration of diuretics, vitamin D analogues, or phosphate binders. Longitudinal analysis of plasma oxalate measured 3-monthly in selected patients showed marked variability of oxalate/creatinine and oxalate/urea ratios.

Long term survival on haemodialysis in primary hyperoxaluria.

Results of treatment of end-stage renal failure (ESRF) in patients with primary hyperoxaluria have been generally poor, largely due to the inability of any treatment regime to match the endogenous overproduction of oxalate. The severity of the disease varies widely, as reflected by the differences in age at onset of ESRF. This variability may influence the results of treatment of ESRF in these patients. The longest reported survival on haemodialysis of a patient with primary hyperoxaluria is eight and a half years. We report a patient who survived for eleven years on haemodialysis after reaching ESRF due to primary hyperoxaluria, and suggest that this prolonged survival was due to relatively mild disease severity rather than exceptional treatment.

Central pulse pressure in patients with chronic kidney disease and in renal transplant recipients.

Patients with chronic kidney disease (CKD) and renal transplant recipients (RTR) have increased cardiovascular risk. The value of measuring central pulse pressure (cPP) over brachial pulse pressure (pPP) is not known. Central PP was measured in 597 patients (364 CKD:233 RTR). In multivariate analysis, age and female gender positively correlated with cPP; heart rate and estimated glomerular filtration rate negatively correlated with cPP. Associations for age, heart rate and gender persisted after additional adjustment for pPP and aortic wave reflection. This model accounted for 91% of the variability in cPP, with pPP alone accounting for 74%. Results were similar when both patient groups were analysed separately. A subset of patients with CKD had aortic pulse wave velocity (PWV) and left ventricular mass index (LVMI) measured. There were no differences in the univariate correlations between PWV (r=0.368 vs 0.315; P=0.4) or LVMI (r=0.125 vs 0.163; P=0.7); nor in the multivariate models created for PWV (P=0.1) or LVMI (P=0.1) when either cPP or pPP were used. This study demonstrates that in these patients most of the variability in cPP can be explained by pPP. Additionally, cPP does not appear to provide additional information beyond pPP in determining PWV and LVMI.

Variation between centres in access to renal transplantation in UK: longitudinal cohort study.

OBJECTIVE: To assess whether equity exists in access to renal transplantation in the UK after adjustment for case mix in incident patients with end stage renal disease. DESIGN: Longitudinal cohort study. SETTING: UK Renal Registry and UK Transplant Registry. PARTICIPANTS: All incident renal replacement treatment patients (n=16 202) from 65 renal centres submitting data to the UK Renal Registry between 1 January 2003 and 31 December 2005, followed until 31 December 2008 (or until transplantation or death, whichever was earliest). OUTCOME MEASURES: Proportion of incident dialysis patients at each renal centre who were registered on the national transplant list; time taken to achieve registration; and proportion of patients subsequently transplanted. RESULTS: We found that recipients' age, ethnicity, and primary renal diagnosis were associated with the likelihood of accessing the waiting list or receiving a transplant. After adjustment for case mix, significant inter-centre variability existed in access to the transplant list (change in -2LogL=89.9, df=1, P<0.001), in the time taken to register patients on the waiting list (change in -2LogL=247.4, df=64, P<0.001), in receipt of a renal transplant from a donor after brain stem death (change in -2LogL=15.1, df=1, P=0.001), and in receipt of a renal transplant from a living donor or a donor after cardiac death (change in -2LogL=46.1, df=1, P<0.001). CONCLUSIONS: Significant variation in access to renal transplantation exists between centres within the UK that cannot be explained by differences in case mix.

Echocardiographic assessment of systolic function in dialysis patients.

Echocardiography has been widely used to investigate cardiac function in uraemic patients. There is no doubt about the validity of this technique in certain situations, particularly the demonstration of structural abnormalities and pericardial effusions. However, the assessment of cardiac function by measurement of cardiac dimensions and their rate of change is complicated by the profound influence of altered loading conditions, common in uraemia, on the measurements obtained. This is a particular problem in the assessment of changes in cardiac function during haemodialysis. Even studies utilising isovolaemic dialysis are open to criticism, due to the effects of altered afterload on cardiac emptying. Recently the experimental finding that end-systolic volume is independent of end-diastolic volume and linearly related to afterload has raised the possibility that non-invasive assessment of end-systolic indices may allow load-independent assessment of intrinsic cardiac contractility in patients. However, none of the studies using these indices in uraemic patients has validated the assumption that they are indeed load-independent in this clinical situation. Evidence is presented suggesting that the end-systolic pressure:volume relationship is altered by the administration of a volume load and that manipulation of afterload without autonomic blockade results in markedly increased contractility, presumably due to reflex sympathetic activity. More work is required before these indices are used uncritically in dialysis patients.

Cardiac arrest associated with hypokalaemia in a patient receiving mithramycin.

The case is reported of a patient who developed severe hypokalaemia, leading to cardiac arrest, while receiving mithramycin for painful Paget's disease. The patient was also receiving antihypertensive and anti-anginal treatment including bendrofluazide, but plasma potassium before the administration of mithramycin was normal. Hypokalaemia has been reported in previous studies of the use of mithramycin but has received little attention. The drug should be used with great care in patients with cardiovascular disease and in those receiving diuretics.

Calcium phosphate stones during long-term acetazolamide treatment for epilepsy.

We report a case of recurrent renal calculi containing calcium phosphate associated with long-term acetazolamide treatment for epilepsy. Unfortunately, the cause of stone formation was not recognised for many years, by which time irreversible renal damage had occurred.