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Update in Nephrology
2003–2004 Series: Update Sessions from ACP's 2003 Annual Session
This account of important, recent clinical advances in nephrology focuses on 3 key topics of interest: hypertension, proteinuria, and renal-replacement therapy. Two single studies—one in the area of nephrolithiasis and the other dealing with glomerulonephritis in the form of lupus-related nephropathy—are also reviewed. The goal was to select studies that provide pathophysiologic insight into a given problem or that are likely to alter clinical practice.
Nephrolithiasis
Alternative Diet Halved the Risk for Recurrent Calcium Oxalate Stones in Hypercalciuric Men
In this 5-year trial, 120 men who had chronic idiopathic hypercalciuria (urinary calcium excretion exceeding 300 mg [17.5 mmol] per day) and recurrent calcium oxalate stones were randomly assigned to receive either a traditional low-calcium diet that provided no more than about 10 mmol of calcium per day or a normal-calcium diet (30 mmol/d) with reduced amounts of animal protein (52 g/d) and salt (59 mmol/d). The authors hypothesized that the latter diet may decrease oxalate excretion. Men in both groups received 2 liters (3 in warm weather) of water each day. Stones recurred in 23 of 60 participants given a low-calcium diet but in only 12 of 60 participants given the alternative diet. The relative risk for recurrence in the latter group was 0.49 (95% CI, 0.24 to 0.98; P = 0.04) or 0.37 (CI, 0.18 to 0.87; P = 0.006) after adjustment for the total number of stones formed before randomization and the number of episodes of colic in the previous year. Calcium excretion declined by about 4.2 mmol per day in both groups. The difference was in oxalate excretion, which increased by approximately 5.4 mg per day on the conventional diet and decreased by about 7.2 mg per day in men given the experimental diet.
The substantial reduction in stone formation in the context of a biological rationale is enough evidence for clinicians …
