Update on Nephrolithiasis

Abstract

Many recent papers analyze the association between renal stone disease and other diseases that are typical of industrialized countries. Epidemiology studies from large series indicate that the prevalence of nephrolithiasis is higher among patients with metabolic syndrome, diabetes, and hypertension. Patients with nephrolithiasis also have an increased risk of myocardial infarction and stroke. It has been hypothesized that the common underlying defect could be insulin resistance. This, in turn, alters the urine biochemistry (i.e. more acidic pH and less urine citrate) thereby increasing the propensity of stone forming. In the diabetic rat renal steatosis has been implicated in the reduced production of ammonia, which has been shown to be reversible after PPARγ administration. Furthermore, pioglitazone was shown to be effective in reducing ethylene glycol-induced renal injury. Another significant association concerns gout. Two recent papers report that both calcium and uric acid stone disease are more prevalent among patients with gout. The metabolic derangements found in gouty and non-gouty patients were quite similar. CT imaging in patients with gout indicates that the incidence of nephrolithiasis is underestimated if only based on stone history. Finally, stone episodes may occur many years before the first gouty attack. Another interesting issue is that of a potential adverse effect of calcium and vitamin D supplementation on the risk of stone formation. It has been shown that treated post-menopausal women have a slight but significantly higher risk of forming stones, independently of other interfering variables. From this the recommendation to evaluate the actual benefit of supplementation, even more in the face of its ineffectiveness to prevent fractures in older women. Bariatric surgery is increasingly proposed for managing severe obesity, and in the last few years it has shown a widespread use in the US. Previous procedures of digestive diversion were often complicated by hyperoxaluria and renal oxalosis. More recent techniques, including Roux-en-Y gastric bypass and gastric bending, seem to give better outcomes. Hyperoxaluria and hypocitraturia following these procedures induce only minor increases in the risk of forming stones, but some recent reports of renal oxalosis after gastric bypass deserve attention.