Research on stones can be applied quickly to practice


Urologists should recommend that their patients with stones maintain a normal intake of calcium.

Two recent studies deal with the effect of alpha-blockers on ureteral stones. A number of groups have examined the ability of alpha-blockers to facilitate stone passage, but researchers from the University of Wisconsin, Madison, are among the first to explain the specific physiologic mechanism. They demonstrate that alpha-1 receptor blockade reduces spontaneous ureteral contractility and suggest that the mechanism of alpha-1 antagonism on ureteral stone passage may involve the reversal of the contractile effect of epinephrine on ureteral smooth muscle.

This effect was confirmed in a randomized, prospective clinical trial presented by Italian researchers from the University of Modena and Reggio Emilia. Their data suggest that alpha-blockers taken as an adjunct to shock wave lithotripsy lessen the time to stone passage, reduce the need for pain medication, and decrease the time patients are out of work. Urologists would do well to consider an alpha-blocker trial in patients with stones 8 mm or smaller in size whose pain can be controlled.

Therefore, moderation in dietary calcium is the key. Urologists should recommend that their patients with calcium oxalate stones maintain a normal intake of calcium-one to two servings of dairy products per day for the majority of patients. This seems a reasonable compromise between the practice of placing all patients with calcium stones on restricted-calcium diets and the recommendation that such patients should increase their calcium intake based on a slew of epidemiologic studies from the early and mid-1990s showing calcium intake to be inversely related to stone formation.

Finally, Cleveland Clinic researchers have released a valuable clinical study for urologists faced with patients who have undergone jejuno-ileal bypass, or JIB. Practicing urologists need to know when patients have had previous bariatric procedures-especially intestinal bypass surgery, which can increase the risk of stone formation-and conduct an appropriate metabolic evaluation. If the patient has any stone risk factors that were initiated or exacerbated by bariatric surgery, medical management is recommended. Failing that, the urologist should recommend a takedown of the bariatric procedure.

It will be relatively simple for urologists to take this information and apply it immediately to their clinical practices. As we improve our grasp of what causes stone disease and how stones pass spontaneously, we can better serve patients suffering from this often-debilitating illness.

Dr. Preminger, a member of the Urology Times editorial council, is professor of urology and director of the Comprehensive Kidney Stone Center at Duke University Medical Center, Durham, NC.

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