Medullary sponge kidney.

"Medullary sponge kidney" applies to pathologically dilated collecting tubules within one or more renal pyramids of one or both kidneys, almost always diagnosed radiographically, of uncertain etiology, and presenting a clinical spectrum varying from an asymptomatic, incidental finding to severely complicating calcareous-infective disease, renal insufficiency, and death. Recognition of the characteristic urographic pattern affords the patient presenting clinically with hematuria, ureteral colic, urinary tract infection, or nephrocalcinosis a prompt diagnosis with a frequently benign prognosis, and usually averts more extensive or invasive investigations.