Definition, Etiology, DiagnosisTop
Medullary sponge kidney (MSK) is usually identified following imaging evaluation of flank pain, kidney stones, hematuria, or urinary tract infections. On IV pyelography or computed tomography (CT) imaging MSK is associated with nephrocalcinosis, small 1 to 7 mm medullary cysts, and enlargement of the pyramids without overall renal enlargement. Factors increasing the risk for calcium stone formation, such as hypercalciuria, hyperuricosuria, hypocitraturia, and hyperoxaluria, are present. The cause of MSK remains unknown. About half of patients with MSK have a positive family history but no definitive genetic cause has been found.
MSK follows a benign course and does not progress to chronic kidney disease. The main complications include kidney stones and urinary tract infections. There is an association with reduced bone mineral density. In asymptomatic patients no specific monitoring is required. In those with a history of a kidney stone, a full diagnostic workup is indicated, with stone prophylaxis based on the results.