The medullary sponge kidney (MSK) is a congenital anomaly of the renal medulla characterized by fusiform and cystic dilatation of the collecting tubules confined to the renal pyramids. The aim of this study is to evaluate the metabolic risk factors and effect of extracorporeal shock wave lithotripsy (ESWL) and complications in an MSK with nephrocalcinosis.

We compared stone metabolic studies between 45 patients with MSK and 279 non-MSK patients. We evaluated the effect of ESWL for MSK. Group A patients received ESWL and follow-up within 3 months and Group B patients had a period of cessation for more than 6 months. The frequency of complications between group A and group B patients was compared.

There were no statistically differences between the MSK group and non-MSK group of patients in the stone metabolic studies. Among the 45 patients with MSK, 26 (58%) had one or several of the following metabolic disorders: hypocitraturia (36.7%), hypercalciuria (18.3%), hyperoxaluria (16.3%), hyperuricosuria (16.3%), low urine volume (12.4%). The percentage of patients that experienced more than 75% of a reduction of stone burden on plain films was 48.8%, 25-75% of the reduction was 35.6%, and less than 25% of the reduction was 15.6%. The most common complication was renal colic (17.7%). Renal colic and stone re-growth was shown to have a more significant association with group B patients as compared to group A patients.

ESWL reduced the stone burden more than 75% in 48.8% of MSK patients with nephrocalcinosis, and prevented flank pain, and obstructive uropathy. Therefore, we plan to develop treatments that are more effective.