Background: Medullary sponge kidney (MSK) is a congenital, non-hereditary anomaly characterized by dilation of the precalix ducts. It is often associated with other diseases, and its symptoms are linked to frequent complications, such as sepsis of the urinary system and the renal colic of nephrolithiasis. However, MSK is rare in association with glomerulonephritis (GNP), as can be seen from medical literature data that shows only one case (reported in 1974) in which MSK with a concomitant focal sclerosing glomerulonephritis was noted. In this report, we describe a case of MSK that was found after a routine renal echograph and biopsy of a mesangial GNP previously diagnosed at another center. The echographic results showing typical MSK was confirmed by means of RX urography and renal TC. The MSK-glomerulonephritis combination appears to be completely random, because the involved structures (the collecting duct and the glomerule) have different embryologic origin. Therefore, a pathogenic hypothesis common to the two anomalies seems rather unlikely.
Conclusions: Although MSK is a usually benign disease, because a compromise of glomerular filtration that occurs in approximately 10% of cases, proper diagnosis is important to allow prophylactic intervention aimed at the reduction of complications that could reduce overall renal function when associated with other nephropathies. Renal echography is an important diagnostic tool that may reveal more cases of MSK than previously reported.