Multicystic kidney disease is commonly described as a congenital dysplasia which is usually unilateral and not productive of symptoms. The kidney is devoid of function, and there is no familial tendency (1). It often causes an abdominal mass and is most frequent in the neonatal period when nephroblastoma may be suspected (2). The lesion may persist into adult life and be accidentally discovered as a result of investigation of abdominal trauma (Case III). Secondary changes such as calcification and bone formation may then be observed. The excretory urogram results in no evidence of function on the affected side. The appearance of large simple cysts or multilocular cysts is not encountered and should not be confused with this entity. Retrograde studies are generally fruitless, as the ureter may be atretic. The specimen consists of a mass, not easily recognized as kidney, composed of multiple cysts of various sizes, some of which may be quite large (3, 4). The cysts are lined with cuboidal or flat epithelium...