Medullary sponge kidney disease.

Abstract

Although medullary sponge kidney disease has been described in the Italian and Swedish literature it is infrequently reported in the English and North American journals. It is not accepted by all as a disease entity, and its importance is somewhat minimized because of the frequent statements that it is benign. It is, perhaps, looked upon as a disease of interest only to radiologists and a curiosity of little importance. The material in the University of Michigan Medical Center has been surveyed, and forty patients with this entity compose the basis for this report. The historical aspects are now widely known, and the earliest descriptions by Lenarduzzi (1) and Cacci and Ricci (2) are established. The monograph of Ekström et al. (3) and the several papers by Lindvall (4) have created in our institution the idea that this is a “Swedish” disease. It consists of a cystic dilatation of the collecting tubules in the renal pyramids. These vary in size and distribution affecting all or only one or a few pyramids. These cavities mayor may not contain calculi, and the disease is diagnosed in the absence of calculi. The etiology is assumed to be congenital, and there are those who would associate it with polycystic disease (5). Vermooten has indicated that the etiology may be the result of uric acid crystal obstruction during the fetal period (6). It is less frequently described in children and seems to be primarily an adult affliction. In 1960 Reilly and Neuhauser reported 11 cases which appeared to be associated with cystic disease of the liver, and they believed that this disease represented an uncommon form of polycystic disease (7). Edith Potter has indicated that cystic dilatation of the collecting tubules does not exist except with accompanying cystic liver involvement and is invariably fatal (5). These fetal and pediatric forms of the disease are not identified in the adult (8). In fact, if adult medullary sponge kidney disease were not complicated by pyelonephritis, calculus formation, and hemorrhage, it would surely attract little attention. Differential Diagnosis The differentiation of this entity from renal tuberculosis is sometimes difficult and may require urine culture if the tuberculosis is confined to the renal pyramids. However, the cavities formed by this infectious disease are irregular in form and size and usually fill secondarily from the pelvis. Timed films after the injection of the urographic contrast medium may elucidate this problem (3). Hyperparathyroidism is more likely to result in calcifications of large or varying size not strictly confined to the renal pyramids. Renal tubular acidosis may present genuine problems of differentiation but is distinguished by the uniformity of involvement of every pyramid of both kidneys, with all the calcifications of about the same size and shape. There also is an absence of demonstrable dilatation or cystic deformity of the collecting tubules. Small localized areas of papillary necrosis and calicine diverticula can prove troublesome to the inexperienced observer.