Solitary Cysts of the Kidney

Abstract

THE causative factors involved in the production of solitary cysts of the kidney have been subject to considerable discussion for a long period of time. Cysts of the kidney in general have long been recognized by anatomists. In fact, they were described by Fabry of Hilden who died in 1624, and have been studied by other distinguished anatomists, including Willis and Morgagni. However, the exact etiology has never been satisfactorily determined. Etiologic Theories.—One etiologic theory explains the development of the cyst on the basis of a mechanical blockage of the collecting tubules, with subsequent retrodilatation. Other authors contend that it is due to a retention incident to interstitial nephritis. A third theory states that the cyst may be caused by a persistence of the “anlagen or rudiments of uriniferous tubules in the vesicular phase of development and their later expansion.” Still another hypothesis is that failure of the S-shaped anlagen of uriniferous tubules to unite with the straight collecting ducts may be the causative factor. The failure of the uriniferous tubules to join the collecting ducts of higher orders (later generations) after having become detached from such ducts of a lower order is also considered as involved in the production of cysts. The belated appearance of disconnected cavities in a uriniferous tubule which had remained solid during its formation has also been presented as an instrumental factor. Finally, the secondary compression of collecting or secretory tubules caused by local inflammatory processes, as congenital syphilis, is considered by others to offer a satisfactory explanation for the production of cysts. Recently, Hepler (1) has experimentally produced such cysts in the kidney of a rabbit by fulgurating a papilla and ligating the artery which supplied the same pyramid. He thus produced an obstruction to urinary secretion and an anemia of the obstructed secretory tissue. Symptomatology.—In many cases, the cyst is relatively small and does not interfere with renal function, and hence produces no symptoms. In such instances, the finding of the cyst is coincidental at necropsy. When the cyst enlarges it may attain sufficient size to exert pressure on adjacent organs, or the presence of a mass may be noted by the patient. Occasionally a dull dragging or aching in the loin or hypochondrium may be experienced. As a general rule, urinary symptoms do not predominate, although in rare instances hematuria has been reported. Diagnosis.—As stated previously, the small cysts are asymptomatic; no symptoms referable to the urinary tract occur and their presence is not suspected. The larger cysts are usually confused with hydronephrosis, polycystic kidney, ovarian cysts, and occasionally renal neoplasm. The roentgenogram may show the outline of the cyst, especially if it arises from the lower pole of the kidney and has attained moderate size.