Peripelvic Cysts of the Kidney

Peripelvic cysts of the kidney may be defined as cysts which are situated in the hilus of the kidney, intimately associated with the renal pelvis and calyces. They may be simple or multiloculated, single or multiple. Unlike the common simple cysts of the kidney parenchyma, peripelvic cysts are not buried within the renal parenchyma nor are they present as a mass in either pole or along the external surface of the kidney. Instead, they compress and displace the renal pelvis and vascular pedicle. If large enough, they may protrude from the renal hilus. Peripelvic cysts which are large enough to cause symptoms or be detectable on radiographs are rare and have been seldom reported in the urological or radiological literature. Smaller multiloculated hilar cysts, however, which are not detectable in vivo are not unusual, being said to occur in over 1 per cent of routine autopsies (1). Henthorne (3) found 20 cases of peripelvic cysts at autopsy. These varied in size from microscopic to 5 cm. in diameter. Scholl (6) described 2 cysts of sufficient size to cause distortion of the renal pelvis on the urogram. Both of these exerted pressure on the structures of the renal hilus and were apparently related to significant hypertension. Only a few additional reports of large peripelvic cysts are to be found in the literature (2, 4, 5). Analysis of a large series of renal masses studied by nephrotomography in the New York Hospital-Cornell Medical Center during the last four years yields a total of 117 simple cysts of the renal parenchyma. In this same series there are only 7 masses with the appearance of peripelvic hilar cysts. This indicates their relative rarity. The pathogenesis of these cysts is obscure. They probably originate in the hi-lus of the kidney rather than from the adjacent renal parenchyma or from the renal pelvis. Henthorne believes that they are lymphatic cysts which may have developed in areas of lymphatic ectasia due to chronic inflammatory changes. Other authors suggest that they are congenital cysts arising from embryonic rests. Allen (1) suggests an origin from remnants of the wolffian body. Haslinger (2) believes that they may have developed from meso-nephric remnants. Clinical Material We have collected a total of 13 cases of renal hilar masses demonstrated by pyelography in recent years. It was originally believed that all of these were cysts. Subsequent surgical exploration has proved 7 to be peripelvic cysts, while 2 were found to be lipomas of the renal hilus, believed to represent hypertrophy of the peripelvic fat. The remaining 4 cases have not been explored. Three of the proved cysts distorted the renal pelvis enough to cause partial obstruction and caliectasis. In one of these cases there was an associated pyelonephritis with symptoms. In none of the other cases were there symptoms which could be produced by the cysts.