High failure rate of indwelling ureteral stents in patients with extrinsic obstruction: experience at 2 institutions.

The indwelling ureteral stent commonly is used to bypass 2 types of obstruction: 1) intrinsic obstruction usually due to stones or ureteropelvic junction abnormalities or 2) extrinsic compression, for example by retroperitoneal tumor. To determine the success of this intervention at 2 institutions the medical records of all patients undergoing cystoscopic placement of a stent for ureteral obstruction were reviewed. Procedures were classified by several parameters, including the type and location of the ureteral obstruction, indications for stent placement and success of the procedure. Stent failure was defined arbitrarily as clinical occlusion of the stent within 30 days of placement. X-rays were reviewed as available to measure stricture length and location in patients with extrinsic obstruction. Of the procedures at Brigham and Women's Hospital in Boston, where silicone stents are used almost exclusively, 23 perforated indwelling stents placed for intrinsic obstruction were uniformly successful. In contrast, of 24 stents placed for extrinsic obstruction 11 failed (p less than 0.0005). At Beth Israel Hospital, where polyurethane stents are used most commonly, all 21 perforated indwelling stents placed for intrinsic obstruction were successful, while 9 of 22 stents placed for extrinsic obstruction failed (5 within the first 24 hours of placement, p less than 0.0005). The only parameter that seemed to be a predictor of stent failure was luminal size, and this only in silicone catheters. The reasons for this surprising failure rate of internal stents in the face of extrinsic obstruction are not known but may be related to previous studies that describe a relationship among ureteral peristalsis, venting side holes and flow rate.(ABSTRACT TRUNCATED AT 250 WORDS)