Coated v noncoated ureteral metal stents: an experimental model.

PURPOSE: The purpose of the present study was to compare the standard metal stents with internally and externally coated metal stents in the pig model. MATERIALS AND METHODS: In nine female pigs weighing between 25 and 30 kg, the metal stents were randomly placed in either the right or left ureter, for a total of 18 stented ureters. Six ureters were stented with a Wallstent (Schneider, Zurich, Switzerland), six with a Passager stent (Boston Scientific, Natick, MA, USA), and six with a Corvita endoluminal graft (CEG) (Boston Scientific, Natick, MA, USA). Patency was examined by nephrostotomography 24 hours and 21 days after the initial procedure. RESULTS: Free flow of urine through the stents into the bladder was revealed in all ureters with the exemption of four cases where a Passager stent migrated into the bladder, jeopardizing ureteral patency. The Wallstent generated mild inflammation with metaplasia of the urothelium; the CEG a more pronounced inflammatory response in the adjacent ureter; and the Passager stent severe inflammatory reaction with necrosis of the urothelium. The sections of the Wallstents revealed the presence of a mild polypoid reaction adherent to the internal surface of the devices. The coated stents showed no tissue ingrowth through the lining material into the ureteral lumen, and thus, the urothelium was compressed beneath the prostheses. CONCLUSIONS: Our experimental results suggest that the standard Wallstent generates less inflammation of the surrounding tissues than coated stents. The coated stents have the advantage of minimal tissue ingrowth but have a tendency to migrate toward the bladder.

Percutaneous treatment of large symptomatic renal cysts.

PURPOSE: To evaluate the efficacy of alcohol in combination with tetracycline for the treatment of symptomatic renal cysts. PATIENTS AND METHODS: Twenty-four patients age 45 to 77 years (mean 66 years) with a large (5-13-cm; mean 7.5-cm) symptomatic renal cyst associated with flank pain were treated by aspiration under ultrasound guidance and injection of alcohol and tetracycline. Patients were followed with ultrasonography at 1, 6, and 12 months and once a year thereafter. RESULTS: The aspirated volume ranged from 65 to 1500 mL (mean 360.5 mL). Two patients experienced mild pain during alcohol injection, but the procedure was completed successfully. One patient reported severe pain after tetracycline injection. The tetracycline was immediately aspirated, and the procedure was then aborted. The remaining patients were relieved of their symptoms after treatment, and they remained symptom free during a mean follow-up of 20 months (range 7-36 months). CONCLUSIONS: The combination of alcohol and tetracycline is safe and effective and offers a very favorable minimally invasive therapeutic alternative for the treatment of symptomatic renal cysts.