New combined approach in metallic ureteral stenting to avoid urothelial hyperplasia: study in swine model.

Abstract

PURPOSE: We assessed the therapeutic value of a new treatment option for ureteral strictures that may avoid urothelial hyperplasia, which is the main cause of metallic stent failure. MATERIALS AND METHODS: We used 24 pigs in this study. An experimental model of ureteral stricture was induced in all animals. Obstruction was confirmed by ultrasound and retrograde ureteropyelogram 6 weeks after model creation. The pigs were then randomly allocated to 2 experimental groups. Therapy involved placement of a 6 × 30 mm metallic ureteral covered stent in the ureteral stricture in group 1 and subsequent endoureterotomy at the ureteral segments adjacent to the 2 ends of the stent in group 2. A double pigtail stent was then deployed for 3 weeks. Completion studies 6 months after therapy included retrograde ureteropyelogram, endoluminal ultrasound and ureteroscopy to assess urothelial hyperplasia formation. RESULTS: At the end of the study evidence of urothelial hyperplasia was seen in 50% of the pigs in group 1 and in 29% in group 2. Four and 2 cases of cranial stent migration in groups 1 and 2, respectively, were seen at 6 months. Hyperplasia and renal involvement were statistically significantly different between the groups with more damage in group 1 than in group 2. CONCLUSIONS: Hyperplasia was markedly reduced when ureteral peristalsis was inhibited by endoureterotomy at the area of interaction between the stent and the ureter.