LONG-TERM EFFECTS OF URETERAL STENT AFTER URETERAL DILATION

Balloon dilation of the right ureterovesical junction (UVJ) and distal ureter to three times its normal caliber was performed in 12 pigs. A right double-J (D-J) stent was inserted after dilation in 6 pigs. Bila teral upper tract dynamics with different perfusion rates (0.5, 2 and 4 ml. per minute) were recorded before dilation, immediately after dil ation, and then 4 and 7 weeks after dilation. Immediate and late anteg rade nephrostograms as well as suprapubic cystograms were taken. Grade 3 reflux occurred in 100% of animals at 7 weeks on the dilated, stent ed ureter and no reflux on the dilated, nonstented ureter. At 7 weeks on the dilated, stented side, significant growth (>100,000, colonies) of Pseudomonas species was noted in all animals. Creatinine clearance was significantly reduced on the dilated, stented side when compared t o the dilated, nonstented side at 7 weeks. Histologic examination of t he dilated, stented and dilated, nonstented ureters at 4 weeks reveale d a segmental muscular defect with muscular regeneration starting from the edge of the defect, particularly in the innermost region. At 7 we eks, there was a more advanced, but similar, pattern of muscular regen eration in both groups. However, at 7 weeks, metaplastic changes of th e ureter and chronic pyelonephritis were evident on the dilated, stent ed ureter. Electron microscopy showed that myofibroblasts played a maj or role in the healing process with new muscle formation. At 4 weeks, no significant morphologic difference was found between the dilated, s tented and dilated, nonstented ureters. At 7 weeks, however, it appear ed that the ureteric stent resulted in damage and deterioration of ren al function without affecting muscular regeneration of the ureter. We conclude that the changes observed could be entirely due to the infect ion associated with the stent rather the stent itself.