Assessment of optimal balloon size for rupture of the ureteropelvic junction and mid-ureter in a porcine model

Purpose: Balloon dilation potentially represents a safer and simpler technique for the treatment of ureteropelvic junction (UPJ) obstruction and ureteral strictures. Using a porcine model, we sought to establish the optimal balloon size for endoballoon rupture of the UPJ and ureter. Materials and Methods: The efficacy of endoballoon rupture of the proximal and middle ureter with 24F, 30F, and 36F balloon catheters was compared in 19 female minipigs. At the proximal ureter, the effect of the rate of dilation also was evaluated for each balloon size. Extravasation of methylene blue-stained contrast material was assessed with retrograde pyelograms and direct laparoscopic vision. After acute sacrifice, the dilated segments were evaluated histologically with hematoxylin and eosin and Masson's trichrome staining. Results: At the proximal ureter, free extravasation of contrast was observed in 61% of the rapid inflation and 72% of the slow inflation trials; contained extravasation was noted in 28% of the rapid inflation and 17% of the slow inflation trials. Except for two of the 24F slow inflation trials, all of the proximal ureteral trials produced at least one full-thickness tear into the periureteral fat. Grossly, the tears appeared linear with various lengths and no consistent orientation. Rapid inflation and increasing balloon size tended to produce a ureterotomy with less damage to the ureter surrounding the tear. At the mid-ureter, none of the balloon sizes consistently produced a transmural tear. Conclusions: Rapid dilation and use of a 36F balloon capable of maintaining a low profile after inflation may result in a cleaner proximal ureterotomy with less distortion of the untorn neighboring proximal ureter. Both 36F and 30F balloons consistently produced a full-thickness proximal ureterotomy in normal porcine tissue. For mid-ureteral strictures, balloon dilation to even 36F may fail to create a suitable ureterotomy. However, it must be noted that dysplastic or scarred tissue may respond differently to dilation than the more elastic normal porcine tissues used in this study.