Comparison of bladder rupture pressure after intestinal bladder augmentation (ileocystoplasty) and myomyotomy (autoaugmentation).

OBJECTIVES: To compare the risk of bladder rupture of bladder augmentation using ileocystoplasty versus that of autoaugmentation with myomyotomy in a rat model.

METHODS: Bladder rupture pressure and volume of three groups of female Sprague-Dawley rats were determined by cystometry. The first group of 11 rats had undergone ileocystoplasty using a detubularized 1 -cm segment of ileum. A second group of 9 rats had undergone autoaugmentation with myomyotomy. One month after surgery the animals were studied cystometrically to determine the bladder rupture pressure, then killed. A third group, consisting of 10 nonoperated rats, was studied and served as controls.

RESULTS: Nonoperated, control rat bladders were able to sustain 154 +/- 43 mm Hg pressure and 2.5 +/- 2.0 mL volume prior to bladder rupture. Conventional ileocystoplasty was noted to increase bladder capacity to 4.0 +/- 1.9 mL, but decrease rupture pressure to 111 +/- 49 mm Hg. Myomyotomy resulted in a mean bladder rupture volume of 1.2 +/- 0.4 mL, with a rupture pressure of 101 +/- 13 mm Hg. The rupture pressure after myomyotomy is significantly lower than that of the native bladder (P < 0.001), whereas the rupture volume after myomyotomy is significantly lower than either after the ileocystoplasty or with the native bladder (P < 0.001). Bladder rupture occurred at the augmented ileal bladder dome in 7 of 11 ileocystoplasty animals and at the anastomotic suture line in 4 animals. Bladder rupture occurred at the area of bladder diverticulum in all 9 myomyotomy animals. Among controls, no specific site pattern of bladder rupture was noted.

CONCLUSIONS: Bladder augmentation with myomyotomy increases vulnerability to urinary extravasation, evidenced by a significantly reduced rupture pressure and bladder volume at rupture when compared to the native bladder.