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.