Laplace's law and the risks and prevention of bladder rupture after enterocystoplasty and bladder autoaugmentation

The purpose of this study was to utilize a rat model of bladder augmentation to determine the effect on bladder rupture pressure and volume of bladders augmented using myomyotomy autoaugmentation, intestinal patch ileocystoplasty alone, and a combination of ileocystoplasty and detrusor‐myoplasty techniques. Four groups of female rats were studied: 1) sham animals served as controls, 2) ileocystoplasty, 3) autoaugmentation using a myomyotomy technique, and 4) ileocystoplasty reinforced with a rectus muscle flap to envelop the augmented bladder (detrusor‐myoplasty). One month after surgery bladder rupture pressure and volume were determined by cystometry. Sham control rats manifested bladder rupture at a mean pressure of 154 ± 43 mmHg and mean volume of 2.5 ± 2.0 ml. Myomyotomy animals demonstrated a diminished mean rupture pressure and rupture volume (101 ± 13 mmHg and 1.2 ± 0.4 ml, respectively) compared to control (both P < 0.05). Ileocystoplasty animals demonstrated bladder rupture at a significantly higher volume of 4.0 ± 1.9 ml than either myomyotomy or control animals (P < 0.05), although rupture pressure of 111 ± 49 mmHg did not differ significantly from control values (P = 0.55). The combination of ileocystoplasty and detrusor‐myoplasty yielded a statistically significant increase in rupture pressure (262 ± 108 mmHg) than the other three groups (P < 0.05). Rupture volume in this group of animals did not differ significantly from animals with ileocystoplasty but without detrusor‐myoplasty (P = 0.46). Bladder autoaugmentation results in a significantly reduced rupture pressure and volume than noted in the native bladder. Although ileocystoplasty significantly increases bladder capacity, the risk of urinary extravasation is also increased with this technique. The combination of ileocystoplasty and detrusor‐myoplasty affords not only an increase in bladder capacity, but also significantly increases rupture pressure and thereby decreases the risk of bladder rupture after bladder augmentation. © 1996 Wiley‐Liss, Inc.