Micturition after gastrocystoplasty and gastric bladder replacement

We determine the function of gastric tissue as a reservoir for urine and driving force for urination.

A total of 12 men 15 to 45 years old underwent gastrocystoplasty (8) or gastric bladder replacement (4). In 1 patient bladder neck reconstruction was performed with augmentation using the same gastric segment. Ten patients were followed for 1 to 2 years, and evaluated subjectively and objectively, including a urodynamic study 6 months postoperatively.

No patient had dysuria or hematuria, despite urinary pH of 5 or less. Mean bladder capacity after augmentation increased from 130 (range 60 to 150) to 420 ml. (range 400 to 470), and was 350 ml. (range 340 to 380) after gastric replacement. Uninhibited contractions occurred only when bladder filling reached 71 to 92% of ultimate capacity with a mean amplitude of 22 cm. water (range 5 to 38). Patients with a gastric neobladder demonstrated an interrupted biphasic flow pattern with a mean maximum flow rate of 12 ml. per second (range 11.5 to 12.8). Urine was evacuated mainly by contraction of the gastric bladder (74%) in stage 1 and by abdominal straining (80%) in stage 2 of voiding.

Stomach seems to be an ideal source of material for bladder augmentation or replacement. The high capacity, low pressure reservoir provided by gastric tissue is probably due to the nature of the involuntary contractions, which occur only late in filling with a low amplitude. Also, the gastric neobladder is evacuated mainly by contraction of its musculature, supplemented with abdominal straining at the end of voiding.