An experimental canine model was developed to quantitate the net transmural ion flux of colon and gastric segments used for augmentation cystoplasty. Gastrocystoplasty (4) or colocystoplasty (4) was constructed in 8 female mongrels. Acute intravenous saline and acid loading experiments were performed 2 to 4 weeks after cystoplasty. The mean solute excretion rates for sodium, chloride, phosphorus and ammonia exhibited opposite trends during acute saline and acid loading in this experimental model. The net flux of chloride, ammonia, phosphorus and sodium ions in the colocystoplasty animals was from the mucosa/urine surface to the serum (reabsorption). The opposite trend was true for the gastrocystoplasty. By not reabsorbing ammonium chloride, the gastrocystoplasty preserved an important renal mechanism for systemic acid elimination. This may help to prevent the hyperchloremic metabolic acidosis that can develop when urine comes in contact with small or large bowel segments.
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