Metabolic acidosis after bladder replacement: comparison of severity and reversibility in ileal and colonic reservoirs.

Metabolic acidosis developed frequently after ureterosigmoidostomy and rectosigmoid bladder construction but has been reported rarely after the newer methods of continent urinary diversion which also employ intestinal reservoirs. We created an animal model in which to compare the metabolic effects of bladder replacement with segments of ileum or colon and the potential for reversing these derangements with nicotinic acid and chlorpromazine. One year after six dogs' bladders were replaced by colon (three) or ileum (three), all dogs appeared in excellent health and were free of urinary tract obstruction and clinical infection. Both groups of dogs were severely acidotic with diminished arterial pH and arterial and venous total CO2 concentrations although normal serum electrolytes and creatinine concentrations were maintained. Both groups of dogs absorbed approximately one half the urinary sodium, chloride and urea presented to their intestinal reservoirs. After treatment with nicotinic acid and chlorpromazine, the metabolic status of both groups of animals improved. Although nicotinic acid reduced urinary excretion of electrolytes more effectively than chlorpromazine, nicotinic acid was not more effective for reversing metabolic acidosis. When nicotinic acid was provided as an adjunct to sodium bicarbonate therapy in two animals acidosis was corrected at reduced doses of sodium bicarbonate. Based upon this work in an animal model, there does not appear to be a metabolic advantage to intestinal reservoirs which incorporate ileum versus colon. However, asymptomatic patients with normal serum electrolytes and creatinine concentrations may be acidotic. The effects of long term mild acidosis are unknown. However, if therapy is required to prevent diminution of whole body buffers or changes in bone density specific therapy with nicotinic acid or chlorpromazine may reduce the requirement for alkali for correction of metabolic acidosis.