Ammonia Production in the Human Colon

In 14 healthy volunteers, studied by colonic perfusion technics, colonic ammonia output during steady-state conditions was 1782 ± 233 μg per hour (S.E.). Colonic outputs and concentrations of ammonia in four patients with cirrhosis and encephalopathy were similar. In these patients, blood ammonia concentrations fell during cleansing by perfusion. Treatment with neomycin reduced colonic ammonia concentration and outputs; the urease inhibitor acetohydroxamic acid reduced colonic ammonia output by a systemic effect but had no effect when perfused through the colon. Outputs of ammonia by the colon studied by perfusion approximated the total produced in the cleansed organ. Accumulation of ammonia in the colon was consistent with simple ionic diffusion and production by bacteria. These data validate the rationale for management of hepatic coma, stress the efficacy of effective cleansing of the colon and describe a human model for assessment of therapy.