The contribution of the colon to electrolyte and water conservation in man.

Abstract

Abstract The compositions of terminal ileal contents and feces were compared in 5 healthy volunteers and in 2 patients with diarrhea; continuous sampling of the ileum was done during the slow infusion of a nonabsorbable marker under standard dietary conditions. By these means, colonic inflow, fecal output, and colonic absorption were quantified. With a standard diet in health, 1,500 ml. of water, 200 mEq. of sodium, 100 mEq. of chloride, 10 mEq. of potassium, 15 mEq. of calcium, and 9 mEq. of magnesium entered the colon each day. Fecal excretion of water, sodium, chloride, and potassium was small, and the colon absorbed more than 95 per cent of the sodium, chloride, and water and 50 per cent of the potassium traversing the ileocecal region. Small values for mean absorption of magnesium and secretion of calcium by the colon were also found. In a patient with severe nontropical sprue in relapse, colonic inflow was more than twice that in health and, despite colonic reabsorption of 3,000 ml. of water and electrolytes each day, severe diarrhea was present. In a patient with ileal resection and severe diarrhea, which was corrected by cholestyramine administration, excessive fecal volume was caused in part by colonic dysfunction. In two healthy subjects, the volume and the electrolyte content of the proximal ileum were approximately 50 per cent greater than those of the terminal ileum.