Stool contains 50 to100 mmol/l of potassium. Diarrhea is usually associated with significant losses of bicarbonate and hence a metabolic acidosis. This may be further increased by the effects of hypovolemia; the consequent shift of potassium from cells may mask the true extent of potassium depletion. In certain conditions, such as villous adenomas of the rectum and non-insulin-secreting islet cell tumors, diarrhea may contain high chloride concentrations. In such cases potassium loss occurs without an accompanying acid-base disturbance; hence hypokalemia tends to be more profound for a given whole-body potassium deficit. Laxative abuse similarly produces a profound hypokalemia without alterations in acid-base status. Patients with ureterosigmoidostomies, where urine is allowed to stagnate in the colon, may develop a profound hypokalemic hypochloremic acidosis. Potassium losses are increased in conditions of rapid intestinal transit, small bowel fistulas, intestinal drains, malabsorption, and small bowel bypass.
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