The toxemia of acute duodenal fistula is due for the most part to a loss of the acid and chloride of the gastric and the pancreatic juice discharged through the fistula. The discharge of acid turns the tide of the neutrality of the blood strongly toward alkalinity, and the loss to the body of chloride reduces the chloride in the blood from the minimal normal of 560 mg. to as low as 320 mg. Toxemias in general are accompanied by an elevation in blood urea due, in some instances, to their production of a toxic nephritis, preventing elimination of urea, and infrequently to an increase in the amount of urea formed by the breaking down of body tissue. An elevation of blood urea occurs whether the toxemia is the result of gastro-intestinal, biliary or urinary obstruction, as well as during the last stages of any serious illness.1Duodenal fistula does