Abstract

Faecal concentrations and output of short chain fatty acids (SCFA) were assessed on successive days by gas-liquid chromatography in 24 patients with acute watery diarrhoea. Absorption of water and sodium from the rectum was also measured by a dialysis technique in 17 of these patients and in nine normal subjects in the presence and absence of luminal SCFA. Faecal SCFA concentrations were low on the first day of diarrhoea (mean (SEM) 9.9 (5.8) mmol/kg) and increased to 94.8 (16.4) mmol/kg by the fifth day. Faecal output of SCFA corresponded to these figures. Net water absorption, in the absence of luminal SCFA, was stopped in patients with acute diarrhoea (-59 (81) nl/cm2/min) compared with healthy controls (+322 (63) nl/cm2/min) (p < 0.01). Luminal SCFA restored net water absorption to +184 (67) nl/cm2/min in patients with acute diarrhoea (p < 0.01). Net absorption of sodium decreased in patients with acute diarrhoea in the absence of luminal SCFA, but returned to normal with luminal SCFA. Net secretion of potassium increased in acute diarrhoea, and did not change in the presence of SCFA. Defective absorption from the rectum in acute diarrhoea is reversed by luminal SCFA. The reduction of luminal SCFA in acute diarrhoea treated conventionally may be a factor contributing to colonic dysfunction.