A comparison of stool fluid and stool dialysate obtained in vivo.

Stool fluid has been obtained for analysis by homogenization and high speed centrifugation of fresh stool. This fluid, from two healthy individuals with soft stools has been compared with stool dialysate obtained in vivo by retrieval of swallowed dialysis bags from their stools. Stool fluid was more acid, with a higher osmolality, an increased concentration of organic anions, sugar and ammonia, and a lower bicarbonate concentration than dialysate in vivo. It is suggested that in the individuals studied, dialysate in vivo may not be in equilibrium with the stool fluid surrounding it, and may not represent a true dialysate of faecal water.