Failure of the human rectum to absorb electrolytes and water.

Absorption of electrolytes and water from the human rectum was quantified by sequential sampling of physiological solutions instilled into the rectum and by the method of continuous intraluminal perfusion. The absorptive function of the rectum measured by the perfusion technique was also compared with that of the entire large intestine. The rectum did not absorb sodium, chloride, or water from isotonic solutions, even after 90 minutes of exposure. The remainder of the colon effectively absorbed sodium, chloride, and water at a rate of approximately 1% of the infused load per minute of contact between perfusates and mucosa.