The Role of the Colon in Urea Metabolism in Man

Abstract

1. The urea content of ileostomy effluent has been measured by the urease method as an indirect estimate of the urea concentration in the lumen of the normal ileum. 2. The plasma disappearance of intravenously administered[14C]urea was used to study intestinal urea breakdown. Normal subjects on high and low protein diets and patients with either excised (i.e. with ileostomies) or excluded colons were studied. 3. The 24 h intestinal urea breakdown was considerably greater than the quantity of urea estimated to be entering the colon from the ileum and across the colonic mucosa. 4. Intestinal urea breakdown increased with increase in dietary protein and decreased with, but was not abolished by, exclusion or excision of the colon. 5. Our results suggest that the colonic lumen is not the only site of intestinal ureolysis and that significant quantities of urea must be broken down either at a juxtamucosal site or in the ileum.

A Controlled Clinical Trial of Nicotinohydroxamic Acid and Neomycin in Advanced Chronic Liver Disease

“…When the rate of urea hydrolysis is calculated from the recovery of l4C-labeled urea, urea is decom posed less by about 8% in patients with the surgically excised colons [7], The urinary ex cretion of l4C-urea increases by about 10% after administration of NM, but the drug causes no change in the recovery of ammonia from the colon and rectum [21]. Therefore, it may be concluded that urea is mainly decom posed by bacterial as well as mucous mem brane urease, but the exact mechanism of urea hydrolysis in vivo is yet to be clarified.…”

Role of Fermentable Carbohydrate Supplements in the Course of Uremia

“…Some urea could be utilized in the distal ileum which presents a high permeability for this molecule (Gibson et al, 1976). However, the bacterial population in the terminal ileum is only one thousandth or so of that in the colon.…”

Carbon Dioxide Formation and Elimination in Man

“…The breakdown of urea normally takes place in the intestine (28,29,56,57,58,59,60) by means of urease-producing bacteria (61,62) which colonize the newborn infant's intestine, which initially after birth is sterile. This colonization is considered to take place during the first days of life, but according to my hypothesis it is delayed, inhibited or in some other way insufficient in those infants who develop respiratory insufficiency leading to sudden infant death.…”