IN THE management of many hematologic and hepatic disorders, it is useful to know the daily output of fecal urobilinogen. The values for output may serve as an index of the degree of activity of a hemolytic process, since there is a direct relationship between the rate at which degradation of hemoglobin occurs and the daily excretion of urobilinogen in the stool.
Destruction of hemoglobin occurs in the reticuloendothelial system, chiefly in the liver and spleen. Bilirubin is formed in the liver and excreted into the intestine. There it is reduced by bacterial action to urobilinogen, which in reality consists of mesobilirubinogen and stercobilinogen, according to Watson.1a The amount of urobilinogen depends on the reduction of bilirubin to urobilinogen.
Part of the fecal urobilinogen is reabsorbed into the portal circulation and returned to the liver to be reexcreted in the bile. A smaller part is absorbed into the general