Under normal circumstances, a tiny amount of urobilinogen, if any, is excreted in the urine.

Any deterioration in liver function reduces its ability to process the recirculated urobilinogen.

Some urobilinogen is reabsorbed, taken up into the circulation and excreted by the kidney.

There is also urobilinogen in the urine.

From here urobilinogen can take two pathways.

The degree of color change is proportional to the amount of urobilinogen in the urine sample.

Stercobilinogen (fecal urobilinogen) is a chemical created by bacteria in the gut.

Urobilinogen leaves the body in faeces, in a pigment called stercobilin.

With limited urobilinogen available for reabsorption and excretion, the amount of urobilin found in the urine is low.

This bilirubin is further converted to colorless urobilinogen.

This constitutes the normal "enterohepatic urobilinogen cycle".

Further metabolism of urobilinogen into stercobilin while in the bowels accounts for the brown color of stool.

If a urine sample is left to oxidize in air to form urobilin the reagent will not detect the urobilinogen.

This vitamin may interfere with certain laboratory tests (including urine test for urobilinogen), possibly causing false test results.

Intestines metabolise bilirubin into urobilinogen.

Poorly stored samples can yield false negative results as the urobilinogen suffers photo oxidation to urobilin that does not react.

Increased amounts of bilirubin are formed in hemolysis, which generates increased urobilinogen in the gut.

Part of the urobilinogen is reabsorbed in the intestine then circulated in the blood to the liver where it is excreted.

In biliary obstruction, below-normal amounts of conjugated bilirubin reach the intestine for conversion to urobilinogen.

Urine analysis revealed high levels of proteins, ketones and sugar in many patients, along with blood and urobilinogen in lesser numbers.

A small part of this recirculated urobilinogen is filtered out by the kidneys and appears in urine (less than 1 mg/dl urine).

Low urine urobilinogen may result from complete obstructive jaundice or treatment with broad-spectrum antibiotics, which destroy the intestinal bacterial flora.

(Obstruction of bilirubin passage into the gut or failure of urobilinogen production in the gut.)

This difference between increased urine bilirubin and increased urine urobilinogen helps to distinguish between various disorders in those systems.