Urobilinogen is a byproduct of hemoglobin breakdown. It is produced in the intestinal tract due to the action of bacteria on bilirubin. Almost half of the urobilinogen produced recirculates through the liver and then returns to the intestines through the bile duct. Urobilinogen is then excreted in the feces and converted to urobilin by bacterial enzymes.
As the urobilinogen circulates in the blood to the liver, a portion of it is diverted to the kidneys and appears as urinary urobilinogen. Up to 1 mg/dL or Ehrlich unit of urobilinogen is present in normal urine. A result of 2.0 mg/dL represents the transition from normal to abnormal levels of urobilinogen, and the patient should be evaluated further. It is important to note that the chemical reagent strip cannot determine the absence of urobilinogen, so a negative result is impossible.
