Bilirubin, which is formed from the degradation of hemoglobin, is transformed through the action of bacterial enzymes into urobilinogen after it enters the intestines. Some of the urobilinogen formed in the intestine is excreted as part of the feces, where it is oxidized to urobilin; another portion is absorbed into the portal bloodstream and carried to the liver, where it is metabolized and excreted in the bile. Traces of urobilinogen in the blood that escape removal by the liver are carried to the kidneys and excreted in the urine. This is the basis of the urine urobilinogen test. Unlike bilirubin, urobilinogen is colorless.

Urine urobilinogen is one of the most sensitive tests available to determine impaired liver function. Urinary urobilinogen is increased by any condition that causes an increase in the production of bilirubin and by any disease that prevents the liver from normally removing the reabsorbed urobilinogen from the portal circulation. An increased urobilinogen level is one of the earliest signs of liver disease and hemolytic disorders.

Although it cannot be determined by reagent strip, the absence of urobilinogen is also diagnostically significant and represents an obstruction of the bile duct.

Random specimen: 0.2–1 Ehrlich U/dL or <1 mg/dL

2-hour specimen: 0.1–1.0 Ehrlich U/2 hr or <1 mg/2 hr

24-hour specimen: 0.5–4.0 Ehrlich U/24 hr or 0.5–4.0 mg/d

1. Follow instructions for collecting a timed 24-hour, 2-hour, or random specimen. Check with the laboratory for specific protocols.

2. Perform the 2-hour timed collection from 1:00 p.m. to 3:00 p.m. (1300–1500) or from 2:00 p.m. to 4:00 p.m. (1400–1600) for best results because peak excretion occurs during this time. No preservatives are necessary. Record the total amount of urine voided. Protect the collection receptacle from light. Test immediately after specimen collection is completed.

1. Urine urobilinogen is increased when there is:

   1. Increased destruction of RBCs

      1. Hemolytic anemias

      2. Pernicious anemia (megaloblastic)

      3. Malaria

   2. Hemorrhage into tissues

      1. Pulmonary infarction

      2. Excessive bruising

   3. Hepatic damage

      1. Biliary disease

      2. Cirrhosis (viral and chemical)

      3. Acute hepatitis

   4. Cholangitis

2. Urine urobilinogen is decreased or absent when normal amounts of bilirubin are not excreted into the intestinal tract. This usually indicates partial or complete obstruction of the bile ducts. The stool is pale in color. Decreased urinary urobilinogen is associated with:

   1. Cholelithiasis

   2. Severe inflammation of the biliary ducts

   3. Cancer of the head of the pancreas

3. During antibiotic therapy, suppression of normal gut flora may prevent the breakdown of bilirubin to urobilinogen; therefore, urine levels will be decreased or absent.

4. More comprehensive information is obtained when the tests for urobilinogen and bilirubin are correlated (see Table 3.5 for comparisons).

Pretest Patient Care

1. Explain purpose of test, procedure for urine collection, and interfering factors.

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

1. Drugs that may affect urobilinogen levels include those that cause cholestasis and those that reduce the bacterial flora in the gastrointestinal tract. Review and update medication list; consult pharmacist if necessary.

2. Peak excretion is known to occur from noon to 4:00 p.m. (1600). The amount of urobilinogen in the urine is subject to diurnal variation.

3. Strongly alkaline urine shows a higher urobilinogen level, and strongly acidic urine shows a lower urobilinogen level.

4. Drugs that may cause increased urobilinogen include drugs that cause hemolysis. Review and update medication list; consult pharmacist if necessary.

5. If the urine is highly colored, the strip will be difficult to read.