Urobilinogen

The urobilinogen test detects impaired liver function by measuring urine levels of urobilinogen, the colorless, water-soluble product that results from the reduction of bilirubin by intestinal bacteria. Absent or altered urobilinogen levels can indicate hepatic damage or dysfunction. Increased urine urobilinogen levels may indicate hemolysis of red blood cells.

Quantitative analysis of urine urobilinogen involves addition of Ehrlich's reagent to a 2 hour urine specimen. The resulting color reaction is read promptly by spectrophotometry.

Purpose

• To aid diagnosis of extrahepatic obstruction, such as blockage of the common bile duct
• To aid differential diagnosis of hepatic and hematologic disorders

Patient Preparation

• Explain to the patient that this test helps assess liver and biliary tract function.
• Inform him that he needn't restrict fluids or food, except for bananas, which he should avoid for 48 hours before the test.
• Tell him that the test requires a 2 hour urine specimen, and teach him how to collect it.

Procedure And Posttest Care

• Most laboratories request a random urine specimen; others prefer a 2-hour specimen, usually during the afternoon (ideally, between I p.m. and 3 p.m.), when urobilinogen levels peak.
• Tell the patient he may resume his normal diet.
• Resume administration of drugs withheld during the test.

Precautions

• Send the specimen to the laboratory immediately. This test must be performed within 30 minutes of collection because urobilinogen quickly oxidizes to an orange compound called urobilin.

Reference values

Normally, urine urobilinogen values are less than 4 mg/24 hours.

Abnormal Findings

Interfering Factors

• Failure to observe pretest restrictions or to immediately send the specimen to the laboratory
• Para-aminosalicylic acid, phenazopyridine, procaine, phenothiazines, and sulfonamides (possible decrease)