Understanding Urobilinogen (UURO) on Urinalysis
Urobilinogen (UURO) on urinalysis is a metabolite of bilirubin that indicates liver function and hemolytic processes, with normal values typically ranging from 0.1-1.0 mg/dL. 1, 2
What is Urobilinogen?
- Urobilinogen is a colorless byproduct formed when intestinal bacteria break down bilirubin in the digestive tract 2
- After formation in the intestines, some urobilinogen is reabsorbed into the bloodstream and filtered by the kidneys into urine 3
- It is measured on routine urinalysis using dipstick tests impregnated with Ehrlich's reagent (dimethylaminobenzaldehyde) 3
Normal Values and Interpretation
- Normal urinary urobilinogen levels typically range from 0.1 to 1.0 mg/dL 4
- Values of 2.0 mg/dL or higher are generally considered abnormal 4
- Urobilinogen measurement has greatest clinical utility when using a normal/abnormal threshold of 2.0/4.0 mg/dL 4
Clinical Significance
Elevated Urobilinogen (>1.0 mg/dL)
- May indicate increased red blood cell destruction (hemolysis) 2
- Can suggest liver dysfunction or damage 4
- May be present in certain hepatic diseases 3
- Can be elevated in patients with porphyrias (a falsely high reading due to cross-reactivity with porphobilinogen) 5
Decreased or Absent Urobilinogen (<0.1 mg/dL)
- May indicate complete biliary obstruction (preventing bilirubin from reaching intestines) 3
- Can occur with broad-spectrum antibiotic use (which reduces intestinal bacteria that convert bilirubin to urobilinogen) 2
Diagnostic Value and Limitations
- Urobilinogen has moderate sensitivity (70-74%) for detecting elevated serum bilirubin but lower sensitivity (43-53%) for other liver function test abnormalities 4
- Specificity ranges from 77-87% for detecting liver function abnormalities 4
- Should be interpreted in conjunction with other urinalysis parameters and clinical findings, not in isolation 1, 6
- False positive results can occur in patients with acute hepatic porphyria due to cross-reactivity with porphobilinogen 5
Important Considerations
- Urobilinogen is just one component of a complete urinalysis and should be interpreted alongside other parameters like bilirubin, protein, and microscopic findings 2
- Fresh urine specimens are essential for accurate urobilinogen measurement as it can degrade when exposed to light 2
- The test has limited utility as a standalone screening tool for intra-abdominal injury in trauma patients 7
- Dipstick quality control is important when measuring urobilinogen and other urinary parameters 8
Clinical Application
- Urobilinogen testing is commonly used as part of quality control in urine sample collection and processing 8
- It can help identify patient status and allow exclusion of deviating samples in research and clinical settings 8
- When elevated alongside other abnormal liver function tests, it may warrant further hepatic evaluation 4
Understanding urobilinogen's presence on urinalysis provides valuable information about hepatobiliary function and hemolytic processes, but results should always be interpreted within the broader clinical context.