What are the diagnostic tests and labs for scleral icterus (yellowing of the sclera) and dark urine?

From the Guidelines

Scleral icterus and dark urine in patients require a comprehensive diagnostic approach, starting with magnetic resonance cholangiopancreaticography (MRCP) as the preferred diagnostic test, to rule out primary sclerosing cholangitis (PSC) and other liver or biliary tract diseases. The presence of scleral icterus and dark urine suggests hyperbilirubinemia, which can be due to various causes including liver dysfunction, biliary obstruction, or hemolytic disorders 1.

Diagnostic Approach

The diagnostic approach should include:

• Comprehensive blood tests such as complete blood count (CBC), comprehensive metabolic panel (CMP), liver function tests (LFTs), and coagulation studies
• Measurement of total and direct bilirubin levels to determine the type of jaundice
• Hepatitis viral panel (A, B, C) and autoimmune markers (ANA, anti-smooth muscle antibodies) to rule out autoimmune hepatitis
• Ceruloplasmin for Wilson's disease
• Urinalysis to check for bilirubin and urobilinogen
• Imaging studies such as abdominal ultrasound, CT scan, or MRCP to evaluate the biliary tract for obstruction

Importance of MRCP

MRCP is the preferred diagnostic test for PSC, with a pooled sensitivity and specificity of 86% and 94%, respectively 1. It is a non-invasive, quick, and cost-effective test that can provide information on bile duct thickness and enhancement, the status of hepatic parenchyma, and complications of liver disease.

Clinical Considerations

Patients with scleral icterus and dark urine require prompt medical attention, as these symptoms may indicate serious conditions ranging from viral hepatitis to biliary obstruction or hemolytic disorders. The pattern of laboratory abnormalities helps distinguish between different causes, and a thorough diagnostic approach is necessary to determine the underlying cause of hyperbilirubinemia. Elevated alkaline phosphatase with jaundice points toward biliary obstruction, while elevated transaminases with jaundice suggests hepatocellular injury 1.

From the Research

Scleral Icterus and Dark Urine Tests and Labs

• Scleral icterus is a clinical manifestation of jaundice, which occurs when the serum bilirubin level exceeds 2.5 to 3 mg/dL 2
• The detection of scleral icterus is influenced by the level of training of the examiner, with medical students being more likely to produce false-positive results 3
• Laboratory tests used to evaluate liver function and diagnose the underlying cause of jaundice include:
  • Serum bilirubin levels (conjugated and unconjugated)
  • Alkaline phosphatase
  • Alanine aminotransferase (ALT)
  • Aspartate aminotransferase (AST)
  • Total protein 4, 2, 5
• An elevated conjugated bilirubin level implies hepatocellular disease or biliary obstruction in most settings 5
• Dark urine can be a symptom of liver disease, and evaluation of liver function tests, including bilirubin levels, can help diagnose the underlying cause 2
• The evaluation of hepatocellular injury includes testing for viral hepatitis, nonalcoholic fatty liver disease, alcoholic liver disease, and other conditions 5
• A liver biopsy may be considered when serologic testing and imaging fail to elucidate a diagnosis, to stage a condition, or when multiple diagnoses are possible 5