Distinguishing Hepatic vs. Post-Hepatic Jaundice by Bilirubin Levels
The key distinction is that hepatic jaundice typically shows elevated conjugated bilirubin with a mixed pattern of liver enzymes, while post-hepatic (obstructive) jaundice shows predominantly conjugated hyperbilirubinemia with markedly elevated alkaline phosphatase and imaging evidence of biliary dilation. 1, 2
Bilirubin Pattern Differences
Post-Hepatic (Obstructive) Jaundice
- Conjugated (direct) bilirubin is predominantly elevated, as the liver can still conjugate bilirubin but cannot excrete it due to mechanical obstruction 2, 3
- The conjugated fraction typically represents >50% of total bilirubin in obstructive causes 1
- Urine bilirubin is positive, indicating conjugated hyperbilirubinemia is present 2
- Common causes include choledocholithiasis, biliary strictures, cholangiocarcinoma, and pancreatic malignancy 4, 2
Hepatic (Intrahepatic) Jaundice
- Shows conjugated hyperbilirubinemia but with a mixed pattern, as hepatocellular dysfunction affects both conjugation and excretion 2, 3
- The liver's ability to conjugate bilirubin is impaired, leading to variable elevations of both conjugated and unconjugated fractions 4
- Common causes include hepatitis, alcoholic liver disease, cirrhosis decompensation, and drug-induced liver injury 4, 2
Critical Enzyme Pattern Distinctions
Post-Hepatic Pattern
- Alkaline phosphatase is markedly elevated (often >3-4 times upper limit of normal) 5, 3
- AST and ALT are mildly elevated or normal 3
- Gamma-glutamyltransferase (GGT) is significantly elevated, confirming hepatobiliary origin 1, 3
Hepatic Pattern
- AST and ALT are significantly elevated (often >10 times upper limit of normal in acute hepatitis) 3
- Alkaline phosphatase is mildly elevated or normal 5
- Synthetic function markers (albumin, PT/INR) are often abnormal, indicating hepatocellular dysfunction 5, 6
Imaging Confirmation Algorithm
Abdominal ultrasound is the mandatory first-line imaging study for all jaundiced patients to definitively distinguish these entities 7, 1:
Post-Hepatic Findings
- Biliary dilation is present with specificity of 71-97% for detecting obstruction 7, 1
- Common bile duct diameter >6mm (or >8mm if post-cholecystectomy) indicates obstruction 1
- May visualize the obstructing lesion (stone, mass, stricture) 7
Hepatic Findings
- No biliary dilation is present, confirming absence of mechanical obstruction 7, 1
- May show features of cirrhosis: nodular liver surface (86% sensitive on undersurface), volume redistribution, or signs of portal hypertension 7, 1
- Parenchymal changes suggesting hepatitis or steatosis may be visible 7
Common Pitfall to Avoid
Do not rely solely on bilirubin levels without enzyme patterns and imaging, as both hepatic and post-hepatic causes produce conjugated hyperbilirubinemia 2, 3. The critical error is assuming all conjugated hyperbilirubinemia is obstructive—hepatocellular disease commonly causes conjugated hyperbilirubinemia through impaired excretion despite intact conjugation 4, 2.
When Initial Evaluation is Equivocal
If ultrasound shows biliary dilation but no clear obstructing cause, MRI with MRCP is recommended to evaluate for strictures, stones, or tumors with higher sensitivity than ultrasound 1. For suspected hepatocellular disease with negative ultrasound, liver biopsy may be necessary when imaging and laboratory tests remain inconclusive 7, 1.