What are the typical liver function test (LFT) findings in obstructive jaundice?

Liver Function Test Findings in Obstructive Jaundice

Obstructive jaundice characteristically presents with a cholestatic pattern featuring elevated alkaline phosphatase (ALP) and conjugated (direct) bilirubin, though the traditional teaching that ALP rises more than aminotransferases applies primarily to malignant strictures rather than stone disease. 1

Primary Laboratory Pattern

Cholestatic Enzyme Elevation

• Alkaline phosphatase (ALP) is the hallmark enzyme elevation in obstructive jaundice, typically elevated with or without concurrent gamma-glutamyl transpeptidase (GGT) elevation 1
• GGT elevation confirms hepatic origin of ALP when both are elevated, distinguishing it from bone or other non-hepatic sources 1
• In acute calculous cholecystitis with common bile duct stones, GGT shows sensitivity of 80.6% and specificity of 75.3% at a cut-off of 224 IU/L 1

Bilirubin Pattern

• Conjugated (direct) hyperbilirubinemia predominates in obstructive jaundice, resulting from impaired biliary excretion 1
• Serum bilirubin at cut-off of 22.23 μmol/L demonstrates sensitivity of 0.84 and specificity of 0.91 for common bile duct stones 1
• Clinical jaundice becomes visible when total bilirubin exceeds 2.5-3 mg/dL 2

Critical Distinction: Strictures vs. Stone Disease

Malignant Strictures Pattern

• ALP elevation exceeds AST elevation (median 4.3× normal upper limit vs. 2.6× normal upper limit) in malignant biliary strictures 3
• Higher median bilirubin, AST, and ALP levels compared to stone disease 3

Stone Disease Pattern (Important Caveat)

• AST may equal or even exceed ALP elevation during acute obstruction from stones, contradicting conventional teaching 3
• At maximum enzyme derangement, median AST elevation (4.4× normal upper limit) exceeds ALP (2.4× normal upper limit) 3
• During acute pain episodes, AST rises more prominently than ALP 3
• Clinicians must consider biliary obstruction even when AST is the predominantly elevated enzyme 3

Aminotransferase Patterns

Transaminase Elevation Characteristics

• ALT and AST are typically mildly to moderately elevated (approximately 2× normal upper limit at ERCP) in stone disease 3
• In acute calculous cholecystitis without common bile duct stones, 51% show elevated ALT and 41% show elevated AST 1
• Among patients with confirmed common bile duct stones, 90% have elevated ALT and 77% have raised ALP 1

Synthetic Function Markers

Albumin and Coagulation

• Albumin and prothrombin time reflect actual hepatic synthetic function rather than just biliary obstruction 1
• These parameters help differentiate acute from chronic liver disease 1
• In pure obstructive jaundice without underlying parenchymal disease, synthetic function typically remains preserved initially 1

Temporal Evolution of LFTs

Dynamic Changes

• LFTs in stone disease show significant decrease within 4 days in patients without common bile duct stones, which does not occur in those with persistent obstruction 1
• After stone removal, all LFT values improve significantly at mean follow-up of 4.3 days 1
• This temporal pattern can aid in distinguishing transient from persistent obstruction 1

Diagnostic Limitations

Important Caveats

• Elevated LFTs or bilirubin alone are insufficient for diagnosing common bile duct stones in acute cholecystitis, requiring additional imaging 1
• Normal LFTs have negative predictive value of 97%, but positive predictive value of any abnormal LFT is only 15% 1
• 15-50% of acute cholecystitis patients show LFT elevation without common bile duct stones due to inflammatory processes 1
• The plasma amino acid pattern shows near-normal levels in obstructive jaundice, contrasting with hepatocellular disease where most amino acids are elevated 4

Clinical Algorithm

When evaluating suspected obstructive jaundice:

1. Measure complete hepatic panel including ALP, GGT, ALT, AST, total and conjugated bilirubin 1
2. If ALP elevated, confirm hepatic origin with GGT 1
3. Assess conjugated vs. unconjugated bilirubin to confirm cholestatic pattern 1
4. Do not exclude biliary obstruction based solely on AST predominance, especially in acute presentations 3
5. Proceed to imaging (ultrasound as first-line) regardless of specific enzyme pattern when clinical suspicion exists 1
6. Monitor LFT trends over 4 days to distinguish transient from persistent obstruction 1