Core concept: Cholestatic vs. hepatocellular vs. hemolytic liver enzyme patterns
Acute cholangitis from a common bile duct stone produces a
cholestatic (obstructive) pattern. The key laboratory signature is a
disproportionate rise in direct (conjugated) bilirubin with marked elevation of the cholestatic enzymes ALP and GGT, while ALT is only mildly to moderately increased. This reflects the pathophysiology: obstruction increases pressure within the biliary tree, causing conjugated bilirubin to reflux into the bloodstream and inducing synthesis of canalicular enzymes (ALP, GGT) by biliary epithelial cells. Hepatocellular damage is secondary and limited, so ALT does not dominate the picture.
Watch out! The ratio of ALT to ALP is the single most useful discriminator. In obstruction, ALP and GGT rise far more than ALT; in hepatitis, ALT rises far more than ALP.
Panel-by-panel analysis
| Panel | Direct bilirubin (0–0.3 mg/dL) | Indirect bilirubin (0.2–0.8 mg/dL) | ALP (44–147 U/L) | GGT (9–48 U/L) | ALT (7–56 U/L) | Pattern | Interpretation |
|---|
| 1 | 5.8 | 0.9 | 480 | 520 | 110 | Cholestatic | Bile duct obstruction |
| 2 | 0.3 | 3.9 | 98 | 30 | 25 | Indirect hyperbilirubinemia | Hemolysis |
| 3 | 0.2 | 0.5 | 410 | 28 | 30 | Isolated ALP elevation | Bone source (e.g., Paget disease, metastasis) |
| 4 | 2.4 | 1.6 | 160 | 90 | 1,850 | Hepatocellular | Acute hepatitis |
Why Panel 1 fits this patient
The patient has fever with chills, jaundice, and RUQ pain—the classic triad of acute cholangitis. Biliary obstruction from a common bile duct stone is the predominant mechanism, and the laboratory pattern must reflect that obstruction. Panel 1 shows direct bilirubin of
5.8 mg/dL (markedly elevated), ALP of
480 U/L, and GGT of
520 U/L, while ALT is only
110 U/L. The direct bilirubin fraction dominates, which is expected because conjugated bilirubin cannot be excreted into an obstructed duct and backs up into the blood. The ALP and GGT rise together because both are induced in the biliary epithelium under increased ductal pressure. ALT elevation is modest because hepatocyte necrosis is not the primary event in early obstruction.
Key point! GGT is the confirmatory enzyme for a hepatic origin of ALP. When ALP is high but GGT is normal, the ALP is likely from bone, not the liver.
Why the other panels are incorrect
Panel 2 shows indirect bilirubin of
3.9 mg/dL with normal direct bilirubin, ALP, GGT, and ALT. This is the pattern of
unconjugated hyperbilirubinemia, most commonly from hemolysis. In hemolysis, the liver conjugates bilirubin normally, but the supply of unconjugated bilirubin overwhelms the conjugating capacity. Biliary obstruction does not selectively raise indirect bilirubin.
Panel 3 shows ALP of
410 U/L with a normal GGT of
28 U/L and normal bilirubin. The normal GGT is the critical clue. ALP exists in both liver and bone, but GGT is specific to the hepatobiliary system. An isolated ALP elevation with normal GGT points to a
bone source such as Paget disease, osteoblastic metastases, or healing fractures—not biliary obstruction. In true cholestasis, GGT rises in parallel with ALP.
Panel 4 shows ALT of
1,850 U/L with ALP of only
160 U/L. The ALT is more than 10 times the ALP, which is the hallmark of
hepatocellular injury such as viral or toxic hepatitis. Although direct and indirect bilirubin are both elevated, the enzyme pattern is dominated by massive hepatocyte necrosis, not ductal obstruction. In cholangitis, ALT may rise, but it does not approach the magnitude seen in acute hepatitis.
Clinical correlation with acute cholangitis
Acute cholangitis is a bacterial infection of the biliary system that occurs when bile flow is obstructed, most commonly by a common bile duct stone. The obstruction raises intrabiliary pressure, which promotes bacterial translocation from the gut into the biliary tree and then into the systemic circulation, producing fever and chills. The laboratory profile mirrors this sequence: conjugated bilirubin and cholestatic enzymes rise early, while transaminases rise only modestly unless there is secondary hepatocellular damage. Early recognition of the cholestatic pattern supports prompt intervention—intravenous fluids, antibiotics, and biliary drainage—which improves outcomes in this potentially life-threatening condition.