From the Guidelines
Elevated alkaline phosphatase (ALP) levels higher than aspartate transaminase (AST) and alanine transaminase (ALT) are highly suggestive of biliary obstruction. To diagnose biliary obstruction, imaging studies such as ultrasonography 1 or magnetic resonance cholangiopancreatography (MRCP) 1 can be employed.
Key Diagnostic Steps
- Laboratory tests: including gamma-glutamyl transferase (GGT) and 5'-nucleotidase can help confirm the diagnosis 1
- Imaging studies:
- Endoscopic retrograde cholangiopancreatography (ERCP) can be performed to visualize the biliary tree and relieve obstruction 1
Important Considerations
- Choledocholithiasis is the most common cause of extrahepatic biliary obstruction and elevated ALP of liver origin 1
- Other etiologies of extrahepatic biliary obstruction include malignant obstruction, biliary strictures, and infections 1
- Intrahepatic cholestasis may be caused by infiltrative liver diseases such as sarcoidosis, amyloidosis, and hepatic metastases 1
From the Research
Diagnosis of Biliary Obstruction
The diagnosis of biliary obstruction can be complex, and liver function tests (LFTs) play a crucial role in identifying the underlying cause.
- In patients with biliary obstruction, alkaline phosphatase (ALP) levels are often elevated, and this elevation can be higher than that of aspartate transaminase (AST) or alanine transaminase (ALT) 2.
- However, in some cases of obstructive stone disease, the rise in AST may equal or even exceed that of ALP, especially during maximum jaundice and painful episodes 2, 3.
- The combination of serum gamma-glutamyltransferase (GGT) and ALP can be useful in predicting the diagnosis of asymptomatic choledocholithiasis secondary to cholecystolithiasis, with a sensitivity and specificity of 93.5% and 85.1%, respectively 4.
- Elevated levels of ALP and GGT have also been associated with acute cholangitis, and the threshold values of these enzymes can be used to diagnose this condition 5.
Laboratory Findings
Laboratory findings can vary depending on the underlying cause of biliary obstruction.
- In early-stage primary biliary cholangitis (PBC), ALT and AST levels may be normal or mildly elevated, while GGT levels are more robustly elevated 6.
- ALP levels may be normal in some patients with early-stage PBC, but can be elevated in others 6.
- The presence of anti-mitochondria antibody (AMA) and AMA-M2 can be useful in diagnosing PBC, but when these antibodies are negative, the presence of anti-nuclear antibody (ANA) especially ANA centromere positivity may suggest the possibility of early PBC 6.