Elevated ALP with Normal AST/ALT: Diagnostic Approach

Pathophysiology and Significance

• An elevated alkaline phosphatase (ALP) of 159 with normal AST and ALT levels strongly suggests a cholestatic pattern of liver injury, most likely due to biliary obstruction, infiltrative liver disease, or bone pathology rather than primary hepatocellular disease 1, 2
• Isolated ALP elevation (without impairment of other liver enzymes) raises suspicion of cholestatic disease, which can be due to obstruction of biliary outflow or impairment in bilirubin uptake 1
• Normal AST and ALT levels indicate absence of significant hepatocellular injury, as these enzymes are specific markers of liver cell damage 3, 2

Common Causes of Isolated ALP Elevation

Hepatobiliary Causes:

• Biliary obstruction (stones, strictures, tumors) 1, 4
• Primary biliary cholangitis 5
• Drug-induced cholestasis 6

Diagnostic Approach

• The American College of Radiology recommends abdominal ultrasound as the first-line investigation to evaluate biliary tract and liver parenchyma 1, 7
• Measure gamma-glutamyl transferase (GGT) to confirm hepatic origin of ALP elevation, if elevated, confirms hepatobiliary source 5
• Consider ALP isoenzyme fractionation if GGT is normal 5
• Anti-mitochondrial antibodies for primary biliary cholangitis 5
• MRCP (magnetic resonance cholangiopancreatography) if biliary obstruction is suspected but not seen on ultrasound 4

Follow-up Recommendations

• If initial evaluation is negative, monitor ALP levels over time 1