Alkaline Phosphatase
February 15th, 2021
Overview
Alkaline phosphatase (ALP) is an enzyme normally found in liver, bone, intestine, late placenta and kidney. Its elevation is often used to diagnose cholestatic liver dysfunction, though it may also be elevated in bone disease as well as certain other conditions.
Normal Range
- 35 - 100 U/L
Significance
- ALP is used as a marker of cholestasis, though may also be raised in the setting of certain non-hepatic conditions.
ALP and GGT may also be mildly elevated in the presence of hepatocellular disease, with predominant derangement of the transaminases.
Cholestatic LFT Derangement
Look For
- Elevated ALP and GGT
- Mildly elevated ALT / AST
- Elevated conjugated bilirubin
Causes of Cholestasis
Intrahepatic Cholestasis
- Hepatitis (viral or alcoholic)
- Autoimmune liver disease - primary biliary cirrhosis, primary sclerosing cholangitis
- Infiltrative liver disease - amyloidosis, sarcoidosis, tuberculosis, lymphoma
- Malignancy - hepatocellular carcinoma, cholangiocarcinoma, metastasis
- Non-malignant mass - abscess, cystic liver disease, haematoma
- Sepsis
- Acalculous cholecystitis
- Intrahepatic cholestasis of pregnancy
- Total parenteral nutrition
- Drugs - augmentin, isoniazid, rifampicin, chlorpromazine
Extrahepatic Cholestasis
- Choledocholithiasis
- Bile duct stricture
- Parasitic infection of bile duct
- Primary sclerosing cholangitis
- Pancreatitis
- Pancreatic cyst
- Malignancy - pancreas, ampulla, common bile duct, gallbladder
Isolated ALP Elevation
Significance
- Suggestive of a non-hepatobiliary cause.
Causes of Isolated ALP Elevation
- Bone pathology - fracture, osteomyelitis, osteomalacia / Ricket's, bony metastasis, Paget's disease
- Rapid bone growth (adolescents)
- Late pregnancy
- Hyperthyroidism
- Congestive cardiac failure
- End stage renal failure
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