Evaluation and Management of Elevated Alkaline Phosphatase

Introduction to Elevated ALP

The American College of Radiology suggests that elevated alkaline phosphatase (ALP) is most commonly associated with cholestatic liver disease, bone disorders, or malignancy, and requires systematic evaluation to determine the source and underlying cause 1, 2

ALP is primarily produced in the liver, present in the canalicular membrane of hepatocytes and biliary epithelium, as stated by the American College of Radiology 1
ALP is also produced in bone, especially during growth periods and in bone disorders, according to the American College of Radiology 1
Other tissues, such as intestines, kidneys, white blood cells, and placenta, produce ALP in smaller amounts, as noted by the American College of Radiology 1

The American College of Radiology recommends measuring gamma-glutamyl transferase (GGT) to differentiate between hepatic and non-hepatic origin of elevated ALP, as GGT is found in liver, kidneys, intestine, prostate, and pancreas, but not in bone 1
Concomitantly elevated GGT confirms liver as the likely source, while normal GGT with elevated ALP suggests bone origin, as stated by the American College of Radiology 1
The American College of Radiology also suggests considering ALP isoenzyme fractionation to differentiate between liver, bone, and intestinal isoenzymes 3
Measuring 5'-nucleotidase can also help, as elevations generally signal hepatobiliary disease, according to Alimentary Pharmacology and Therapeutics 4

If hepatic origin is suspected, common causes include extrahepatic biliary obstruction, intrahepatic cholestasis, and other liver conditions, such as cirrhosis, chronic or viral hepatitis, and congestive heart failure, as noted by the American College of Radiology 1, 2, 5
If bone origin is suspected, possible causes include Paget's disease, bone metastases, fractures, and high bone turnover in postmenopausal women, according to the American College of Radiology 1

The American College of Radiology recommends reviewing patient history, including age, medication review, and symptoms of underlying disease, to help determine the source of elevated ALP 1, 6
Initial laboratory workup should include confirming elevated ALP, measuring GGT, and checking other liver function tests, such as bilirubin and transaminases, as stated by the American College of Radiology and Alimentary Pharmacology and Therapeutics 1, 3
Imaging studies, such as abdominal ultrasound, MRI abdomen with MRCP, or contrast-enhanced CT, may be necessary based on suspected source, according to the American College of Radiology 1, 2, 5

The American College of Radiology notes that extremely high ALP levels (>1000 IU/L) are most commonly associated with serious underlying conditions, such as malignant biliary obstruction or infiltrative liver disease 5
Elevated ALP in postmenopausal women may be due to high bone turnover and can normalize with bisphosphonate therapy, as stated by Alimentary Pharmacology and Therapeutics 6

The American College of Radiology warns against assuming all ALP elevations are liver-related, and recommends confirming source with GGT 1
Overlooking malignancy, neglecting bone sources, and missing cholangiocarcinoma are other common pitfalls to avoid, as noted by the American College of Radiology and Alimentary Pharmacology and Therapeutics 1, 6