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Learning/Medicine

ELEVATED ALKALINE PHOSPHATASE

by 차도닥 2021. 8. 18.

In patients with cholestasis, the alkaline phosphatase is typically elevated to at least four times the upper limit of normal.

 

The gamma-glutamyl transpeptidase (GGT) may also be elevated in the setting of cholestasis.

 

 Patients with a predominantly cholestatic pattern typically undergo a right upper quadrant ultrasound to further characterize the cholestasis as intrahepatic or extrahepatic; the latter is suggested by biliary tract dilatation.

 

To confirm that an isolated elevation in the alkaline phosphatase is coming from the liver, a GGT level or serum 5'-nucleotidase level should be obtained. These tests are usually elevated in parallel with the alkaline phosphatase in liver disorders but are not increased in bone disorders. An elevated serum alkaline phosphatase with a normal GGT or 5'-nucleotidase should prompt an evaluation for bone diseases.

 

An elevated bone alkaline phosphatase is indicative of high bone turnover, which may be caused by several disorders including healing fractures, osteomalacia, hyperparathyroidism, hyperthyroidism, Paget disease of bone, osteogenic sarcoma, and bone metastases. We generally refer such patients to an endocrinologist for evaluation. Initial testing may include measurement of serum calcium, parathyroid hormone, 25-hydroxy vitamin D, and imaging with bone scintigraphy.

 

Differential diagnosis — If the alkaline phosphatase elevation is isolated (ie, the other routine liver biochemical test levels are normal), is confirmed to be of hepatic origin, and persists over time, chronic cholestatic or infiltrative liver diseases should be considered. The most common causes include partial bile duct obstruction, primary biliary cholangitis (PBC), primary sclerosing cholangitis, and certain drugs, such as androgenic steroids and phenytoin. Infiltrative diseases include sarcoidosis, other granulomatous diseases, amyloidosis, and, less often, unsuspected cancer that is metastatic to the liver.