Which condition can lead to marked elevations in ALP due to extrahepatic obstruction?

Marked elevations in alkaline phosphatase (ALP) levels are often associated with conditions that cause biliary obstruction. Extrahepatic obstruction, particularly due to gallstones, can lead to an increase in ALP because biliary obstruction prevents the normal flow of bile from the liver to the duodenum. When bile is obstructed, the pressure in the biliary tree increases, which stimulates the liver cells to produce and release more alkaline phosphatase into the bloodstream.

In contrast, acute liver failure, cirrhosis, and non-alcoholic fatty liver disease primarily affect liver function and may alter various liver enzyme levels, including AST, ALT, and sometimes ALP, but they do not typically result in marked elevations specifically due to an obstruction of the bile ducts. These conditions may lead to different patterns of enzyme elevation based on their specific pathophysiology, but gallstones align directly with the mechanism of extrahepatic obstruction, making this choice correct.