What laboratory findings indicate obstruction due to colledocholithiasis?

• A. ↑Amylase and ↑Lipase
• B. ↑Alkaline phosphatase and ↑Direct bilirubin
• C. ↑Total bilirubin and ↑Lipid levels
• D. ↓Alkaline phosphatase and ↑Indirect bilirubin

Answer: (B)

The presence of colledocholithiasis, which refers to the obstruction of the common bile duct by gallstones, typically leads to specific changes in laboratory findings. In this case, an increase in alkaline phosphatase and direct bilirubin is particularly indicative of biliary obstruction.

Alkaline phosphatase is an enzyme that is associated with the bile ducts. When there is an obstruction in the biliary system, such as that caused by gallstones in the common bile duct, the enzyme levels rise due to increased pressure and damage to the biliary epithelium.

Direct bilirubin, meanwhile, is the conjugated form of bilirubin that is produced when the liver processes un-conjugated bilirubin. When there is obstruction, conjugated bilirubin cannot be excreted into the intestine and instead spills over into the bloodstream, resulting in elevated levels.

The combination of elevated alkaline phosphatase and direct bilirubin thus confirms the suspicion of obstruction due to colledocholithiasis, making this option the most fitting answer.

In contrast, other options either reflect values that are not characteristic of biliary obstruction or do not specifically indicate the typical laboratory changes associated with colledocholithiasis.