In biliary obstruction, which laboratory result is typically decreased?

In biliary obstruction, which laboratory result is typically decreased?

• A. Urine bilirubin
• B. Fecal urobilinogen
• C. Serum total bilirubin
• D. Direct bilirubin

Answer: (B)

Blockage of the bile ducts prevents bile, including conjugated bilirubin, from reaching the intestine. Without bile in the gut, intestinal bacteria have less bilirubin to convert into urobilinogen, so fecal urobilinogen decreases. This is why stool can appear lighter and why the amount of urobilinogen in stool drops. In contrast, bilirubin builds up in the blood and is shed into urine as conjugated bilirubin, so urine bilirubin and direct (conjugated) bilirubin in serum increase, and total bilirubin rises. Thus, fecal urobilinogen is typically decreased in biliary obstruction.

Blockage of the bile ducts prevents bile, including conjugated bilirubin, from reaching the intestine. Without bile in the gut, intestinal bacteria have less bilirubin to convert into urobilinogen, so fecal urobilinogen decreases. This is why stool can appear lighter and why the amount of urobilinogen in stool drops. In contrast, bilirubin builds up in the blood and is shed into urine as conjugated bilirubin, so urine bilirubin and direct (conjugated) bilirubin in serum increase, and total bilirubin rises. Thus, fecal urobilinogen is typically decreased in biliary obstruction.