In complete obstruction of the common bile duct, which urinary finding is typical?

In complete obstruction of the common bile duct, which urinary finding is typical?

• A. Positive urine bilirubin
• B. Negative urine urobilinogen
• C. Positive urine urobilinogen
• D. Negative urine bilirubin

Answer: (A)

When the common bile duct is completely obstructed, bile cannot reach the intestine. The liver keeps conjugating bilirubin, and this conjugated (direct) bilirubin is water-soluble, so it spills into the bloodstream and is filtered by the kidneys into urine. This makes urine bilirubin positive (bilirubinuria). At the same time, since bile—and the bilirubin that would reach the gut—is not reaching the intestines, there’s little substrate for intestinal bacteria to convert into urobilinogen. As a result, urinary urobilinogen is decreased or negative. So the typical pattern is positive urine bilirubin with reduced or absent urine urobilinogen.

When the common bile duct is completely obstructed, bile cannot reach the intestine. The liver keeps conjugating bilirubin, and this conjugated (direct) bilirubin is water-soluble, so it spills into the bloodstream and is filtered by the kidneys into urine. This makes urine bilirubin positive (bilirubinuria).

At the same time, since bile—and the bilirubin that would reach the gut—is not reaching the intestines, there’s little substrate for intestinal bacteria to convert into urobilinogen. As a result, urinary urobilinogen is decreased or negative. So the typical pattern is positive urine bilirubin with reduced or absent urine urobilinogen.