In common bile duct obstruction, which change occurs in urine coloration?

In common bile duct obstruction, which change occurs in urine coloration?

• A. Light-colored urine
• B. Dark-colored urine
• C. Foamy urine
• D. Cloudy urine

Answer: (B)

Blockage of the common bile duct prevents bile from reaching the intestine, so conjugated bilirubin backs up into the bloodstream and is excreted by the kidneys. Because conjugated bilirubin is water-soluble, it colors the urine dark amber to brown. This is why dark-colored urine is seen with obstructive jaundice. Light-colored urine would suggest lack of bilirubin in urine, foamy urine points to proteinuria, and cloudy urine usually hints at infection or crystals, not a bilirubin-related obstruction.

Blockage of the common bile duct prevents bile from reaching the intestine, so conjugated bilirubin backs up into the bloodstream and is excreted by the kidneys. Because conjugated bilirubin is water-soluble, it colors the urine dark amber to brown. This is why dark-colored urine is seen with obstructive jaundice. Light-colored urine would suggest lack of bilirubin in urine, foamy urine points to proteinuria, and cloudy urine usually hints at infection or crystals, not a bilirubin-related obstruction.