This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which is NOT seen in urine in obstructive jaundice? 
Select and explain. 
A. Urobilinogen, B. Direct bilirubin, C. Both of the above, D. None of the above
A: Urobilinogen
Answer: A: Urobilinogen 
Explanation: Normally, there are mere traces of urobilinogen in the urine. In complete obstruction of the bile duct, no urobilinogen is found in the urine, since bilirubin has no access to the intestine, where it can be conveed to urobilinogen. In this case, the presence of bilirubin (conjugated) in the urine without urobilinogen suggests obstructive jaundice, either intrahepatic or posthepatic. Ref: Murray R.K. (2011). Chapter 31. Porphyrins & Bile Pigments. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.