**Core Concept**
In obstructive jaundice, the flow of bile is obstructed, causing a buildup of conjugated bilirubin in the blood and its subsequent excretion in the urine. This condition is characterized by an increase in conjugated (direct) bilirubin levels, leading to a decrease in urobilinogen production due to the lack of bilirubin reaching the intestines for conversion.

**Why the Correct Answer is Right**
Obstructive jaundice occurs when there is a blockage in the bile ducts, preventing the normal flow of bile from the liver into the small intestine. This blockage leads to a significant increase in conjugated bilirubin levels in the blood, which is then excreted in the urine. The absence of urobilinogen in the urine is a key diagnostic feature, as it indicates that bilirubin is not reaching the intestines for conversion to urobilinogen. The liver's conjugation of bilirubin to glucuronic acid is unaffected in obstructive jaundice, resulting in elevated conjugated bilirubin levels.

**Why Each Wrong Option is Incorrect**
**Option A:** Gilbert syndrome is characterized by a mild increase in unconjugated (indirect) bilirubin levels, which would not result in an increase in bilirubin in the urine. Additionally, urobilinogen levels would be normal or increased in Gilbert syndrome.
**Option B:** Hemolytic jaundice is associated with an increase in unconjugated bilirubin levels due to the breakdown of red blood cells, not conjugated bilirubin. Urobilinogen levels would be increased in the urine due to the increased bilirubin reaching the intestines.
**Option C:** Viral hepatitis can cause an increase in both conjugated and unconjugated bilirubin levels, but it would not typically result in the absence of urobilinogen in the urine.

**Clinical Pearl / High-Yield Fact**
Obstructive jaundice can be caused by various factors, including gallstones, tumors, and inflammation of the bile ducts (cholangitis). It is essential to differentiate obstructive jaundice from other causes of jaundice, such as hemolytic jaundice and viral hepatitis, based on the presence or absence of urobilinogen in the urine.

✓ Correct Answer: D. Obstructive jaundice