**Core Concept**
A portosystemic shunt is a surgical procedure that aims to reduce portal hypertension by creating a direct connection between the portal and systemic circulations. However, this procedure can lead to hepatic encephalopathy due to the diversion of blood from the liver, bypassing detoxification processes. Therefore, it is crucial to identify patients who would benefit from this procedure while minimizing potential risks.

**Why the Correct Answer is Right**
The correct answer is related to the contraindications of portosystemic shunt, particularly those conditions that increase the risk of hepatic encephalopathy. Patients with advanced liver disease, particularly those with cirrhosis and a high MELD score, are at increased risk of developing hepatic encephalopathy post-shunt. This is because the liver's ability to detoxify ammonia and other toxins is compromised in advanced liver disease.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because while ascites is a complication of portal hypertension, it is not a contraindication for portosystemic shunt. In fact, shunt surgery may be beneficial in selected patients with ascites due to portal hypertension.
* **Option B:** This option is incorrect because a high platelet count is not a contraindication for portosystemic shunt. In fact, thrombocytopenia (low platelet count) is a more common complication of cirrhosis and portal hypertension.
* **Option C:** This option is incorrect because while a high bilirubin level may indicate liver dysfunction, it is not a direct contraindication for portosystemic shunt. The decision to proceed with shunt surgery depends on the underlying liver disease and the patient's overall clinical status.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that portosystemic shunt is not a "cure" for portal hypertension but rather a palliative procedure aimed at reducing symptoms and improving quality of life in selected patients. The decision to proceed with shunt surgery should be made on a case-by-case basis, taking into account the patient's underlying liver disease, clinical status, and potential risks and benefits.

**Correct Answer: D. Advanced liver disease, particularly cirrhosis with a high MELD score.**