## **Core Concept**
Portal hypertension is a condition characterized by increased pressure within the portal vein, which carries blood from the gastrointestinal tract, spleen, and pancreas to the liver. The hepatic venous pressure gradient (HVPG) is a key parameter used to define portal hypertension. It measures the pressure difference between the wedged hepatic vein and the free hepatic vein.

## **Why the Correct Answer is Right**
The correct answer, **10 mmHg**, is the threshold value for defining portal hypertension based on the hepatic venous pressure gradient. Normally, the HVPG is around 1-10 mmHg. When the HVPG exceeds 10 mmHg, it indicates the presence of portal hypertension, which can lead to complications such as varices, ascites, and hepatic encephalopathy. The HVPG is measured by inserting a catheter into the hepatic vein and recording the pressure difference.

## **Why Each Wrong Option is Incorrect**
* **Option A: 5 mmHg** - This value is within the normal range for HVPG and does not indicate portal hypertension.
* **Option B: 7 mmHg** - Similarly, this value is also within the normal range and does not signify portal hypertension.
* **Option D: 15 mmHg** - Although this value indicates significant portal hypertension, it is not the threshold value for defining the condition.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that portal hypertension can be graded based on the HVPG: mild (10-15 mmHg), moderate (16-20 mmHg), and severe (>20 mmHg). This grading helps in assessing the risk of complications and guiding management.

## **Correct Answer: C. 10 mmHg.**