A 67-year-old man has severe cirrhosis of the liver. He most likely has enlarged anastomoses between which of the following pairs of veins?
**Core Concept**
The question is testing the understanding of the pathophysiological changes that occur in the liver due to cirrhosis. In liver cirrhosis, the increased resistance to blood flow in the liver sinusoids leads to the formation of collateral blood vessels, which are enlarged anastomoses between veins. These anastomoses allow blood to bypass the liver and recirculate through the systemic circulation.
**Why the Correct Answer is Right**
In liver cirrhosis, the increased resistance to blood flow in the liver sinusoids leads to the formation of collateral blood vessels. The most significant anastomoses are between the superior and inferior mesenteric veins, which form the superior and inferior mesenteric-caval anastomoses. This is due to the increased pressure in the portal vein, which leads to the formation of collateral veins that drain into the systemic circulation. The superior mesenteric vein drains the small intestine, while the inferior mesenteric vein drains the large intestine.
**Why Each Wrong Option is Incorrect**
* **Option A:** The splenic vein does not directly form anastomoses with the inferior vena cava.
* **Option B:** The hepatic veins drain directly into the inferior vena cava and do not form anastomoses with the superior or inferior mesenteric veins.
* **Option D:** The portal vein is the main vein that carries blood from the gastrointestinal tract to the liver, but it does not form anastomoses with the inferior vena cava.
**Clinical Pearl / High-Yield Fact**
In liver cirrhosis, the formation of collateral blood vessels can lead to the development of varices, which are dilated veins that can rupture and cause severe bleeding. The most common varices are esophageal and gastric varices, which are caused by the anastomosis between the left gastric vein and the esophageal veins.
**Correct Answer:** C. Superior mesenteric-portal anastomosis and inferior mesenteric-portal anastomosis