Caput Medusae results from the recanalization of the paraumbilical veins, which are remnants of the umbilical vein. In portal hypertension, increased pressure in the portal venous system leads to shunting of blood from the portal system to the systemic circulation. This shunting occurs through various portosystemic anastomoses, including those around the umbilicus. The paraumbilical veins connect the portal vein (specifically, the left portal vein branch via the falciform ligament) to the superficial epigastric veins (which drain into the systemic circulation via the superior and inferior vena cava systems). When these veins dilate due to increased flow, they become visible on the abdominal wall, creating the characteristic "Medusa head" appearance.
| Feature | Portal Hypertension (Caput Medusae) | Inferior Vena Cava (IVC) Obstruction | Superior Vena Cava (SVC) Obstruction |
|---|---|---|---|
| Vein Distribution | Periumbilical, radiating outwards | Flanks, lower abdomen, groin, legs | Chest wall, neck, upper extremities |
| Blood Flow Direction | Away from umbilicus (upwards towards SVC, downwards towards IVC) | Upwards towards SVC (from lower abdomen/legs) | Downwards towards IVC (from chest/neck/arms) |
| Associated Signs | Ascites, jaundice, splenomegaly, spider angiomas, palmar erythema | Lower limb edema, renal dysfunction, hepatomegaly | Facial plethora, neck vein distension, upper limb edema, dyspnea |
| Underlying Cause | Cirrhosis (most common), portal vein thrombosis, schistosomiasis | Thrombus, tumor compression, retroperitoneal fibrosis | Lung cancer, lymphoma, mediastinal fibrosis |
Harrison's Principles of Internal Medicine, Ch 339; Bailey & Love's Short Practice of Surgery, Ch 59
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