Portal Obstruction

The veins of the portal system have no valves. The portal vein is formed by the union of the splenic and superior mesenteric veins and the gastric, pyloric, and cystic veins. The splenic receives the blood from the spleen, the stomach, and pancreas, the descending colon, sigmoid flexure, and rectum. The superior hemorrhoidal vein drains the rectum and empties into the inferior mesenteric, which passes into the splenic and finally into the portal vein. The superior mesenteric vein drains the remainder of the large and small intestine.

In cirrhosis, carcinoma, and occasionaly gall-stones, the flow of blood through the portal vein is interfered with; hence arise congestions of the various parts which it drains. In the abdomen ascites is produced; the distended and varicose veins of the stomach sometimes rupture, causing haematemesis; diarrhoea may occur, and dilatation of the hemorrhoidal veins produces hemorrhoids.

Especially when there also is pressure on the vena cava the superficial and deep veins of the abdominal wall become enlarged (see page 380). The main anastomoses are: (1) between the gastric (coronary) vein of the stomach and the oesophageal veins which empty into the vena azygos major; (2) between the epigastries (superficial and deep) below and the terminal branch of the internal mammary above; (3) between the epigastric veins and portal vein through the para-umbilical vein (caput medusae, page 380); (4) through the thoracico-epigastrica between the axillary and epigastric (see Fig. 392, page 380); (5) between the superior hemorrhoidal and the middle hemorrhoidal, emptying into the internal pudic.