THE ABDOMEN appreciated especially well on sagittal and coronal imaging. Poor differentiation between the normal spleen and tumour may be improved by the use of reticuloendothelial contrast agents. Scintigraphy Activity may be seen in splenunculi in addition to the normal spleen. Portography (See also the section on portal system.) This may be performed by splenic puncture via the ninth or tenth interspace posteriorly, remembering that the costodiaphragmatic recess of the pleura always extends to the level of the lower pole of the spleen.
Superior mesenteric vein This lies to the right of the superior mesenteric artery and drains the area supplied by this artery. Its branches are similar except proximally and are as follows: • Right gastroepiploic and inferior pancreaticoduodenal proximally; • Jejunal and ileal branches to its left side; • Ileocolic, right colic and midcolic branches to its right side. Inferior mesenteric vein This lies to the left of the inferior mesenteric artery and drains its area of supply in the colon via the: • Left colic, sigmoid and superior rectal veins; and • Some pancreatic branches.
THE PORTAL VENOUS SYSTEM (Figs 5.44 and 5.45) Blood from the gastrointestinal tract (not including the anus), the spleen, pancreas and gallbladder drains to the liver via the portal venous system. This consists of the superior and inferior mesenteric and the splenic veins, which unite to form the portal vein. There are valves in this system in the fetus and young infant but not in the adult.
Fig. 5 . 4 4 Portal venous system.
The splenic vein Four or five branches leave the splenic hilum and unite to form the splenic vein. Occasionally, a vein from the upper pole of the spleen joins the splenic vein more proximally (the superior polar vein). Proximally the splenic vein receives the short gastric veins and the left gastroepiploic
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