The splenic vein and its tributaries are shown in red in this schema of the portal system of veins.
The splenic vein has farther to go than its artery because it has to cross the median plane to reach the beginning of the splenic vein; and it is a little lower than the artery because it is behind the pancreas; the artery begins in the median plane and runs along the upper border of the pancreas.
Origin, relations, and termination
The splenic vein begins in the lieno-renal ligament by the union of five or six veins that issue from the hilum of the spleen. It emerges from the ligament and runs toward the right behind the body of the pancreas across the left kidney, the left crus of the diaphragm and the aorta, to end on the front of the inferior vena cava by joining the superior mesenteric vein to form the portal vein. It crosses the aorta between the origins of the celiac and superior mesenteric arteries, and is closely related to both of them – the celiac above it, the superior mesenteric below it.
Besides its splenic tributaries, the short gastric and left gastro-epiploic veins from the stomach join it near its origin or may join these tributaries; small pancreatic veins join it throughout its course; and the inferior mesenteric, bringing blood from the rectum and the distal half of the colon, joins it at any part of its last two inches – and may even join the commencement of the portal vein or the end of the superior mesenteric.