Anatomy and vascular supply

The normal spleen lies in the left hypochondrium, adjacent to the tail of the pancreas, the greater curve of the stomach and the upper pole of the left kidney. It weighs approximately 10 grams at birth, gaining the full adult weight of 150 grams by 15 years. With enlargement from any cause, it expands caudally and medially and may extend across the midline to reach the right iliac fossa. The shape of the normal spleen is a compressed ovoid, with a convex lateral surface and concave medial (hilar) aspect. The upper pole is usually more rounded and bulky than the lower. The antero-medial border is sometimes irregular and, in some individuals, bears one or more notches which may become prominent if the spleen enlarges. Ectopic splenic location and splenunculi are described in Chapter 9.

Blood supply is via the splenic artery, which branches from the coeliac plexus and passes along the superior border of the pancreas. It often follows a tortuous course in older individuals and its wall may become heavily calcified. The splenic vein drains blood from the organ to the portal vein by a parallel route. Lymphatic channels from the spleen also follow this route. Afferent lymphatics have not been described, which should not be surprising in view of the spleen's key role as a filter and immune response organ for the bloodstream.