Gross specimen of a human spleen showing splenomegaly, an enlargement of the spleen (normal length is 11cm). When the length of the spleen is greater than 20 cm, the splenomegaly is considered severe. Common causes include infections, cirrhosis, abnormal red blood cell destruction and portal hypertension. Visceral surface. At centre is the hilum of the spleen, the entry and exit point of the blood vessels and the tissue that supports the organ. Blood vessels are usually surrounded by adipose (fat) tissue,(yellowish).