The spleen is concealed at the left hypochondrium and is not palpable under normal conditions. It is associated with the posterior portions of the left 9th, 10th, and 11th ribs—separated from them by the diaphragm and the costodiaphragmatic recess (Fig. 15.1).

If one divides the spleen into three parts, the upper third is related to the lower lobe of the left lung, the middle third to the left costodiaphragmatic recess, and the lower third to the left pleura and costal origin of the diaphragm.

For all practical purposes, the spleen has two surfaces: parietal and visceral (Fig. 15.2). The convex parietal surface is related to the diaphragm, and the concave visceral surface is related to the surfaces of the stomach, kidney, colon, and tail of the pancreas. On the concave hilar surface, the entrance and exit of the splenic vessels at the splenic portals in most specimens form the letter S, which is evident if one connects the upper polar, hilar, and lower polar vessels.

A double layer of peritoneum covers the entire spleen, except for the hilum (Fig. 15.3).

At the hilum, the visceral peritoneum joins the right layer of the greater omentum and forms the gastrosplenic and splenorenal ligaments, the two chief ligaments of the spleen (Figs. 15.4 and 15.5). These two ligaments form the splenic pedicle. The splenic capsule is formed by the visceral peritoneum; it is as friable as the spleen itself and as easily injured (Fig. 15.4).

The superior pole of the spleen lies close to the stomach and may be fixed to it. The inferior pole lies 5–7 cm from the stomach. The gastrosplenic ligament contains the short gastric arteries above and the left gastroepiploic vessels below; it should be incised only between clamps or preferably after the vessels are ligated one by one. Transfixion sutures may be used.

The splenorenal ligament envelops the splenic vessels and the tail of the pancreas. The outer layer of the splenorenal ligament forms the posterior layer of the gastrosplenic ligament. Careless division of the former may injure the short gastric vessels. Bleeding from these vessels may be the result of too-enthusiastic deep posterior excavation by the index and middle fingers of an operator seeking to mobilize and retract the spleen to the right. The splenorenal ligament itself is nearly avascular and may be incised, but the fingers should stop at the pedicle (Fig. 15.6).

The spleen has several minor ligaments, and their names indicate their connections (Fig. 15.5): the splenophrenic, splenocolic, pancreaticosplenic, pancreaticocolic, and phrenicocolic ligaments and the presplenic fold. The splenophrenic ligament (Fig. 15.5) is the reflection of the leaves of the mesentery to the posterior body wall and to the inferior surface of the diaphragm at the area of the upper pole of the spleen close to the stomach. It is usually avascular, but it should be inspected for possible bleeding after section.

Tortuous or aberrant inferior polar vessels of the spleen or a left gastroepiploic artery can lie close enough to the splenocolic ligament to be injured by careless incision of the ligament, possibly resulting in massive bleeding. The ligament should be incised between clamps.

The pancreaticosplenic ligament (Fig. 15.5) is said to be present when the tail of the pancreas does not touch the spleen.

The pancreaticocolic ligament (Fig. 15.5) is the upper extension of the transverse mesocolon and is somewhat of a bridge from the tail or body of the pancreas to the splenic flexure of the colon (Fig. 15.7).

The “phrenicocolic ligament” is not a splenic ligament; i.e., it is not connected to the spleen, but the spleen rests upon it. It extends between the splenic flexure of the colon and the diaphragm and constitutes the “splenic floor” (Fig. 15.5).

The presplenic fold is a peritoneal fold anterior to the gastrosplenic ligament (Fig. 15.5), often containing the left gastroepiploic vessels. Excessive traction on this fold during upper abdominal operations can result in a tear in the splenic capsule.

We propose that the term segments be used when referring to splenic parts separated by avascular planes, elsewhere called lobes. Studies indicate that the majority of the population has two splenic segments—superior and inferior. However, three and more segments have been reported in the literature.

The reported incidence of accessory spleens in autopsies varies from approximately 20 to 30 %. In approximately 60 % of affected patients, only one accessory spleen is present. In 20 %, two such spleens are present, and in 17 %, there are three or more splenic structures. Two-thirds to three-fourths of accessory spleens are located at or near the hilum of the normal organ, and about 20 % are embedded in the tail of the pancreas. The remainder are distributed along the splenic artery, in the omentum, in the mesentery, or beneath the peritoneum (Fig. 15.11). They range from 0.2 to 10 cm in size, resembling lymph nodes or miniature spleens.