The most important problem during spleen surgery is bleeding, from the hilar vessels or the splenic parenchyma itself; it can occur at any stage of the operation and may be difficult to stop. Peri- and postoperative bleeds occur in up to 10 % of cases and depend on concomitant diseases and risk factors. Patients with haematological diseases and/or anticoagulant therapy are at greater risk; portal hypertension is a further risk factor.

Injuries to neighbouring organs, such as the flexure of the left colon and especially the tail of the pancreas, are far less common but pose serious complications. Postoperative pancreatitis can follow an injury, but blood supply to the tail of the pancreas may be compromised by proximal ligature of the splenic vessels, causing necrosis and possible formation of persisting fistulas.

Key elements for complication-free splenic surgery are knowledge of the surgical anatomy and laparoscopic expertise, as well as adherence to preventive measures and to the step-by-step dissection techniques.

For its size, the spleen is very well perfused. It is a soft lymphatic organ and contains about 1/4 of the body’s total lymphoid tissue, but unlike the lymph nodes, it is integrated into the blood rather than lymphatic circulatory system. The hilum of the spleen is located roughly in the middle of the visceral surface, where the branches of the splenic artery enter and the tributaries of the splenic vein leave. This is the only place where it is not covered by the peritoneum. The spleen is suspended in the left upper quadrant by the splenophrenic, gastrosplenic and splenocolic ligaments; its physiological position and its shape can vary according to the position and distension of the neighbouring organs and the position of the body.

Generally the splenic artery has one branch each to the upper and lower poles and itself enters the spleen in the middle of the hilum so that the spleen can be divided into three segments: upper, middle and lower. These segments are quite autonomous in their arterial and venous circulation. The segments are superposed perpendicularly along the long axis of the spleen and are separated by poorly vascularised planes. The splenic branches are considered to be nonanastomosing terminal arteries, except for some intrahilar shunts; there are also a few intersegmental vessels that allow subtotal permeation of the segments with an increase in pressure. Intersegmental connections allow ligature of the main vessel or a catheter embolisation, which is usually be tolerated without total necrosis. Thanks to these poorly vascularised intersegmental zones, the spleen can be partially resected with minimal blood loss.

Based on the distribution of blood vessels within the splenic parenchyma, we distinguish between a central zone near the hilum, a peripheral zone distant from the hilum and an intermediate zone between the two. Understanding these zones of vascularisation is important for classifying the severity of splenic injuries, particularly intraoperative injuries. An intraoperative injury that involves only peripheral (subcapsular) parenchyma opens the peripheral arterioles and venous sinuses. The trabecular vessels are affected in the intermediate area. Parenchymal injuries of the medial surface penetrating into the central zone often damage the segmental vessels. Surgical measures are determined by the nature and degree of vascular injuries.