Splenic Hilum

The splenic hilum is a slit-like indentation on the medial (visceral) surface of the spleen where the organ’s vascular and lymphatic structures, along with autonomic nerves, enter and exit. Unlike many other organs where the hilum is centrally located, the splenic hilum lies near the superior part of the visceral surface, close to the pancreatic tail. It serves as a critical anatomical and surgical landmark, especially during splenectomy or interventions involving the splenic vessels.

Structure

The hilum is not a distinct anatomical structure on its own but rather a gateway formed by a break in the splenic capsule. It is bordered by peritoneal reflections of the gastrosplenic ligament anteriorly and the splenorenal ligament posteriorly. These ligaments carry the vessels that traverse the hilum.

The parenchyma around the hilum contains both white pulp (lymphoid nodules) and red pulp (vascular sinusoids), but these do not reach the hilum itself, which is occupied by connective tissue and vessel branches.

Location

The splenic hilum is located on the visceral surface of the spleen, slightly above the midpoint of the medial border. It lies in close proximity to the tail of the pancreas, often overlapping or contacting it within the splenorenal ligament.

Function

The splenic hilum functions primarily as the conduit for entry and exit of vascular, lymphatic, and nervous structures:

• Vascular entry: Splenic artery divides into several segmental branches at or just before the hilum.
• Venous drainage: Blood collected from the spleen exits via tributaries of the splenic vein.
• Lymphatic flow: Lymphatic drainage passes through the hilum toward the pancreaticosplenic and celiac lymph nodes.
• Nervous control: Sympathetic fibers enter the hilum to regulate blood flow and splenic contraction.

Clinical Significance

The splenic hilum is a surgically sensitive area with major clinical implications:

• Splenectomy: Ligation of the splenic artery and vein must be performed at or near the hilum during removal of the spleen. Care must be taken to avoid injury to the pancreatic tail.
• Trauma: Hilum is a common site of laceration during blunt abdominal trauma due to its central role in vascular supply.
• Splenic cysts or tumors: May originate or expand toward the hilum, potentially compressing vessels and leading to infarction or rupture.
• Pancreatic tail surgery: Given its proximity to the hilum, distal pancreatectomy often involves careful dissection of the hilum or splenic vessel ligation.
• Splenic artery aneurysm: Frequently found near the hilum; rupture poses a life-threatening risk and requires urgent intervention.

Understanding the anatomy of the splenic hilum is essential for abdominal surgeons, radiologists, and emergency physicians. It serves as the anatomical nexus for the spleen's blood supply and lymphatic drainage, and its proximity to adjacent organs increases the risk during surgical procedures.