Diaphragmatic Surface of the Spleen

The diaphragmatic surface of the spleen is the smooth, convex, outer surface that lies in direct contact with the diaphragm. It forms the majority of the external surface of the spleen and is oriented superiorly, posteriorly, and laterally. This surface is closely related to the inferior surface of the left hemidiaphragm, and through it, to the lower thoracic cavity — including the pleura and the base of the left lung.

Structure

This surface is dome-shaped and convex to match the contour of the diaphragm. It is covered by the visceral peritoneum, except at the splenic hilum. Unlike the visceral surface, the diaphragmatic surface lacks impressions or indentations from neighboring organs and remains relatively uniform.

Histologically, it consists of the splenic capsule and dense connective tissue overlying the parenchyma of the spleen, primarily composed of:

• White pulp: Lymphoid tissue involved in immune surveillance
• Red pulp: Blood-filled sinusoids responsible for filtration and recycling of red blood cells

Location

The diaphragmatic surface faces the posterolateral abdominal wall and lies directly beneath the left dome of the diaphragm. Its precise anatomical relationships are summarized below:

Function

While the diaphragmatic surface itself does not serve a distinct physiological role separate from the spleen, it plays a key structural function:

• Positioning: Allows the spleen to rest snugly against the diaphragm, contributing to its posterolateral orientation
• Protection: Protected by the lower rib cage, minimizing the risk of rupture during minor trauma
• Respiratory mobility: Moves slightly with the diaphragm during respiration, which can be appreciated in imaging and clinical palpation

Clinical Significance

The diaphragmatic surface is important in several clinical contexts:

• Splenic rupture: The convex surface is most exposed in blunt abdominal trauma. Fractures of the 9th–11th ribs may damage this surface and cause intra-abdominal bleeding.
• Radiological imaging: Best seen on cross-sectional imaging (CT, MRI) as the outer contour of the spleen; helps differentiate normal from pathological enlargement or laceration.
• Surgical access: During splenectomy, understanding the smooth and exposed location of this surface helps in mobilizing the spleen away from the diaphragm.
• Referred pain: Irritation of the diaphragm (e.g., from splenic rupture or abscess) can cause referred pain to the left shoulder — known as Kehr's sign.

The diaphragmatic surface forms a key anatomical interface between the abdominal and thoracic cavities. Though it appears simple in structure, its anatomical positioning has critical implications for trauma assessment, imaging, and surgery.