The spleen is the largest organ in the lymphatic system. Often described as a “biological filter,” it plays a dual role in managing your immune response and recycling old red blood cells. Located deep in the Upper Left Quadrant (LUQ), it is a vital but delicate organ.
The spleen lies tucked under the protection of the 9th, 10th, and 11th ribs on the left side. It sits between the fundus of the stomach and the diaphragm.
Clinical Significance: If the spleen becomes irritated or ruptures, it can cause referred pain to the left shoulder. This is known as Kehr’s Sign, caused by the phrenic nerve being irritated by blood or inflammation near the diaphragm.
A healthy spleen is roughly the size of a clenched fist. In anatomy, students often use the “odd number” mnemonic: it is roughly 1 x 3 x 5 inches, weighs about 7 ounces, and lies between ribs 9 and 11.
Clinical Significance: A normal spleen is not palpable. If a doctor can feel the spleen below the left costal margin, it has usually doubled in size, indicating Splenomegaly (caused by infections like mononucleosis, liver disease, or blood cancers).
The spleen is almost entirely covered by peritoneum (the lining of the abdominal cavity). This makes it highly mobile but also means it is contained within a “bag” of serous fluid.
Clinical Significance: Because it is so vascular and sits within the peritoneal space, a splenic injury can lead to rapid, massive internal bleeding (intraperitoneal hemorrhage), which is a surgical emergency.
The spleen has two main faces: the smooth diaphragmatic surface (facing the ribs) and the visceral surface (facing the internal organs). The visceral surface has “dents” or impressions where it touches the stomach, left kidney, and colon.
Clinical Significance: Tumors or displacements in the stomach or left kidney can shift the position of the spleen, making it appear enlarged on imaging when it is actually just displaced.
The upper (superior) edge of the spleen usually has one or more notches. These are remnants of the spleen’s development from multiple smaller “lobules” in the embryo.
Clinical Significance: During physical examination, these notches help a clinician distinguish a large spleen from an enlarged left kidney. A kidney will feel smooth, whereas a spleen may have a distinct “cleft.”
The Hilum is the “entryway” on the concave medial surface. This is where the splenic artery enters and the splenic vein exits, along with nerves and lymphatic vessels.
Clinical Significance: The “tail” of the pancreas sits very close to the splenic hilum. Surgeons performing a splenectomy must be extremely careful not to damage the pancreas, which could lead to a pancreatic fistula.
The spleen is held in place by two primary ligaments: the Gastrosplenic ligament (connecting it to the stomach) and the Splenorenal ligament (connecting it to the left kidney).
Clinical Significance: If these ligaments are too loose, it can result in a “Wandering Spleen.” This rare condition allows the spleen to migrate in the abdomen, risking torsion (twisting of the blood supply), which can cause the organ tissue to die (infarction).
Internally, the spleen consists of two functionally different types of tissue:
White Pulp: Part of the immune system; it produces and grows white blood cells (lymphocytes).
Red Pulp: The “blood filter”; it removes old or damaged red blood cells and stores a reserve of platelets.
Clinical Significance: Disorders of the white pulp are often linked to lymphoma, while red pulp issues can lead to hemolytic anemia (where blood cells are destroyed too quickly).
The Splenic Artery is famous for its “corkscrew” or tortuous appearance. It is a major branch of the celiac trunk.
Clinical Significance: This artery is a common site for Splenic Artery Aneurysms. While often silent, they are particularly dangerous during pregnancy; a rupture carries a high mortality rate for both mother and fetus.
The spleen is encased in a very thin, “paper-like” capsule of fibroelastic tissue. Unlike the liver or kidneys, this capsule offers very little protection against blunt force.
Clinical Significance: Even a minor “blunt trauma” (like a seatbelt injury or a fall) can cause a Splenic Rupture. In patients with an enlarged spleen (from “Mono”), the capsule becomes even thinner, which is why athletes are restricted from contact sports during recovery.
| Feature | Clinical Finding |
| Palpability | If felt, the spleen is likely $\ge$ 2x its normal size. |
| Kehr’s Sign | Left shoulder pain indicating blood in the abdomen. |
| Splenectomy | Removal of the spleen increases the risk of “Overwhelming Post-Splenectomy Infection” (OPSI); patients require specific vaccinations. |
| Accessory Spleens | Up to 10% of people have a small “mini-spleen” near the hilum. |
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