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Spleen

The spleen is the largest lymphoid organ of the body, located in the left upper quadrant of the abdomen, beneath the diaphragm and adjacent to the 9th–11th ribs. It is an intraperitoneal organ, attached to the stomach and left kidney by the gastrosplenic and splenorenal ligaments. The spleen is ovoid in shape, with a convex diaphragmatic surface and a concave visceral surface containing the splenic hilum, where vessels and lymphatics enter and exit. Histologically, it is composed of white pulp (lymphoid tissue) and red pulp (vascular sinusoids), enabling both immune and hematologic functions.

Synonyms

  • Lien

  • Splenic organ

  • Abdominal lymphoid organ

Function

  • Filters abnormal or aged red blood cells

  • Participates in immune surveillance and antibody production via white pulp

  • Acts as a reservoir for platelets and blood cells

  • Plays a role in iron metabolism and recycling from hemoglobin

  • Provides defense against bloodborne pathogens

โ€‹Arterial Supply

  • Supplied by the splenic artery, the largest branch of the celiac trunk

  • At the hilum, it divides into several segmental branches, each supplying different splenic segments (surgical importance, as ligation can preserve viable tissue)

Venous Drainage

  • Blood drains via the splenic vein, which leaves at the hilum

  • The splenic vein joins the superior mesenteric vein to form the portal vein, making the spleen part of the portal circulation

  • Tributaries include the short gastric veins and left gastroepiploic vein

Nerve Supply

  • Derived from the celiac plexus

  • Predominantly sympathetic fibers regulate splenic blood flow and capsule contraction (no direct parasympathetic innervation)

MRI Appearance

T1-weighted images:

  • Normal spleen is homogeneously low to intermediate signal intensity, slightly lower than the liver

  • Splenic hilum vessels appear as flow voids

  • Focal lesions (cysts, infarcts, tumors) may appear hypointense compared to normal splenic tissue

T2-weighted images:

  • Normal spleen appears moderately hyperintense, but lower than simple fluid

  • Cysts and fluid collections appear bright hyperintense

  • Infarcts or fibrosis may appear as wedge-shaped hypointense regions

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, highlighting inflammatory or infiltrative lesions

  • Abnormal lesions (infection, infarct, tumor) appear bright hyperintense compared to normal parenchyma

T1 Post-Contrast (Gadolinium-enhanced):

  • Spleen enhances in a heterogeneous, mottled pattern in the arterial phase due to its sinusoidal circulation

  • Becomes homogeneously enhanced in the venous and delayed phases

  • Pathologies such as tumors or infarcts may enhance abnormally or remain non-enhancing

CT Appearance

Non-contrast CT:

  • Spleen appears as a homogeneous soft tissue density organ in the left upper quadrant

  • Density is slightly higher than the liver

  • Calcifications may be seen in prior granulomatous disease

Contrast-enhanced CT (CECT):

  • Shows a characteristic heterogeneous arterial enhancement that becomes homogeneous in the portal venous phase

  • Excellent for detecting splenic trauma (lacerations, hematomas), infarcts, abscesses, cysts, or tumors

  • Splenomegaly is well assessed by CT volume measurement

MRI images

Spleen anatomy MRI axial image -img-00000-00000

CT image

Spleen anatomy CT axial image -img-00000-00000

CT images

Spleen CT coronal image

CT images

Spleen CT SAG IMAGE