Splenomegaly and Hypersplenism

Congestive

– Right heart failure, portal hypertension, sickle cell disease (in acute setting), and splenic vein thrombosis

Hematologic

– Polycythemia vera, myelofibrosis, and hemoglobinopathies

Inflammatory/infectious

– Mononucleosis and HIV/AIDS most common infections to result in splenomegaly

– Sarcoid may result in mild splenomegaly with multiple small hypodensities in liver and spleen

Space-occupying lesions

– Space-occupying masses in spleen do not commonly cause splenomegaly and are more likely to replace normal splenic tissue

– Cysts, lymphoma, metastases, and primary splenic tumors may very rarely cause splenomegaly

Storage and infiltrative disorders

– Primary or secondary hemochromatosis, amyloidosis, and glycogen storage diseases

CLINICAL ISSUES

• Complications include splenic rupture and hypersplenism

Hypersplenism: Hyperfunctioning spleen removes normal RBC, WBC, and platelets from circulation

(Left) Frontal radiograph demonstrates “fullness” in the left upper quadrant. The inferior edge of an enlarged spleen is evident.

(Right) Coronal T2 MR demonstrates a markedly enlarged spleen in a patient with myelodysplastic syndrome. The most common causes of massive splenomegaly are cirrhosis/portal hypertension, lymphoma, chronic myelogenous leukemia, extramedullary hematopoiesis, myelofibrosis, and Gaucher disease.

(Left) Axial CECT shows a small, cirrhotic liver with widened fissures and signs of portal hypertension, including splenomegaly and varices . In most patients with splenomegaly, there are clues as to the underlying cause on the imaging study, as in this case.

(Right) Coronal CECT in an asymptomatic patient demonstrates a mildly enlarged spleen with multiple ill-defined hypodense nodules in a patient with known sarcoidosis. Lymphoma and metastatic disease could have a very similar appearance.

TERMINOLOGY

Abbreviations

• Splenomegaly (SMG)

• Hypersplenism (HS)

Definitions

• SMG: Splenic enlargement caused by a number of different underlying congestive, hematologic, inflammatory/infectious, neoplastic, or infiltrative disorders

• Hypersplenism: Syndrome consisting of splenomegaly and pancytopenia in which bone marrow is either normal or hyperreactive

IMAGING

General Features

• Best diagnostic clue

↑ volume of spleen with convex medial border

• Size

No consensus on absolute size thresholds for SMG: Different sources suggest different measurements

Normal spleen is ≤ 13 cm in length

– Width and breadth are usually ≤ 6 and 8 cm, respectively

Splenic index: Normally 120-480 cm³ (product of length, breadth, and width of spleen)

Splenic weight: Splenic index × 0.55

– Normal weight: 100-250 g

SMG: Anteroposterior (AP) diameter > 2/3 distance of AP diameter of abdominal cavity

• Morphology

SMG is often associated with abnormal contour of spleen, including rounding of poles and convexity of medial border

Radiographic Findings

• Radiography

Normal-sized spleen usually not visualized

SMG: Splenic tip below 12th rib

Marked SMG may displace stomach medially

Displacement of splenic flexure of colon (splenic flexure usually anteromedial to spleen)

Calcification within or adjacent to spleen

CT Findings

• SMG is usually due to 1 of 5 general etiologies

• Congestive

Right heart failure: Cardiomegaly with distension of hepatic veins/IVC and passive hepatic congestion

Portal hypertension: Splenomegaly with varices, nodular shrunken liver, ascites, and other signs of portal hypertension

Splenic or portal vein occlusion or thrombosis (often due to pancreatitis or pancreatic tumors)

Sickle cell disease

– Acute phase: Diffusely decreased splenic density with splenomegaly

– Chronic phase: Development of small autoinfarcted, calcified spleen

• Hematologic

Polycythemia vera

Leukemia

Myelofibrosis: SMG due to extramedullary hematopoiesis

– May be associated with other signs of extramedullary hematopoiesis (such as paraspinal soft tissue masses)

Hemoglobinopathies: May cause splenomegaly (thalassemia) or small, infarcted spleen (sickle cell [SC])

Acute splenic infarction: Global or wedge-shaped hypoenhancement of splenic parenchyma

• Inflammatory/infectious

Mononucleosis

Hepatitis: Splenomegaly due to viremia or cirrhosis with portal hypertension

AIDS: SMG may reflect chronic viremia, opportunistic infection, or lymphoma

IV drug abuse: SMG due to chronic low-level sepsis

Tuberculosis, histoplasmosis: Multifocal low-density granulomas acutely that heal as calcified foci

Sarcoidosis: Often associated with innumerable small hypodense splenic granulomas, ± upper abdominal lymphadenopathy, ± hepatomegaly with similar hypodense hepatic granulomas