Splenic mass

Splenic mass is a common finding on imaging modalities. It may be part of the presenting complaint, or be an incidental finding on a screening examination. Splenic masses have multiple etiologies and presentations, and iterative imaging and sampling may be required for diagnosis.

Radiographic features

Solitary plenic masses are generally accepted as being > 4 cm in size and deforming the splenic capsule. Smaller lesions are often termed nodules.

Radiography

The spleen is normally visible on the lateral and ventrodorsal projections of abdominal radiographs. A mass on the proximal extremity of the spleen displaces the left kidney caudally and deforms the normal triangular shape of the spleen to a rounded or irregular, enlarged shape. If on the distal extremity of the spleen, the mass is usually visible on the lateral projection caudal to the liver. Masses can be difficult to see unless they are large given the overlying organs. Multiple large masses may occur on the spleen.

Ultrasound

Splenic masses are often of mixed echogenicity with areas of hypoechoic or anechoic tissue. More complex masses are associated with neoplasia such as hemangiosarcoma, or hemorrhage. These two disorders may be present concurrently. Masses that are more uniform and closer to spleen in echogenicity are more likely to be nodular hyperplasia. These can also undergo necrosis and become complex in character. Hyperechoic masses may be associated with fat or fibrosis, such as myelolipoma.

CT

Splenic masses may be diagnosed on CT, however it is not usually a primary modality for diagnosis. Splenic masses have similar characteristics to the other modalities, and may be characterized as complex, with fluid or hypoattenuating components. Fatty tissue is easier to discriminate on CT and indicates a more benign lesion. Contrast medium will highlight the vascular and non-vascular regions of the mass. Lesions with less than 55 HU on contrast CT images tend to be malignant.

Complications

A common complication is rupture of the splenic mass and hemorrhage into the peritoneal space. This may cause an acute presentation due to decreased hematocrit. Depending on the amount of effusion, the mass can be obscured by the poor peritoneal detail. A mass effect may still be visible, displacing small intestine away from the mass, to help identify this lesion.

If the splenic mass is due to hemangiosarcoma, metastases may be present in the liver, adrenal glands, and other organs. Abdominal ultrasound is useful to investigate the other abdominal organs and identify additional lesions.

Differential diagnosis

Differential diagnoses for a solitary mass include:

• hemangiosarcoma

• hematoma

• fibrosarcoma

• nodular hyperplasia

• granuloma

• cyst/abscess (rare)

In instances where the mass is superimposed on the caudal border of the liver, a pedunculated liver mass may be a differential diagnosis on radiographs. This can be differentiated from a splenic mass using abdominal ultrasound. In general, masses cranial to the stomach are liver in origin, and masses caudal to the stomach are spleen.

See also

• splenic nodules

• multiple splenic masses

• splenomegaly