Ultrasonography of The Spleen
In ultrasonography of the spleen, a focused beam of high-frequency sound waves passes into the left upper quadrant of the abdomen, creating echoes that vary with changes in tissue density. These are displayed on a monitor as real-time images that indicate the size, shape, and position of the spleen and surrounding viscera.
Ultrasonography is indicated in patients with an upper left quadrant mass of unknown origin; with known splenomegaly, to evaluate changes in splenic size; with left upper quadrant pain and local tenderness; and with recent abdominal trauma.
Procedure and posttest care
The splenic parenchyma normally demonstrates a homogeneous, low level echo pattern; its individual vascular channels aren't usually apparent. The superior and lateral splenic borders are clearly defined, each having a convex margin. The undersurface and medial borders, in contrast, show indentations from surrounding organs (stomach, left kidney, and pancreas).
The hilar region, where the vascular pedicle enters the spleen, commonly produces an area of highly reflective echoes. The medial surface is generally concave, which helps differentiate between left upper quadrant masses and an enlarged spleen. Even when splenomegaly is present, the spleen generally remains concave medially unless a space-occupying lesion distorts this contour.
Ultrasonography can show splenomegaly, but it usually doesn't indicate the cause; a computed tomography (CT) scan can provide more specific information. Splenomegaly is generally accompanied by increased echogenicity. Enlarged vascular channels are commonly visible, especially in the hilar region. If space-occupying lesions distort the splenic contour, liver-spleen scanning should be performed to confirm splenomegaly.
Abdominal trauma may result in splenic rupture or subcapsular hematoma. In splenic rupture, ultrasonography demonstrates splenomegaly and an irregular, sonolucent area (the presence of free intraperitoneal fluid); however, these findings must be confirmed by arteriography. In subcapsular hematoma, ultrasonography shows splenomegaly, as well as a double contour, altered splenic position, and a relatively sonolucent area on the periphery of the spleen. The double contour results from blood accumulation between the splenic parenchyma and the intact splenic capsule. As the spleen enlarges, a transverse section shows its anterior margin extending more anteriorly than the aorta. Ultrasonography may be difficult and painful after abdominal trauma because the transducer may have to pass across ftactured ribs and contusions; CT scanning, which differentiates blood and fluid in the peritoneal space, should be used instead.
In subphrenic abscess, ultrasonography shows a sonolucent area beneath the diaphragm. Clinical findings may differentiate between abscess and blood or fluid accumulation.
Used with liver-spleen scanning, ultrasonography differentiates cold spots as cystic or solid lesions. It shows cysts as spherical, sonolucent areas with well-defined, regular margins with acoustic enhancement behind them. When ultrasonography fails to identify a cyst as splenic or extrasplenic - especially if the cyst is located in the upper pole of the left kidney and the adrenal gland, or in the tail of the pancreas - a CT scan and arteriography are used. Ultrasonography can readily clarify cystic cold spots, but using a CT scan with a contrast medium is superior for evaluating primary and metastatic tumors. Ultrasonography usually fails to identify tumors associated with lymphoma and chronic leukemias because these resemble tumors of the splenic parenchyma.
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