Diagnostic Ultrasound - Abdomen and Pelvis

Splenic Infarct
TERMINOLOGY
Abbreviations
• Splenic artery (SA); splenic vein (SV)
Definitions
• Global or segmental parenchymal splenic ischemia and
necrosis caused by vascular occlusion
IMAGING
General Features
• Best diagnostic clue
○ Hypoechoic region within splenic parenchyma on
grayscale US that is avascular on Color Doppler
○ Key concepts
– Acute infarction: Hypo- to anechoic (depending on
stage), avascular; different patterns, size, morphology
□ Bright band sign
– Chronic infarction: Atrophic, scarred spleen
– Assess for underlying cause
□ Presence of splenomegaly
□ Evaluate splenic artery and vein for occlusion or
thrombosis
• Location
○ Infarction: Classically in peripheral location (i.e., abutting
splenic capsule), but may be nonperipheral
○ SA occlusion: Usually entire artery; or distal only
○ SV thrombosis: Entire vein or distal only (near hilum)
• Size
○ Focal (polar or central location) vs. global (entire spleen)
• Morphology
○ Classic acute infarct: Peripheral wedge-shaped
○ Other appearances: Rounded/spherical or peripheral
band
Ultrasonographic Findings
• Grayscale ultrasound
○ Acute infarct
– Classic: Hypoechoic, peripheral, wedge-shaped region
– Grayscale findings may not appear for 24-48 hours
after loss of blood flow
– Over time, may become iso- to hyperechoic
– Bright band sign: Parallel thin specular reflectors
perpendicular to US beam within hypoechoic
parenchymal lesions
○ Chronic infarct: Atrophy, scarring/indentation of splenic
contour,± calcification
○ Acute SA occlusion: Grayscale diagnosis unlikely
○ Chronic SA occlusion: Absence of SA (scarred)
○ SV thrombosis (SVT): Echogenic material in SV (with
good visualization)
– Look for neoplastic mass surrounding/invading SV
• Color Doppler
○ Acute infarct: Classically avascular or hypovascular;
power Doppler helpful to confirm
○ Acute SA occlusion: SA visible but no blood flow in part
or all of lumen
○ Chronic SA occlusion: Nonvisualization of all or part of
SA, with possible visualization of collaterals
○ Acute SV thrombosis: SV visualized but no flow on color
Doppler
– Tumor invasion: Mass adjacent to/surrounding SV;
low-resistance arterial flow in tumor vessels
– Note: Visualization of blood flow in splenic hilar
branches does not exclude SV thrombosis
○ Chronic SV thrombosis: Nonvisualization of part or all of
SV (scarred)
– Classic findings: Massive left-sided venous collaterals
(splenogastric or splenorenal) without findings
indicative of portal hypertension
CT Findings
• Acute segmental: Wedge-shaped or rounded lowattenuation/hypovascular
area
• Acute global: Complete nonenhancement of spleen ±
cortical rim sign
• Chronic: Atrophy,± calcification; absence (complete
autoinfarction)
MR Findings
• T1: Acute, ↑ signal in areas of hemorrhagic infarction;
Chronic,↓ signal; no C+
• T2:↑ signal in area of infarct
Imaging Recommendations
• Best imaging tool
○ Contrast-enhanced CT or MR more accurate than US for
most splenic vascular disorders
• Protocol advice
○ Color and power Doppler US are essential for US
diagnosis; grayscale value alone is limited
DIFFERENTIAL DIAGNOSIS
Splenic Laceration/Hematoma
• Hematoma may be indistinguishable by imaging alone
depending on stage
• History of trauma is crucial
Splenic Cyst/Mass
• Abscess or complex splenic cysts may mimic infarct if
contents are echogenic
• May be consequence of infarction (i.e., superinfection or
pseudocyst)
Splenic Metastases
• May see blood flow in lesion(s)
• Metastases to spleen are not common due to lack of
afferent lymphatics and contractile motion of the spleen
which may squeeze tumor emboli out
• If spleen involved with metastases, typically liver involved as
well
Splenic Lymphoma
• May appear as marked splenomegaly, multiple hypoechoic
masses, or single large mass in spleen
PATHOLOGY
General Features
• Etiology
○ Infarction due to embolization
Diagnoses: Spleen
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