Diagnostic Ultrasound - Abdomen and Pelvis

Splenic Cyst
TERMINOLOGY
Definitions
• Cystic parenchymal lesions of spleen
IMAGING
General Features
• Best diagnostic clue
○ Anechoic to hypoechoic, avascular, sharply defined
spherical lesion with posterior acoustic enhancement
• Location
○ Usually subcapsular (65%)
• Size
○ Variable
• Key concepts
○ 2 classification schemes of splenic cysts
– Primary (congenital) vs. secondary (acquired)
□ Primary: Epidermoid cyst
□ Secondary: Due to trauma (hematoma), infarction,
infection, pancreatitis
– True vs. false/pseudocyst
□ True: Epithelial lined; includes epidermoid and
parasitic (e.g., hydatid) cysts
□ False: No epithelial lining; may have fibrous wall;
includes post-traumatic, infectious (nonparasitic), or
degenerative
– "Primary" & "true" or "secondary" & "false/pseudo"
often treated as synonymous
□ However, not all secondary cysts are pseudocysts;
hydatid cyst is an example of a secondary (acquired)
true cyst
○ Congenital cysts comprise about 20% of splenic cysts
– Epidermoid cyst most common
– Splenic cysts related to autosomal dominant
polycystic kidney disease (ADPKD) are rare (> 5% of
ADPKD)
– More commonly encountered in children and young
adults
○ Acquired cysts are more common (about 80%)
– Wall calcification more common (38-50%) than in
primary cysts (10-15%)
– Generally, higher incidence of debris and smaller size
than primary cysts, though can be large
○ Often impossible to distinguish primary vs. secondary (or
true vs. false) cysts by imaging
Ultrasonographic Findings
• Grayscale ultrasound
○ Well-defined anechoic or hypoechoic lesion ± posterior
acoustic enhancement
○ Congenital cysts
– Anechoic, smooth borders, nondetectable walls ±
trabeculation (36%), posterior acoustic enhancement
– If complicated: Septations, internal echoes
(hemorrhage, inflammatory debris); floating debris
within cyst may produce mobile, uniform internal
echoes ("snowstorm" or "pseudosolid" appearance),
thick wall ± calcification
○ Acquired cysts
– Post-traumatic: Anechoic or mixed with internal
echoes, echogenic wall, ± calcification, ± trabeculation
of cyst wall (15%)
– Parasitic (hydatid cyst): ± internal small daughter cysts
and floating membranes ± calcification, hydatid sand
• Color Doppler
○ Avascular on color or power Doppler
Radiographic Findings
• May see curvilinear or plaque-like wall calcification
CT Findings
• Congenital cyst
○ Solitary, well-defined, spherical, unilocular cystic lesion
(water or near water HU)
○ If hemorrhagic, infected, proteinaceous: ↑ attenuation
or septation
○ No rim or intracystic enhancement, may have calcified
wall (uncommon)
• Acquired cyst
○ Nonparasitic/post-traumatic: Usually small, solitary,
sharply defined, water HU, ± wall calcification (may
resemble eggshell)
○ Hydatid cyst: Peripheral calcification, ± daughter cysts;
liver involvement far more common
MR Findings
• Congenital cyst
○ T1WI:↓ signal, variable intensity if infected or
hemorrhagic; T2WI: ↑ signal
• Acquired cyst
○ T1WI: ↓ signal, variable intensity (blood); T2WI: ↑ signal
○ Calcification or hemosiderin deposited in wall
– T1WI & T2WI: ↓ signal
○ Hematoma: Varied intensity based on age & evolution of
blood products
– After 3 weeks, appears cystic: T1WI ↓; T2WI ↑
Imaging Recommendations
• Best imaging tool
○ Ultrasound for initial evaluation; if needed, CT or MR for
further characterization
• Protocol advice
○ Patient is best scanned in supine or right lateral
decubitus position following deep inspiration with US
transducer along long axis of spleen
DIFFERENTIAL DIAGNOSIS
Inflammatory or Infection
• Pyogenic abscess
○ Solitary or multiple, well defined, ± irregular shape,
hypoechoic to anechoic depending on stage of
liquefaction/necrosis, ± gas within abscess
• Fungal abscess
○ e.g., Candida, Aspergillus, Cryptococcus
○ Usually microabscesses: Multiple, small, well-defined,
hypoechoic to echogenic, throughout parenchyma
• Granulomatous abscesses
○ e.g., TB, atypical mycobacterium (MAC); cat-scratch
○ Multiple small, well-defined, hypoechoic lesions
Diagnoses: Spleen
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