KEY FACTS
Terminology
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Dilated rete testis
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Cystic transformation of rete testis
Imaging
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Frequently bilateral
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Usually asymmetric involvement
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Branching tubules converging at mediastinum testis
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Dilated tubules create lace-like or fishnet appearance
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Adjacent parenchyma is normal
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Associated ipsilateral spermatoceles are common
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Tubules are avascular and fluid filled
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No flow on color Doppler imaging
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MR performed for confirmation if cystic malignant neoplasm cannot be ruled out
Top Differential Diagnoses
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Testicular carcinoma
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Mixed germ cell tumors with teratomatous components will often have cystic areas
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Does not form network of tubules
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Intratesticular varicocele
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Characteristic color flow on Doppler
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Testicular infarct
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Avascular wedge-shaped area with sharp borders
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Clinical Issues
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Generally nonpalpable and asymptomatic
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May be found when doing ultrasound for related issue, such as epididymal cyst
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Often seen in setting of prior vasectomy
Scanning Tips
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Check with color or power Doppler to ensure lesion is avascular
> left 
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within the mediastinum testis, consistent with tubular ectasia of the rete testis.
