Key points
- Benign cystic dilation of the rete testis, usually an incidental finding in men over 50 years; bilateral in roughly one-third of cases (reported 29-69%), often asymmetric
- Caused by obstruction at or distal to the efferent ductules at the epididymal head; commonly associated with spermatoceles and epididymal cysts
- Diagnostic confidence is highest when the process is bilateral, centered on the mediastinum testis and accompanied by epididymal cysts, with normal tumour markers
- Can present with obstructive azoospermia and infertility
- No surgery, biopsy or follow-up is required; misreading it as malignancy leads to unnecessary orchiectomy
Imaging findings
- Ultrasound: cluster of anechoic rounded and serpiginous tubular structures a few millimetres wide, centered on the mediastinum testis, without solid areas, calcification or mass effect on adjacent parenchyma
- The normal rete testis is a hypoechoic region at the testicular hilum with finger-like projections into the parenchyma; ectasia dilates these channels
- Color Doppler: no internal flow in the dilated channels
- MRI: reserved for equivocal cases; signal follows the coexisting spermatocele, hypointense to testis on T1 and proton density images and inconspicuous on T2, unlike tumours
Differential diagnosis
- Intratesticular varicocele – venous flow on Doppler that augments with Valsalva
- Cystic neoplasm, especially teratoma – solid components, calcification, mass effect, raised markers
- Cystic dysplasia of the testis – congenital, presents in children
- Epididymal cystadenoma – extratesticular, in the epididymal head; consider von Hippel-Lindau when bilateral
What to do next
- No treatment, biopsy or follow-up once the characteristic features are present
- MRI only when sonographic features are equivocal or clinical concern for malignancy persists
References
- Dogra VS, Gottlieb RH, Rubens DJ, Liao L. Benign intratesticular cystic lesions: US features. Radiographics. 2001;21 Spec No:S273-81. PMID: 11598263.
- Brown DL, Benson CB, Doherty FJ, Doubilet PM, DiSalvo DN, Van Alstyne GA, et al. Cystic testicular mass caused by dilated rete testis: sonographic findings in 31 cases. AJR Am J Roentgenol. 1992;158(6):1257-9. PMID: 1590118.
- Rouvière O, Bouvier R, Pangaud C, Jeune C, Dawahra M, Lyonnet D. Tubular ectasia of the rete testis: a potential pitfall in scrotal imaging. Eur Radiol. 1999;9(9):1862-8. PMID: 10602964.
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