Congenital or acquired serous fluid contained within layers of scrotal tunica vaginalis

Scrotal fluid surrounding testis, except for “bare area” where tunica vaginalis does not cover testis and is attached to epididymis

Intrascrotal, external to testis and epididymis

Not within scrotal wall

Specific anatomic location: Tunica vaginalis

Simple or complex avascular fluid

High-resolution US (9-15 MHz) is modality of choice

Congenital or communicating hydrocele is due to failure of processus vaginalis to close

Secondary occurrence in adults due to epididymitis, trauma, surgery, or tumor

Simple fluid collection within tunica vaginalis

Chronic cases show thickened tunica with septation

Complex fluid may be seen in acute infection or afterward

Scrotal hematoma may be slow to resolve and manifest as complex collection

Congenital hydroceles usually resolve by 18 months of age

25-50% of acquired hydroceles are associated with trauma

10% of testicular tumors have associated hydrocele

Surgical hydrocelectomy: Open drainage of fluid and oversewing of hydrocele sac edges

Aspiration and sclerotherapy: Less invasive approach with slightly higher risk of recurrence

Look for hydroceles along anterolateral aspect of testis

Cholesterol crystals cause low-level mobile echoes and cannot be distinguished from inflammatory debris; beware of artifacts on color Doppler

Scan with minimal pressure to visualize fluid overlying testis; too much pressure may compress scrotum and lead to underestimation of size of hydrocele