Last revised by Matt A. Morgan on 7 Nov 2023

Hydroceles are acquired or congenital serous fluid collections between the layers of the tunica vaginalis surrounding a testis or spermatic cord. They present with painless scrotal enlargement. On imaging, hydroceles appear as simple fluid on all modalities, unless complicated by infection or hemorrhage.

Hydroceles can be diagnosed at any age, with congenital hydroceles being more common in children.

Most hydroceles are acquired and present with progressing painless scrotal mass. During the physical examination, hydrocele characteristically transilluminates when evaluated with a light source. They can become painful if infected (see pyocele).

There are two main subtypes of congenital hydrocele:

In the communicating type, fluid collects around a patent processus vaginalis which failed to successfully obliterate.

The spermatic cord hydrocele is further subdivided into:

  • encysted type (spermatic cord cyst): no communication with the peritoneum or tunica vaginalis

  • funicular type (funiculocele)

    • communicates with the peritoneum at the internal ring and does not surround the testis

    • more common in children and premature infants 2

Ultrasound is the first modality usually used to evaluate hydrocele, which presents as a simple fluid collection. It is avascular on Doppler evaluation. It may contain septations, calcifications or cholesterol 2.

Communicating, infantile and vaginal hydroceles will be seen intimately surrounding the adjacent testis. In contrast, spermatic cord hydroceles such as funicular hydrocele (funiculocele) and encysted hydrocele will not surround the testis, rather being found along the spermatic cord.

Hydroceles can also appear larger with straining (Valsalva maneuver) 2. They may contain fibrous adhesions, giving a beaded appearance to the spermatic cord (pachyvaginalitis) 3.

On MRI, signal characteristics of the hydroceles are

  • T1: low signal

  • T2: high signal

This represents the serous fluid of an uncomplicated hydrocele.

In infants, most hydroceles (around 90%) resolve spontaneously, and they are thought to result from incomplete obliteration of the processus vaginalis 4. It is important to assess for any associated herniations in these patients.

Imaging differential considerations include

Rarely, a scrotal tunica cyst or scrotal mesothelioma can look like a hydrocele, but they are usually easily distinguishable.

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