Epididymis !

The epididymis is a coiled tube along the back of each testis; it stores sperm and lets them mature until they can swim.

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What it is

A tightly coiled tube, about 6 m long if uncoiled, packed into a comma-shaped structure along the back of the testis: head, body and tail.

What it does

Stores sperm and lets them mature so they gain the ability to swim; its tail continues as the ductus deferens.

Key facts

Where: Along the posterolateral border of the testis: head (upper pole, receives the efferent ductules), body and tail (lower pole), which continues as the ductus deferens
Blood supply: Testicular artery; artery to the ductus deferens (tail); veins to the pampiniform plexus
Nerve: Autonomic fibres of the testicular plexus and of the pelvic plexus along the ductus deferens
Function: Stores, concentrates and matures sperm (they gain motility); epididymitis is a common cause of scrotal pain; spermatoceles arise from it

Relations

In front: Testis, joined at the head by the efferent ductules; laterally a recess of the tunica vaginalis separates its body from the testis
Above: Head at the upper pole of the testis, often carrying the appendix of the epididymis
Below: Tail at the lower pole, continuing as the ductus deferens, which turns up along its medial side
Behind: Spermatic cord vessels and the scrotal wall

How to find it

Felt along the back of the testis as a soft ridge, thicker above (head) and below (tail), normally a little tender; the ductus deferens rises from the tail.

Examination

Prehn sign: lifting the scrotum eases pain in epididymitis but not in torsion; only a supporting sign
Cremasteric reflex: usually present in epididymitis, often absent in torsion
Transillumination: a spermatocele lets light through; a solid mass does not

On imaging

Scrotal ultrasound with colour Doppler: in epididymitis the epididymis is enlarged with increased blood flow; spermatoceles are thin-walled cysts above the testis.

Common problems

Epididymitis: painful swelling, often from an infection.
Cysts (spermatoceles), usually harmless.

How it is diagnosed

Examination; scrotal ultrasound; urine tests.

Treatment

Antibiotics, rest and scrotal support for epididymitis.

Clinical notes

Scarring after infection can block it and cause obstructive azoospermia; sperm can be retrieved surgically from it for assisted reproduction

Anatomical variants

Appendix of the epididymis: a small vestigial remnant at its head that can twist and mimic torsion in boys

Development

Forms from the mesonephric (Wolffian) duct, with the efferent ductules from mesonephric tubules, under the influence of testosterone.

Test yourself

Think of the answer, then tap the question to see it.

How does epididymitis differ clinically from testicular torsion?

Epididymitis begins more gradually, often with fever and urinary symptoms, with tenderness at the back of the testis; Doppler ultrasound settles doubt.

What are the usual causes of epididymitis by age?

Younger sexually active men: chlamydia, gonorrhoea. Older men: bowel bacteria from urinary infection or obstruction.

What is the Prehn sign, and how reliable is it?

Lifting the scrotum eases pain in epididymitis but not in torsion; it is only a supporting sign.

How is a spermatocele of the epididymis distinguished from a testicular mass?

It arises from the head, is felt separate from and above the testis, and transilluminates; a testicular mass is treated as cancer until proven otherwise.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): epididymis
Official Spanish (DeCS): Epidídimo
English (TA2): Epididymis

Sources: Anatomy, Abdomen and Pelvis, Male Genitourinary Tract.

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Representative model, for educational purposes only.