Epididymitis usually results from pyogenic organisms, such as Escherichia coli, chlamydia, Neisseria gonorrhoeae, and Pseudomonas aeruginosa. Infection usually results from established urinary tract infection
or prostatitis extending to the epididymis through the lumen of the vas deferens. Rarely, epididymitis is secondary to a distant infection, such as pharyngitis or tuberculosis, that spreads through the lymphatic system or, less commonly, the bloodstream.

Trauma may reactivate a dormant infection or initiate a new one. In addition, epididymitis is a complication of prostatectomy and may also result from chemical irritation by extravasation of urine through the vas deferens.

Epididymitis may spread to the testis, causing orchitis. Bilateral epididymitis may cause sterility.

The patient may complain of unilateral, dull, aching pain radiating to the spermatic cord, lower abdomen, and flank and an extremely heavy feeling in the scrotum. He may also exhibit erythema, a high fever, and malaise. The patient may walk with a characteristic waddle—an attempt to protect the groin and scrotum during walking. An acute hydrocele may occur as a reaction to the inflammatory process.