Pathophysiology
Clinical meaning
Epididymitis is inflammation of the epididymis, the coiled tube posterior to the testis that stores and transports sperm. In men under 35, the most common cause is sexually transmitted infections (Chlamydia trachomatis and Neisseria gonorrhoeae) ascending through the vas deferens. In men over 35, urinary tract pathogens (E. coli, Pseudomonas) are more common, often associated with urinary tract obstruction, recent urological procedures, or BPH. The inflammation causes unilateral scrotal pain, swelling, and erythema that typically develops gradually over days (differentiating it from testicular torsion which presents with sudden onset). Prehn sign (relief of pain with scrotal elevation) is classically positive in epididymitis but has limited reliability. Cremasteric reflex is typically preserved in epididymitis but absent in torsion. Doppler ultrasound shows increased blood flow in epididymitis (versus decreased flow in torsion). Untreated epididymitis can progress to epididymo-orchitis, abscess formation, and infertility from ductal obstruction.