Epididymitis
Epididymitis is inflammation of the epididymis (the tube behind the testicle), usually from infection, treated per the CDC Sexually Transmitted Infections Treatment Guidelines, 2021.
Symptoms
Gradual-onset testicular pain and swelling, often with redness and warmth of the scrotum, sometimes with fever or urinary symptoms.
Causes and risk
In sexually active men under 35, chlamydia and gonorrhea are the most common causes; in older men or those with recent urinary instrumentation, E. coli and other urinary bacteria are more likely.
How it is evaluated
Increased blood flow to the epididymis on Doppler ultrasound supports the diagnosis and helps distinguish it from torsion, where blood flow is absent; an absent cremasteric reflex favors torsion over epididymitis.
Treatment
STI-related epididymitis is treated with ceftriaxone (an injection) plus doxycycline per CDC guidelines; non-STI cases from urinary bacteria are treated with a different antibiotic class. Because the ceftriaxone injection can't be self-administered, confirmed or suspected STI cases need an in-person visit.
When to seek care
Sudden, severe pain -- as opposed to the gradual onset typical of epididymitis -- raises concern for testicular torsion, a true surgical emergency with roughly a 6-hour window to save the testicle. When in doubt, go to the emergency department rather than wait.