Epididymitis is inflammation of the epididymis, the tube that sits behind your testicle. You usually notice it as pain and swelling on one side of the scrotum, building over hours to days. Under 35 a chlamydia or gonorrhoea often sits behind it, above that age more often a bacterium from the urinary tract.
One thing comes before everything else.
Testicular pain that arrives suddenly and severely needs a doctor the same day. That is not a testing question. The reason is testicular torsion, a twisted testicle, which can look much the same at the start.
Speed matters there. Waiting on a test result is exactly the wrong move in that scenario.
Here is what strikes me about this topic: almost every page treats epididymitis as one single thing. It isn't. Your age and your sex life largely decide what sits behind it, and therefore whether an STI test is even the right question.
That is what the rest of this article is about.
What is epididymitis?
The epididymis is a coiled tube at the back of your testicle where sperm cells mature and are stored. When that tube becomes inflamed it swells and turns painful. Doctors call that epididymitis, and when the testicle itself joins in they call it epididymo-orchitis.
It is not rare. The European guideline on this condition reports an incidence of 2.45 cases per 1,000 men in the United Kingdom (Street, 2017).
The bacterium almost always gets in from below. From the urethra or the prostate it travels up the vas deferens into the epididymis.
That is the same route that leads to pelvic inflammatory disease in women. It just ends in different anatomy. In men the start of it is often a bout of urethritis you barely noticed.
When is it urgent?
Scrotal pain that comes on suddenly and severely within a few hours needs same-day assessment. The same goes for a high fever, nausea, or a scrotum that looks red and tight. Epididymitis usually builds more slowly, over hours to days, but that difference cannot be judged reliably from the outside.
This is the one paragraph in this article where I am asking you to order nothing.
The table below exists to make that choice easier.
| What you notice | What that usually means | Sensible first step |
|---|---|---|
| Sudden, severe pain in one testicle, arriving within a few hours | This is no longer a testing question, torsion has to be ruled out | See a doctor or out-of-hours care the same day, do not test |
| Pain and swelling building over a few days, with fever | Fits an inflammation that needs assessment | GP, an STI test can run alongside |
| Nagging pain on one side, no fever, risk contact behind you | Can fit an STI that has moved upward | GP, plus a targeted chlamydia and gonorrhoea test |
| Burning urination or discharge, no scrotal pain yet | More often fits urethritis | Targeted STI test, and discuss the symptoms |
| No symptoms, but unprotected contact with a new partner | A silent infection cannot be ruled out | Test after the right waiting time |
| Dull pain that has been there for months, without swelling | More often fits something other than an acute infection | GP, this is not an urgent question |
A table does not make a diagnosis. What it does is stop you waiting on a result when what you actually need is a doctor.
How do you recognise epididymitis?
Usually by pain and swelling on one side of the scrotum that worsens over hours to days. The epididymis often feels thickened and tender, and the skin around it can be warm and red. Fever can come with it, and some men also notice burning urination or discharge from the urethra.
There is one thing men tell us strikingly often.
The symptoms didn't start in the scrotum. They started with some burning on urination, a week or two earlier, and that settled on its own. That fits the route from below.
What you can do yourself is watch for change. New pain on one side, or swelling that wasn't there yesterday. Those are the things a GP can work with.
Symptoms can also be absent entirely in the STI underneath. Chlamydia runs silently in many men, and then the epididymitis is the first thing anyone notices.
Is it caused by an STI?
That depends heavily on your age and your sex life. In sexually active men under roughly 35, chlamydia and gonorrhoea are often the cause. Above 35, and in men who are not having sex, it is more often a urinary tract organism that has travelled up from the urethra or the prostate.
That split is the practical core of this article.
The European guideline draws the same line, describing the approach for sexually active men separately from the over-35 group (Street, 2017). So not every epididymitis comes from an STI. And you can't simply write it off as an ordinary inflammation either.
The bacteria behind it in younger men are the same ones that travel upward in women. Research into that ascent describes how sexually transmitted pathogens move up from the lower genital tract (Darville, 2021).
Picture this: you are 26, you have had increasing pain on the left side of your scrotum for two days, and you had a new partner six weeks ago. No sudden spike, but clearly worse than it was. An STI is a real possibility then, and both a GP and a test belong in the picture.
If you run into the other route, the urinary one, the prostate often plays a part. The NIH classification of prostatitis separates an acute bacterial form from the chronic pictures (Krieger, 1999). More on that in prostatitis and the STI link.
The Dutch national institute RIVM reports the same thing year after year. Chlamydia is the most frequently found STI here, with the highest numbers among people under twenty-five. You can get checked with us through a test for chlamydia, gonorrhoea and trichomonas, without an appointment and without anything reaching your GP records.
How is it treated?
With antibiotics prescribed by a doctor, chosen for the likely cause. That is exactly why the age split carries so much weight: an STI calls for a different choice than a urinary infection. Alongside that, rest, scrotal support and pain relief are often part of the advice, and symptoms usually settle over days to weeks.
What you do not do is reach for an old course of antibiotics in the cupboard.
The chance it matches the right bacterium is small, and it makes a later test less reliable. The Dutch GP standard on the STI consultation describes how GPs here look at these complaints. Thuisarts.nl explains in plain language what to expect from such a visit.
Two things get forgotten a lot. If an STI turns out to be involved, your partner should be treated as well. And finishing the course counts even if the pain is gone after three days.
If the symptoms do not settle, have it reassessed rather than waiting it out.
Can it affect your fertility?
It can, though that is unusual when the inflammation is treated in time. The European guideline lists abscess formation, testicular infarction and infertility among the possible complications (Street, 2017). The epididymis is the tube sperm cells have to pass through, and scar tissue can narrow that passage.
That is the same logic as with fallopian tubes, just on the other side.
Read those complications in proportion. They describe inflammation that runs severely or is treated late. They do not describe everyone with a tender scrotum.
What does follow is why there is urgency in finding the underlying infection. The damage comes mostly from the stretch of time in which nobody knew anything was going on. We took that reasoning further on the female side in pelvic inflammatory disease and its consequences.
Why this is the male counterpart of pelvic inflammatory disease
Because it is the same infection in different anatomy: in women chlamydia and gonorrhoea travel up to the fallopian tubes, in men to the epididymis. Same bacteria, same route from below, same time course. Only the name and the organs differ, which is why on paper they look like two separate conditions.
That connection is almost never drawn on Dutch pages. I think that is a missed opportunity.
For couples getting checked together it is the most useful picture there is. One untreated chlamydia can end up in her fallopian tubes and in his epididymis.
How chlamydia behaves in men is covered in chlamydia in men.
If you are noticing pain that came on fast, call your GP today. If the symptoms are mild and you had a risk contact, book a targeted chlamydia and gonorrhoea test.
Further reading
For the start of the upward route: urethritis.
For the wider symptom picture in men: STI symptoms in men.
References
- Street EJ, et al. The 2016 European guideline on the management of epididymo-orchitis. International Journal of STD and AIDS, 2017;28(8):744-749. PMID 28632112.
- Darville T. Pelvic Inflammatory Disease Due to Neisseria gonorrhoeae and Chlamydia trachomatis: Immune Evasion Mechanisms and Pathogenic Disease Pathways. The Journal of Infectious Diseases, 2021. PMID 34396413.
- Krieger JN, et al. NIH consensus definition and classification of prostatitis. JAMA, 1999;282(3):236-7. PMID 10422990.
- RIVM, Sexually transmitted infections in the Netherlands, annual report. Accessed July 2026.
- NHG-Standaard Het soa-consult, Dutch College of General Practitioners. Accessed July 2026.
- Thuisarts.nl, I have pain in my scrotum. Accessed July 2026.
Every test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
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