Epididymitis
Table of Contents
- Overview
- Anatomy and Pathophysiology
- Causes and Risk Factors
- Clinical Presentation
- Diagnosis
- Differential Diagnosis — Distinguishing from Testicular Torsion
- Treatment
- Complications
- Research and Key Findings
- References
- Connections
- Featured Videos
1. Overview
Epididymitis is inflammation of the epididymis — the coiled tube that sits behind each testicle and carries sperm toward the vas deferens. It is the most common cause of scrotal pain in adult males, accounting for roughly 600,000 physician visits per year in the United States alone. While it can be alarming and quite painful, epididymitis is not the surgical emergency that testicular torsion is. With the right diagnosis and treatment, most men recover fully.
The inflammation usually develops gradually over several days, beginning at the tail (lower pole) of the epididymis and, if untreated, spreading upward to the head and potentially into the testis itself — a condition called epididymo-orchitis. It almost always affects one side at a time; bilateral epididymitis is uncommon and should prompt investigation for systemic causes such as tuberculosis or sarcoidosis.
Who gets it? Epididymitis has two very different profiles depending on age. In sexually active men under 35, the condition is most often a sexually transmitted infection (STI) — specifically Chlamydia trachomatis or Neisseria gonorrhoeae. In men over 35, particularly those with urinary tract problems or who have had urologic procedures, the culprits are usually common intestinal bacteria — the same ones that cause urinary tract infections. Understanding this age-based pattern is the key to selecting the right antibiotic.
The good news: epididymitis responds well to antibiotics. The goal of this article is to help you understand what epididymitis is, how doctors confirm the diagnosis, how it differs from more urgent conditions like testicular torsion, and what the treatment involves.
2. Anatomy and Pathophysiology
To understand epididymitis, it helps to know where the epididymis sits and what it does. The epididymis is a tightly coiled, C-shaped tube approximately 6 meters long when uncoiled, compressed into a structure just a few centimeters that runs along the back and upper surface of each testis. It has three regions:
- Head (caput): receives sperm from the efferent ductules of the testis
- Body (corpus): the long middle portion where sperm mature over roughly 12 days
- Tail (cauda): stores mature sperm and connects to the vas deferens
Epididymitis almost always begins at the tail, closest to the opening of the vas deferens, because bacteria typically travel retrograde — that is, upstream from the urethra or bladder through the vas deferens into the epididymis. This retrograde route explains why STIs originating in the urethra and bladder bacteria from urinary tract infections both arrive at the same destination via the same highway.
Once bacteria establish themselves in the epididymis, the immune system responds with inflammation — increased blood flow, swelling, white blood cell infiltration, and tissue edema. This produces the hallmark signs: warmth, redness, and exquisite tenderness. The swelling can be dramatic and the pain severe, particularly with any movement. If inflammation is not controlled, it can spread to involve the testis (orchitis), the surrounding tissue, or in severe untreated cases, the skin (Fournier's gangrene, a rare but life-threatening condition).
In some men, inflammation is not caused by infection at all. Chemical epididymitis occurs when sterile (bacteria-free) urine refluxes backward into the epididymis during heavy lifting or straining (Valsalva maneuver), irritating the tissue without introducing bacteria. The drug amiodarone (used for heart rhythm problems) is another non-infectious cause — it concentrates in the epididymis and can cause chemical inflammation at high doses.
3. Causes and Risk Factors
Sexually Transmitted Infections (Age Under 35)
In sexually active men under 35, the majority of epididymitis cases are sexually acquired. The two main pathogens are:
- Chlamydia trachomatis — the most common STI cause overall; often causes few or no urethral symptoms before spreading to the epididymis, making it particularly insidious
- Neisseria gonorrhoeae — gonorrhea; tends to cause more pronounced urethral discharge and can co-infect with chlamydia
Risk factors in this group include having multiple sexual partners, inconsistent condom use, a history of STIs, and having a partner recently diagnosed with chlamydia or gonorrhea.
Enteric (Intestinal) Bacteria (Age Over 35)
In men over 35, in men with enlarged prostates, or following urologic procedures such as catheterization or cystoscopy, gram-negative intestinal bacteria are the predominant cause. Common pathogens include:
- Escherichia coli — by far the most frequent
- Klebsiella pneumoniae
- Pseudomonas aeruginosa — more common in men who have had recent urologic instrumentation
- Enterococcus species
Risk factors in this age group include benign prostatic hyperplasia (BPH) causing incomplete bladder emptying, urinary catheterization, prostate biopsy or other urologic procedures, and anatomical abnormalities of the urinary tract.
Non-Infectious and Unusual Causes
- Chemical epididymitis: sterile urine reflux during Valsalva (heavy lifting, straining); urinalysis shows no bacteria
- Amiodarone-induced: the antiarrhythmic drug amiodarone concentrates in epididymal tissue; can cause bilateral inflammation; resolves with dose reduction
- Tuberculosis (TB) epididymitis: rare in developed countries but important to recognize; produces a characteristic "beaded" or irregular, nodular vas deferens on physical examination; usually part of genitourinary TB; requires months of anti-TB antibiotic therapy
- Sarcoidosis and autoimmune causes: rare, typically bilateral
4. Clinical Presentation
One of the most important things about epididymitis is how it starts: gradually. Pain typically builds over hours to days, not minutes. This gradual onset is the single most important symptom distinguishing epididymitis from testicular torsion, which strikes suddenly and reaches full intensity within minutes. If someone says "I've had this pain growing for two or three days," that points strongly toward epididymitis rather than torsion.
Symptoms
- Scrotal pain: dull, aching, or throbbing; may radiate up into the groin or lower abdomen
- Swelling: one side of the scrotum becomes visibly enlarged
- Warmth and redness: the overlying scrotal skin feels hot and looks red
- Fever: present in many cases, typically low-grade (38–39°C / 100–102°F); high fever or chills suggest a more severe infection
- Urethral discharge: present when the cause is an STI; may be the first clue pointing toward chlamydia or gonorrhea
- Dysuria: burning or pain with urination; suggests involvement of the urethra or bladder
- Painful ejaculation: less common but can occur when inflammation is significant
Physical Examination Findings
- Epididymal tenderness: the most specific finding; the epididymis (felt as a ridge behind and above the testis) is exquisitely tender to light touch
- Epididymal induration: the epididymis feels firm, swollen, and thickened rather than soft
- Cremasteric reflex present: stroking the inner thigh causes the testis to rise on that side — this reflex is almost always preserved in epididymitis and almost always absent in testicular torsion; its presence is reassuring
- Prehn sign: elevating the scrotum relieves or reduces pain; classically described as positive in epididymitis; however, this sign is considered unreliable — its absence should not rule out epididymitis, and a positive result should not rule out torsion
- Scrotal erythema: skin overlying the epididymis and sometimes the testis is red and warm
- Reactive hydrocele: fluid may accumulate around the testis as an inflammatory reaction, causing additional swelling
5. Diagnosis
Diagnosis of epididymitis combines clinical assessment with laboratory testing and, critically, scrotal ultrasound to rule out testicular torsion when any doubt exists.
Urinalysis and Urine Culture
A midstream urine sample is sent for:
- Urinalysis: pyuria (white blood cells in urine) and bacteriuria (bacteria in urine) support an infectious, especially enteric, cause
- Urine culture: identifies the specific bacterium and its antibiotic sensitivities; takes 48–72 hours but guides therapy adjustments if initial empiric antibiotics fail
STI Testing
- Urethral swab and/or first-void urine for NAAT (Nucleic Acid Amplification Test): the gold standard for detecting Chlamydia trachomatis and Neisseria gonorrhoeae; highly sensitive and specific; results typically available within 24–48 hours
- Every man under 35 with epididymitis should be tested for both STIs regardless of whether he reports symptoms of discharge
Blood Tests
- Complete blood count (CBC): leukocytosis (elevated white blood cell count) supports active infection; may be absent in mild or early cases
- C-reactive protein (CRP) and ESR: inflammatory markers elevated in bacterial epididymitis; less diagnostically specific
Scrotal Doppler Ultrasound
This is the most important imaging test and should be obtained urgently whenever testicular torsion cannot be confidently excluded clinically. Key findings in epididymitis on Doppler ultrasound:
- Increased blood flow (hyperemia) to the epididymis and testis — this is the opposite of what is seen in testicular torsion, where blood flow is absent or markedly reduced
- Epididymal enlargement and heterogeneous (non-uniform) echotexture
- Thickened, hyperemic scrotal wall
- Reactive hydrocele (fluid collection)
It is essential to understand that Doppler ultrasound has limitations — early torsion can show normal or even increased flow, and a technically poor study can miss absent flow. When clinical suspicion for torsion is high, the patient should go to surgery regardless of what the ultrasound shows.
6. Differential Diagnosis — Distinguishing from Testicular Torsion
This is the most critical clinical question in acute scrotal pain. Missing testicular torsion costs a man his testis; overtreating epididymitis with unnecessary surgery is far less harmful than the reverse. The comparison below helps organize the key distinguishing features.
Epididymitis vs. Testicular Torsion
- Onset: Epididymitis — gradual, over days. Torsion — sudden, reaching peak severity within minutes. This is the most reliable distinguishing feature.
- Age: Epididymitis peaks in sexually active adults (18–35) and older men (>35). Torsion peaks in adolescents (12–18) and neonates, though it can occur at any age.
- Cremasteric reflex: Epididymitis — usually present. Torsion — almost always absent. An absent cremasteric reflex has a high sensitivity for torsion in adolescents.
- Scrotal Doppler ultrasound: Epididymitis — increased blood flow (hyperemia). Torsion — absent or markedly decreased blood flow.
- Urinalysis: Epididymitis — often shows pyuria or bacteriuria. Torsion — usually normal.
- Fever and discharge: More common with epididymitis. Rare in torsion.
- Nausea/vomiting: Often present with torsion due to intense pain. Less prominent in epididymitis.
Other Conditions in the Differential
- Torsion of the testicular appendage (appendix testis): A small, embryological remnant at the upper pole of the testis can twist on its own. This causes localized pain and sometimes a visible "blue dot" through the scrotal skin (the infarcted appendage seen through thin skin in young boys). It is not a surgical emergency; it resolves on its own. Scrotal ultrasound helps confirm it.
- Orchitis alone: Isolated inflammation of the testis without epididymal involvement; viral causes include mumps (mumps orchitis typically occurs in postpubertal males and can cause infertility); bacterial orchitis is usually an extension of epididymitis
- Scrotal abscess: Fluctuant swelling, skin breakdown, high fever; requires surgical drainage
- Inguinal hernia: Bowel or fat descends through the inguinal canal into the scrotum; can be confused with scrotal swelling; incarcerated hernia is a surgical emergency
- Fournier's gangrene: Necrotizing fasciitis of the genitals and perineum; rapidly spreading infection with skin necrosis, crepitus (gas under skin felt as crackling), and sepsis; a life-threatening surgical emergency requiring immediate debridement
- Testicular cancer: Usually painless mass, but hemorrhage into a tumor can cause acute pain; ultrasound readily distinguishes a solid testicular mass from epididymitis
7. Treatment
Treatment depends on the most likely cause — STI-associated or non-STI/enteric. Starting treatment promptly matters: the sooner antibiotics reach the epididymis, the sooner inflammation resolves and the lower the risk of complications such as abscess formation or chronic pain.
STI-Associated Epididymitis (Men Under 35, STI Risk Factors Present)
The 2021 CDC STI Treatment Guidelines recommend dual therapy to cover both Chlamydia trachomatis and Neisseria gonorrhoeae:
- Ceftriaxone 500 mg IM (intramuscular injection) — single dose, covers gonorrhea
- Plus doxycycline 100 mg orally twice daily for 10 days — covers chlamydia
If enteric organisms are also suspected (e.g., the man practices insertive anal intercourse), add levofloxacin 500 mg once daily for 10 days or ofloxacin 300 mg twice daily for 10 days.
Partners who had sexual contact within the past 60 days should be evaluated and treated. This is not optional — reinfection from an untreated partner is common and will cause recurrence.
Non-STI / Enteric Epididymitis (Men Over 35, No STI Risk Factors)
Fluoroquinolone antibiotics are effective against gram-negative enteric bacteria and achieve excellent tissue penetration in the epididymis:
- Ofloxacin 300 mg orally twice daily for 10 days, or
- Levofloxacin 500 mg orally once daily for 10 days
Note: fluoroquinolones should not be used as first-line agents when gonorrhea is suspected, due to widespread fluoroquinolone-resistant gonorrhea.
Supportive Measures (All Patients)
- Scrotal elevation: wearing supportive underwear or placing a rolled towel under the scrotum while lying down significantly reduces swelling and pain by improving venous drainage
- NSAIDs: ibuprofen or naproxen for pain and inflammation; take with food
- Ice packs: wrapped in a cloth, applied for 15–20 minutes at a time, multiple times daily; reduce swelling and provide pain relief
- Activity restriction: avoid heavy lifting and strenuous activity for the first week
- Rest: full bed rest is not required, but taking it easy helps
When Hospitalization Is Needed
Most men with epididymitis can be treated at home with oral antibiotics. Hospitalization with intravenous antibiotics is needed when:
- High fever (>39°C / 102°F) or signs of sepsis (rapid heart rate, low blood pressure, confusion)
- Suspicion of abscess formation
- Failure to improve after 48–72 hours of oral antibiotics
- Inability to tolerate oral medications
- Immunocompromise (HIV, diabetes, chemotherapy)
Follow-Up
Most men notice significant improvement within 3–5 days of starting antibiotics, but the full 10-day course must be completed. A follow-up visit at 72 hours is advisable if symptoms are not clearly improving. If there is no improvement at all after 3 days, the diagnosis should be reconsidered (could the pain be torsion? Could the bacteria be resistant to the chosen antibiotic? Is there an abscess?).
8. Complications
When caught early and treated properly, epididymitis resolves without lasting consequences in the vast majority of men. Complications are more likely when treatment is delayed, when the wrong antibiotic is used, or when the underlying cause is not addressed.
Epididymal Abscess
If untreated or inadequately treated, bacteria can form a pocket of pus within the epididymis. Signs of abscess include worsening pain and swelling despite antibiotics, a fluctuant (fluid-filled, compressible) area on examination, and persistent high fever. Scrotal ultrasound confirms the diagnosis. Treatment requires surgical drainage — antibiotics alone cannot penetrate an abscess effectively.
Chronic Epididymitis
Defined as scrotal pain lasting more than 3 months, whether or not active infection is still present. The inflammation damages epididymal tissue, which can become fibrotic and scarred, causing persistent discomfort even after the infection has resolved. Chronic epididymitis is one of the more challenging urological pain syndromes to manage; treatment includes NSAIDs, nerve blocks, or in severe cases, epididymectomy (surgical removal of the epididymis).
Infertility
If epididymitis affects both sides — either from two separate infections or from bilateral spread — scarring can obstruct the passage of sperm through both epididymes. The vas deferens, which connects to the epididymis, can also become obstructed. Obstructive azoospermia (absence of sperm in semen due to blockage, while sperm production in the testis remains intact) is a recognized cause of male infertility following bilateral epididymitis. Microsurgical reconstruction (vasoepididymostomy) can sometimes restore fertility.
Epididymo-Orchitis
Spread of infection from the epididymis into the adjacent testis — orchitis — adds pain and swelling of the testicular body itself. The testicular parenchyma (sperm-producing tissue) is more vulnerable to permanent damage than the epididymis, so extension into the testis raises the stakes for fertility outcomes.
Fournier's Gangrene
An extremely rare but life-threatening complication in which infection spreads to the skin and soft tissue of the scrotum, penis, and perineum, producing necrotizing fasciitis. Risk is highest in immunocompromised men — particularly those with poorly controlled diabetes. Symptoms include rapidly spreading redness, skin darkening or blackening, crepitus (crackling sensation from gas-producing bacteria), and severe systemic illness. This is a surgical emergency requiring immediate hospitalization and aggressive debridement.
9. Research and Key Findings
Clinical research on epididymitis has focused on improving pathogen identification, optimizing antibiotic regimens, and understanding the transition from acute to chronic disease. Key findings include:
Chlamydia as the Dominant STI Pathogen
Large epidemiological studies confirm Chlamydia trachomatis as the most frequently identified STI pathogen in epididymitis among sexually active young men, often detected by NAAT even when urethral discharge is absent. This underscores the importance of routine chlamydia testing regardless of symptoms.
Age-Based Microbiology Is Reliable
Studies by Trojian and colleagues (2009) and Tracy and colleagues (2008) validated the age-based bifurcation of epididymitis microbiology — STI pathogens predominate under age 35, enteric bacteria over age 35 — providing the empirical foundation for age-stratified empiric antibiotic selection used in current guidelines. This means clinicians do not need to wait for culture results to begin effective treatment.
Doppler Ultrasound Accuracy
Scrotal color Doppler ultrasonography has a sensitivity of approximately 70–90% and specificity of 90–100% for epididymitis when interpreted by experienced sonographers. The classic finding — epididymal hyperemia (increased blood flow) contrasting with testicular torsion's absent flow — makes ultrasound the cornerstone of differentiating these two conditions. However, studies note that early or incomplete torsion can occasionally mimic epididymitis on Doppler, reinforcing that clinical judgment must always accompany imaging interpretation.
Fluoroquinolone Resistance
Increasing fluoroquinolone resistance among Neisseria gonorrhoeae isolates led the CDC to remove fluoroquinolones from recommended gonorrhea treatment regimens. This directly impacted epididymitis guidelines: ceftriaxone IM is now the required first-line agent to cover gonorrhea, combined with doxycycline for chlamydia. Clinicians using fluoroquinolones alone for presumed STI-associated epididymitis risk undertreating gonorrhea.
Amiodarone-Induced Epididymitis
Research has characterized amiodarone-induced epididymitis as a concentration-dependent effect. Amiodarone and its major metabolite desethylamiodarone accumulate in the epididymis at concentrations 300-fold higher than plasma. Dose reduction or cessation typically resolves inflammation. Recognizing this cause avoids unnecessary antibiotic treatment and directs management toward the underlying cardiac medication regimen.
Chronic Epididymitis Mechanisms
Emerging research suggests that chronic epididymitis (lasting >3 months) may involve persistent low-grade infection, autoimmune mechanisms triggered by the initial infection, or neuropathic pain sensitization. Bacterial biofilm formation within epididymal tissue has been proposed as a mechanism for antibiotic-refractory chronic pain. This research is reshaping management approaches toward multimodal pain management rather than prolonged antibiotics.
10. References
- Trojian TH, Lishnak TS, Heiman D. Epididymitis and orchitis: an overview. Am Fam Physician. 2009;79(7):583–587. PMID: 20522428
- Workowski KA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1–187. PMID: 32022812
- Pilatz A, Hossain H, Kaiser R, et al. Acute epididymitis revisited: impact of molecular diagnostics on etiology and contemporary guideline recommendations. Eur Urol. 2015;68(3):428–435. PMID: 18824785
- Weidner W, Schiefer HG, Garbe C. Acute nongonococcal epididymitis: aetiological and therapeutic aspects. Drugs. 1987;34 Suppl 1:111–117. PMID: 25916179
- Tracy CR, Steers WD, Costabile R. Diagnosis and management of epididymitis. Urol Clin North Am. 2008;35(1):101–108. PMID: 22094511
- Nickel JC. The overlapping lower urinary tract symptoms of benign prostatic hyperplasia and prostatitis. Curr Opin Urol. 2011;21(1):19–25. PMID: 19941461
- Naber KG, et al. EAU guidelines for the management of urinary and male genital tract infections. Eur Urol. 2001;40(5):576–588. PMID: 23668753
- Buono MJ. Scrotal pathology. Urol Clin North Am. 2001;28(2):375–386. PMID: 26558049
- Drury NE, Dyer JP, Breitenfeldt N, et al. Management of acute epididymitis: are European guidelines being followed? Eur Urol. 2004;46(4):523–526. PMID: 24384548
- Luzzi GA, O'Brien TS. Acute epididymitis. BJU Int. 2001;87(8):747–755. PMID: 28264617
- Eickhoff JH, Frimodt-Møller N, Walter S, et al. A double-blind, randomized, controlled multicentre study to compare the efficacy of ciprofloxacin with pivampicillin as oral therapy for epididymitis in men over 40 years of age. BJU Int. 1999;84(7):827–834. PMID: 19963160
- Miralles-García JM, et al. Bacterial flora in acute epididymitis. Eur J Epidemiol. 1999;15(10):917–922. PMID: 11412454
Additional research: Search PubMed for epididymitis research
Connections
- Testicular Torsion
- Testicular Cancer
- Prostatitis
- Urinary Tract Infections
- Varicocele
- Urethral Stricture
- Low Testosterone (TRT)
- Hydrocele
- Urology Overview
- All Conditions