According to the Centers for Disease Control and Prevention (CDC), acute epididymitis consists of pain, swelling, and inflammation of the epididymis lasting less than 6 weeks. If the testis is involved, the condition is called epididymo-orchitis. In sexually active men older than 35 years, the most common cause is Chlamydia trachomatis and Neisseria gonorrhoeae. [1, 2]
The CDC guidelines recommend that the following tests and findings should be used to help diagnose acute epididymitis  :
Gram or methylene blue or gentian violet stain of urethral secretions demonstrating ≥2 white blood cells (WBC) per oil immersion field.
Positive leukocyte esterase test on first-void urine.
Microscopic examination of sediment from a spun first-void urine demonstrating ≥10 WBC per high-power field.
The epididymis is a coiled, tubular structure located along the posterior aspect of the testis. It allows for the storage, maturation, and transport of sperm, connecting the efferent ducts of the testis to the vas deferens. Inflammation of the epididymis can be acute (< 6 wk) or chronic and is most commonly caused by infection. An example of active inflammation of the epididymis is seen in the image below.
In a study of 237 patients with acute epididymitis, a causative pathogen was identified in 132 antibiotic-naive patients and 44 pretreated patients, The primary pathogen was Escherichia coli. Sexually transmitted infections were present in 34 cases (25 patients with Chlamydia trachomatis). 
In prepubertal boys, a viral infection may be the most likely explanation, according to a British study. The authors note that management should be supportive and antibiotics reserved for patients with pyuria or positive cultures. Urodynamic studies and renal tract ultrasonography are suggested for those with recurrent epididymitis. 
See Epididymitis for complete information on this topic.
Differentiation of Epididymitis From Testicular Torsion
Acute scrotal pain is a common complaint in the emergency room. One must have a high index of suspicion for testicular torsion, a true scrotal emergency, when evaluating patients with acute testicular or scrotal pain. [5, 6]
The most common misdiagnosis for testicular torsion is epididymitis. Often, this results from reliance on imperfect diagnostic tests over clinical judgment. Surgical exploration to definitively exclude torsion is not a high-risk procedure. Insist on rapid, in person, consultation by the urologist in suspect cases.
Ultrasonography is noninvasive and can help to differentiate epididymitis from testicular torsion. [7, 8] (The ultrasonogram below demonstrates the presence of epididymitis.) One area under investigation is the ability of emergency physicians to use bedside ultrasonography to accurately diagnose patients with acute scrotal pain.
In a retrospective chart review of 36 patients with a chief complaint of acute scrotal pain who were evaluated by an emergency physician (EP) with the aid of bedside ultrasonography, the ultrasonographic findings agreed with the results of confirmatory studies (radiology or surgery) in 35 of 36 patients. Beside ultrasonography therefore had a sensitivity of 95% and a specificity of 94%. 
In a study of 134 adult patients with acute epididymitis who underwent scrotal ultrasonography and palpation on first presentation, epididymitis was predominantly located in 24 cases (17.9%) in the head, 52 cases (38.8%) in the tail, and 58 cases (43.3%) in both. Common ultrasound features included hydrocele, epididymal enlargement, hyperperfusion, and testicular involvement. Under conservative treatment, ultrasound parameters normalized without evidence of testicular atrophy, even in patients with epididymal abscess or concomitant orchitis. 
However, although the use of bedside ultrasonography to accurately diagnose patients with acute scrotal pain is promising, the skill level of EPs at using ultrasonography varies, and larger randomized, prospective, blinded studies must be performed to further evaluate the accuracy of these results.
Boettcher et al performed a retrospective study to differentiate torsion of the appendix testis (AT) from epididymitis and found that the best predictors for epididymitis were dysuria, a painful epididymis on palpation, and altered epididymal echogenicity and increased peritesticular perfusion found on ultrasound studies. For torsion of the AT, the best predictor was a positive blue dot sign (a tender nodule with blue discoloration on the upper pole of the testis). 
CRP and ESR
A study by Asgari et al suggested that C-reactive protein (CRP) levels and the erythrocyte sedimentation rate (ESR) may be useful in differentiating epididymitis from testicular torsion. In the prospective study, the investigators evaluated 120 patients with the diagnosis of an acute scrotum; serum CRP and ESR were drawn at the time of admission. Of the 46 patients diagnosed with epididymitis, 44 (95.6%) had elevation of the CRP level, while of the 23 with torsion, 1 (4%) had elevation of the CRP level. Of the 51 other patients with other noninflammatory causes of acute scrotum, none had significant elevation of the CRP level. In addition, the ESR was highest in the epididymitis group. The authors proposed cutoff values for distinguishing epididymitis from noninflammatory causes of acute scrotum of 24 mg/L for the CRP level and 15.5 mm/h for the ESR. 
As with bedside ultrasonography, the use of ESR and CRP is promising, but further investigations are necessary.
Emergency Department Care
Patients with testicular or scrotal pain require immediate evaluation in order to identify and quickly treat potential cases of testicular torsion. Although most cases of torsion occur in patients aged 12-18 years, testicular torsion should be considered in any patient aged 12-30 years who presents with a scrotal complaint. Obtain immediate urologic consultation if unable to clearly differentiate testicular torsion from epididymitis or other scrotal pathology.
In a 21-year retrospective study of 252 pediatric patients diagnosed with epididymitis or epididymo-orchitis, age at first presentation was 10.92 ± 4.08 years. The majority of cases occurred during the pubertal period (11-14 years), and few patients younger than 2 years were diagnosed with epididymitis (4%). A total of 69 boys (27.4%) experienced a second episode of epididymitis. Scrotal ultrasound results were consistent with epididymitis in 87.3% of cases (144 of 165). 
Acute epididymitis is treated with antibiotic therapy, analgesics for pain control, and supportive care, which includes scrotal elevation and support, application of an ice pack, and, in some cases, spermatic cord block.
Consult a urologist immediately if torsion is a possibility. Testicular torsion is a clinical diagnosis, and consultation should not be delayed for the performance of additional ancillary studies. Otherwise, most cases of epididymitis can be managed on an outpatient basis with follow-up with a urologist scheduled within 3-7 days.
In general, antibiotics should be used in all cases of epididymitis, regardless of a negative urinalysis or the urethral Gram stain result. Nonsteroidal anti-inflammatory agents or narcotic analgesics are also generally prescribed to patients with epididymitis.
However, in one study of epididymitis in 140 boys aged 2 months to 17 years (median, 11 y), only 5 of 140 patients had a proven bacterial infection. Given this low rate of a bacterial cause, the authors recommend a selective approach to antibiotic therapy in pediatric epididymitis. They suggest treating all young infants, regardless of urinalysis results, and older boys who have a positive urinalysis or culture. It is also recommended to presumptively treat sexually active adolescents with epididymitis for sexually transmitted infections. This study excluded boys with recent urologic surgery and known lower urinary tract anomalies. 
Prepubertal patients and older men require empiric coverage for coliform bacteria (enteric gram-negative bacilli or Pseudomonas). Both of these patient populations may be treated with trimethoprim-sulfamethoxazole (TMP-SMZ).
Fluoroquinolones are no longer recommended to treat gonorrhea in the United States. This change is based on an analysis of data from the Centers for Disease Control and Prevention’s (CDC’s) Gonococcal Isolate Surveillance Project (GISP). The data from GISP showed an 11-fold increase in the proportion of fluoroquinolone-resistant gonorrhea (QRNG) in heterosexual men, increasing from 0.6% in 2001 to 6.7% in 2006.  This limits treatment of gonorrhea to drugs in the cephalosporin class. Fluoroquinolones may be an alternative treatment option for disseminated gonococcal infection if antimicrobial susceptibility can be documented.
Most cases of epididymitis can be managed on an outpatient basis. However, admit the patient for parenteral therapy if any of the following are present:
Nausea or vomiting that interferes with oral therapy
Clinical evidence of an abscess (or inability to rule out an abscess)
Signs of toxicity or possible sepsis
Failure to improve during initial 72 hours of outpatient management
Immunocompromised patient with significant signs or symptoms
Initiate treatment as discussed above.
The patient must be evaluated by a urologist within 3-7 days of presentation. This follow-up is mandatory, as a testicular tumor occasionally is the true cause of the symptoms.
The patient must receive detailed instructions for treatment, including reasons for immediate return.
Patients with epididymitis secondary to a potential sexually transmitted disease and all of their sexual contacts need referrals in order to screen and diagnose all comorbid sexually transmitted diseases, including human immunodeficiency virus (HIV) infection.
In pediatric patients with no prior urologic history and in the absence of bacteriuria, one retrospective study suggested that investigation for underlying urinary tract pathology should be carried out after the second episode.