Epididymitis: Practice Essentials, Anatomy, Etiology (original) (raw)

The exact etiology of acute epididymitis is unclear; however, it is believed to be caused by the retrograde passage of urine from the prostatic urethra to the epididymis via the ejaculatory ducts and vas deferens. Obstruction of the prostate or urethra and congenital anomalies create a predisposition for reflux. Normally, the oblique angle of the ejaculatory ducts through the dense prostatic tissue prevents reflux. Fifty-six percent of men older than 60 years who have epididymitis exhibit concurrent bladder outlet obstruction (BOO), such as a urethral stricture or benign prostatic hyperplasia (BPH).

Reflux may also be induced by Valsalva maneuvers or strenuous exertion. This can be seen in athletes such as weight lifters. Epididymitis is commonly found to develop during strenuous exertion in conjunction with a full bladder.

Instrumentation and indwelling catheters are common risk factors for acute epididymitis.

Epididymitis may be accompanied by urethritis or prostatitis.

Acute epididymo-orchitis

Infection that is severe and extends to the adjacent testicle is termed acute epididymo-orchitis. [2] The etiology of acute epididymo-orchitis varies with the age of the patient and may be a bacterial, nonbacterial infectious, noninfectious, or idiopathic process.

Infections with urinary coliforms (eg, E coli, Pseudomonas species, Proteus species, Klebsiella species) are the most common cause in children and in men older than 35 years. Ureaplasma urealyticum, Corynebacterium species, Mycoplasma species, and Mima polymorpha have also been isolated. Systemic Haemophilus influenzae and Neisseria meningitides infections are rare. In men who are the insertive partner during anal intercourse, infections with coliform bacteria are also a common etiology. [3]

Chlamydia is the most common cause in sexually active men younger than 35 years (accounting for up to 50% of cases, although laboratory evidence of chlamydia may be absent in up to 90% of cases). [4] Infections with the following pathogens also occur in this population:

Tuberculous epididymitis can occur in endemic areas and is still the most common form of urogenital tuberculosis (TB). It is believed to spread hematogenously and often involves the kidneys.

Epididymo-orchitis may develop following bacillus Calmette-Guérin (BCG) treatment for superficial bladder cancer (at a rate of 0.4%).

Viral epididymitis is thought to be the predominant etiology of pediatric epididymitis. It is defined by the absence of pyuria. Although mumps is the most common viral cause of epididymitis, coxsackievirus A, varicella, and echoviral infections have also been identified.

Other rare infections (eg, brucellosis, [5] coccidioidomycosis, blastomycosis, cytomegalovirus [CMV], candidiasis, CMV in human immunodeficiency virus [HIV] infection, nontuberculous mycobacteria) have been implicated in epididymitis but usually occur in immunocompromised hosts.

Roughly 1 in 1000 men who undergo vasectomy describe a postvasectomy pain syndrome of chronic, dull, aching pain in the epididymis and testicle. The pain is most likely secondary to chronic epididymal congestion of sperm and fluid that continues to be produced after the vasectomy. The epididymis can become distended from back pressure of this fluid, particularly following the close-ended vasectomy technique. When sperm extravasates from the end of the vas deferens, such as can occur in the open-ended vasectomy technique, a sperm granuloma may develop, with a resulting inflammatory reaction.

Men older than 40 years may have BOO (eg, BPH) or a urogenital malformation that predisposes them to urethrovasal reflux and the development of epididymitis. Such reflux can also be induced iatrogenically after certain surgical procedures, such as transurethral resection of the ejaculatory ducts, resulting in epididymitis. It can also be a result of heavy physical activity such as weight lifting.

In children, infection is less common an etiology. One study of a pediatric emergency department found only 4 (4.1%) of 97 children diagnosed with epididymitis had a positive urine culture. [6] Children may have various congenital abnormalities or functional voiding problems that increase the risk of reflux into the ejaculatory ducts. For example, epididymitis may be related to urethral abnormalities, an ectopic ureter, an ectopic vas deferens, detrusor sphincter dyssynergia, or vesicoureteral reflux. In rare cases, children with anorectal malformations and resulting rectourinary fistulae may have resulting bacterial causes of epididymitis. [7]

Acute epididymo-orchitis has been described in 12-19% of individuals with Behçet syndrome. It is also associated with Henoch-Schönlein purpura in the pediatric population, most likely as part of a systemic inflammatory process. Up to 38% of patients with Henoch-Schönlein have scrotal involvement (range, 2-38%).

Epididymitis is a rare adverse effect of long-term amiodarone use, occurring in less than 1% of patients taking the drug, with onset ranging from 4 to 71 months after starting amiodarone. [8] Epididymitis in these patients develops secondary to high drug concentrations, usually in the head of the epididymis. This is a dose-dependent phenomenon and typically occurs at dosages greater than 200 mg daily. Epididymal levels of the drug are up to 300 times those of the serum, resulting in antiamiodarone HCl antibodies that subsequently attack the epididymis, resulting in the symptoms of epididymitis. Histologic analysis reveals focal fibrosis and lymphocytic infiltration of epididymal tissues.

Sarcoidosis affects the genitourinary system in up to 5% of cases, typically presenting with epididymal nodules. Trauma to the scrotum can also be a precipitating event, while some cases are idiopathic.

Etiology of chronic epididymitis

The etiology of chronic epididymitis includes the following:

Etiology of acute orchitis

Causes of acute orchitis include the following:

With regard to a viral etiology, roughly one third of postpubertal boys with mumps have concomitant orchitis. Coxsackievirus type A, varicella, and echoviral, adenoviral, enteroviral, influenzal, and parainfluenzal infections are rare.