Acute epididymitis

Acute epididymitis may be caused by many different infectious organisms and a few non-infectious causes.[1][2] The aetiology of bacterial epididymitis is largely dependent on age, sexual practices, and the presence of urinary tract abnormalities or history of instrumentation.[1][14]

Studies have highlighted a shift in age distribution, causative organism, and the importance of sexual activity on the aetiology of epididymitis.[14] Among sexually active men of all ages, STI pathogens including Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma genitalium are common causes of epididymitis.[15] Men who are the insertive partner during anal intercourse may also develop acute epididymitis from enteric organisms (e.g., Escherichia coli).[15]

In older men (>35 years), infection may be due to non-sexually transmitted infection with common uropathogens, such as Escherichia coli and Proteus sp.[14] In this group, infection may also be associated with other risk factors, such as bladder outlet obstruction, recent instrumentation of the urinary tract, or systemic illness.[1][14][15]

The delineation of patients with epididymitis by age is arbitrary, and a degree of crossover exists in terms of aetiology. While some sexual practices are significantly associated with the presence of STIs, half of all STI pathogens were detected in sexually active people who did not report such risks.[16] This highlights the importance of screening all sexually active men with epididymitis for STI pathogens.

Tuberculous epididymitis may occur in endemic areas. The epididymis is a common site of haematogenous implantation of the tuberculosis bacilli following primary pulmonary infection and may remain latent for decades.[17][18] Tuberculous epididymo-orchitis is also a rare complication of intravesical BCG therapy for bladder cancer.[17][19] Epididymitis is an uncommon complication of brucellosis. Infection with brucella primarily occurs in endemic areas from direct contact with infected animals or ingestion of their non-pasteurised milk.[12] Candidal infection is an uncommon cause of epididymitis. Men at risk of Candida sp. infection are usually immunosuppressed (e.g., diabetes) and have had instrumentation of the urinary tract.[20][21]

Viral epididymitis is rare in the adult population, but an increase of mumps epididymitis has been seen in the UK due to the 2005 mumps epidemic in one cohort of non-immunised adults.[3] In children, epididymitis may be a post-infectious inflammatory phenomenon following a viral infection.[11][22]

Rare non-infectious causes of acute epididymitis include a reversible sterile epididymitis resulting from therapy with the antiarrhythmic drug amiodarone,[4] and an association with vasculitic processes in Behçet's syndrome and Henoch-Schönlein purpura.[5][6]

The pathophysiology of acute epididymitis is postulated to occur secondary to retrograde ascent of urinary pathogens from the urethra and bladder, via the ejaculatory ducts and vas deferens, to the epididymis.[12] The inflammatory process starts in the tail of the epididymis and subsequently spreads to the body and head of the epididymis. In many cases, the testis is involved in the inflammatory process, and the condition is referred to as epididymo-orchitis. The mechanism underlying non-bacterial epididymitis, whether drug-induced or vasculitic, is unknown.

Classification based on aetiological factors

Bacterial infection[1][2]

Sexually transmitted infection (Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma genitalium) in sexually active men.
Enteric pathogens in men who are the insertive partner in anal intercourse.
Non-sexually transmitted infection (enteric pathogens, such as Escherichia coli, tuberculosis, brucella, or candida infection).

Viral

Mumps orchitis may occur as part of an outbreak, as reported in the UK in 2005-2006.[3]

Drug-induced

A reversible, sterile epididymitis is a rare adverse effect of therapy with the anti-arrhythmic drug amiodarone.[4]

Vasculitic

Rare cases of epididymitis have been reported in patients with Behçet's syndrome and Henoch-Schönlein purpura.[5][6]

Idiopathic

No apparent risk factors, and cause remains unknown.

Aetiology

Pathophysiology

Classification

Classification based on aetiological factors