Causes

Epididymitis has a number of causes, including:

• Sexually transmitted disease (STD). STDs, particularly gonorrhea and chlamydia, are the most common cause of epididymitis in young, sexually active men.
• Other infections. Boys, older men and homosexual men are more likely to have epididymitis caused by a non-sexually transmitted bacterial infection. For men who've had urinary tract infections or prostate infections, bacteria may spread from the infected site to the epididymis. Rarely, epididymitis is caused by a fungal infection.
• The heart medication amiodarone. In some cases, this anti-arrhythmic medication causes inflammation of the epididymis. Epididymitis caused by amiodarone is treated by reducing the dose of amiodarone or by changing medications.
• Tuberculosis. In some cases, tuberculosis can cause epididymitis.
• Urine in the epididymis. Known as chemical epididymitis, this occurs when urine flows backward into the epididymis. It most commonly occurs with heavy lifting or straining.

Pathophysiology

Instrumentation and indwelling catheters are common risk factors for acute epididymitis. Epididymitis may also be accompanied by urethritis or prostatitis. Tuberculous epididymitis may be the presenting feature of genitourinary tuberculosis (TB), which develops via hematogenous spread. Other bloodstream infections may seed the scrotum, especially in children. In a study by Chiang et al, 2 of 7 infants had either Escherichia coliNeisseria meningitides sepsis associated with epididymo-orchitis

Causes

• The etiology of acute epididymo-orchitis varies depending the age of the patient and may involve a bacterial, nonbacterial infectious, noninfectious, or idiopathic process.  
• • Nonspecific bacterial infections: 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 N meningitides infections are rare. In homosexual men, infections with coliform bacteria are also a common etiology.
  • Sexually transmitted diseases (STDs): 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). Infections with Neisseria gonorrhoeae, Treponema pallidum, Trichomonas species, and Gardnerella vaginalis also occur in this population.
  • Tuberculous epididymitis: This can occur in endemic areas and is still the most common form of urogenital TB. It is believed to spread hematogenously and often involves the kidneys. Epididymo-orchitis may develop following bacille Calmette-Guérin (BCG) treatment for superficial bladder cancer (at a rate of 0.4%).
  • Viral epididymitis: This 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, coccidioidomycosis, blastomycosis, cytomegalovirus [CMV], candidiasis, CMV in HIV) have been implicated 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.  
  • Obstruction: 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; children may have various congenital abnormalities or functional voiding problems that increase the risk of reflux into the ejaculatory ducts.
  • Vasculitic syndromes: Acute epididymitis-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%).  
  • Amiodarone epididymitis is secondary to high drug concentrations, usually in the head of the epididymis, and can occur in up to 3-11% of patients taking the drug. 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 anti-amiodarone HCl antibodies that subsequently attack the epididymis, resulting in the symptoms of epididymitis. Histological 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 be a precipitating event.
  • Some cases are idiopathic.
• Etiology of chronic epididymitis  
• • Inadequate treatment of acute epididymitis
  • Recurrent epididymitis
  • Associated with a granulomatous reaction (most commonly Mycobacterium tuberculosis)  
  • Associated with a chronic disease process such as Behçet syndrome 
• Etiology of acute orchitis  
• • Viral: Mumps orchitis was once the most common etiology; however, since the introduction of the mumps vaccine in 1985, this has been virtually eliminated. 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. 
  • Bacterial and pyogenic infections: Infections with E coli, Klebsiella species, Pseudomonas species, Staphylococcus species, and Streptococcus species are unusual. 
  • Granulomatous: T pallidum, M tuberculosis, Mycobacterium leprae, Actinomyces, and fungal diseases are rare.
  • Trauma 
  • Idiopathic