Introduction: Epididymitis is a common urologic disease with possible severe consequences such as abscess formation, testicular infarction, recurrent infection, chronic pain, spread of infection to sexual partners, and infertility. Clinical epididymitis is often treated with antibiotics in the absence of culture-proven bacterial infection. Bacterial epididymitis most likely arises from retrograde inoculation of the epididymis via the vas deferens in the setting of urinary tract infection. Can retrograde infection of the epididymis occur in men who have undergone vasectomy? The objective of this study was to determine if infection of the epididymis can occur via retrograde progression from the lower urinary tract following vasectomy.

Methods: Twenty-one adult Sprague Dawley rats were divided into three groups: bilateral sham vasectomy followed by left-sided sham inoculation (Group A); bilateral sham vasectomy followed by left-sided inoculation of Escherichia coli into the vas deferens (Group B) and; bilateral vasectomy followed by left-sided inoculation of E. coli into the vas deferens (Group C). Three days after innoculation animals were sacrificed and the distal epididymidies contiguous with the proximal vas deferens were removed for routine histology. In other animals the epididymidies and proximal vas deferens were removed for protein isolation. Protein samples were assayed for nine cytokines including IL-1a, IL-1b, IL-2, IL-4, IL-6, IL-10, TNFa, INFg, and GM-CSF via solution phase multiplex.

Results: Histologically, the proximal vas of vasectomized inoculated animals (Group C) was unchanged compared to sham operated, sham inoculated (Group A). Injection of E. coli into the vas deferens of sham vasectomized animals (Group B) resulted in the presence of leukocyte infiltrates in the proximal vas. The levels of the assayed cytokines were unaffected by vasectomy alone or vasectomy plus E. coli (Group C); however, IL-1a, IL-1b, and IL-4 were significantly elevated in the E. coli inoculated patent system (Group B). Further, in no case did injection of E. coli induce an inflammatory response in the contralateral epididymis/proximal vas.

Conclusion: Bacterial epididymitis in the rat results in the upregulation of the proinflammatory cytokines IL-1a, IL-1b, and IL-4, and vasectomy limits the retrograde transmission of infection to the epididymis. The incidence of bacterial epididymitis in a vasectomized population has not been addressed. The current data suggests that bacterial epididimitis following vasectomy is unlikely, and treatment with antibiotics should be limited.

	S-S	S-E	V-E
IL-1a	74.9 ± 11.3 a	883.7 ± 426.7 b	53.8 ± 4.9 a
IL-1b	197.2 ± 54.2 a	2238.8 ± 839.5 b	78.8 ± 3.8 a
IL-4	288.1 ± 65.7 a	439.7 ± 82.4 b	232.4 ± 18.7 ab

S-S is sham vasectomy with sham inoculum; S-E is sham vasectomy with injection of E. coli; V-E is vasectomy with E. coli injection. All values are in pg/µl ± standard error. Values labeled “a” do not differ from other values labeled “a” but do differ from values labeled “b”, p<0.05.