The Aetiology and Treatment Outcomes of Epididymo-Orchitis: A 2025 Clinic-Based Review

Background: Epididymo-orchitis can be caused by sexually transmitted pathogens, including Neisseria gonorrhoeae, Chlamydia trachomatis, and Mycoplasma genitalium, or entero-bacteria. The aim of this study was to explore the demographics, microbiological findings, and treatment outcomes of patients presenting to a tertiary sexual health clinic with epididymo-orchitis. Methods: We reviewed the clinical notes of 200 randomly selected patients seen in the clinic with a diagnosis of epididymo-orchitis between 2021 and 2025. We extracted data on demographics, microbiological findings, follow-up, and clinical response rate to treatment. Results: The median age was 33 years (Interquartile range (IQR) = 24–44), 97 (49%) identified as MSM, 11 (6%) were living with HIV (all MSM), and 55 out of the 86 HIV-negative MSM (64%) were using HIV pre-exposure prophylaxis. In total, 35 (18%, 95% confidence intervals = 12.5–23.5%) people were diagnosed with a causative organism: 17 (9%) C. trachomatis, 10 (5%) N. gonorrhoeae, 7 (4%) M. genitalium, 3 (2%) Escherichia coli. Overall, 91 out of 200 (46%) had a documented partner notification plan. Conclusions: A minority of men attending our sexually transmitted infection clinic with clinical epididymo-orchitis have positive microbiology, including M. genitalium. More work is needed to understand the clinical pathophysiology of epididymo-orchitis to streamline treatment algorithms.