Epididymitis rates in Australian hospitals 2009-2018: Ecological analysis

Objectives: To investigate rates of acute epididymitis diagnosed in Australian hospital settings. Methods: Yearly hospital admission and emergency department (ED) rates of epididymitis as primary diagnoses were calculated for 15-44-year-old men for three states (Victoria, New South Wales, Queensland) from 2009 to 2014 using population denominators. Zero inflated Poisson regression models were used to analyse variation in rates by year, age, and residential area. Additionally, we investigated national epididymitis admission trends from 2009 to 2018 using generalised linear models. Results: Between 2009 and 2014, there was a total of 7375 admissions and 17 281 ED presentations for which epididymitis was the main reason for care. Most epididymitis diagnoses (94.0% in admissions, 99.7% in EDs) were without abscess, and 2.5% of admissions were for chlamydial epididymitis. Almost a quarter (23.3%) of epididymitis diagnosed in EDs resulted in hospital admission. In 2014, the epididymitis rate per 100 000 men was 38.7 in admissions and 91.9 in EDs. Comparing 2014 with 2009, the overall epididymitis diagnosis rate increased in admissions by 32% (adjusted incident rate ratio (aIRR) 1.32, 95% CI 1.20 to 1.44) and in ED attendances by 40% (aIRR 1.40, 95% CI 1.31 to 1.49). By age, the highest rates were among men 35-44 years in admissions and men 15-24 years in EDs. National admission rates of epididymitis during 2009-2018 showed a similar pattern. Conclusion: Rates of epididymitis diagnosis in hospital admission and ED presentations increased. Different age-related rates in these settings suggest a different aetiology or differential severity by age group.