Higher Incidence of Pyogenic Liver Abscess in an Upper Midwest Hospital System: A 5-Year Study With Emphasis on Rural Impact.

INTRODUCTION: Incidences of hepatic abscesses are increasing nationally. Current estimates of national incidence range from 8 to 20 abscesses per 100,000 hospital admissions. Understanding risk factors is essential for efficient diagnosis and treatment of hepatic abscess. This study aimed to assess if hepatic abscess incidence in a Midwest cohort was higher in rural areas compared to metropolitan areas. Water infrastructure factors were also considered.

METHODS: A retrospective chart review was completed for all patients admitted with a diagnosis of hepatic abscess to an upper Midwest hospital system in South Dakota between Jan. 1, 2016 and Dec. 31, 2019. Microbiology cultures and patient demographic data were collected including age, gender, hometown, and ethnicity. Risk factors assessed included a history of abdominal surgery, gallbladder disease, sepsis, diverticulitis, cancer, and diabetes. The incidence of hepatic abscesses was calculated using the Poisson rate test and confidence interval equation. Averages of each risk factor were calculated. Finally, the hometowns were utilized to create a heat map of disease burden, which was then compared to the density of private wells in those areas.

RESULTS: There were 116 confirmed cases of adult hepatic abscess admitted to the hospital between 2016 and 2019. The corrected incidence was 95.66 abscesses per 100,000 hospitalized patients per year. Rural areas had a higher per capita incidence of abscesses and higher density of private wells.

CONCLUSIONS: The incidence of patients with hepatic abscesses was significantly higher than the national average in this single-center study. Demographics, especially geographic location, may play an important role in abscess rates. Rural location may be affecting the incidence of hepatic abscesses, and might be one explanation of the much higher than expected incidence found in this study. Water infrastructure, as defined as incidence of private wells in the area, could be a contributing factor as much of the rural area is reliant on untreated groundwater from wells. The study was limited by data availability on true water source usage for patients with hepatic abscesses. Another limitation to this study is the lack of multicenter involvement.