Published: 24 December 2020| Version 1 | DOI: 10.17632/3r8s7f4f85.1
Takeaki Sato


Background: Psoas abscess (PA) is an uncommon disease. Although PA is associated with significant morbidity and mortality, its epidemiology and clinical characteristics remain unknown. This study aimed to evaluate the epidemiological and clinical features and outcomes of patients with PA in a prefectural-wide study. Materials and Methods: This was a multicenter retrospective cohort study conducted between 2010 and 2012 in the Miyagi prefecture with a population of 2,344,062 in 2011. Adult patients with PA were enrolled from 71 secondary and tertiary care hospitals. Results: There were 57 patients with adult PA in the Miyagi prefecture. The median age of the patients was 72 years, and 67% patients were male. Fever and flank pain were the primary symptoms in 82% and 74% of patients, respectively. Ten patients (18%) had septic shock, and the hospital mortality rate was 12%. Secondary PA was present in 72% of cases, and the most common origin was pyogenic spondylitis. Of the patients with secondary PA, 44% had an epidural abscess. The most common pathogens were Staphylococcus aureus, and 11% (6 cases) of the cases were caused by methicillin-resistant S. aureus. Conclusion: In the Miyagi prefecture of Japan, the estimated prevalence of PA was 1.21/100,000 population years and hospital mortality was 12%. Secondary PA accounted for more than 70% of the cases, and S. aureus was the most common causative pathogen.


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1. Study design This was a multicenter retrospective cohort study. Settings: Using medical records, we collected the clinical data of patients with PA who were admitted between April 2010 and March 2012. Data collection was completed in March 2017. Participants: We selected patients with PA for analysis. The inclusion criterion was diagnosis of PA using CT by staff radiologists at each hospital. The exclusion criterion was transfer to another hospital within the same prefecture for acute phase management. 2.Data collection Data collection: Clinical background data including age, sex, body mass index (BMI), Charlson comorbidity index, and primary symptoms (fever and pain in the flank area) were collected. At the time of PA diagnosis, vital signs; time to diagnosis from onset of symptoms; presence of sepsis and septic shock; and laboratory data including the C-reactive protein level, white blood cell count, and platelet count and maximum abscess diameter on CT in the transaxial view were collected. Moreover, we recorded the causative pathogens, type of PA (primary or secondary), and the type of management (conservative or drainage, percutaneous or surgical). Clinical outcomes were analyzed using hospital mortality and hospital stay of survived patients as parameters. 3. Data definitions Primary abscess was defined as PA due to the hematogenous spread of an infection from a distant site. If PA from a distant site was unknown and blood culture was positive, it was defined as primary PA. Secondary PA was defined as PA due to the direct expansion of adjacent infectious processes. Fever was defined as an axial temperature of 38.3°C or higher at the time of primary symptoms. Pathogens were identified as bacteria isolated from pus culture and/or two sets of blood cultures. Samples were considered to be contaminated if common skin bacteria (Corynebacterium spp., Bacillus spp., Propionibacterium spp., Viridans streptococci, Micrococcus spp., and coagulase-negative Staphylococcus spp.) were cultured in only one of the blood cultures. Sepsis was defined as a systemic inflammatory response syndrome induced by infection. Septic shock was defined as a state of acute circulatory failure characterized by persistent arterial hypotension unexplained by other causes per the Sepsis-2 definition. Conservative therapy was defined as intravenous antimicrobial use without drainage. CT-guided abscess drainage without open surgical procedures was defined as percutaneous drainage. If open surgical drainage was applied, cases were defined as “surgical” regardless of additional percutaneous drainage. The timing of the intervention was at the physician’s discretion. The maximum diameter of the abscess on CT was a single data set chosen from the largest abscess, even if there were bilateral PA.


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