Retrospective review of clinical presentations, microbiology and outcome of psoas abscess in a regional hospital

Abstract

Background: The clinical features of psoas abscess in local setting, including the microbial causes, the prevalence and etiologies of secondary psoas abscess, have not been well described. Objective: To review the clinical features and outcome of patients with psoas abscess in a regional hospital Method: A retrospective study was conducted. Patients with psoas abscess who were admitted into Tuen Mun Hospital from 1st January 2006 and 31st December 2010 were included. The clinical presentations, etiologies, microbiology, treatment, hospital stay, ICU admission and outcome were reviewed. Results: Forty-two cases were included. Five cases developed psoas abscess after admission. The average age was 60.9 ± 16.4 years (ranged 27 to 96 years). Twelve of them had diabetes mellitus and seven of them were intravenous drug abusers. The most common presenting symptoms were back, hip or thigh pain (43% [16/37]). Fever was present on presentation in 41% (15/37) of cases and four patients presented with fever only. Diagnosis was made by computerized tomography scan in 95.2% (40/42) of all the cases. Twenty-three cases were considered to be secondary and the most common etiology was infective spondylitis or spondylodiscitis. The most causative organism of primary psoas abscess was Staphylococcus aureus while secondary psoas abscesses were more commonly caused by organisms from gastrointestinal and genitourinary tracts. There was no statistical difference in the proportions of cases with bacteremia (p=0.404) between primary and secondary psoas abscess. Primary psoas abscess appeared to be associated with higher mortality but not to the extent of statistical significance (26.3% [5/19] Vs 4.3% [1/23]; p=0.075) while secondary psoas abscess had longer length of hospital stay (mean 62.1 days Vs 34 days; p=0.007). Half of the cases were treated with CT guided drainage and six cases were treated conservatively. Others were treated with ultrasound guided or surgical drainage. The overall in-hospital mortality rate was 14.3% (6/42). There was no significant difference in the mortality regardless of the causative organisms, the presence of bacteremia and background of diabetes mellitus. Elderly patients (more than 70) appeared to have higher mortality (66.7% [4/6]Vs 25% [9/36]; p=0.063). Mortality was not shown to be related to the delay in making diagnosis. Conclusion: Psoas abscess is an uncommon condition. Most patients presented with only nonspecific symptoms leading to the difficulty in making an early diagnosis. A larger proportion of secondary psoas abscess was encountered and the etiology profile was different from oversea experiences.