Etiology and outcome of iliopsoas muscle abscess in Korea; changes over a decade

Objectives: Iliopsoas muscle abscess (IPA) is considered a rare disease whose etiology has changed depending on the country and antibiotic selection pressure. This study evaluates the changes in etiology, clinical outcome, and risk factors for mortality for IPA. Methods: We reviewed the medical records of a total of 116 patients with IPA who were admitted to 4 university hospitals in Korea over the 11 years, and compared the etiology between 2001 and 2006 (period 1, n=44) and 2007-2012 (period 2, n=72). Results: Among 75 cases with a definitive microbial diagnosis, the predominant etiological organisms were Staphylococcus aureus (45.3%), followed by Mycobacterium tuberculosis (14.7%) and Klebsiella pneumoniae (9.3%). The percentage of MRSA in period 2 increased remarkably compared to period 1, from 25% to 44.4%, and incidence of M. tuberculosis from 7.1% to 19.1%, although these were not statistically significant. The overall mortality was 6.8% in period 1, and 13.9% in period 2, and sepsis as an initial manifestation (OR 293.5, CI 7.1-12,034.4, P=0.003) and serum creatinine level (OR 0.43, CI 0.23-0.80, P=0.008) were independent predictors of mortality. Invasive procedure improved the prognosis in cases with microbiologic confirmed pyogenic psoas abscess (46/50 [92%] vs. 9/14 [64.3%], P=0.008). Conclusion: The incidence of MRSA as a cause of IPA is on the increase. Although the overall prevalence of tuberculosis is decreasing, tuberculosis is still an important cause of IPA. Initial clinical status and invasive intervention can lead to favorable outcomes.