Multiple Retroperitoneal Abscesses Caused by Citrobacter koseri Are Associated with a Poor Prognosis.

Citrobacter koseri causes opportunistic infections in various organs. We herein report an 84-year-old man with diabetes mellitus who presented to our hospital with left hip pain and walking difficulty. Computed tomography showed an extensive abscess with gas production, mainly in the left retroperitoneal space, caused by C. koseri infection. Despite daily cleaning of the wound and antimicrobial therapy (with surgical drainage), the patient developed repeated pneumonia and small bowel hemorrhaging caused by disseminated intravascular coagulation and died on day 65 of hospitalization. Overall, retroperitoneal abscesses caused by C. koseri are rare, and multiple abscesses may show a poor prognosis.