[A case of subphrenic abscess in a very elderly patient relieved by conservative treatment].

A patient in her 90s with rheumatoid arthritis was admitted to the hospital. She was brought to the emergency department with a complaint of a fever and diagnosed with a urinary tract infection on admission, and antimicrobial therapy was started. On day 8 of admission, abdominal ultrasonography revealed a right subphrenic abscess due to cholecystitis with perforation. The patient consulted with the Department of Surgery, but drainage was deemed difficult due to the anatomical location of the gallbladder, and conservative treatment with antibiotics was continued. After two months of intravenous antimicrobial therapy, the abscess shrank, and the patient was discharged from the hospital after switching to oral antimicrobial therapy. At a follow-up visit two weeks after discharge, the abscess was confirmed to have disappeared, the oral antimicrobial therapy was discontinued, with no abscess recurrence noted. The principle of treatment for subphrenic abscess is the administration of broad-spectrum antimicrobial agents that cover enterobacteria and anaerobes, and drainage at appropriate times. Indeed, drainage is performed in most of the reported cases of subphrenic abscesses. However, in very elderly patients or those in whom puncture is difficult, conservative treatment while carefully checking imaging findings and other potentially involved factors may be an option.