Impact of Evaluating Antibiotic Concentrations in Abdominal Abscesses Percutaneously Drained

Background: Appropriate antibiotic therapy and prompt drainage are essential for optimal results with abdominal abscesses.

Methods: In this prospective study, 47 abdominal abscesses from 42 patients over 2 years who had percutaneous drainage were evaluated. Antibiotic concentrations were evaluated from the abscess fluid and correlated with clinical and microbiologic cure.

Results: Only 23% of patients had appropriate antibiotic selection with optimal concentrations for the bacteria recovered. Piperacillin/tazobactam, cefepime, and metronidazole provided adequate concentrations in all except the largest abscesses, whereas fluconazole required higher doses in all abscesses. Vancomycin and ciprofloxacin levels were inadequate in most abscesses. With gram-negative aerobes, the use of appropriate antibiotics resulted in a relatively higher incidence of presumed eradication (100% [4 of 4] vs 75% [9 of 12], P = .26). With ≥ 3 organisms identified, clinical failure was significant (58% vs 13%, P = .01).

Conclusions: For optimal treatment, abdominal abscesses require prompt drainage and properly selected antibiotics at adequate doses. Essential information can be obtained from abscess cultures and their antibiotic concentrations.