Inadequate Antibiotic Therapy Results in Higher Recurrence Rate after Drainage of Complicated Peri-Rectal Abscess.

Background: Recommended treatment for complicated peri-rectal abscess is incision and drainage (I&D) in conjunction with antibiotics. However, there is no standard antibiotic regimen for post-operative therapy described in the published literature. Our hypothesis was that appropriate post-operative antibiotic therapy after emergency I&D of complicated peri-rectal abscess will improve patient outcomes. Methods: Data from 58 patients with complicated peri-rectal abscess who underwent emergency I&D were analyzed retrospectively. Demographic, microbiologic, and antibiotic data were abstracted. Adequateness of antibiotics was judged by susceptibility data when available or by comparing the antibiotic spectrum with the type of organisms grown in culture when susceptibility data were not available. The Student t -test and χ ² test were used to analyze continuous and categorical variables, respectively. Multivariable analysis was used to adjust for confounding variables influencing recurrence rates. Results: Of the 58 patients reviewed, 12 were excluded because there was no culture information available or the culture showed no growth. Of the remaining 46 patients, 33 (72%) were male and 29 (63%) were African American. The mean age was 39.4 ± 16.4 years and the Body Mass Index was 28.4 ± 6.6 kg/m ² . Culture data revealed mixed aerobic/anaerobic organisms in 17 (37%), mixed aerobic organisms in 15 (32.6%), gram-positive organisms in 9 (19.6%), gram-negative organisms in 2 (4.4%), and other organisms in 3 (6.6%). Twenty-five patients (54.4%) received adequate antibiotic coverage with the remainder inadequately covered. The inadequate antibiotic therapy cohort had a higher re-admission rate for abscess recurrence (n = 6 [28.6%] versus n = 1 [4%]; p = 0.021). More than half were readmitted 30 days or more after the index procedure. There were no differences in length of stay (LOS), intensive care unit LOS, or Charlson Comorbidity Index between the groups. Conclusion: Inadequate antibiotic coverage after I&D of complicated peri-rectal abscess resulted in a six-fold increase in the re-admission rate. A standard oral protocol combining antibiotics covering typical gram-positive, gram-negative, and anaerobic organisms should provide adequate coverage after surgical drainage. Additional prospective studies are needed to elucidate the optimal antibiotic regimen for these patients.