Recurrence and incidence of fistula after urgent drainage of an anal abscess. Long-term results.

Introduction: Anal abscess is the most frequent urgent proctological problem. The recurrence rate and reported incidence of fistula after drainage and debridement of an anal abscess is widely variable. The objective of this study is to analyse the long-term recurrence rate and the incidence of fistula after drainage and urgent debridement of an anal abscess.

Methods: Retrospective observational study of a prospective cohort with anal abscess of cryptoglandular origin. All patients (n = 303) were evaluated two months and one year after the intervention. At the 5 year, all the medical records were reviewed and a telephone call or appointment was made for an assessment if necessary. Specific antecedents of anal pathology, abscess characteristics, time and type of recurrence, presence of symptoms in the first revision and presence of clinical and/or ultrasound fistula were recorded.

Results: Mean follow-up 119.7 months. Recurrence rate 48.2% (82.2% in the first year). Two hundred twenty-two ultrasounds performed. Incidence of ultrasound fistula: 70% symptomatic vs. 2.4% asymptomatic (p < 0.001). Global incidence of fistula 40.3%. The history of anal pathology and the presence of symptoms in the postoperative review significantly increase the possibility of recurrence (p < 0.001). The fistula is statistically more frequent if the abscess recurs (p < 0.001).

Conclusion: After drainage and debridement of an anal abscess, half of the patients relapse and 40% develop fistula especially in the first year, so longer follow-ups are not necessary. Endoanal ultrasound for the evaluation of the presence of fistula is highly questionable in the absence of signs or symptoms.