Perianal Abscess Recurrence and Fistula Formation: Antibiotics Following Incision and Drainage Trial

Most perianal abscesses (PA) result from an infection originating in anal crypts that extend into anal glands in the intersphincteric plane. Patients commonly present to the ER and usually require surgical intervention, which poses a burden on the healthcare system. If left undrained, a PA can expand into the adjacent tissues as well as progress to systemic infection. One of the major complications of PA are perianal fistulae; the creation of a tract between the anal canal and the perianal skin that is lined with granulation tissue or skin cells. Up to 1/3 of patients with a PA will develop a fistula; which occurs if a PA drains spontaneously through the perianal skin, and the infection becomes chronic. If this happens, surgical intervention is needed and abscesses may reoccur. Post incision and drainage (I\&D) antibiotics in PA have been used to address complications but their use is still controversial and there are no specific recommendations on their use to prevent the formations of fistulae. Recent findings from a systematic review (6 studies, N=817 patients) published in 2019 demonstrated that antibiotic use following I\&D of PA was associated with a 36% lower odds of fistula formation, though the quality of the evidence was low. As there are no established prophylactic treatments for fistulae, and because they are difficult to treat, further study of this simple intervention seems warranted. In this trial, adults with a PA requiring I\&D will be randomly assigned to receive standard of care with antibiotics or standard of care without antibiotics after I\&D. This trial will be conducted under the IMPACTS (Innovative, Multicentre, Patient-centred Approach to Clinical Trials in Surgery) program umbrella and will follow IMPACTS methodology. For the Vanguard trial, the aim is to determine the feasibility of conducting a definitive trial. Future outcomes of interest are incidence of fistula formation (defined as drainage of the perianal region at or after 2 mont