Postoperative Packing of Perianal Abscess Cavities (PPAC2): randomized clinical trial

BACKGROUND: Perianal abscess is common. Traditionally, postoperative perianal abscess cavities are managed with internal wound packing, a practice not supported by evidence. The aim of this randomized clinical trial (RCT) was to assess if non-packing is less painful and if it is associated with adverse outcomes. METHODS: The Postoperative Packing of Perianal Abscess Cavities (PPAC2) trial was a multicentre, RCT (two-group parallel design) of adult participants admitted to an NHS hospital for incision and drainage of a primary perianal abscess. Participants were randomized 1:1 (via an online system) to receive continued postoperative wound packing or non-packing. Blinded data were collected via symptom diaries, telephone, and clinics over 6 months. The objective was to determine whether non-packing of perianal abscess cavities is less painful than packing, without an increase in perianal fistula or abscess recurrence. The primary outcome was pain (mean maximum pain score on a 100-point visual analogue scale). RESULTS: Between February 2018 and March 2020, 433 participants (mean age 42 years) were randomized across 50 sites. Two hundred and thirteen participants allocated to packing reported higher pain scores than 220 allocated to non-packing (38.2 versus 28.2, mean difference 9.9; P < 0.0001). The occurrence of fistula-in-ano was low in both groups: 32/213 (15 per cent) in the packing group and 24/220 (11 per cent) in the non-packing group (OR 0.69, 95 per cent c.i. 0.39 to 1.22; P = 0.20). The proportion of patients with abscess recurrence was also low: 13/223 (6 per cent) in the non-packing group and 7/213 (3 per cent) in the packing group (OR 1.85, 95 per cent c.i. 0.72 to 4.73; P = 0.20). CONCLUSION: Avoiding abscess cavity packing is less painful without a negative morbidity risk. REGISTRATION NUMBER: ISRCTN93273484 (https://www.isrctn.com/ISRCTN93273484). REGISTRATION NUMBER: NCT03315169 (http://clinicaltrials.gov)