Critically Appraised Topic: Traditional Incision & Drainage vs. Loop Drainage for Cutaneous Abscesses

Study #1: A prospective randomized controlled trial of traditional I&D and Loop drainage of abscesses performed at high volume level 1 trauma/tertiary care center. Inclusion criteria included any patient with subcutaneous abscesses requiring drainage (only enrolled during research team presence as convenience sample). Exclusion criteria included location on hand/foot/face, operative intervention, or admission. Primary outcome was failure rate defined as needing repeat drainage, operative intervention, or IV antibiotics. Secondary outcomes included ease of procedure and pain both during and 36 hours after procedure. 109 patients underwent I&D, 108 patients underwent loop drainage, for a total of 217 meeting targeted enrollment goal of 212. Failure rates overall were 20% in the I&D group versus 13% in the Loop group (p=0.25). Stratified failure rates stratified were as follows: adults 18%  in the I&D group versus 22% in the loop group(p=0.82) and children (<19yr) 21% in the I&D group versus 0% loop group (p=0.002). Of secondary outcomes, significant differences included ease of care over the first 36 hours, pain over the first 36 hours, and overall satisfaction at 10 days (p=0.002, p=0.004, p=0.005 respectively). Strengths include the randomized prospective study design, meeting enrollment goal to determine a difference of proportion of 0.09 between two groups (power of 80%, significance of 5%), and similar demographics between groups. Limitations include the convenience sample nature of study, no blinding, and discrepancy between sedation use between adults and children. The design also  did not initially plan for children vs adults subanalysis in initial study design but there was a post hoc power analysis to assess adequacy of children sample size, 5 short of goal.  

Study #2: A prospective, randomized, unblinded noninferiority study of traditional I&D vs loop technique in children at urban tertiary care peds hospital. Inclusion criteria included age of 28d-18yr, and abscess > 1cm requiring drainage. Exclusion criteria included non-English or non-Spanish speaking, unwillingness for follow up, surgical requirement, admission, and immunocompromised states. Primary outcome was failure rate defined as reinstrumentation or admission for IV antibiotics within 14 days. Secondary outcomes included pain reduction, care ease, and cosmetic satisfaction (using Likert, Hollander, satisfaction scales). 82 patients enrolled however 81 analyzed as 1 dropped from I&D group. Total of 40 in I&D and 41 in loop group, 1 shy of enrollment goal of 82.  Failure rate of 7.3% in loop group vs 7.5% in I&D group, CI of -11.2% ←>11.6%, with non-inferiority margin of 23%, proving non inferiority.  There were no significant differences in any of the secondary outcomes. To note, a sensitivity analysis was performed due to the one patient dropped from the I&D showing no impact on outcome.  

Strengths include the location of the study at a large urban tertiary care center, similar characteristics between groups (including antibiotics and sedation use), sensitivity analysis for dropped subject. Limitations include limited size (thus missing enrollment goal for determination of risk difference of noninferiority threshold of 23%, power 80%, significance 5%), convenience sample approach, unblinded study.  


Overall, I think it is rather difficult to study this topic with extremely difficult to control variables such as provider discretion for sedation, antibiotic use, inherent inability to blind, and to control for patient follow up (which is crucially important in such a topic). With the pediatric population, loop drainage technique is just as, if not more, effective than traditional I&D with easier care.  I will likely perform loop drainage on pediatrics and possibly on adults that may not be compliant with packing changes or follow ups.  


1. Ladde J, Baker S, Lilburn N, Wan M, Papa L. A Randomized Controlled Trial of Novel Loop Drainage Technique Versus Standard Incision and Drainage in the Treatment of Skin Abscesses. Acad Emerg Med. 2020 Dec;27(12):1229-1240. doi: 10.1111/acem.14106. Epub 2020 Oct 11. PMID: 32770686. 

2. Rencher L, Whitaker W, Schechter-Perkins E, Wilkinson M. Comparison of Minimally Invasive Loop Drainage and Standard Incision and Drainage of Cutaneous Abscesses in Children Presenting to a Pediatric Emergency Department: A Prospective, Randomized, Noninferiority Trial. Pediatr Emerg Care. 2021 Oct 1;37(10):e615-e620. doi: 10.1097/PEC.0000000000001732. PMID: 30839438.