Antibiotics After Incision and Drainage to Prevent Fistula Formation After First Episode of Perianal Abscess (RAPID)

July 9, 2026 updated by: Mohamad Abdulhai, University of Illinois at Chicago

Randomized Antibiotics for Prevention of Fistula After Incision and Drainage of First-Episode Perianal Abscess (RAPID): A Randomized Controlled Trial

The goal of this clinical trial is to learn if antibiotics can prevent the formation of fistula-in-ano after incision and drainage of a first time of perianal abscess in adults. A perianal abscess is a collection of infected fluid near the anus. A Fistula-in-ano is an abnormal tunnel that can form between the anal canal and the skin after an abscess.

The main questions it aims to answer are:

Does taking antibiotics after incision and drainage of a perianal abscess lower the chance of developing a Fistula-in-ano? What medical problems or side effects do participants have after taking antibiotics or not taking antibiotics?

Researchers will compare participants who recieve antibiotics after abscess drainage with paticipants who do not recieve antibiotics after abscess drainage, to see if antibiotics lower the chance of developing a Fistula-in-ano.

Participants will:

Be randomly assigned to recieve antibiotics for 7 days after abscess incision and drainage or to not recieve antibiotics after abscess incision and drainage.

Attend follow-up clinic visits after incision and drainage as part of their standard of care.

Complete follow-up phone call about 12 months after incision and drainage. Allow the study team to review their medical record for abscess treatment, symptoms, recurrence, fistula-in-ano formation, additional procedures, and antibiotics side effects.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

This is a single-center, randomized, open-label clinical trial evaluating whether a 7-day course of postoperative antibiotics after standard of care incision and drainage of a first-time perianal abscess reduces subsequent anal fistula formation compared with no postoperative antibiotics.

Perianal abscess is a common anorectal condition treated primarily with incision and drainage. After drainage, some patients later develop an anal fistula, which is an abnormal tract between the anal canal and the perianal skin. The role of routine antibiotics after adequate drainage remains uncertain, especially in patients without high-risk clinical features that would otherwise require antibiotics as part of standard care. This study is designed to evaluate whether a short postoperative antibiotic course can reduce fistula formation after a first episode of perianal abscess.

Eligible adult participants with a first-time perianal abscess requiring incision and drainage will be randomized in a 1:1 ratio to either postoperative antibiotics or no postoperative antibiotics. Participants assigned to the antibiotic arm will receive amoxicillin/clavulanate for 7 days. Participants with penicillin allergy may receive ciprofloxacin plus metronidazole instead. Participants assigned to the no-antibiotic arm will not receive postoperative antibiotics unless antibiotics are later determined to be medically necessary by the treating clinician.

All participants will receive standard clinical care for the perianal abscess, including incision and drainage as determined by the treating surgical team. The study does not change the technical approach to drainage or other clinically indicated care. The research intervention is the randomized postoperative antibiotic strategy.

Participants will be followed through routine clinical visits and a 12-month follow-up phone call. The study will collect information from the medical record and follow-up contacts regarding fistula formation, recurrent abscess, additional procedures or treatment, emergency department visits or readmissions, antibiotic use, medication adherence, and antibiotic-related adverse events. The findings may help clarify whether routine postoperative antibiotics should be used after drainage of first-time perianal abscess in patients without other clinical indications for antibiotics.

Study Type

Interventional

Enrollment (Estimated)

236

Phase

  • Phase 4

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • Illinois
      • Chicago, Illinois, United States, 60612
        • University of Illinois at Chicago

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age 18 years or older
  • First episode of perianal abscess requiring incision and drainage
  • Able to provide informed consent
  • English or Spanish speaking patient
  • Treating surgical team has determined that incision and drainage is clinically indicated as part of standard care

Exclusion Criteria:

  • Known fistula-in-ano at presentation
  • Prior perianal abscess within 12 months
  • History of inflammatory bowel disease, including Crohn's disease or ulcerative colitis
  • Known or suspected anorectal malignancy
  • Necrotizing soft tissue infection or Fournier's gangrene
  • Systemic infection or sepsis
  • Significant surrounding cellulitis or extensive soft-tissue infection for which antibiotics are clinically indicated
  • Immunocompromised or immunosuppressed status, including active chemotherapy or radiation therapy, history of transplant, chronic systemic steroids, biologic immunosuppressive therapy, advanced or uncontrolled HIV/AIDS, or other clinically significant immunosuppression
  • Cardiac condition requiring antibiotic prophylaxis or antibiotic therapy for procedures involving infected tissue
  • Need for non-study antibiotics at the time of enrollment for another infection or medical indication
  • Contraindication, allergy, or intolerance to all study antibiotic regimens
  • Pregnant
  • Prisoner
  • Minor
  • Adult unable to provide informed consent

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Antibiotics after Incision and Drainage
Participants assigned to this arm will receive antibiotics for 7 days after standard of care incision and drainage of a first-time perianal abscess. The planned antibiotic regimen is amoxicillin/clavulanate. Participants with penicillin allergy may receive ciprofloxacin plus metronidazole instead.
Drug: Amoxicillin + Clavulanate
Participants assigned to the antibiotics after incision and drainage arm will receive amoxicillin/clavulanate 875/125 mg by mouth twice daily for 7 days after standard of care incision and drainage.
Drug: Ciprofloxacin + Metronidazole
Participants assigned to the antibiotics after incision and drainage arm who have a penicillin allergy may receive ciprofloxacin 500 mg by mouth twice daily plus metronidazole 500 mg by mouth three times daily for 7 days after standard of care incision and drainage.
No Intervention: No antibiotics after Incision and Drainage
Participants randomized to this arm will not receive postoperative antibiotics after standard of care incision and drainage, unless antibiotics are later determined to be clinically necessary by the treating clinician. Any antibiotic use after randomization will be recorded, and participants may continue study follow-up unless they withdraw or the study team determines that stopping participation is necessary for safety.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Number of participants who develop fistula in ano within 6 months after incision and drainage
Time Frame: 6 months after incision and drainage
Anal fistula formation will be assessed as a binary outcome for each participant. Fistula will be defined as documentation of a clinically diagnosed anal fistula during follow-up, based on clinical examination, imaging, operative or procedure findings, or medical record documentation.
6 months after incision and drainage

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Number of participants who develop Fistula in Ano within 12 months after incision and drainage
Time Frame: 12 months after incision and drainage
Anal fistula formation within 12 months will be assessed as a binary outcome for each participant. Participants will be counted as having developed a Fistula in Ano if a clinically diagnosed anal fistula is documented within 12 months after incision and drainage. Documentation may be based on clinical examination, imaging, operative or procedure findings, medical record review, or participant report during the 12-month follow-up phone call and confirmed by clinical documentation when available.
12 months after incision and drainage
Number of participants who develop recurrent perianal abscess within 12 months after incision and drainage.
Time Frame: 12 months after incision and drainage
Recurrent perianal abscess will be assessedas a binary outcome for each participant. Recurrent perianal abscess will be defined as documentation of a new or recurrent perianal abscess during follow-up, including clinical diagnosis, emergency department visit, clinic visit, imaging, or need for repeat drainage or procedure.
12 months after incision and drainage
Number of participants who require an additional abscess or fistula related procedure or intervention within 12 months after incision and drainage.
Time Frame: 12 months after incision and drainage
The need fo additional procedure or intervention will be assessed as a binary outcome for each participant. Participants will be counted as requiring an addictional procedure or intervention if any abscess or fistula related procedure is documented within 12 months after incision and drainage. Procedures may include repeat incision and drainage, examination under anesthesia, seton placement, fistulotomy, fistula repair, or other abscess or fistula related intervention documented in the medical record.
12 months after incision and drainage
Number of participants with an abscess or fistula emergency department visit or hospital readmission within 12 months after incision and drainage.
Time Frame: 12 months after incision and drainage
Emergency department visits or hospital readmissions will be assessed as a composite binary outcome for each participant. Participants will be counted in this outcome if they have at least one emergency department visit or at least one hospital readmission related to perianal abscess, fistula, wound infection, worsening symptoms, recurrent abscess, or complications of the assigned postoperative management strategy within 12 months after incision and drainage. Events will be identified through medical record review and follow-up assessments.
12 months after incision and drainage
Number of participants with antibiotic adverse events by event type within 30 days after incision and drainage.
Time Frame: Within 30 days after incision and drainage
Antibiotic adverse events will include medication side effects or complications, documented during follow-up or through medical record review. These include nausea, vomiting, diarrhea, rash, allergic reaction, yeast infection, clostridioides difficile infection, tendon symptoms, neurologic symptoms, liver-related symptoms, or other adverse events attributed to antibiotic therapy. Adverse event will be summarized by event type. The number of participants with each adverse event type will be reported. A participant may be counted in more than one adverse event type if multiple events occur.
Within 30 days after incision and drainage

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Illinois at Chicago

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

August 3, 2026

Primary Completion (Estimated)

February 3, 2029

Study Completion (Estimated)

August 3, 2029

Study Registration Dates

First Submitted

July 2, 2026

First Submitted That Met QC Criteria

July 9, 2026

First Posted (Actual)

July 15, 2026

Study Record Updates

Last Update Posted (Actual)

July 15, 2026

Last Update Submitted That Met QC Criteria

July 9, 2026

Last Verified

June 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • STUDY2026-0396

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be made publicly available. Aggregate study results will be reported as required and may be published in scientific presentations or manuscripts.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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