Comparison of Surgery and Medicine on the Impact of Diverticulitis (COSMID) trial: a protocol for a pragmatic randomised study of diverticulitis treatment in the USA.

INTRODUCTION: Each year, millions of people experience recurrent diverticulitis episodes. Elective sigmoid colon resection reduces the risk of recurrence, but The American Society of Colon and Rectal Surgeons recommends individualising surgical decisions based on the impact of the condition on a patient's quality of life (QoL). However, no threshold for QoL impairment has been established to guide decision-making, and evidence comparing elective colectomy with medical management in terms of QoL limitation is limited. To address these gaps and to guide treatment decision-making, we designed the Comparison of Surgery and Medicine on the Impact of Diverticulitis (COSMID) trial.The COSMID trial is a large, pragmatic randomised trial including patients with QoL-limiting diverticulitis that aims to determine if partial colectomy is superior to medical management and explore subgroups that are more likely to respond to each treatment.

METHODS AND ANALYSIS: COSMID will recruit 250 English-speaking and Spanish-speaking adults with imaging-confirmed and QoL-limiting diverticulitis (defined using a modified diverticulitis-related QoL survey). Participants are randomly assigned to undergo elective partial colectomy or receive comprehensive medical management (eg, selected from options including fibre, probiotics, mesalamine and rifaximin). A total of 100 patients who decline randomisation but consent to follow-up will be included in a parallel observational cohort. The primary outcome is the time-averaged score of the Gastrointestinal Quality of Life Index at 6, 9 and 12 months after randomisation. Secondary outcomes include clinical adverse events, healthcare utilisation, recurrent episodes of diverticulitis and additional patient-reported outcomes like the Diverticulitis Quality of Life instrument, decisional regret and work productivity. Exploratory analyses aim to identify differential treatment effects based on patients' characteristics.

ETHICS AND DISSEMINATION: This trial was approved by the Vanderbilt Institutional Review Board (IRB) on 26 August 2019 (IRB #191217). Vanderbilt serves as the institutional review board of record for the following study sites: Albany Medical College, Allegheny Health, Atrium Health Carolinas Medical Center, Virginia Mason Medical Center, Boston University Medical Center, Cedars-Sinai Medical Center, UT Health Lyndon B. Johnson Hospital, Medical University of South Carolina, New York-Presbyterian Queens, Stanford University, University of Pennsylvania, University of California San Diego, University of California San Francisco, University of Colorado Denver, University of Florida, University of Iowa, University of Utah, University of Washington Medical Center, University of South Florida, University of Rochester Medical Center, University of Texas Southwestern Medical Center, Virginia Commonwealth University, Lahey Hospital & Medical Center, Weill Cornell Medical Center and Northwell Health. Rush University Medical Center (approved 8 January 2020), Columbia University Medical Center (approved 28 January 2020), Northwestern University (approved 19 March 2020), Mount Carmel Health System (approved 5 May 2020) and Memorial Health University Medical Center (approved 4 April 2022) are regulated and were approved by their respective IRBs. Results from this trial will be presented at international conferences and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER: NCT04095663.