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DiverticulitisCOSMIDNCT04095663

Comparison of Surgery and Medicine on the Impact of Diverticulitis (COSMID) Trial

A study testing Partial Colectomy and Medical Management in people with Diverticulitis, run by University of Washington at 29 sites in United States.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
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Trial summary

The COSMID (Comparison of Surgery and Medicine on the Impact of Diverticulitis) trial is a pragmatic, patient-level randomized superiority trial of elective colectomy vs. best medical management for patients with quality of life (QoL) limiting diverticular disease. Read more about this study

Who is it for?
Ages 18 years and older
Conditions the study is for
Diverticulitis
What is being tested?
Partial Colectomy and Medical Management
Could I receive a placebo?
No, everyone receives an active treatment
How many people
255 participants
Where
29 sitesUnited States
Study dates
1 Oct 2019to 1 Feb 2027
Phase
Interventional
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Adults ≥18 years
  • At least one episode of diverticulitis confirmed by CT scan and a colonoscopy (completed or scheduled) to rule out or screen for other colon pathology concordant with screening guidelines
  • Persistent signs, symptoms, or concerns related to diverticulitis after recovery from an episode of left-sided diverticulitis as confirmed with self-reported QoL limitation.

Who cannot join

  • Unable to consent in English or Spanish
  • Current diagnosis or previous endoscopic or surgical interventions for fistula, or stricture or current significant bleeding, related to diverticular disease
  • Last episode of acute diverticulitis currently unresolved (i.e., on antibiotics for diverticulitis; drain in place)
  • Previous operation for diverticulitis
  • Right-sided diverticulitis
  • Immunodeficiency (e.g., absolute neutrophil count <500/mm3, chronic immunosuppressive drugs like oral corticosteroids, anti-TNF agents, or known AIDS [i.e., recent CD4 count <200] assessed by patient history)
Show all 18Show fewer
  • Actively undergoing chemotherapy or radiation for malignancy
  • Expectant or concurrent hemodialysis, peritoneal dialysis, treatments using indwelling venous catheters, or conditions putting patient at risk for bacterial seeding
  • Diagnosis of inflammatory bowel disease (i.e., Crohn's, ulcerative colitis)
  • Taking prescription medication for irritable bowel syndrome
  • Intolerance or allergy to all medications in the medical management arm
  • Comorbid or prior surgical conditions that contraindicate elective surgery (e.g., liver failure, renal failure, malignancy, "frozen abdomen") as determined by surgeon
  • Abdominal/pelvic surgery within the past month
  • Pregnant or expecting to become pregnant in the 30 days following baseline/screening
  • Unable to consent to research or self-respond to follow-up surveys (e.g., altered mental status)
  • Currently incarcerated in a detention facility or in police custody (patients wearing a monitoring device can be enrolled) at baseline/screening
  • Prior enrollment in the COSMID study or planning on enrollment in another investigational drug or vaccine while on study treatment
  • Unable or unwilling to return or be contacted for and/or complete research surveys.

Trial locations and contacts

29 sites in 1 country.

29 sites in 1 country

United States29 sites
  • Albany Medical College

    Albany, New York, 12208

  • Boston University Medical Center

    Boston, Massachusetts, 02118

  • Lahey Clinic

    Burlington, Massachusetts, 01805

  • Medical University of South Carolina

    Charleston, South Carolina, 29425

  • Atrium Health-Carolinas Medical Center

    Charlotte, North Carolina, 28203

  • Rush University Medical Center

    Chicago, Illinois, 60612

  • Mount Carmel Health Systems

    Columbus, Ohio, 43213

  • UT Southwestern Medical Center

    Dallas, Texas, 75390

  • University of Colorado

    Denver, Colorado, 80045

  • Northwestern University

    Evanston, Illinois, 60201

  • New York Presbyterian-Queens

    Flushing, New York, 11355

  • University of Florida

    Gainesville, Florida, 32608

  • UTHealth Houston

    Houston, Texas, 77026

  • University of Iowa Healthcare

    Iowa City, Iowa, 52242

  • Cedars-Sinai Medical Center

    Los Angeles, California, 90048

  • Columbia University Medical Center

    New York, New York, 10027

  • Weill Cornell Medicine

    New York, New York, 10065

  • Penn Medicine

    Philadelphia, Pennsylvania, 19104

  • Allegheny-Singer Research Institute

    Pittsburgh, Pennsylvania, 15212

  • VCU Medical Center

    Richmond, Virginia, 23298

  • University of Rochester Medical Center

    Rochester, New York, 14618

  • University of Utah Health

    Salt Lake City, Utah, 84112

  • UC San Diego Health

    San Diego, California, 92103

  • UCSF Health

    San Francisco, California, 94143

  • Memorial Health University Medical Center

    Savannah, Georgia, 31404

  • Benaroya Research Institute at Virginia Mason

    Seattle, Washington, 98101

  • University of Washington

    Seattle, Washington, 98105

  • Stanford University Medical Center

    Stanford, California, 94305

  • University of South Florida

    Tampa, Florida, 33606

Other trials in United States

About this study

The COSMID (Comparison of Surgery and Medicine on the Impact of Diverticulitis) trial is a pragmatic, patient-level randomized superiority trial of elective colectomy vs. best medical management for patients with quality of life (QoL) limiting diverticular disease. A parallel observational cohort will include those who are disinclined to have their treatment choice randomized, but are willing to contribute information about their outcomes. The goal of the COSMID trial is to answer the question: For patients with QoL-limiting diverticular disease, is elective colectomy more effective than best medical management? The hypothesis being tested in the COSMID trial is that patient-reported outcomes (PROs) among patients in the surgery arm will be superior to those in the best medical management arm.

Read the detailed description

For over 50 years, professional society recommendations for the management of uncomplicated diverticulitis included early elective surgery to prevent the need for an emergency operation and avoid the risk of colostomy. Over the last 15 years the notion that a patient must have a certain number of episodes of acute uncomplicated diverticulitis (AUD) before undergoing elective colectomy has changed dramatically. This was, in part, due to studies showing that emergency surgery for complicated disease is much more likely to be needed during the first episode of diverticulitis, making the notion of prophylactic elective colectomy for AUD less relevant. Furthermore, clinicians realized that most recurrent episodes of AUD could be managed with outpatient antibiotics alone and that "best medical management" - including fiber supplementation, mesalazine, rifamycin and probiotics - could reduce symptoms between episodes of AUD. All of the components of best medical management have some, albeit limited, evidence of effectiveness, most in improving symptoms rather than reducing the risk of recurrence and are relatively safe and inexpensive. Best medical management is far less invasive than elective surgery but infrequently prescribed the US, in part because of limited insurance coverage. Alternatively, resection removes the diseased segment of colon, does relieve symptoms and decreases the risk of recurrence.

In 2014, guidelines from the American Society of Colorectal Surgeons (ASCRS) abandoned "episode count" as an indication for surgery in patients with AUD and instead recommended individualizing the decision to operate for AUD based on the "effects on lifestyle (professional and personal) of recurrent attacks". Decision making about surgery in patients with lingering symptoms after recovery from an episode of AUD has not been the specific focus of an ASCRS guideline, but recommendations about elective surgery emphasize individualizing decision making based on the overall impact of the disease on the patient.These recommendations for individualization of treatment based on the quality of life (QoL) impact of recurrent AUD and lingering symptoms highlight the decision that hundreds of thousands of people now have to make each year. Based on the effect of the disease on their QoL they must choose between two very different treatment options: elective colectomy vs. best medical management. While the recommendation to individualize treatment based on the QoL impact is a step forward in advancing patient-centered care, the comparative effectiveness of these two treatments on symptoms and QoL has not been well studied.

This will be a multi-site, open randomized trial in which participants with either recurrent AUD or lingering symptoms after an episode of AUD are randomized to one of two initial treatment strategies, elective segmental colectomy (performed laparoscopically when possible) and best medical management.

Conditions
Diverticulitis
Being tested
Partial Colectomy, Medical Management
Medical subject headings
Diverticulitis

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Partial ColectomyProcedure or surgery

    Most partial colectomies are performed using a laparoscopic approach, when possible, and surgeons sometimes use a temporary, protective stoma if the re-connection is considered high risk.

  • Medical ManagementOther

    Patients will be offered a varying combination of tools from the best medical management "toolbox" (diet and exercise, fiber supplementation/probiotics, and rifamycin/mesalazine) depending on what they have already tried. Based on the "evidence-based best medical toolbox" clinicians will be asked to consider rifamycin (dose/frequency) for those with AUD who are not responding to diet and exercise and mesalazine (dose/frequency) for those with lingering symptoms who are not responding to diet and exercise.

Study groups in NCT04095663
Study groupRoleWhat they receive
Partial ColectomyActive comparatorElective segmental colectomy for diverticular disease involves removal of the segment of colon (most commonly sigmoid and/or left colon) where there has been disease identified by computed tomography imaging or colonoscopy. Elective colectomy usually removes the affected colon along with adjacent segments that have diverticula, with a primary anastomosis performed to reestablish bowel continuity. Most surgeons now perform the procedure using a laparoscopic approach, when possible, and sometimes use a temporary, protective stoma if the re-connection is considered high-risk. The technique for laparoscopic resection is not specified by the protocol (allows for any number of laparoscopic port sites, all incision types, hand-assistance and robotic) with details of the technique recorded. If randomized to elective colectomy, patients will be encouraged to undergo the procedure within 6 weeks of assignment.
Receives: Procedure: Partial Colectomy
Medical ManagementActive comparatorMedical management for diverticular disease has been used for over 30 years and includes a set of interventions, all components of which have been the subject of small, but often positive trials. All patients randomized to medical management or who select it as their treatment in the observational cohort will view a video (provided in English and Spanish) that explains each element of the medical management "toolbox": diet and exercise recommendations, fiber supplementation (e.g., augmenting dietary fiber or over the counter fiber supplements), with mesalazine tablets or suppositories, probiotics and rifamycin. In consultation with their physician, they will be recommended to a regimen of diet and exercise and fiber supplementation. Clinicians will be asked to consider rifamycin (dose/frequency) for those with AUD who are not responding to diet and exercise and mesalazine (dose/frequency) for those with lingering symptoms who are not responding to diet and exercise.
Receives: Other: Medical Management

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Patient-reported quality of life as measured by Gastrointestinal Quality of Life Index (GIQLI)

    A 36-item questionnaire assessing 5 domains: GI symptoms, physical function, emotional well-being, social well-being, and perception of medical treatment measured by a single item question. Each item has 5 response choices (i.e., all of the time, most of the time, some of the time, a little of the time, never). In addition, the measure produces an overall quality of life score (0-144) where higher numbers indicate greater QoL.

    Measured: Mean GIQLI at 6, 9, and 12 months following randomization to treatment

Secondary outcomes (4)
  1. Diverticulitis Quality of Life (DV-QoL) instrument

    A 17-item questionnaire including a pain scale and questions about about physical, emotional, and social effects of diverticulitis over the past 2 weeks, with a total score ranging from 0 (best) to 10 (worst) with higher scores reflecting worse quality of life effects from diverticulitis.

    Measured: Baseline, 12 months, 24 months

  2. Patient-Reported Outcomes Measurement Information System (PROMIS) Global Health measure

    A 10-item instrument measuring domains that can be scored into a Global Physical Health component and Global Mental Health component. Each item includes 5 response choices, with the exception of the common 11-point pain intensity item ("How would you rate your pain on average?" with 0=no pain and 10=worst imaginable pain), where higher scores reflect more severe symptoms/impairment.

    Measured: Baseline; 6, 12, 24, 36 months

  3. Decision Regret Scale

    A 5-item validated questionnaire that measures regret among patients following a specific treatment decision. Scores range from 0-100 and higher scores reflect higher levels of regret. While developed for use in patients undergoing treatment for cancer, the questions are general in nature and adaptable to diverse clinical experiences.

    Measured: 6 and 36 months

  4. Work Productivity and Activity Impairment instrument

    A 6-item instrument used to measure the effect of general health and symptom severity on work productivity and regular activities during the past seven days. Scores are calculated applying algorithms to the five numerical responses, three of which are continuous variables (hours) and two of which are a scale from 0-10, then converting to a percentage, with higher WPAI scores indicating greater impairment and less productivity.

    The WPAI measures work productivity loss due to general health or a specified health problem. This questionnaire has been validated for use in many gastrointestinal diseases, including gastroesophageal reflux disease, irritable bowel syndrome, and Crohn's disease.

    Measured: Baseline; 6, 12, 18, 24, 30, 36 months

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted19 Sep 2019
  2. Study start1 Oct 2019
  3. Primary completion1 Feb 2027 (estimated)
  4. Study completion1 Feb 2027 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Masking
None (open label)
Enrolment
255 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT04095663
Sponsor's protocol ID
STUDY00007409
Acronym
COSMID
Status last verified
Feb 2026
First submitted
28 Aug 2019
Last updated
19 Feb 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
Yes: Data and results from this proposal stand to develop research that may have a lasting value beyond the term of the award and will be archived and preserved, supporting access to third parties interested in replication and verification of our results and data reuse by other investigators planning future studies. We will prepare and share a complete, cleaned, de-identified copy of the final dataset used in conducting the final analyses upon which the accepted primary study publication is based. The final dataset will include participants' treatment group assignment, demographics and patient reported outcomes (GIQLI survey). Data collected on clinical variables will also include: NSQIP-defined complications major complications, dates and details of healthcare utilization including hospitalizations, length of stay, use of imaging, colectomy details and associated pathology results, and medication use.

Publications

  • Hantouli MN, Schmicker RH, Tufte JE, Ali FG, Bennett RD, Cohan JN, Comstock BA, Curran T, Davidson GH, Eisenstein S, Fischkoff KN, Fleming FJ, Gribovskaja-Rupp I, Jafari MD, Kessler LG, Krane MK, Lawrence SO, McCormick JT, Millas SG, Morris AM, Pullar KM, Reinke CE, Saraidaridis JT, Simianu VV, Watkins SP, White NB, Wick EC, Wieghard N, Flum DR, Read TE; COSMID Collaborative. 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. BMJ Open. 2026 Jan 8;16(1):e098309. doi: 10.1136/bmjopen-2024-098309.

    PubMed 41506759

Questions about this trial

What is this clinical trial studying?

A study testing Partial Colectomy and Medical Management in people with Diverticulitis, run by University of Washington at 29 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 3 inclusion and 18 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 19 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 29 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Patient-reported quality of life as measured by Gastrointestinal Quality of Life Index (GIQLI) (time frame: Mean GIQLI at 6, 9, and 12 months following randomization to treatment). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04095663, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 Feb 2026.

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