P2448 - Preparing for Success: Enhanced Bowel Preparation Protocol Significantly Reduces Inadequate Colonoscopy Preparation, a Retrospective Study of 1,850 Patients

Monday, October 27, 2025

10:30 AM - 4:00 PM PDT

Location: Exhibit Hall

Has Audio

Presenting Author(s)

RS

Ruchi Sharma, MD

University of Iowa Hospital and Clinics
Coralville, IA

Ruchi Sharma, MD¹, Fadi Niyazi, MD², Alan Gunderson, MD³
1University of Iowa Hospital and Clinics, Coralville, IA; 2Minnesota Gastroenterology, Plymouth, MN; 3University of Iowa Hospital and Clinics, Iowa City, IA

Introduction:

Inadequate bowel preparation leads to cancellation or incomplete visualization in 6–30% of colonoscopies, highlighting the need for improved bowel preparation protocols.

Methods:

At our institution, the standard bowel preparation consisted of a 3-day low-fiber diet, 1 day of clear liquids, and a split-dose regimen of 64 oz polyethylene glycol (PEG). A modified protocol was introduced, extending the duration of low-fiber diet to 7 days and adding 20 mg of bisacodyl and 500 mg of simethicone the evening before the procedure. We conducted a retrospective analysis of 1,850 patients undergoing colonoscopy (925 patients in each arm). Variables assessed included demographic characteristics (age, gender, BMI), comorbidities (e.g., diabetes, cirrhosis, stroke, dementia, IBD, constipation), prior abdominal surgery, ASA class, functional status, incarceration status, substance use (alcohol, tobacco, marijuana), and medication use (narcotics, benzodiazepines, methadone, tricyclic antidepressants [TCAs], other antidepressants, anticholinergics, antipsychotics, laxatives).

Results: Factors independently associated with poor bowel preparation included anticholinergic use (OR 1.4, p = 0.007), baseline laxative use (OR 1.77, p = 0.008), higher ASA class (OR 1.77, p < 0.001), and marijuana use (OR 1.9, p = 0.018). TCA use demonstrated a trend toward significance (OR 1.8, p = 0.072). Following implementation of the updated protocol, “excellent” preparation rates improved from 35.51% to 42.49%, and “poor” preparation rates decreased from 3.78% to 1.62% (χ² = 11.65, p = 0.009). The combined “inadequate or poor” preparation rate declined from 10.7% to 7.78% (χ² = 4.69, p = 0.03). On multivariate analysis, the updated protocol was associated with reduced odds of inadequate or poor preparation (OR 0.66, 95% CI: 0.47–0.93, p = 0.017).

Discussion: A 7-day low-fiber diet combined with bisacodyl and simethicone significantly improves bowel preparation quality compared to the standard regimen. These modifications reduced inadequate preparation rates and have the potential to enhance colonoscopy outcomes.

Figure: Factors associated with poor bowel preparation for colonoscopy. On multivariate analysis extending the low-residue diet from 3 to 7 days and adding 20 mg of bisacodyl and 500 mg of simethicone to the standard PEG-based regimen significantly improved bowel preparation quality

Disclosures:

Ruchi Sharma indicated no relevant financial relationships.

Fadi Niyazi indicated no relevant financial relationships.

Alan Gunderson indicated no relevant financial relationships.

Ruchi Sharma, MD¹, Fadi Niyazi, MD², Alan Gunderson, MD³. P2448 - Preparing for Success: Enhanced Bowel Preparation Protocol Significantly Reduces Inadequate Colonoscopy Preparation, a Retrospective Study of 1,850 Patients, ACG 2025 Annual Scientific Meeting Abstracts. Phoenix, AZ: American College of Gastroenterology.