GLP-1 Receptor Agonists and Early Proctologic Effects in Morbid Obesity

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are increasingly used in the treatment of obesity and type 2 diabetes mellitus. Although gastrointestinal adverse effects such as constipation, diarrhea, nausea, delayed gastric emptying, and altered bowel habits are well recognized, their potential impact on anorectal symptoms and proctologic diseases remains poorly investigated.

Changes in bowel habits and stool consistency associated with GLP-1 RA therapy may contribute to the development or progression of anorectal disorders including hemorrhoidal disease, anal fissures, perianal irritation, pruritus ani, and fecal incontinence. However, prospective clinical data evaluating these associations are lacking.

This prospective observational cohort study aims to evaluate the early proctologic effects of GLP-1 receptor agonist therapy in morbidly obese patients. Participants who are newly prescribed GLP-1 RA treatment will undergo baseline assessment before treatment initiation and follow-up evaluation at 3 months.

Baseline evaluation will include demographic characteristics, comorbidities, bowel habit assessment, anorectal symptom assessment, and standardized proctologic examination including perianal inspection, digital rectal examination, and anoscopy. Follow-up evaluation at 3 months will reassess symptoms and repeat proctologic examination.

The primary objective is to determine the incidence of newly developed proctologic diseases during the first 3 months after initiation of GLP-1 receptor agonist therapy. Secondary objectives include evaluating changes in anorectal symptom severity, bowel habits, progression of pre-existing anorectal disease, and the relationship between weight loss magnitude and anorectal symptoms.

• GLP-1 receptor agonist therapy (Drug): Participants will receive GLP-1 receptor agonist treatment as part of routine clinical care. The study does not assign treatment but prospectively evaluates proctologic outcomes following treatment initiation.

Primary outcomes

• Incidence of newly developed proctologic disease [3 months]: Patients developing newly diagnosed anorectal pathology after initiation of GLP-1 receptor agonist therapy, including hemorrhoidal disease, anal fissure, pruritus ani, perianal irritation, or other proctologic conditions identified during follow-up examination.

Secondary outcomes

• Change in anorectal symptom severity [Baseline to 3 months]: Comparison of anorectal symptom severity between baseline and 3-month follow-up assessment.
• Change in bowel movement frequency [Baseline to 3 months]: Change in the number of bowel movements per week between baseline and 3-month follow-up after initiation of GLP-1 receptor agonist therapy.
• Number of participants with worsening of pre-existing anorectal disease [3 months]: Number of participants demonstrating worsening of previously diagnosed anorectal disease based on changes in symptoms and findings on proctologic examination, including perianal inspection, digital rectal examination, and anoscopy.
• Correlation between percent body weight loss and anorectal symptom score [3 months]: Correlation between percentage body weight loss and change in anorectal symptom score from baseline to 3-month follow-up after initiation of GLP-1 receptor agonist therapy.
• Change in Bristol Stool Form Scale score [Baseline to 3 months]: Change in Bristol Stool Form Scale score (Bristol Stool Form Scale, range 1-7; lower scores indicate harder stools and higher scores indicate looser stools) between baseline and 3-month follow-up.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Age ≥18 years
* Morbid obesity (BMI ≥40 kg/m² or BMI ≥35 kg/m² with obesity-related comorbidities)
* Newly prescribed GLP-1 receptor agonist therapy
* Ability and willingness to provide written informed consent
* Ability to attend 3-month follow-up visit

Exclusion Criteria:

* Inflammatory bowel disease
* Perianal Crohn's disease
* History of anorectal malignancy
* Previous pelvic radiotherapy
* Anorectal surgery within the previous 3 months
* Pregnancy
* Neurogenic bowel dysfunction
* Inability to comply with follow-up visits
* Discontinuation of GLP-1 receptor agonist therapy before follow-up assessment
* Active anorectal infection or abscess

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• Results publication: Shankar A, Sharma A, Vinas A, Chilton RJ. GLP-1 receptor agonists and delayed gastric emptying: implications for invasive cardiac interventions and surgery. Cardiovasc Endocrinol Metab. 2024 Dec 4;14(1):e00321. doi: 10.1097/XCE.0000000000000321. eCollection 2025 Mar. PMID 39649679
• Results publication: Wadden TA, Bailey TS, Billings LK, Davies M, Frias JP, Koroleva A, Lingvay I, O'Neil PM, Rubino DM, Skovgaard D, Wallenstein SOR, Garvey WT; STEP 3 Investigators. Effect of Subcutaneous Semaglutide vs Placebo as an Adjunct to Intensive Behavioral Therapy on Body Weight in Adults With Overweight or Obesity: The STEP 3 Randomized Clinical Trial. JAMA. 2021 Apr 13;325(14):1403-1413. doi: 10.1001/jama.2021.1831. PMID 33625476