EP572 - Incidence of Pouch Adenomas in Familial Adenomatous Polyposis After Restorative Proctocolectomy

Purpose/Background: Familial adenomatous polyposis (FAP) is characterized by the presence of hundreds of colorectal adenomas, with almost 100% risk of malignant transformation. Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) is the most commonly indicated surgical procedure. However, even after removal of the colon and rectum, new adenomas may develop in other segments of the gastrointestinal tract and in the ileal pouch, with potential progression to carcinoma. This study aimed to analyze the risk factors and the occurrence of adenomas and carcinomas in the afferent ileal loop and/or ileal pouch of patients with FAP undergoing restorative proctocolectomy with handsewn IPAA.

Methods/Interventions: A retrospective study was conducted, including patients who underwent surgery for FAP between 1984 and 2023. Descriptive analysis included means, medians, standard deviations, and absolute and relative frequencies. Comparisons between groups with and without pouch adenomas were performed using the Mann-Whitney, Chi-square, or Fisher's exact tests. Univariate and multivariate logistic regression models were applied to identify factors associated with adenoma occurrence, with a significance level of 5% (p < 0.05), using SAS software v9.4. The local Research Ethics Committee approved the study.

Results/Outcomes: Seventy-one patients were included, with a mean age at surgery of 27.9 (± 10.3) years, predominantly female (57.7%) and white (83.1%). Pouch adenomas occurred in 42 patients (59.2%) and in the afferent loop in 7 (9.9%); only one patient (1.4%) developed adenocarcinoma in the ileal pouch. All patients with adenomas in the afferent loop also had adenomas in the ileal pouch. The median time between surgery and the diagnosis of the first adenoma was 12 years (4-37). Most adenomas (78.6%) measured less than 10 mm, with 69% being tubular and 31% tubulovillous; two had a serrated component, and 14.3% presented high-grade dysplasia. In univariate analysis, longer follow-up (OR 1.007; 95% CI 1.001-1.012; p = 0.0146) and the presence of duodenal adenomas (OR 5.452; 95% CI 1.013-29.326; p = 0.0482) were associated with the occurrence of pouch adenomas. No significant associations were found with age, sex, race, desmoid tumor, or adenocarcinoma in the surgical specimen or preoperative polyp. In multivariate analysis, follow-up duration remained the variable most strongly associated with pouch adenoma occurrence, an association that was statistically expressed by the number of pouch endoscopies (OR 1.633; 95% CI 1.210-2.204; p = 0.0013), which reflects longer follow-up and surveillance intensity rather than an independent biological risk factor.

Conclusion/Discussion: Pouch adenomas were frequent findings after restorative proctocolectomy with IPAA in patients with FAP and were associated with the presence of duodenal adenomas. Malignant transformation was rare. Prolonged follow-up was the primary determinant of adenoma occurrence, underscoring the importance of continuous and systematic long-term endoscopic surveillance.

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