Adverse Events after Colorectal Polypectomy in Patients with Amyloidosis: Risk Assessment Using Propensity Score Matching.

INTRODUCTION: Amyloidosis may increase the risk of post-polypectomy bleeding due to mucosal and vascular fragility. We compared adverse events after colorectal polypectomy between patients with and without amyloidosis and explored risk factors for immediate post-polypectomy bleeding (IPPB). METHODS: This retrospective investigation included 21 amyloidosis patients (71 polyps) and 110 non-amyloidosis patients (298 polyps) who underwent cold snare polypectomy (CSP) or endoscopic mucosal resection (EMR) between 2005 and 2024. Propensity score matching compared IPPB, delayed bleeding, and perforation. In the matched cohort, risk factors for IPPB were evaluated using generalized estimating equation (GEE) logistic regression clustered by patient ID. In the amyloidosis group, histological predictors (amyloid deposition and location) were assessed, and receiver operating characteristic (ROC) analysis evaluated polyp size. RESULTS: IPPB occurred significantly more frequently in the amyloidosis group than in the matched non-amyloidosis group (p = 0.008). In multivariable GEE analysis, amyloidosis remained independently associated with IPPB (adjusted OR 3.20, 95% CI: 1.14-8.99; p = 0.027). In amyloidosis patients, muscularis mucosae deposition was associated with IPPB (p = 0.017); multivariate analysis suggested muscularis mucosae deposition (OR 6.55, 95% CI: 1.59-27.00; p = 0.009) and EMR (OR 8.26, 95% CI: 1.41-48.60; p = 0.020) as predictors. ROC analysis yielded an area under the ROC curve of 0.66 with a 6-mm cutoff. CONCLUSIONS: Amyloidosis was independently associated with increased IPPB risk after colorectal polypectomy. Muscularis mucosae deposition and EMR may help identify higher-risk lesions in amyloidosis, and CSP may be considered when feasible to reduce bleeding risk.