Background: Large (≥20mm) non-pedunculated colorectal lesions are frequently referred to specialty centers for endoscopic resection. These lesions are technically challenging to resectand associated with substantially greater risk than smaller lesions. Patients with such polypsoften have synchronous lesions. We sought to identify evidence for whether synchronouslesions were sometimes the true basis for referral of large non-pedunculated colorectal polypsfrom community endoscopists to a tertiary center.
 Methods: We utilized a prospectively collected database of 1356 consecutive referred patients to an expert colonoscopist at our tertiary center between August 2019 and May 2023. We identified patients with ≥30 precancerous lesions resected from the colorectum during their first two colonoscopies at our center. Patients in the database with the same gender, within 3 yearsof age, and with the same location (proximal vs. distal colon) of the index large lesion referred for resection were identified as controls. Groups were compared for the size of index lesion, number of polyps resected by both centers, and size of polyps resected.
 Results: Among 1356 patients, 49 (3.6%) had ≥30 precancerous lesions resected at our center. Compared to controls, the index lesion was smaller in patients with ≥30 lesions (mean 28.9mmvs 23.3mm). Among patients with ≥30 synchronous polyps, the referring physician resected 10.6% of all synchronous lesions, compared to 47.8% in the control group (p<0.0001). Inpatients with ≥30 lesions, 84% of all synchronous lesions were <10mm, 15% were 10-19mm, and only 1% were >20mm.
 Conclusion: Our results suggest a subset of patients with large non-pedunculated colorectal precancerous lesions referred to tertiary centers are referred because of the number of lesions present, rather than technical challenges associated with resection of individual lesions. The rationale for these referrals is uncertain. It may lie in the reimbursement system, which only compensates physicians for the first polypectomy.