Endoscopic submucosal dissection (ESD) enables en-bloc resection of large or fibrotic colorectal lesions that are not amenable to snare-based techniques. Its uptake for proximal colonic lesions in Western practice remains limited, largely due to technical complexity and anatomical challenges. The Saline Immersion/irrigation TEchnique (SITE) has emerged as a strategy to help overcome these limitations. This study evaluated the procedural efficacy and safety of SITE-facilitated ESD for proximal colonic lesions in a tertiary center.

All proximal colonic ESDs performed between April 2018 and October 2025 were retrospectively analyzed from a prospectively maintained institutional database. All cases were discussed in a multidisciplinary team meeting beforehand. SITE was applied in every procedure, in combination with the pocket-creation method (PCM) or its variants. Baseline characteristics, procedural parameters, histopathological outcomes and adverse events were recorded.

Of 106 lesions referred for ESD, eight (7.5%) procedures were abandoned due to intra-procedural detection of deep submucosal invasion, and 12 lesions were resected using snare-based techniques. Eighty-six lesions were removed by ESD and included in the analysis. Eighty-two procedures (95.3%) were performed under operator-delivered conscious sedation. Mean patient age was 68 ± 9.1 years, and 51 patients (59.3%) were male. Lesion location was caecum (n = 29), ascending colon (n = 41) and transverse colon (n = 16). Nine lesions (10.5%) were recurrent.

Median lesion size was 40 mm (IQR 35–58.8) × 35 mm (IQR 25–50). En-bloc resection was achieved in all cases. Resection status was R0 in 76 (88.3%), R1 in 8 (9.3%) and Rx in 2 (2.3%). Median resection time was 120 min (IQR 90–160), with a median dissection speed of 10.8 mm²/min (IQR 6.2–16.1). Histopathology revealed low-grade dysplasia in 68 lesions (79%), high-grade dysplasia in 10 (11.6%), SM1 cancer in 1 (1.2%), deeply invasive cancer in 3 (3.5%) and sessile serrated lesions with dysplasia in 4 (4.7%).

Among the eight R1 resections, four were vertical and four lateral. Three patients with vertical R1 margins and invasive cancer underwent surgery, with residual cancer identified in one case. The remaining vertical R1 (LGD) lesion was successfully managed endoscopically. Six patients had lateral R1/Rx resections, all LGD; only one case—located at the ileocecal valve—developed recurrence, which was treated endoscopically.

Four adverse events occurred (4.7%): two microperforations and one delayed bleed requiring embolization. None required surgical intervention. Thirty-two patients (37.2%) were admitted, with a median length of stay of 1 day (IQR 1–2). Defect closure was achieved in 60 cases (69.7%).

SITE-facilitated ESD for proximal colonic lesions was performed predominantly under conscious sedation and achieved consistently high en-bloc and R0 resection rates with low adverse-event rates. These results support consideration for routine adoption for right-sided colonic ESD. Further multicenter prospective studies are needed to validate these outcomes as the preferred approach for proximal colonic ESD.