Introduction Colorectal polyps with a focus of malignancy, identified postpolypectomy, pose a management challenge of whether endoscopic treatment is adequate or whether further surgical resection is required. This study assessed 12- and 20-MHz colonoscopic ultrasound to evaluate the presence of residual disease and local lymph nodes.

Method Consecutive cases of all colorectal polyps with a focus of malignancy were included. Colonoscopic high-frequency ultrasound was performed (20-MHz mini-probes for residual polyps and 12-MHz ultrasound for local lymph nodes) in the region of previous polypectomy. Biopsies were taken of the polypectomy site if any abnormalities were seen.

Results Fifty malignant polyps (sigmoid, n = 19; rectum, n = 25; descending colon, n = 1; transverse colon, n = 1; hepatic flexure, n = 2; ascending colon, n = 1; and caecum, n = 1) were identified. 3 were neuroendocrine tumours and 47 were invasive adenocarcinomas; 9 were intramucosal and 38 were submucosal (seven sm1 lesions in the upper third of the submucosa; 11 sm2 lesions in the middle third of the submucosa, seven sm3 lesions in the lower third of the submucosa, one Haggitt level 1, one Haggitt level 2, two Haggitt level 3 and 9 with an unspecified submucosa level). Two patients had T2 tumours extending into the muscularis propria. Excision was histologically complete in 31 patients, five had involved margins and histology was uncertain in fourteen owing to diathermy artefacts or piecemeal resections. High-frequency 12- and 20-MHz ultrasound imaging was normal in 40 patients and four had changes either subsequently proved to be scar related or due to minor benign polyp recurrence. At the time of writing, 39 (89%) of the 44 patients were disease free without further surgery. Five of the 21 patients underwent surgery, despite normal high-frequency ultrasound findings, because of submucosal invasion (sm1 or sm2) and uncertain completeness of resection. The specimens were free of cancer in all five patients.

Conclusion High frequency mini probe ultrasound is feasible in the colon and rectum for the assessment of the polypectomy site post endoscopic resection of malignant polyps. Definitive management cannot be exclusively based on the ultrasound findings but this may act as a useful adjunct to histology in providing a more complete prediction of poorer prognosis.

Disclosure of interest None Declared.