Aim 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 Twenty-one malignant polyps (sigmoid, n = 10; rectum, n = 8; transverse colon, n = 1; ascending colon, n = 1; and caecum, n = 1) were identified. All were invasive adenocarcinomas; 12 were intramucosal and nine were submucosal (seven sm1 lesions in the upper third of the submucosa; and two sm2 lesions in the middle third of the submucosa). Excision was histologically complete in 12 patients, four had involved margins and histology was uncertain in five owing to diathermy artefacts. Further colonoscopy revealed a residual abnormality in eight patients. The 12- and 20-MHz ultrasound imaging revealed mucosal irregularity with normal bowel-wall layers and no lymph-node involvement, with normal histology. High-frequency ultrasound was normal in the remaining 13 patients. At the time of writing, 15 (72%) of the 21 patients were disease free without further surgery. Six 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 six patients.
Conclusion High-frequency ultrasound is feasible for the assessment of colorectal malignant polyps.