What is the recommended treatment for a flat polypoidal lesion in the caecum that shows high grade dysplasia?

In cases where a flat polypoidal lesion in the caecum exhibits high-grade dysplasia, the recommended treatment is right hemicolectomy. This approach is taken because high-grade dysplasia in a colorectal polyp indicates a significant risk for progression to colorectal cancer. The presence of this dysplastic change within the polyp suggests that the lesion has a potential for malignancy, and removing a segment of the colon that includes both the lesion and a margin of healthy tissue is essential for ensuring complete resection and providing the best chance for a cure.

In contrast, while colonoscopy might be utilized for diagnostic purposes or for polypectomy in certain cases, it is not sufficient as a definitive treatment option for lesions demonstrating high-grade dysplasia, particularly when they are flat and may not be amenable to complete resection endoscopically. Radiotherapy and chemotherapy are treatments generally reserved for advanced disease rather than for flat lesions with high-grade dysplasia, as these modalities are not effective for localized lesions at this early stage. Thus, a right hemicolectomy is the most appropriate intervention to prevent the potential progression of the lesion into colorectal cancer.