Sonographic evaluation of a villous rectal lesion is helpful in determining the presence of tumour invasion. The presence of an intact hyperechoic submu-cosal interface indicates lack of tumour invasion into the submucosa. Heintz et al.  believe that ERUS cannot differentiate between villous adenoma and invasive cancers because neither the muscolaris mucosae nor the submucosa is sonographically definable and the first hypoechoic layer corresponds anatomically with the mucosa and the submucosa. They suggest that uT0 and uT1 tumours, which manifest as a broadening of the first hypoechoic layer, should be classified together. Instead Adams and Wong  disagree with this interpretation and consider the first hypoechoic layer as the mucosa and muscolaris mucosae and the middle hyperechoic layer as the submucosa. Consequently for such Authors lesions that expand the inner hypoechoic layer and are surrounded by a uniform middle hyperechoic layer are considered villous adenoma (Fig. 9) and lesions that expand the inner hypoechoic layer and have distinct echo defects of the middle hyperechoic layer are considered uT1 tumours. Technical difficulties associated with scanning vil-lous adenoma can be due to very large lesions that tend to attenuate rectal layers and lesions with a very large exophytic component. In large carpeting lesions, careful evaluation of the entire tumour is necessary to determine that a small area of invasion has not been overlooked. In some polyps the complex structure produce fixed artefacts over one part of the rectal wall, obscuring the image. Snare biopsy of lesions before referral to ERUS produces a burn artefact, which can lead to tumour overstaging.
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