Imaging of Rectal Tumours

LEARNING OBJECTIVES -To describe the most used imaging modalities (MRI, TRUS and CT) and their different techniques in the studium of rectal tumours. -To show the application of the imaging in the local tumour evaluation and stadiation (infiltration of deep layers of the wall, relationship with the mesorectal fascia and extension to local limph adenopaties). ABSTRACT Colorectal carcinoma is one of the most common malignancies. To select the best therapeutical approach, a correct evaluation and regional staging of rectal carcinoma by imaging methods is mandatory. A good preparation (cleansing enema and distention) is usefull to any imaging modalities. Transrectal ultrasound (TRUS)is considered the gold standard in the recognition of the rectal wall layers with some limitations (stenosing and proximal lesions) presenting a limited FOV. MRI can be performed with body, endorectal or phased array coils; the last one present high spatial and contrast resolution, wide FOV, evaluating both stenosing and proximal lesions. CT present wide FOV but lower sensitivity for T and sphincter infiltration, although multidetector spiral technology improved its results. The mesorectal fascia and the mesorectal and pelvic lymph nodes can be explored by both MRI and CT. Less frequent lesion (adenomas or GIST) present particular features, detectable by imaging.