Important imaging considerations in the pre-operative assessment of rectal cancer

The role of imaging has become central in the pre-operative decision-making process for patients with rectal cancer. The detailed information that is available from high-resolution imaging studies not only provides prognostic information but also allows the surgeon to anticipate potential pitfalls during the operation. The greater the amount of detail known about the tumour, the more selective one can be in the use of pre-operative radiotherapy, which can reduce unnecessary morbidity for minimal gain. Magnetic resonance imaging (MRI) is the most useful modality for the local staging of rectal cancer as it provides the most detail on the important prognostic factors that influence treatment. These include height of tumour from the anal verge, tumour depth of penetration, nodal disease, venous invasion, involvement of the circumferential resection margin. However, endoanal ultrasound (EAUS) is particularly good at staging early tumours and aids in identifying those that are suitable for local excision. We review the important considerations in the pre-operative staging of rectal cancer.