Role of MRI for staging of rectal cancer.

Total mesorectal excision has been established as a standard surgical procedure for rectal cancer. MRI is now routinely used for preoperative staging of rectal cancer and provides accurate assessment of the tumor relative to the circumferential margin, that is, the mesorectal fascia. This identifies patients at risk of local recurrence and those likely to benefit from neoadjuvant therapy. Compared with CT and ultrasound, MRI is more reliable for the evaluation of the extent of locoregional disease, planning radiation therapy, assessing postoperative changes and pelvic recurrence. The evaluation of nodal metastases remains a challenge with routine MRI. In this review, we describe the role of MRI in staging rectal cancer as well as highlight some limitations and recent advances to overcome these.