Background:
For rectal cancer, the decision about neoadjuvant therapy, anterior resection, or local excision depends on an accurate preoperative staging. So far, a definite consensus about the best diagnostic imaging (endorectal ultrasonography, computed tomography, and magnetic resonance [MR] imaging) in patients with primary rectal cancer has not yet been reached. The aim of this study was to evaluate the accuracy, sensitivity and specificity of endoscopic ultrasound (EUS) and magnetic resonance imaging (MRI) with two different methods, in the local preoperative staging of rectal carcinoma.

Methods:
fortysix patients with histologically proven rectal carcinoma were staged with EUS, body and phased-array coil MRI and then underwent radical surgery. Surgical operations included low anterior resection or abdominoperineal resection with total mesorectal excision. The preoperative staging was compared with the histologic findings of the operative specimen.

Results:
The overall accuracy of EUS in the evaluation of T parameter was 76%, of MRI with body coil (MRI-BC) was 57% and of MRI with phased-array coil (MRI-PA) was 72%. The accuracy in the evaluation of N parameter was 62%, 64% and 72% for EUS, MRI-BC and MRI-PA respectively. EUS had better sensitivity (80%) and same specificity (67%) than MRI in the evaluation of T parameter. MRI-PA had better sesitivity (63%) and the same specificity (80%) of the other methods in the evaluation of N parameter

Conclusions:
EUS is still the best method for the assessment of T parameter in the preoperative staging or rectal cancer, but MRI-PA yelded similar results. Even if the evaluation of N parameter is still difficult with a low accuracy and sensitivity for all diagnostic methods, in our results MRI-PA has the best accuracy and sensitivity. Our data suggest that MRI-PA should be considered as the single most accurate method for the preoperative staging of rectal cancer.