Local staging of rectal cancer with transrectal ultrasound and endorectal magnetic resonance imaging: comparison with histologic findings

PURPOSE: The aim of the present study was to compare the accuracy of endorectal coil magnetic resonance imaging with transrectal ultrasound in staging rectal carcinoma. METHODS: Twenty-six consecutive patients with rectal carcinoma, histologically proven by endoscopic biopsy, were staged with both endorectal coil magnetic resonance imaging and transrectal ultrasound and then underwent radical surgery. The preoperative staging was compared with histologic findings of the operative specimen according to TNM classification. RESULTS: Endorectal coil magnetic resonance imaging showed better results but was not statistically significantly different from transrectal ultrasound in evaluating T (accuracy, 84.6 vs. 76.9 percent): four overstaged and no understaged cases for the former and five overstaged cases and one understaged case for the latter. Both procedures showed similar results in evaluating N: 81 percent sensitivity and 66 percent specificity for endorectal coil magnetic resonance imaging and 72 percent sensitivity and 80 percent specificity for transrectal ultrasound. CONCLUSIONS: An accurate locoregional staging of rectal cancer is essential for the planning of optimal therapy for rectal cancer. Endorectal coil magnetic resonance imaging and transrectal ultrasound showed similar results; the former is more expensive, whereas the latter is operator dependent. At present the use of endorectal coil magnetic resonance imaging seems to be justified only in selected low rectal cancers where transrectal ultrasound yielded doubtful results. However, a more extensive study is necessary to compare the advantages of these diagnostic techniques.