Assessment of rectal tumor infiltration utilizing endorectal MR imaging and comparison with endoscopic rectal sonography.

BACKGROUND: The preoperative assessment of depth of invasion of rectal carcinoma is increasingly important as new treatment methodologies are developed. Accuracy of preoperative endorectal MR imaging was therefore compared with that of the endoscopic rectal sonography in determining depth of invasion of rectal carcinomas. METHOD: From March 1993 to April 1994, 10 consecutive patients with biopsy-proven rectal carcinomas were imaged with both endorectal MR imaging and endoscopic rectal sonography. These two studies were performed an average of 2.7 days apart in each patient. All 10 patients had surgical resection of the rectal carcinoma within days of imaging studies. TNM staging of each malignant lesion was correlated with the imaging reports. RESULT: Staging accuracy was 80% for endorectal MR imaging and 70% for endoscopic rectal sonography. With MR imaging, one T2 lesion was overstaged and one T3 lesion was understaged. With sonography, two T2 lesions were overstaged and one T3 lesion was understaged. One MR error resulted from misinterpretation. All other staging errors occurred in patients with tumor spread into, but not through, the muscularis propria or with microscopic spread through this layer. CONCLUSIONS: Endorectal MR imaging and endoscopic rectal sonography have similar accuracy for assessing depth of invasion of rectal carcinoma.