Comparative study of transrectal ultrasonography, pelvic computerized tomography, and magnetic resonance imaging in preoperative staging of rectal cancer

PURPOSE: The preoperative assessment of rectal cancer wall invasion and reg ional lymph node metastasis is essential for the planning of optimal therap y. This study was done to determine the accuracy and clinical usefulness of transrectal ultrasonography, pelvic computed tomography, and magnetic reso nance imaging in preoperative staging. METHODS: A total of 89 patients with rectal cancer were examined with transrectal ultrasonography (n = 89), pel vic computed tomography (n = 69), and magnetic resonance imaging with endor ectal coil (n = 73). The results obtained by these diagnostic modalities we re compared with the histopathologic staging of specimens. RESULTS: In stag ing depth of invasion, the overall accuracy was 81.1 percent (72/89) by tra nsrectal ultrasonography, 65.2 percent (45/69) by computed tomography, and 81 percent (59/73) by magnetic resonance imaging. Overstaging was 10 percen t (9/89) by transrectal ultrasonography, 17.4 percent (12/69) by computed t omography, and 11 percent (8/73) by magnetic resonance imaging; and underst aging was 8 of 89 (8.9 percent) by transrectal ultrasonography, 12 of 69 (1 7.4 percent) by computed tomograph), and 6 of 73 (8 percent) by magnetic re sonance imaging. Ln staging lymph node metastasis, the overall accuracy rat e was 54 of 85 (63.5 percent) in transrectal ultrasonography 39 of 69 (56.5 percent) in computed tomography, and 46 of 73 (63 percent) in magnetic res onance imaging. The sensitivity was 24 of 45 (53.3 percent) in transrectal ultrasonography, 14 of 25 (56 percent) in computed tomography, and 33 of 42 (78.5 percent) in magnetic resonance imaging; and specificity was 30 of 40 (75.0 percent) in transrectal ultrasonography, 25 of 44 (56.8 percent) in computed tomography, and 13 of 31 (41.9 percent) in magnetic resonance imag ing. The accuracy in detection of positive lateral pelvic lymph nodes under magnetic resonance imaging (n = 8) was 12.5 percent. The accuracy in detec tion of posterior vaginal wall invasion was 100 percent in transrectal ultr asonography (n = 7) and 100 percent in magnetic resonance imaging (n = 3), but 28.5 percent in computed tomography (n = n, CONCLUSIONS: Both transrect al ultrasonography and magnetic resonance imaging with endorectal coil exhi bited Similar accuracy and were superior to conventional computed tomograph y in preoperative assessment of depth of invasion and adjacent organ invasi on. Because transrectal ultrasonography is a safer and more cost-effective modality than magnetic resonance imaging, transrectal ultrasonography is an appropriate method for preoperative staging of rectal cancer. Further effo rts will be needed to provide a better staging of lymph node involvement.