Gadolinium enhanced endorectal coil and air enema magnetic resonance imaging as a useful tool in the preoperative examination of patients with rectal carcinoma.

Background/aims: In the present study, we attempted to evaluate the usefulness of gadolinium enhanced endorectal coil and air enema magnetic resonance imaging with slice adjustments in patients with rectal carcinoma.

Methodology: The subjects were patients with rectal cancer from June 1997 to September 1999 who were examined with a 1.5 Tesla magnetic resonance device. Buscopan was administered both intravenously and intramuscularly to reduce motion artifacts. Imaging sequences were obtained for T1 weighed, T2 weighed and T2 fat-saturated images. Slice thickness was 5 mm and interslice gap 3 mm. Endorectal coil insertion and air enema technique were performed with slice adjustments. Images were interpreted according to the criteria of the TNM classification. Lymph node metastasis was diagnosed as positive when the lymph nodes exceeded 5 mm in diameter. Histological and magnetic resonance findings were compared, and diagnostic accuracy was calculated.

Results: Fifty-four consecutive patients were included in this study (37 male, 17 female). There were 10 early cases and 44 advanced cases of rectal cancer. Images with an endorectal coil were obtained in 4 patients. Fifty patients underwent air enema technique. The depth of tumor invasion was accurately diagnosed in all 4 patients undergoing endorectal coil examination. On air enema study, magnetic resonance imaging correctly staged the depth of invasion in 41 of 50 patients (82.0%). Overstaging was seen in 8 of 50 patients (16%), however, only one patient (2.0%) was understaged. Overall accuracy, overstaging and understaging rates were 83.3% (45/54), 14.8% (8/54), and 1.8% (1/54), respectively. On endorectal coil study, accurate diagnosis of lymph node metastasis was obtained in 3 of 4 (75.0%) patients. On air enema study, an accurate diagnosis of lymph node metastasis was obtained in 36 of 50 (72.0%) patients, yielding 75.0% sensitivity and 73.1% specificity. Overall magnetic resonance imaging findings of lymph node metastasis resulted in 72.2% (39/54) diagnostic accuracy, yielding sensitivity of 75.0% (18/24) and specificity of 73.3% (22/30).

Conclusions: We conclude that gadolinium enhanced endorectal coil and air enema magnetic resonance imaging is promising for preoperative evaluation of patients with rectal carcinoma.