Preoperative Evaluation of Lower Rectal Cancer by Pelvic MR with and without Gel Filling

Abstract

Purpose : To assess the usefulness of rectal filling using ultrasonographic gel in patients with lower rectal cancer.

Materials and Methods: Twenty five patients with lower rectal cancer were enrolled. High resolution pelvic MR was performed twice before and after gel filling. Independently and retrospectively, two radiologists reviewed each set of MR images using five-grade scales for sphincter involvement, CRM (circumferential resection margin) involvement and depiction of the tumor. Same two radiologists retrospectively performed consensus review of each set of MR images for tumor distance from the anal verge and T&N staging.

Results: Tumor depiction scores from MR with gel filling were significantly higher than those of MR without distention (p<0.001). Compared to MR without distension, MR with gel filling had no significant differences in prediction of CRM or sphincter involvement (p>0.05). Distance from the anal verge was significantly different between MR with gel filling and rigid endoscopy ($6.8{\pm}1.6cm$ vs. $5.8{\pm}1.6cm$, p=0.001). There were no significant differences between pathological staging and MR staging with or without gel filling.

Conclusion: MR with gel filling improved tumor depiction. And also MR with gel filling revealed same ability for the predictions of CRM or sphincter invasion in patients with lower rectal cancer, comparing with MR without gel filling.