Accuracy of High-Resolution MRI with Lumen Distention in Rectal Cancer Staging and Circumferential Margin Involvement Prediction

OBJECTIVE: To evaluate the accuracy of magnetic resonance imaging (MRI) with lumen distention for rectal cancer staging and circumferential resection margin (CRM) involvement prediction. MATERIALS AND METHODS: Seventy-three patients with primary rectal cancer underwent high-resolution MRI with a phased-array coil performed using 60-80 mL room air rectal distention, 1-3 weeks before surgery. MRI results were compared to postoperative histopathological findings. The overall MRI T staging accuracy was calculated. CRM involvement prediction and the N staging, the accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were assessed for each T stage. The agreement between MRI and histological results was assessed using weighted-kappa statistics. RESULTS: The overall MRI accuracy for T staging was 93.6% (k = 0.85). The accuracy, sensitivity, specificity, PPV and NPV for each T stage were as follows: 91.8%, 86.2%, 95.5%, 92.6% and 91.3% for the group < or = T2; 90.4%, 94.6%, 86.1%, 87.5% and 94% for T3; 98,6%, 85.7%, 100%, 100% and 98.5% for T4, respectively. The predictive CRM accuracy was 94.5% (k = 0.86); the sensitivity, specificity, PPV and NPV were 89.5%, 96.3%, 89.5%, and 96.3% respectively. The N staging accuracy was 68.49% (k = 0.4). CONCLUSION: MRI performed with rectal lumen distention has proved to be an effective technique both for rectal cancer staging and involved CRM predicting.

A Case of Rectal Implantation Cysts at an Anastomosis Site after Laparoscopic Low Anterior Resection for a Rectal Cancer / 대한소화기내시경학회지

Rectal implantation cysts can be caused by continued growth in the submucosa of traumatically misplaced columnar epithelium during previous surgery. Cases of implantation cyst occurring at the site of anastomosis have rarely been reported. Rectal implantation cysts occurring at an anastomosis site after a low anterior resection for rectal cancer need to be distinguished from locally recurrent rectal cancer. Here we present a case of rectal implantation cysts in a patient with rectal cancer who underwent laparoscopic low anterior resection 9 months previously. The diagnosis was made according to the characteristic image findings of endoscopic ultrasonography and enodsocopic ultrasonography-guided fine needle aspiration. This is the first case report of rectal implantation cyst in Korea.

Clinical Significance of Preoperative Magnetic Resonance Imaging in Staging of Rectal Cancer / 대한소화기학회지

Rectal cancer carries poor prognosis because of metastasis and local recurrence. Local recurrence has a profound effect on morbidity and quality of life. Randomized trials have proven that neoadjuvant treatment can significantly reduce local recurrence rate in some selected cases of advanced rectal cancer. Therefore, preoperative staging of rectal cancer has an important impact on treatment plan. Two main factors in predicting the local recurrence are known as the circumferential resection margin (CRM) and the nodal status. Recently, high-resolution magnetic resonance imaging (MRI) is regarded as a superior modality in the preoperative assessment of CRM with high accuracy and reproducibility. However, the results of imaging in predicting of nodal involvement are not satisfactory. In order to increase the accuracy of preoperative nodal staging, several efforts were done to evaluate lymph node by MRI or by pelvic MRI using lymph node-specific contrast agent (ultrasmall superparamagnetic iron oxide, USPIO). In this review, the role of MRI in preoperative evaluation of rectal cancer will be discussed.

Differentiation of Recurrent Rectal Cancer and Postoperative Fibrosis: Preliminary Report by Proton MR Spectroscopy

PURPOSE: To know the differences of proton MR spectroscopic features between recurrent rectal cancer and fibrosis in post-operative period, and to evaluate the possibility to discriminate recurrent rectal cancer from post-operative fibrosis by analysis of proton MR spectra. MATERIALS AND METHODS: We evaluated the proton MR spectra from 25 soft tissue masses in perirectal area that developed in post-operative period after operation for the resection of rectal cancer. Our series included 11 cases of recurrent rectal cancer and 14 of fibrotic mass. All cases of recurrent rectal cancer and post-operative fibrosis were confirmed by biopsy. We evaluated the spectra with an attention to the differences of pattern of the curves between recurrent rectal cancer and post-operative fibrosis. The ratio of peak area of all peaks at 1.6 -4.1ppm to lipid (0.9 - 1.6ppm) [P (1.6 -4.1ppm)/P (0.9 -1.6ppm)] was calculated in recurrent rectal cancer and post-operative fibrosis groups, and compared the results between these groups. We also evaluated the sensitivity and specificity for discriminating recurrent rectal cancer from post-operative fibrosis by analysis of 1 H-MRS. RESULTS: Proton MR spectra of post-operative fibrosis showed significantly diminished amount of lipids compared with that of recurrent rectal cancer. The ratio of P (1.6 -4.1ppm)/P (0.9 -1.6ppm) in post-operative fibrosis was much higher than that of recurrent rectal cancer with statistical significance (p < .05) due to decreased peak area of lipids. Mean (standard deviations of P (1.6 -4.1ppm)/P (0.9 -1.6ppm) in post-operative fibrosis and recurrent rectal cancer group were 2.71 +/-1.48 and 0.29 +/- 0.11, respectively. With a cut-off value of 0.6 for discriminating recurrent rectal cancer from post-operative fibrosis, both the sensitivity and specificity were 100% (11/11, and 14/14). CONCLUSION: Recurrent rectal cancer and post-operative fibrosis can be distinguished from each other by analysis of proton MR spectroscopic features, and 1 H-MRS can be a new method for differential diagnosis between recurrent rectal cancer and post-operative fibrosis.