MRI diagnosis of mesorectal lymph node metastasis in patients with rectal carcinoma. what is the optimal criterion?

BACKGROUND Preoperative diagnosis of lymph node metastasis is often difficult. A number of different criteria have been advocated in the literature, however, an optimal criterion has not yet been determined in patients with rectal carcinoma. PATIENTS AND METHODS Fifty-one patients, undergoing radical surgery with total mesorectal excision, were examined with reference to regional lymph node status. MRI and pathological findings were compared, and an optimal preoperative criterion was clarified by receiver operating characteristic (ROC) analysis. RESULTS Among size, shape and internal structure criteria, size was a significant factor for diagnosing metastatic lymph node on MRI. ROC analysis showed that a criterion of 6-mm or larger in the longitudinal axis was the most reliable in differentiating metastatic and non-metastatic lymph nodes, with overall accuracy of 78%. CONCLUSION A 6-mm longitudinal diameter criterion is thought to be most optimal in the evaluation of mesorectal lymph node status in patients with rectal carcinoma.