Metastases to pelvic lymph nodes from carcinoma in the pelvic cavity: diagnosis using thin-section CT

OBJECTIVE: To assess the accuracy of thin-section computed tomography (CT) in the diagnosis of pelvic lymph nodes affected by metastatic cancer. METHODS: Incremental CT was performed by obtaining 3 mm sections with 3 mm intervals in 34 patients who had carcinoma in the pelvis, pre-operatively and prospectively. CT diagnoses were made before surgery using the cine mode with a manual trackball. Lymph nodes with a maximum short axis diameter of greater than 5 mm were considered enlarged. RESULTS: The accuracy, sensitivity, specificity, positive and negative predictive values of CT diagnoses were 79.7%, 54.5%, 84.9%, 42.9% and 90.0% on a hemipelvis basis; and 79.4%, 85.7%, 77.8%, 50.0% and 95.5% on a patient basis, respectively. There was only one false-negative case on a patient basis analysis. CONCLUSION: Because of a fairly high negative predictive value, negative thin-section CT can be considered an alternative to surgical lymphadenectomy. This is clinically important as unnecessary staging operations and extended surgery are avoided.