ASSESSMENT OF TUMOR INVASION OF THE VENA CAVAL WALL IN RENAL CELL CARCINOMA CASES BY MAGNETIC RESONANCE IMAGING S. A. ASLAM SOHAIB, JAMES TEH, VINOD H. NARGUND, JOHN S. P. LUMLEY, WILLIAM F. HENDRY AND RODNEY H. REZNEK From the Departments of Radiology, Genito-urinary Surgery and Surgery, St. Bartholomew’s Hospital and Queen Mary and Westfield College, University of London, London, United Kingdom ABSTRACT Purpose: We evaluated the role of magnetic resonance imaging (MRI) in patients with renal cancer and inferior vena caval involvement with reference to its ability to characterize the extent and nature of inferior vena caval tumor extension and wall invasion. Materials and Methods: The study included 12 consecutive patients with renal cancer and inferior vena caval involvement. All patients underwent imaging on a 1.5 Tesla MRI unit. Coronal, axial T1 and axial T2-weighted images were performed in all cases, while in 6 3-dimensional gadolinium enhanced magnetic resonance angiography and venography were also performed. Images were assessed for the extent and nature of tumor extension, that is tumor versus thrombus, and invasion of the inferior vena caval wall. Imaging results were compared with operative findings. Results: On MRI the extent and nature of the inferior vena caval tumor was correctly defined in all cases. The sensitivity, specificity and accuracy of inferior vena caval wall invasion were 100%, 89% and 92%, respectively. Conclusions: In patients with renal cancer and inferior vena caval involvement MRI defines the tumor level in the inferior vena cava. It is also a sensitive technique for detecting vessel wall invasion and provides important preoperative information for surgical planning. KEY WORDS: kidney; kidney neoplasms; neoplasm metastases; vena cava, inferior; magnetic resonance imaging Of renal cancer patients 4% to 10% present with involve- ment of the inferior vena cava. 1–3 Vena caval involvement may be due to a pure thrombus consisting of pure blood clot or to tumor extension with blood clot and malignant tissue. In 43% to 64% of cases tumor may invade the inferior vena caval wall. 4, 5 Surgical resection remains the only chance for cure in such patients with a 5-year survival rate of up to 30% to 70% when there is no lymph node involvement or distant metastasis. 4,6–8 The level of inferior vena caval tumor exten- sion has little overall effect on the survival rate in patients who undergo complete removal of the primary tumor with extraction of the inferior vena caval tumor extension. 9 –11 In some cases of supradiaphragmatic inferior vena caval exten- sion cardiopulmonary bypass and circulatory arrest may be necessary. Tumor invasion of the vena caval wall requires resection of the affected segment and vascular reconstruc- tion. Therefore, in addition to accurate preoperative staging, determining the nature of inferior vena caval tumor exten- sion and wall invasion has surgical importance. Magnetic resonance imaging (MRI) has gained acceptance as an accurate technique for determining the presence and extent of inferior vena caval tumor extension. 5, 8, 12, 13 How- ever, there are limited data on the ability of preoperative imaging to predict the nature of inferior vena caval content or venous wall invasion. 5, 14, 15 We evaluated the accuracy of MRI for determining the extent and characterizing the na- ture of inferior vena caval content. We also determined infe- rior vena caval wall invasion. MATERIALS AND METHODS Between 1997 and 2000, 6 males and 6 females 39 to 75 years old (mean age 62) presented with renal cell carcinoma and involvement of the inferior vena cava with no distant metastasis. All 12 patients underwent surgical exploration after staging investigations. Imaging was done using a 1.5 Tesla magnetic resonance unit. All patients underwent coro- nal and axial T1-weighted spin echo images with a repetition-to-echo time of 400 to 640/14 to 20 milliseconds and axial T2-weighted fast spin-echo images with a repetition-to-echo time of 4,000 to 6,000/90 to 110 millisec- onds and an echo train length of 8 to 16. Slice thickness was 5 to 7 mm. and slice gap was 1 to 2 mm. Field of view was 32 to 35 cm. with a matrix size of 256  192 to 256 and 2 or 3 excitations. Magnetic resonance angiography and venography were also performed in 6 patients using a 3-dimensional (3-D) contrast medium enhanced technique. Before administering contrast medium localizing images were obtained using a 3D spoiled gradient echo sequence with 28 sections in the coro- nal plane and a repetition-to-echo time of 8/1.4, flip angle of 30 degrees, 35 to 48 cm. field of view, 32 kHz bandwidth, 256  128 matrix and 1 signal acquired. Each section was 2 to 3 mm. thick. Image volume included the renal hilum posterior and the inferior vena caval anterior. Total breath hold was 22 to 30 seconds. Contrast medium was injected rapidly by hand and image acquisition started within 5 sec- onds. The first pass of contrast medium generated the images in the arterial phase. The sequence was repeated 3 times with a 5-second delay between repetitions. Later phase im- ages generating images in the venous phase of enhancement were evaluated for study purposes. Images were assessed for inferior vena caval content, and its upper extent, nature, vessel wall invasion, wall thickness and inferior vena caval expansion. The superior extent of the inferior vena caval tumor was characterized as infrahepatic, Accepted for publication October 12, 2001. 0022-5347/02/1673-1271/0 THE JOURNAL OF UROLOGY ® Vol. 167, 1271–1275, March 2002 Copyright © 2002 by AMERICAN UROLOGICAL ASSOCIATION,INC. ® Printed in U.S.A. 1271