[Comparative study of MRI and CT x-ray in evaluating the extension of kidney cancer in adults].

The assessment of the extent of kidney cancers with MRI and CT is compared in 40 patients. The appearance of the tumor with MRI is very variable but always heterogeneous. Specific MRI features (tumoral pseudocapsule) provide a higher overall reliability (OR) than with CT for the detection of expansion beyond the capsule and into the kidney: 80% for 60%. Although the overall reliability of MRI is similar to that of CT (92% for 86%), MRI has proved its superiority for the assessment of the limits of endovenous tumoral expansion because of natural flow/thrombus contrast and of the multiple incidences of exploration. There is no significant difference between MRI (OR = 91%) and CT (OR = 88%) or the detection of lymph node involvement. Invasion of neighboring organs is better assessed with multi-incidence MRI. According to Robson's classification, the OR of MRI (77%) is not significantly higher than that of CT (65%). MRI is still a time-consuming and expensive technique, which should be reserved for cases in which iodine is contraindicated and used as a second-intention technique after CT to confirm the invasion of the capsule if partial nephrectomy is indicated, or the better delineate venous or regional invasion which CT could not assess properly.