Predictive value of magnetic resonance imaging and computerized tomography for conservative renal surgery in an ex vivo tumor enucleation study followed by step-sectioning.

Abstract

Due to the early diagnosis of many renal cell cancers, the treatment options of organ conserving surgery is of interest even for patients with a normal contralateral kidney. To our knowledge the predictive value of preoperative investigations in such patients has not been clarified. In a prospective study of 30 patients with stage T1/T2 renal cell carcinoma ex vivo enucleation was performed following tumor nephrectomy. Magnetic resonance imaging (MRI) and computerized tomography (CT) were done preoperatively in all patients. For pathological evaluation the kidneys were step-sectioned in 1 mm. slices. Macroscopic and microscopic findings were compared to those of the preoperative investigations. Mean tumor diameter was 4.6 cm. (range 2.0 to 10.0). Twelve tumors were incidental and smaller than 4 cm. Residual carcinoma due to incomplete resection was found in 4 kidneys with tumors larger than 4 cm. Parenchymal or hilar venous invasion was noted in 4 cases, including 1 in the incidental group. Prediction of renal fat capsule invasion by MRI was highly confirmed by pathological examination. On the other hand, parenchymal venous involvement or secondary renal tumors smaller than 2 cm. could not be predicted by MRI or CT. Neither MRI nor CT predicts complete tumor control when conservative renal surgery is considered. All incidental tumors smaller than 4 cm. could be resected completely by nephron sparing surgery. Nevertheless, microscopic venous invasion was present in 1 of the latter cases.