IMAGING

Differentiation of renal clear cell carcinoma and renal papillary carcinoma using quantitative CT enhancement parameters
Ruppert-Kohlmayr AJ, Uggowitzer M, Meissnitzer T, Ruppert G
Department of Radiology, University Hospital Graz, Graz, Austria
AJR Am J Roentgenol. 2004; 183: 1387-91

• Objective: The purpose of our study was to evaluate quantitative multiphasic CT enhancement patterns of malignant renal neoplasms to enable lesion differentiation by their enhancement characteristics. We used a new method to standardize enhancement measurement in lesions on multiphasic CT not being influenced by intrinsic factors like cardiac output.
• Conclusion: The new correction method is a simple tool for excluding intrinsic influences on the enhancement of lesions. Quantitative enhancement evaluation with this method of the influence of intrinsic factors enables accurate differentiation between renal clear cell carcinoma and renal papillary carcinoma.
  
  
• Editorial Comment
  The authors present an interesting and standardized method of measurements of the attenuation of renal tumors on computed tomographic studies, which are designed to eliminate the influence of intrinsic factors on the measured attenuation values of these lesions. This method was able to differentiate the most common malignant renal tumors accurately and was performed using multiphasic CT (unenhanced, corticomedullary, and nephrographic phases). In this study, the author used an enhancement correcting method in the corticomedullary phase, which allowed them to differentiate renal clear cell carcinoma from renal papillary carcinoma with an accuracy rate of 95.7. In other words this study showed a high enhancement in the corticomedullary phase in renal clear cell carcinoma with a slight washout in the nephrographic phase; it showed a low enhancement in many renal papillary carcinomas - sometimes less than 12 H in the corticomedullary phase - but in the nephrographic phase, the enhancement of renal papillary carcinoma was clearly higher than 12 H.
  Several recent papers have dealt with the CT capabilities of distinguishing the histological type of renal cell carcinoma. The reason for this effort is related to the potential effect of this differentiation in the preoperative and operative strategies. As we know the papillary sub-type of renal cell carcinoma has better prognosis than the clear cell carcinoma. This information might be useful in the management of patients with high surgical risks. Because renal papillary carcinoma are usually hypovascular they may also show less propensity for bleeding during surgical resection or during conservative treatments such radiofrequency ablation or cryotherapy.
  Further studies, with larger number of patients, is necessary to confirm the CT capabilities to differentiate the histological sub-types of renal cell carcinoma.

Dr. Adilson Prando
Chief, Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil