Diagnostic value of multidetector computed tomography for renal sinus fat invasion in renal cell carcinoma patients

Although renal sinus fat invasion has prognostic significance in patients with renal cell carcinomas (RCCs), there are no previous studies about the value of multidetector computed tomography (MDCT) about this issue in the current literature.

A total of 863 consecutive patients (renal sinus fat invasion in 110 patients (12.7%)) from single institutions with surgically-confirmed renal cell carcinoma who underwent MDCT between 2010 and 2012 were included in this study. The area under the curves (AUCs) of the receiver operating characteristic (ROC) analysis was used to compare diagnostic performance. Reference standard was pathologic examination. Weighted κ statistics were used to measure the level of interobserver agreement. Multivariate logistic regression model was used to find the predictors for renal sinus fat invasion. Image analysis was first performed with axial-only CT images. A second analysis was then performed with both axial and coronal CT images. A qualitative analysis was then conducted by two reviewers who reached consensus regarding tumor size, decreased perfusion, tumor margin, vessel displacement, and lymph node metastasis. The reference standard was pathologic evaluation.

The AUCs of the ROC analysis were 0.881 and 0.922 for axial-only images and 0.889 and 0.902 for combined images in both readers. The AUC of tumor size was 0.884, a similar value to that of the reviewers. In multivariate analysis, tumor size, a linear-nodular or nodular type of fat infiltration, and an irregular tumor margin were independent predicting factors for perinephric fat invasion.

MDCT shows relatively high diagnostic performance in detecting perinephric fat invasion of RCC but suffers from a relatively low PPV related to low prevalence of renal sinus fat invasion. Applying tumor size alone we could get similar diagnostic performance to those of radiologists. Tumor size, fat infiltration with a nodular appearance, and an irregular tumor margin were predictors for perinephric invasion.