WCE 2018: Small Renal Masses - Imaging

Paris, France (UroToday.com) An increase in the incidence of renal cell carcinoma (RCC) at a rate of 2-3% has been observed in recent years, without a corresponding change in mortality. This has been attributed largely to incidental detection of indolent tumors, on imaging studies done for unrelated conditions. Imaging of small renal mass has a key role in diagnosis, surgical planning, and postoperative evaluation of functional and oncological outcomes. Triphasic computed tomography (CT) is the gold standard for evaluation of renal tumors. It consists of a non-contrast scan, followed by corticomedullary phase, and the nephrographic phase (latter two phases are contrast-enhanced). Non-contrast CT scan can demonstrate areas of calcification (found in RCC) or macroscopic fat, which almost always confirms the presence of a benign angiomyolipoma. Peak contrast enhancement can indicate the type of tumor; whereas clear cell RCC tends to enhance during the corticomedullary phase, the less vascular papillary RCC shows gradual enhancement during the nephrographic phase.

Magnetic resonance imaging (MRI) is sometimes being utilized in renal tumor imaging, namely when there are contraindications to contrast medium, or when the CT images are inconclusive. T1 weighted images can detect fat and hemosiderin and thus diagnose angiomyolipoma and hemorrhagic cysts, respectively. On the other hand, T2 sequence can better characterize complex cystic tumors and different types of RCC (Figure 1). Despite the high accuracy of both CT and MRI, in 10-20% of cases, the discrimination between benign and malignant renal masses is impossible. In these cases, a biopsy is recommended, if its result may alter the management.

UroToday WCE2018 Proposed imaging algorithm of renal mass
Figure 1. Proposed imaging algorithm of renal mass

Since the introduction of the R.E.N.A.L. Nephrometry Score in 2009, there have been several other scoring systems that asses tumor complexity based on anatomical features (PADUA Score, Centrality Index, Arterial-Based Complexity Score, Diameter-Axial-Polar Score, and Contact Surface Area). In general, these scoring systems have been correlated with operative and ischemia time, blood loss, urine leak, length of stay, and tumor recurrence. Additional scoring systems of non-tumor related anatomy have been studied clinically and include the Mayo Adhesive Probability (MAP) Score and the Renal Pelvis Score. These two are associated with the complexity of the procedure and perioperative outcomes. Other imaging-based adjunct tools for preoperative planning are the 3D reconstruction (from 1 mm CT angiogram slices) and virtual reality of kidney models. Lastly, a 3D model integrated into the robotic console generates a superimposed image of the tumor and blood vessels (augmented reality). In the postoperative settings following partial nephrectomy, contrast-enhanced CT can assess the functional status of the kidney. The percentage of parenchymal volume preserved after tumor resection correlated with the change in eGFR to a greater degree than merely ischemia time.

Presented by: Francesco Porpiglia, MD, Professor,  Department of Urology, University of Turin, Italy

Written by: Shlomi Tapiero, MD, Department of Urology, University of California-Irvine, medical writer for UroToday.com at the 36th World Congress of Endourology (WCE) and SWL - September 20-23, 2018 Paris, France

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