In a study of 73 RCCs, Roy et al [64] showed that the presence of a pseudocapsule on MRI had an accuracy of 93% for clear-cell carcinomas in separating T1/T2 tumors from T3a tumors. Lal et al [65] performed a prospective observational study in 50 patients with RCC, comparing MRI with histopathological findings. In this study, MRI was reported to have a 90% agreement with histopathology for detecting perirenal extension and a 97% agreement with histopathology for detecting tumor extension beyond Gerota fascia [65]. Both contrast-enhanced multidetector CT and MRI are helpful in detecting venous involvement, particularly in the main renal vein and the IVC [33,66]. Increased diameter of the IVC and renal vein, presence of tumor signal both inside and outside the vessel wall, altered signal intensity in the vessel wall, presence of flow around the tumor thrombus, and mobility in different phases are some of the MRI features that are helpful in detecting venous involvement [67,68]. Bland thrombus featuring a uniform signal intensity and lack of enhancement after gadolinium can be distinguished from tumor thrombus, which exhibits intermediate or high signal intensity, heterogeneous intensity, and, more reliably, the presence of small vessels. In a recent study involving 81 patients with RCC, MRI was reported to have a 92% sensitivity, an 86% specificity, an 89% positive predictive value, and a 91% negative predictive value for identifying IVC wall invasion [69]. Pitfalls of MRI include the potential for large tumors to compress the vena cava and cause flow-related artifacts. Such artifacts can be reduced with appropriate saturation pulses. Although MRI of the abdomen with IV contrast is considered in all major guidelines as an adequate method for the staging of RCC, imaging the pelvis for RCC staging is considered optional in the guidelines [5,13]. There is no relevant literature with high-quality evidence regarding the use of MRI of the pelvis in the staging of RCC.
Staging of Renal Cell Carcinoma. In a study of 73 RCCs, Roy et al [64] showed that the presence of a pseudocapsule on MRI had an accuracy of 93% for clear-cell carcinomas in separating T1/T2 tumors from T3a tumors. Lal et al [65] performed a prospective observational study in 50 patients with RCC, comparing MRI with histopathological findings. In this study, MRI was reported to have a 90% agreement with histopathology for detecting perirenal extension and a 97% agreement with histopathology for detecting tumor extension beyond Gerota fascia [65]. Both contrast-enhanced multidetector CT and MRI are helpful in detecting venous involvement, particularly in the main renal vein and the IVC [33,66]. Increased diameter of the IVC and renal vein, presence of tumor signal both inside and outside the vessel wall, altered signal intensity in the vessel wall, presence of flow around the tumor thrombus, and mobility in different phases are some of the MRI features that are helpful in detecting venous involvement [67,68]. Bland thrombus featuring a uniform signal intensity and lack of enhancement after gadolinium can be distinguished from tumor thrombus, which exhibits intermediate or high signal intensity, heterogeneous intensity, and, more reliably, the presence of small vessels. In a recent study involving 81 patients with RCC, MRI was reported to have a 92% sensitivity, an 86% specificity, an 89% positive predictive value, and a 91% negative predictive value for identifying IVC wall invasion [69]. Pitfalls of MRI include the potential for large tumors to compress the vena cava and cause flow-related artifacts. Such artifacts can be reduced with appropriate saturation pulses. Although MRI of the abdomen with IV contrast is considered in all major guidelines as an adequate method for the staging of RCC, imaging the pelvis for RCC staging is considered optional in the guidelines [5,13]. There is no relevant literature with high-quality evidence regarding the use of MRI of the pelvis in the staging of RCC.