To differentiate between hemorrhagic or proteinaceous cysts and RCC, a retrospective study shows that homogenous high T1 signal intensity lesions with smooth borders and lesion to renal parenchyma signal intensity ratio of >1.6 predicted the lesion as a benign cyst [53]. Another study of 144 T1-hyperintense lesions demonstrated that diffuse and marked T1 hyperintensity achieved accuracies of 73.6% to 79.9% for the diagnosis of T1- hyperintense cysts [54]. An angular interface with the renal parenchyma on T2-weighted imaging has been shown to be 78% sensitive and 100% specific for differentiating benign exophytic renal masses from malignant masses [55]. Diffusion-weighted imaging, although less accurate than contrast-enhanced MRI, may have some ability to differentiate solid RCC from oncocytomas and characterize the histologic subtypes of RCC [56]. New and specialized MRI sequences have been proposed for the purposes of characterizing the vascularity of renal lesions in patients with renal dysfunction. For example, one small study of 17 renal lesions used arterial spin labeling to detect blood flow in renal masses, which correlated with malignancy [57]. Cystic Renal Masses In a patient who cannot receive iodinated contrast, MRI without and with IV contrast is a good alternative. MRI may depict findings like an increase in number of septa, septal or wall thickness, and enhancement; these may result in MRI upgrading cystic lesions and thus might alter patient management [29]. Another study of 33 cystic lesions imaged with both 1.5T and 3.0T MRI showed that there is a greater tendency to upgrade cyst complexity and Bosniak cyst category at 3.0T than at 1.5T and thus suggested that serial follow-up of cystic renal lesions be performed at constant field strength [58]. MRU There is no relevant literature regarding the use of MRU in the evaluation of indeterminate renal masses. Indeterminate Renal Mass
Indeterminate Renal Mass. To differentiate between hemorrhagic or proteinaceous cysts and RCC, a retrospective study shows that homogenous high T1 signal intensity lesions with smooth borders and lesion to renal parenchyma signal intensity ratio of >1.6 predicted the lesion as a benign cyst [53]. Another study of 144 T1-hyperintense lesions demonstrated that diffuse and marked T1 hyperintensity achieved accuracies of 73.6% to 79.9% for the diagnosis of T1- hyperintense cysts [54]. An angular interface with the renal parenchyma on T2-weighted imaging has been shown to be 78% sensitive and 100% specific for differentiating benign exophytic renal masses from malignant masses [55]. Diffusion-weighted imaging, although less accurate than contrast-enhanced MRI, may have some ability to differentiate solid RCC from oncocytomas and characterize the histologic subtypes of RCC [56]. New and specialized MRI sequences have been proposed for the purposes of characterizing the vascularity of renal lesions in patients with renal dysfunction. For example, one small study of 17 renal lesions used arterial spin labeling to detect blood flow in renal masses, which correlated with malignancy [57]. Cystic Renal Masses In a patient who cannot receive iodinated contrast, MRI without and with IV contrast is a good alternative. MRI may depict findings like an increase in number of septa, septal or wall thickness, and enhancement; these may result in MRI upgrading cystic lesions and thus might alter patient management [29]. Another study of 33 cystic lesions imaged with both 1.5T and 3.0T MRI showed that there is a greater tendency to upgrade cyst complexity and Bosniak cyst category at 3.0T than at 1.5T and thus suggested that serial follow-up of cystic renal lesions be performed at constant field strength [58]. MRU There is no relevant literature regarding the use of MRU in the evaluation of indeterminate renal masses. Indeterminate Renal Mass