Editing Kidney Cancer: Diagnosis and Evaluation (section)

==== MRI ====
* '''Alternate standard to CT'''
** '''Similar sensitivity and specificity to CT'''
***Sensitivity: 88% (interquartile range [IQR] 81%-94%) CT vs. 87.5% (IQR 75.25%-100%) MRI
***Specificity: 75% (IQR 51%-90%) CT vs. 89% (IQR 75%-96%) MRI
***[https://pubmed.ncbi.nlm.nih.gov/30528378/ Vogel, Christina, et al.] "Imaging in suspected renal-cell carcinoma: systematic review." ''Clinical genitourinary cancer'' 17.2 (2019): e345-e355.
**Considered comparable to CT in characterizing indeterminate renal masses by the American College of Radiology[https://pubmed.ncbi.nlm.nih.gov/33153554/]
**CT may be better for smaller lesions
**'''Most useful in patients in whom contrast is contraindicated because of severe allergy or severe CKD'''
** '''Gadolinium contrast can be given to patients with GFR < 30 mL/min/1.73m2[https://pubmed.ncbi.nlm.nih.gov/33170103/]'''
** '''Nephrogenic systemic fibrosis (NSF)'''
*** Fibrosing dermopathy associated with soft tissue deposition and accumulation of gadolinium
*** '''Potentially serious complication of gadolinium contrast'''
*** '''Very rare'''
**** '''More common with group I gadolinium based contrast agents'''
***** Incidence <0.07% in patients with CKD 4 and 5 with group II agents
***** Group II gadolinium based contrast agents are considered safe for any level of eGFR
****** '''Renal function does not need be screened prior to receiving group II gadolinium based contrast agents'''
*** '''Prevention in patients with ESRD: perform hemodialysis after the MRI scan.'''
* '''Image Sequences'''
**Lesions in upper pole and lower pole may be skipped when scrolling through axial slices, always look at coronal images
**T2WI
***Most useful for anatomic assessment of renal masses
***Usually two T2 sequences, one with fat suppression and one without
***Renal vessels will be dark
**Diffusion weighted imaging
***Sequences with higher b-value more likely useful
*'''Enhancement > 20% is suspicious for RCC'''
* '''For a fat-containing tumor, a T2-weighted image with fat suppression is most likely to identify macroscopic fat and confirm the diagnosis of an angiomyolipoma (AML).'''
* '''Best study for evaluation of invasion into adjacent structures'''
** '''Large tumours may indent and compress adjacent liver parenchyma but seldom actually grow by direct extension into the liver; obliteration of the fat plane between the tumour and adjacent organs (e.g. the liver) on CT can be a misleading finding and should prompt further imaging with MRI'''. In reality, surgical exploration is often required to make an absolute differentiation.