What are the IVU CT and MRI features of bladder cancer?
On IVU, an intraluminal filling defect in the bladder may be seen. This may be solitary or multifocal in spatial extent. On CT and MRI, an intraluminal enhancing bladder mass or focal asymmetric bladder wall thickening is seen, which may again be solitary or multifocal. Superficial calcification in the tumor may be seen in up to 5% of cases on CT. Restricted diffusion in tumor sites may also be visualized on diffusion-weighted images (DWI).
Although CTU is superior to MRU for evaluation of the upper urothelial tract to detect urothelial cancer, MRI is superior to CT for the detection of detrusor muscle invasion by primary tumor, and hence is superior for the local staging and pretreatment planning of bladder cancer. The normal detrusor muscle appears as a low signal intensity layer in the bladder wall on T2-weighted images. If there is focal interruption of this low signal intensity layer by higher signal intensity tumor, particularly in association with restricted diffusion on DWI, then muscle-invasive tumor is likely present. Infiltration of the perivesical fat, invasion of adjacent organs including the body wall, presence of pelvic lymphadenopathy, and presence of distant metastatic disease are indicators of even more advanced stage bladder cancer and are detectable on CT and MRI.
