MR urography for suspected upper tract urothelial carcinoma.

The key components of the MR urography protocol for suspected upper tract urothelial carcinoma are coronal T2-weighted hydrographic sequences without contrast agent and coronal gadolinium-enhanced T1-weighted 3D-spoiled gradient-recalled echo in nephrographic and pyelographic phases. Upper tract urothelial carcinomas can be categorized into papillary tumor, flat tumor, and infiltrative tumor based on the growth pattern and extent. Papillary lesions appear as small filling defects of soft tissue signal on T2-weighted hydrographic and T1-weighted pyelographic phase images. On nephrographic phase images, the lesions show homogeneous enhancement. A flat tumor appears as a segmental area of diffuse thickening and enhancement of the urinary tract wall on nephrographic phase images. Infiltrative tumor often appears as a large heterogeneously enhancing mass. MR urography is a promising alternative for CT urography in the evaluation of upper tract urothelial carcinoma, especially when the patient has a contraindication to iodinated contrast material.