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gram.34 CT can differentiate tumor from other causes of filling defects such as stone or blood clot by measurements of density.35

Although CT is the most accurate imaging procedure available for staging of urothelial tumors,1 it is generally agreed that CT cannot distinguish Ta to T2 lesions (Ta, limited to mucosa; T1, tumor involves the submucosa; T2, muscle invasive tumor).36 Overstaging localized disease as T3 (deep invasion into the renal parenchyma or peripelvic soft tissue) is common, particularly when hydronephrosis is present. However, to detect invasion beyond the pelvic wall or metastatic disease, conventional CT has 85% accuracy,37 and CT plays an important role in defining adjacent organ invasion.38 In the detection of lymph node involvement, CT has specificity of 94% to 100% but variable sensitivity of 47% to 88%.38-40 With use of spiral CT, improved T staging is expected due to better resolution, but no publications are available to date.

MRI is not commonly used for diagnosis and staging of the upper tract TCC. However, MRI is useful for patients who cannot tolerate iodinated contrast material (see Figure 31.6).33 In a study of MRI with nine patients with upper urinary tract transitional cell carcinoma, including gadolinium-enhanced sequences, MRI achieved accuracy of 89% for staging.41 There was understaging of direct tumor invasion into the renal parenchyma in one case.41

Bladder Carcinoma

Cystoscopy is the primary diagnostic procedure for diagnosis and follow-up of bladder carcinomas and is very sensitive in detecting small bladder neoplasms. The stage of tumor at diagnosis determines management and is an important prognostic factor. Clinical staging by cystoscopy, biopsy, and bimanual examination under anesthesia is accurate for superficial tumors (T1 and lower), but a significant error has been shown in staging muscle-invasive tumors (T2a and higher).42,43

CT and MRI are performed for tumor staging once the diagnosis of bladder carcinoma has been established. Bladder tumors are seen as focal or diffuse wall thickening, or a sessile or pedunculated soft tissue mass protruding into the bladder lumen on CT and MR imaging (Figures 31.7, 31.8). Transitional cell carcinoma of the bladder enhances immediately and intensely after bolus injection of iodinated contrast material compared to uninvolved bladder wall on CT or MRI (Figures 31.7, 31.8). In some instances, MRI can differentiate superficial (T2a) and deep muscle invasion (T2b). MRI also allows detection of extravesical spread more readily than with other imaging modalities because of its superior soft tissue differentiation and multiplanar imaging capability. On MRI, transitional cell carcinoma tends to have an intermediate signal intensity, greater than normal muscle on T2-weighted images, and is significantly more intense than muscle on gadolinium-enhanced T1-weighted images. If the inner aspect of the low-intensity bladder wall is irregular, superficial muscle invasion is suspected. If the low-intensity bladder line is disrupted, deep muscle invasion is diagnosed.44-47 Reported overall accuracy of MR imaging in staging of bladder cancer ranges from 73% to 96%, which is 10% to 33% higher than that obtained with CT.47 With the use of gadolinium-containing contrast material, improved detection of small

figure 31.7. Bladder cancer. Axial T1-weighted magnetic resonance (MR) image with fat suppression obtained after gadolinium contrast agent injection shows a large papillary mass arising from the left posterior wall projecting into the bladder lumen. There is contrast enhancement in the central portion of the tumor.

figure 31.7. Bladder cancer. Axial T1-weighted magnetic resonance (MR) image with fat suppression obtained after gadolinium contrast agent injection shows a large papillary mass arising from the left posterior wall projecting into the bladder lumen. There is contrast enhancement in the central portion of the tumor.

tumors and an increase in accuracy of local staging were reported.46 Therefore, MRI is the staging modality of choice for invasive tumors. The use of phased-array external surface coils or endorectal surface coils allows higher signal-to-noise ratio and higher spatial resolution images of the bladder, and these are successfully applied to the imaging of bladder

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