Normal bladder wall morphology in Gd-DTPA-enhanced clinical MR imaging using an endorectal surface coil and histological assessment of submucosal linear enhancement using [14C]Gd-DOTA autoradiography in an animal model.

OBJECTIVE

The purpose of this study was to investigate normal bladder wall morphology in gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA)-enhanced magnetic resonance (MR) imaging using an endorectal surface coil and to perform histological assessment of submucosal linear enhancement with experimental [14C]-gadolinium-tetraazacyclododecane-tetraacetic acid (Gd-DOTA) autoradiography.

METHODS AND MATERIAL

MR imaging of the bladder was performed using an endorectal coil in 13 consecutive patients with bladder carcinoma and T1-, T2-, and Gd-DTPA-enhanced spin-echo images of the bladder wall were compared. After injection of [14C]Gd-DOTA into a hamster, autoradiograms of the bladder wall were obtained and compared with serial histological sections.

RESULTS

The normal bladder wall appeared as a homogeneous layer of intermediate intensity on T1-weighted images. After administration of Gd-DTPA, the bladder wall was visualized as three layers: an inner thin layer of low intensity, a middle layer of marked enhancement, and a thick outer layer of intermediate intensity. The autoradiograms demonstrated dense accumulation of [14C]Gd-DOTA in the submucosal layer. Thus, the inner, middle, and outer layers corresponded to the mucosa, submucosa, and muscularis propria, respectively. The thickness of the bladder wall demonstrated on T2-weighted images was almost equal to that of the outer layer on enhanced T1-weighted images. Thus, T2-weighted images revealed only the muscle layer as an intermediate-intensity band. In the preliminary clinical study, MR imaging invariably showed accurate stages of the bladder carcinoma in 13 patients.

CONCLUSION

In MR imaging of the normal bladder wall, the submucosa was strikingly enhanced after Gd-DTPA administration, separating the bladder wall into three layers. This may have a potential role in the staging of bladder tumors.