Endorectal ultrasonography for the assessment of rectal wall invasion in intrapelvic tumor:A preliminary report

Background: The purpose of the present study was to determine the usefulness of endorectal ultrasonography (ERUS) in assessing rectal wall involvement in intrapelvic tumors. Methods: Rectal wall invasion was assessed in 16 patients; 14 with deeply invasive bladder tumors, one with prostatic leiomyosarcoma, and one with prostatic leiomyoma. Computed tomography (CT), magnetic resonance (MR) imaging and ERUS with a flexible-type radial scanner (7.5 MHz) were used and the results were compared with the histopathologic findings in surgical specimens. Results: The normal rectum was shown by ERUS to be a five- or seven-layer structure. Characteristic abnormal ERUS findings included disappearance of the perirectal fat tissue layer with or without disruption of the propria muscle layer. Endorectal ultrasonography accurately assessed rectal wall involvement in all four patients who had two bladder tumors, plus the one patient with prostatic leiomyoma and the one with prostatic leiomyosarcoma. However, ERUS overstaged one of 12 bladder tumors with no rectal wall involvement, which was strongly adhesive to the rectum because of an inflammatory change but had no tumor invasion. There were no cases of understaging by ERUS. In comparison, CT accurately assessed rectal wall involvement in two patients, but overstaged in three and understaged in two. Magnetic resonance imaging, which was performed in 14 patients, accurately assessed rectal wall involvement in two patients, but overstaged in three and understaged in one. Conclusion: This preliminary study suggests that ERUS more accurately assesses rectal wall involvement in intrapelvic tumor than CT or MRI.