Transrectal sonography of anal sphincter infiltration in lower rectal carcinoma

OBJECTIVE. The purpose of the study was to assess the accuracy of transrect al sonography in determining invasion by lower rectal cancer into the anal canal. SUBJECTS AND METHODS. Thirty-eight patients (14 women, 24 men; mean age, 65 years) with lower rectal cancer underwent transrectal sonography before su rgery. Both depth of infiltration and tumor invasion into the anal canal we re assessed, and results were compared with histopathology of the resected specimens. RESULTS. Infiltration into the anal canal was found histopathologically in 12 (32%) of 38 patients. Transrectal sonography revealed a true-positive di agnosis in 11 of these 12 patients. A false-positive diagnosis of anal cana l infiltration was made in two patients for a sensitivity of 91%, a specifi city of 85% and an accuracy of 92%. In the 11 patients diagnosed correctly on transrectal sonography, the depth of tumor infiltration into the anal ca nal corresponded with histopathology. CONCLUSION. This study shows that transrectal sonography is an accurate met hod for assessment of anal canal infiltration in lower rectal cancer.