Endosonographic staging of rectal carcinoma

Transrectal ultrasonography (US) scanning facilitates the ultrastructural differentiation of the various histologic layers of the rectal wall. In particular, the muscularis propria is represented by the 4th sonographic layer. Rectal carcinoma appears on US as a low echogenic area that suddenly interrupts the regular sequence of parietal layers. Sixty-five patients suffering with carcinoma of the lower two-thirds of the rectum underwent preoperative linear endosonography for staging. The reliability of such a method in assessing the extrarectal spread was evaluated in our study, at the end of which 55 sonographic/histologic correlations were obtained. Four false-negative and 1 false-positive determinations of the presence or absence of extrarectal spread proved that sonography has a sensitivity and specificity of 91%, with a positive predictive value of 97% and a negative predictive value of 71%. Lower results are obtained in lymph node staging: enlarged lymph nodes are seen in only 11/22 C1/C2 patients (11 false negatives) while we were aware of 3 false positives.