[Pretherapeutic endosonography in rectal adenocarcinoma]

The advent of transrectal ultrasonography has contributed to improving therapeutic management of cancer of the rectum. The 7.5 MHz transrectal probe evidences five tissue layers in the rectal wall. The 10-12.5 MHz probe can visualize seven layers. Transrectal ultrasonography can also be used to explore the perirectal environment and detect possible nodes. Echographically, the tumor is seen as an hypoechogenic mass invading the rectal wall outwardly, disorganizing the wall structures. Parietal recurrence is seen as a hypoechogenic heterogeneous thickening. Ultrasonographic surveillance can be proposed for operable patients with a high risk of recurrence. Cautious interpretation is required due to the known limitations of transrectal ultrasonography. Truly invaded nodes may not be seen due to their small size (less than 2-3 mm) or their localization far from the probe (false negatives). Transrectal ultrasonography provides important information for therapeutic decision making in terms of surgical access and/or indications for possible adjuvant therapy. Transanal resection may also be ruled out if there are perirectal nodes. Patients may also be selected for preoperative radiotherapy, possibly associated with chemotherapy.