Ultrasound Methods for Lower Rectal Cancer Staging

For ERUS the patient is prepared with an enema 2h before the study. ERUS is performed in the left lateral decubitus position and always starts with digital examination. Usually no sedation or general anesthesia is needed and the procedure is well tolerated by the patients. After a digital rectal examination is performed the probe covered with a balloon is inserted into the rectum. For better acoustic contact the water filled balloon (usually between 30 and 60 ml water) is used. Some authors describe a modification of the method in which instead of the standard water-balloon filling technique, a sterile contact gel (100-150 ml) was injected into the rectum directly [3]. Our practice is to introduce approximately 50 ml of contact gel inside the balloon and a small amount of gel around it. The gel helps the probe to pass over the rectal tumor, minimizes distortion of the lesion, and improves visualization of the rectal wall. This method prevents the compression of the tumor by the balloon, which can create an image of pseudo-infiltration that can cause an overestimation of the tumor stage.