Endorectal ultrasonography for staging small rectal tumors: technique and contribution to treatment

Thirty-one tumors, lying in the lower two-thirds of the rectum and possibly suitable for local excision, were analyzed by endorectal ultrasonography (EUS) using the Aloka scanner SSD 520. There were 18 sessile villous adenomas (group I) and 13 invasive cancers 3 cm or less (group II). Preoperative endosonographic staging (uT, uN stages) was compared with the histologic analysis of the specimens (pT, pN) and the possible contribution to therapy was evaluated. In group I, the depth of tumor infiltration was accurately assessed in 89% of cases. Malignant transformation was suspected in 4 cases (uT2) and confirmed postoperatively in 3 cases. In group II, the extent of the tumor was correctly evaluated in 84% of cases. With regard to the overall differentiation between T1 and T2/T3 tumors on one hand, and between T1/T2 and T3 lesions on the other hand, the positive predictive values were 93.3% and 100%, respectively. The negative predictive values were 93.7% and 92.8%. In group II the search for regional lymph nodes was positive in 4 cases and negative in 9 cases. An accuracy rate of 82% (sensitivity 75%, specificity 85%) was estimated by analysis of the specimens and postoperative follow-up. The exact performance could not be evaluated because a radical resection was not carried out in most cases. EUS was useful for planning the treatment of villous adenomas. A board full-thickness excision was carried out without delay for the four uT2 villous tumors, allowing safe margins to be obtained in all cases. Using EUS the choice of local excision was questioned for six small invasive cancers (uT3 and/or uN+), although radical resection was carried out for only two. As high sensitivity could not be achieved when detecting lymphatic metastasis, the choice of limited surgery based on EUS staging requires strict postoperative follow-up.