INFLUENCE OF TUMOR POSITION ON ACCURACY OF ENDORECTAL ULTRASOUND STAGING

Endorectal ultrasound is a well-established method of preoperative sta ging of rectal neoplastic lesions. PURPOSE: This study was undertaken to evaluate whether tumor site (in terms of height) and position (with respect to the rectal circumference) have an influence on the reliabi lity of endoluminal ultrasound staging. METHODS: From January 1991 to May 1996, 154 consecutive patients with a total of 162 rectal tumors w ere examined preoperatively using endorectal ultrasound, Apart from st aging all tumors using tile uT/uN classification, tumor level and tumo r position mere recorded prospectively. Neoplasms were subdivided into low rectal (0-6 cm from the anal verge), mid rectal (7-12 cm), and hi gher lesions (>12 cm). Furthermore, the lumen was divided into an ante rior, left lateral, posterior, and right lateral position, and all tum ors, apart from circular lesions (n = 9), were subclassified according ly. RESULTS: Overall, we found 40 (25 percent) adenomas, 15 (9 percent ) T1, 29 (18 percent) T2. 67 (41 percent) TS, and 11 (7 percent) T4 le sions. Overall accuracy was 78 percent, Staging accuracy for low recta l tumors (n = 41) was 68 percent, whereas 76 and 88 per-cent of mid Cn = 96) and high (n = 25) neoplasms were staged correctly, respectively . The difference was not statistically significant. With regard to pos ition, 47 tumors were situated anteriorly (77 percent accuracy), 42 in the left lateral position (69 percent accuracy), 33 posteriorly (75 p ercent accuracy), and 31 in the right lateral position (81 percent acc uracy). Differences did not reach statistical significance. CONCLUSION : Endorectal ultrasound is currently the best method for preoperative assessment of the depth of infiltration of rectal tumors. However, rec tal anatomy seems to affect staging accuracy in the lower rectum becau se the structure of the ampulla recti renders endosonographic examinat ion more difficult. in addition, endosonographic layers are less well defined at this level, Both factors contribute to a Io Ner reliability and predictive value of endorectal ultrasound staging in the lower re ctum, although statistical significance was not reached in this study. On the other hand, tumor position with respect to rectal circumferenc e does not influence the predictive value of endorectal ultrasound.