Intrarectal ultrasonography in rectal cancer staging and in the evaluation of pelvic disease. Clinical uses of intrarectal ultrasound. Accurate preoperative staging of a rectal cancer patient may impact heavily on subsequent management. This study attempts to evaluate the accuracy of intrarectal ultrasonography (IRUS) in staging rectal cancers compared to clinical and pathologic examination. In addition the accuracy of IRUS was assessed in a group of patients with uncertain pelvic-perirectal disease after a negative physical examination. In a prospective manner, 52 cancer patients were staged with digital exam and IRUS. Accuracy rates were 48% and 83%, respectively, compared to pathologic evaluation in assessing wall penetration, and IRUS identified positive lymph nodes in 12 of 17 cases. In patients with pelvic disease, IRUS corresponded with pathologic diagnosis in 15 of 17 cases and revealed new information in 6 patients. Intrarectal ultrasonography appears to be the most accurate imaging technique for staging rectal cancers and demonstrates promise in the evaluation of perirectal-pelvic disease. 