New staging techniques. Endoscopic ultrasound.

Rectal ultrasonography allows detailed images of rectal tumors and provides the most accurate method of staging rectal cancer. Ultrasound assessment of the extent of tumor invasion and lymph node involvement is superior to computed tomography (CT) scan, though CT is still the best method to assess liver involvement. Ultrasound assessment of cancers above the peritoneal reflection is less useful clinically because it currently does not alter management. Outcome studies have not been reported using ultrasound to stage rectal cancer but should be forthcoming. Inflammation present at the leading edge of the tumor is the greatest cause for overstaging, and difficulty in determining tumor involvement into, but not through, the muscularis propria is another important cause of inaccurate staging. Lymph node assessment can be problematic, but future developments in ultrasound-guided fine-needle aspiration cytology holds promise for more accurate assessment of lymph node status. Surgery will remain the standard method to treat rectal cancer, but new methods, such as high-intensity focused ultrasound, may provide new ways to treat some patients.