Endoscopic ultrasound for the characterization and staging of rectal cancer. Current state of the method. Technological advances and perspectives.

Endoscopic ultrasound is the most accurate type of examination for the assessment of rectal tumors. Over the years, the method has advanced from gray-scale examination to intravenous contrast media administration and to different types of elastography. The multimodal approach of tumors (transrectal, transvaginal) is adapted to each case. 3D ultrasound is useful for spatial representation and precise measurement of tumor formations, using CT/MR image reconstruction; color elastography is useful for tumor characterization and staging; endoscopic ultrasound using intravenous contrast agents can help study the amount of contrast agent targeted at the level of the tumor formations and contrast wash-in/wash-out time, based on the curves displayed on the device. The transvaginal approach often allows better visualization of the tumor than the transrectal approach. Performing the procedure with the rectal ampulla distended with contrast agent may be seen as an optimization of the examination methodology. All these aspects are additional methods for gray-scale endoscopic ultrasound, capable of increasing diagnostic accuracy. This paper aims at reviewing the progress of transrectal and transvaginal ultrasound, generically called endoscopic ultrasound, for rectal tumor diagnosis and staging, with emphasis on the current state of the method and its development trends.