How to Perform Anorectal Endoscopic Ultrasonography

Examination of the rectum and anal canal is relatively straightforward. Orientation is very important and, by convention, the urinary bladder and prostate or vagina should be oriented to the 12 o’clock position. Perirectal structures are best imaged by inflating the balloon and collapsing the rectal wall while rectal wall layers are best interrogated by filling the rectum with water. For rectal cancer, the electronic radial is the most efficient instrument but for evaluation of the anal canal, it is mandatory to use radial scanning instruments—either a rigid probe or the flexible electronic radial system.