Anorectal ultrasound is a painless procedure designed to evaluate the anal sphincter muscle. An ultrasound is an examination using high-frequency sound waves to create images of tissue layers beneath the surface. A short ultrasound probe (about the width of a finger) is inserted into the anus and sound waves are bounced off the muscle giving a precise anatomic picture of the muscle. Ultrasound examination involves no radiation and is a very safe procedure. It provides additional information about rectal polyps, rectal cancer, perianal infection, and sphincter muscle injuries The examination takes about 10 minutes to perform.