An anorectal manometry test measures the pressures that the muscles in your back passage (anal canal) can generate, as well as sensation in the rectum and the neural reflexes that are needed for normal bowel movements. You may be referred for this test if you have been experiencing troublesome bowel problems such as constipation or faecal incontinence. These problems can often be caused by injuries, weakness to the anal canal muscles or problems with the wall of your back passage.