This type of constipation has the most specific and effective therapy available. Since the paradoxical muscle contraction is a learned reflex, it is possible to retrain the muscles using anorectal biofeedback exercises. More people with constipation have this type of problem than any of the others described here. This problem is characterized by a constant sensation of fullness or gas in the rectum, which cannot be relieved by passing gas or bowel movements. Most people with hypersensitive rectum also suffer from other symptoms of Irritable Bowel Syndrome.
Recent evidence suggests that both colon and rectum show normal motor activity.
The primary cause of symptoms is a hypersensitivity of sensory nerves of the rectum and sigmoid colon. This abnormality results not only in exaggerated subjective sensations of urgency and rectal fullness to normal amounts of gas and stool, but can also produce these sensations when the rectum is completely empty. When other causes of constipation are ruled out, anorectal manometry, a test which determines the sensitivity of the rectum, can make a positive diagnosis. There is a series of medications which can reduce rectal hypersensitivity in some patients. Some patients benefit from enemas with xylocaine, which will numb the hyper-sensitive nerves.