Anismus is a condition where the muscles around your rectum and pelvic floor fail to coordinate properly when you try to have a bowel movement. Instead of relaxing to let stool pass, these muscles stay tight or even contract harder, essentially working against you. The result is chronic difficulty with defecation despite the urge to go. The condition is also called dyssynergic defecation or pelvic floor dyssynergia.
How Normal Defecation Works, and What Goes Wrong
Having a bowel movement requires a surprisingly coordinated sequence. Your abdominal muscles generate a pushing force, your rectum contracts to move stool downward, and the muscles of your pelvic floor and anal sphincter relax to open the exit. This coordination is a learned behavior, not a pure reflex, which is why it can go wrong.
In anismus, this coordination breaks down in one or more ways. The most common pattern is paradoxical contraction, where the pelvic floor muscles (particularly a sling-shaped muscle called the puborectalis) tighten when they should be loosening. In other cases, the anal sphincter simply fails to relax enough, or the abdominal muscles don’t generate adequate pushing force. Many people have a combination of these problems. The core issue is always the same: the muscles involved in defecation are working against each other instead of in sync.
What It Feels Like
The hallmark experience is straining hard at the toilet with little to show for it. You may feel like something is physically blocking the stool from coming out, even when you can feel it right there. Bowel movements take a long time, often require multiple attempts, and frequently feel incomplete afterward. Some people find they can only pass stool by pressing on their perineum or using a finger to assist.
Because stool sits in the rectum longer than it should, it can become harder and drier, making the problem worse. Over time, many people develop a pattern of avoiding the toilet, using laxatives heavily, or spending extended periods straining, all of which can compound the underlying dysfunction. The condition is frustrating partly because standard constipation remedies like fiber supplements and stool softeners often don’t fully resolve it, since the root problem is muscular, not dietary.
What Causes It
Since the coordinated relaxation needed for defecation is a learned behavior, anything that disrupts that learning or creates chronic tension in the pelvic floor can contribute. Some people develop anismus after childbirth, pelvic surgery, or back injuries that alter nerve signaling to the pelvic muscles. Chronic stress and anxiety can drive persistent pelvic floor tightening. A history of painful bowel movements (from hemorrhoids, fissures, or hard stools) can train the body to clench during defecation as a protective response, and this pattern can persist long after the original pain resolves.
In many cases, no single clear trigger is identified. The dysfunction may develop gradually over years, and by the time symptoms become severe enough to seek help, the abnormal muscle pattern is deeply ingrained.
How It’s Diagnosed
Anismus can’t be diagnosed from symptoms alone, since many causes of constipation feel similar. A formal diagnosis requires at least two of three types of objective tests showing that pelvic floor coordination is impaired.
The simplest is the balloon expulsion test. A small balloon is inserted into the rectum, inflated with about 50 mL of water, and you’re asked to expel it while sitting on a commode in private. Most healthy people can push it out within one minute. Inability to do so suggests a defecation disorder. Notably, body position matters: about 36% of healthy people show a dyssynergic pattern when tested lying down, which is why the sitting position is used.
Anorectal manometry measures the pressures inside the anal canal during rest, squeezing, and pushing. In a normal push, anal pressure drops as the sphincter relaxes. In anismus, pressure rises or stays the same because the muscles are contracting instead. The third test is an imaging study, such as defecography, which takes real-time images while you evacuate a contrast material, showing whether the pelvic floor muscles are opening or staying clenched.
Biofeedback Therapy: The Primary Treatment
Biofeedback is the first-line treatment for anismus, with success rates between 60% and 80%. It works because the underlying problem is a faulty muscle pattern, and patterns can be retrained. During a session, sensors placed near the anal canal pick up electrical signals from the pelvic floor muscles. These signals are displayed on a screen in real time, so you can actually see whether you’re tensing or relaxing when you bear down.
A typical program involves around 10 sessions over a few weeks. The first session usually lasts about an hour, with subsequent sessions running 30 minutes each. You sit in a position that mimics being on the toilet and practice cycles of squeezing, relaxing, and gently straining in 10-second intervals while watching the visual feedback. Alongside the in-clinic work, you’re trained in pelvic floor exercises to practice at home, along with guidance on posture during defecation and dietary adjustments.
Among those who respond well, the improvement tends to last. One long-term study found that nearly 90% of patients who achieved meaningful improvement maintained their gains over the follow-up period. The key skill being learned is straightforward: how to relax the pelvic floor muscles during a push and how to generate effective abdominal pressure at the same time. Once this coordination clicks, it often becomes automatic again.
When Biofeedback Isn’t Enough
For people who don’t respond to biofeedback alone, injections that temporarily paralyze the overactive pelvic floor muscles can be effective. The injection is delivered directly into the puborectalis muscle and the external anal sphincter, causing them to relax for several months. This is typically combined with continued biofeedback training, using the window of relaxation to help retrain the muscles. In one study, this combination approach worked for about 77% of patients with stubborn anismus, with most maintaining satisfaction through an average follow-up of about 8 months.
Surgical division of the puborectalis muscle is a last resort, reserved for severe cases that have failed all other treatments. A systematic review found that the procedure does improve symptoms for many patients, but carries a 10% to 12% risk of fecal incontinence. Bilateral or complete division of the muscle, as opposed to partial division on one side, significantly increases that risk. Because of this trade-off, surgery is approached cautiously.
Dietary and Lifestyle Adjustments
While anismus is fundamentally a muscular coordination problem, keeping stool soft and easy to pass reduces the effort your pelvic floor needs to manage. Aiming for roughly 25 grams of fiber per day from food or supplements helps increase stool frequency, and pairing that with 1.5 to 2 liters of water daily significantly boosts the effect. Neither fiber nor water alone addresses the core dysfunction, but together they make each bowel movement less of a battle.
Positioning also matters. Sitting with your knees raised above your hips (using a footstool, for example) straightens the angle between your rectum and anal canal, reducing how much your puborectalis muscle needs to relax. For someone with anismus, this small mechanical advantage can make a real difference. Avoiding prolonged straining sessions is equally important, as extended pushing against a clenched pelvic floor can worsen muscle tension and lead to secondary problems like hemorrhoids.