Fecal incontinence happens when muscles, nerves, or structures that keep the anus closed stop working properly. About 8% of adults worldwide experience it, with rates climbing to 9.3% in people over 60. The causes range from childbirth injuries and surgical complications to neurological diseases and chronic bowel problems, and many people have more than one contributing factor at once.
Muscle Damage or Weakness
Your ability to hold stool depends heavily on two rings of muscle around the anus. One operates automatically, staying contracted without you thinking about it. The other is under voluntary control, letting you squeeze tighter when you need to. Damage to either one can allow stool to leak out.
The most common source of muscle damage in women is childbirth. Vaginal delivery can stretch or tear these muscles, especially when the baby is large, forceps or vacuum extraction are used, or the doctor makes a surgical cut (episiotomy) to widen the vaginal opening. Obstetric sphincter injuries occur in roughly 0.25% to 7.3% of vaginal deliveries, with first-time mothers at higher risk because of greater tissue resistance during delivery. More than half of women who sustain these injuries report some degree of bowel leakage afterward, regardless of whether symptoms appear immediately or years later around menopause.
Surgery in the anal area is another well-documented cause. Hemorrhoid removal, treatment for anal abscesses or fistulas, and cancer surgery in the rectum or anus can all damage the sphincter muscles. A large meta-analysis covering more than 30,000 patients found that early incontinence after hemorrhoid surgery occurs in roughly 1% to 5% of cases. Late incontinence, appearing months or years after the procedure, still affects 1% to 2.5% of patients. The risk varies with the surgical technique and how much tissue is removed.
Nerve Damage
Even if the muscles themselves are intact, they need functioning nerve signals to do their job. Nerves tell the sphincter muscles when to tighten and the rectum when to push. They also carry the sensory information that lets you feel when stool has arrived and needs attention. When those signals are disrupted, you may not sense the urge to go until it’s too late, or the muscles may not respond even when you try to squeeze.
Several neurological conditions can cause this kind of disruption. Diabetes is one of the most common, because prolonged high blood sugar gradually damages nerves throughout the body, including those serving the bowel. Multiple sclerosis, Parkinson’s disease, and stroke all affect the brain or spinal cord pathways that coordinate bowel control. Spinal cord injuries, depending on their location and severity, can severely impair or eliminate voluntary control of the sphincter. Other conditions linked to nerve-related bowel dysfunction include ALS, cerebral palsy, and spina bifida.
Childbirth can also damage the pudendal nerve, which runs through the pelvic floor. This means some women experience both muscle injury and nerve injury from the same delivery, compounding the problem.
Chronic Diarrhea and Constipation
Both ends of the bowel-habit spectrum can lead to incontinence, though by different mechanisms.
Chronic diarrhea overwhelms the system with volume and urgency. Loose, watery stool is simply harder to hold than formed stool. Conditions like irritable bowel syndrome, inflammatory bowel disease, and infections that cause persistent diarrhea all raise the risk. Even a healthy sphincter can be overcome when the rectum fills rapidly with liquid stool.
Chronic constipation causes incontinence in a less obvious way. When a large mass of hard stool sits in the rectum for an extended period, it stretches the rectal walls and forces the internal sphincter into a chronically relaxed state. Softer, newer stool higher up then seeps around the hard mass and leaks out. This is called overflow incontinence, and it’s particularly common in older adults and children with severe constipation. Treating the underlying impaction, sometimes with laxatives, often restores continence by allowing the sphincter to return to its normal resting tone.
Rectal Prolapse and Structural Problems
Rectal prolapse occurs when the wall of the rectum slides downward and, in severe cases, protrudes through the anus. This physically disrupts the seal that the sphincter muscles create. In some cases, the prolapse is internal, meaning the rectal tissue folds inward (intussusception) without coming all the way out, which tends to cause more constipation than leakage. External prolapse, where tissue is visible outside the body, is more directly associated with incontinence.
Surgical repair of rectal prolapse helps many people, but roughly a third of patients continue to experience some combination of constipation, incontinence, or reduced rectal sensation after the procedure. Other structural issues that can contribute include scarring from radiation therapy to the pelvis, which stiffens the rectal wall and reduces its ability to stretch and store stool normally.
Age, Sex, and Pelvic Floor Decline
Fecal incontinence becomes more common with age. People over 60 are nearly twice as likely to be affected as younger adults (9.3% vs. 4.9%). This reflects the cumulative toll of muscle weakening, nerve degeneration, and reduced tissue elasticity that occurs naturally over decades. Chronic conditions that impair bowel function, like diabetes and neurological disease, also become more prevalent with age.
Women are affected slightly more often than men (9.1% vs. 7.4%), largely because of the added risk from childbirth injuries. The effects of a sphincter tear sustained during delivery may not become apparent until decades later, when age-related muscle loss tips the balance from compensated damage to noticeable leakage. This is why some women first develop symptoms in their 50s or 60s from an injury that occurred in their 20s or 30s.
How Multiple Causes Overlap
Most people with fecal incontinence don’t have a single, isolated cause. A woman might have a minor sphincter tear from childbirth that caused no symptoms for 30 years, then develops diabetes that adds nerve damage, and the combination pushes her past the threshold of continence. Someone recovering from rectal cancer surgery may have both structural changes and nerve disruption from the procedure.
This overlap matters because treatment works best when all contributing factors are addressed. Pelvic floor exercises can strengthen weakened muscles. Managing diarrhea or constipation removes the extra strain on compromised sphincters. Biofeedback therapy can help retrain the coordination between sensation and muscle response. For people with significant structural damage, surgical options exist to repair or reinforce the sphincter. The specific combination of causes shapes which approach, or combination of approaches, is most likely to help.