The main causes of fecal incontinence

Fecal incontinence happens when the muscles or nerves that control your bowel stop working the way they should. The most common culprits are damage to the anal sphincter (the ring of muscle that holds stool in), nerve damage that weakens the signal between your bowel and brain, or loss of the ability to sense when your rectum is full. These problems can develop suddenly or gradually over years.

The condition is not a single disease—it is a symptom with many possible roots. Some causes are temporary and reversible, like severe diarrhea or a medication side effect. Others are long-term, like nerve damage from childbirth or diabetes. Understanding which category yours falls into is the first step toward managing it, because the treatment path depends entirely on what caused the problem.

Key Takeaways

  • Fecal incontinence results from damage to the anal sphincter muscle, nerve damage, or loss of rectal sensation—not from a single disease.
  • Childbirth, especially with forceps or a large tear, is the most common cause in women and can take years to show symptoms.
  • Chronic diarrhea, diabetes, stroke, and spinal cord injury are frequent causes in both men and women.
  • Some causes like medication side effects or severe constipation are reversible; others like nerve damage may be permanent but manageable.
  • A doctor can usually identify the cause through a physical exam, imaging, or specialized tests of muscle and nerve function.

Damage to the anal sphincter muscle

The anal sphincter is actually two muscles working together—an inner one you cannot control and an outer one you can squeeze voluntarily. When either one tears or weakens, stool can leak out without warning. The most common reason this happens is childbirth, particularly if labor involved a large tear (called a perineal laceration), use of forceps, or an episiotomy (a surgical cut to widen the opening). Not all women who tear during childbirth develop incontinence right away; some do not notice symptoms until years later, when the muscle has weakened further with age.

Anal sphincter damage can also result from hemorrhoid surgery, rectal surgery, or a history of anal fissures (painful cracks in the tissue). Trauma from a fall or accident, or repeated straining during bowel movements over many years, can gradually wear down the muscle. In some cases, the muscle itself is intact but simply has lost tone and strength—this is common in older adults and can improve with pelvic floor physical therapy.

Nerve damage and loss of sensation

Your brain and bowel communicate through nerves that run down your spinal cord. These nerves tell you when your rectum is full and trigger the urge to have a bowel movement. If those nerves are damaged, you may not feel the urge at all, or you may not be able to send the signal to tighten your sphincter. This is called fecal urgency or passive incontinence—stool leaks out because you simply did not know it was there.

Nerve damage can happen from diabetes (high blood sugar damages small nerves over time), stroke, spinal cord injury, multiple sclerosis, or Parkinson's disease. Chronic straining during bowel movements can also injure the nerves that sense fullness. In some cases, the nerve damage is permanent; in others, like after a stroke, some nerve function may return over weeks or months as the brain heals.

Chronic diarrhea and loose stools

The anal sphincter is designed to hold solid stool. Liquid stool is much harder to contain, so chronic diarrhea is one of the most common causes of fecal incontinence. Diarrhea can stem from inflammatory bowel disease (Crohn's disease or ulcerative colitis), irritable bowel syndrome (IBS), celiac disease, food intolerances, or infections. Some people develop chronic diarrhea after gallbladder removal or bowel surgery. Certain medications, including antibiotics and chemotherapy drugs, can also trigger it.

The good news is that treating the underlying diarrhea often resolves the incontinence. If your doctor can identify and treat the cause—whether that is adjusting a medication, managing IBS, or treating an infection—your bowel control may return. This is why telling your doctor when the incontinence started and what else is happening with your bowel is so important.

Constipation and impaction

Severe constipation can paradoxically cause incontinence. When stool sits in the colon too long, it hardens into a mass called an impaction. Liquid stool from higher up in the bowel seeps around the impacted mass and leaks out, often without warning. This is called overflow incontinence and is more common in older adults, people taking opioid pain medications, and those who ignore the urge to have a bowel movement repeatedly.

Overflow incontinence is usually reversible. A doctor can remove the impacted stool and then work with you on bowel habits, diet, hydration, and sometimes medication to prevent it from happening again. This is one of the few causes of fecal incontinence where the solution is relatively straightforward.

Age-related changes and muscle weakness

As you age, the anal sphincter naturally loses some tone and strength, and the rectum becomes less stretchy. At the same time, the nerves that sense fullness may not work as well. These changes do not automatically cause incontinence, but they make it more likely if other problems develop—like diarrhea, a medication side effect, or a fall that injures the pelvic floor. Older adults are also more likely to have multiple causes at once, which can make the problem harder to sort out.

Age-related incontinence is not inevitable, and it is not something you have to accept. Pelvic floor physical therapy, dietary changes, and sometimes medication can help significantly, even in people in their 80s and 90s.

Other medical conditions and medications

Several conditions affect bowel control indirectly. Dementia can cause incontinence because a person forgets to use the toilet or does not recognize the urge. Severe depression or anxiety can disrupt normal bowel function. Hypothyroidism (an underactive thyroid) slows digestion and can lead to constipation or diarrhea. Medications are also a common culprit: antibiotics kill helpful gut bacteria and cause diarrhea, laxatives can lead to overflow incontinence if overused, and anticholinergic drugs (used for allergies, depression, or overactive bladder) can cause severe constipation.

If your incontinence started after you began a new medication or after a change in your health, mention that to your doctor. Sometimes the solution is as simple as adjusting the dose, switching to a different drug, or treating the underlying condition.

Frequently Asked Questions

Can fecal incontinence be caused by something serious like cancer?

Bowel cancer can cause changes in bowel habits, but fecal incontinence is not a typical early symptom. However, any new or worsening incontinence should be evaluated by a doctor to rule out serious causes and identify what is actually happening. A physical exam and sometimes imaging can determine whether cancer or another serious condition is involved.

Is fecal incontinence always permanent?

No. Some causes are temporary or reversible—diarrhea from an infection, constipation with impaction, or medication side effects can all be treated. Other causes, like nerve damage from diabetes or spinal cord injury, may be permanent but can still be managed with diet, medications, and pelvic floor exercises. Your doctor can explain which category your situation falls into.

Can childbirth cause fecal incontinence years later?

Yes. Tears to the anal sphincter during childbirth may not cause noticeable incontinence right away, but the muscle weakens over time. Symptoms can appear months or years after delivery, especially as you age or if other factors (like chronic diarrhea) develop. This is why it is important to mention your birth history to your doctor.

What should I tell my doctor to help them figure out the cause?

Tell them when the incontinence started, whether it is constant or comes and goes, what your stool is usually like (solid, loose, or watery), any recent changes in diet or medications, and whether you have had surgery, childbirth, or injury to the pelvic area. Also mention any other health conditions like diabetes, IBS, or neurological problems. The more detail you provide, the easier it is for your doctor to narrow down the cause.

Do I need special tests to find out what is causing my incontinence?

A physical exam and your medical history often tell the story. Your doctor may order imaging like an ultrasound or MRI to look at the sphincter muscle, or specialized tests like anorectal manometry (which measures muscle strength) or defecography (which shows how well you can empty your bowel). Not everyone needs all these tests—your doctor will order only what is needed based on what they find during the exam.