Problems with the normal functioning of the rectum, anus or central nervous system (CNS) can lead to fecal incontinence. Such difficulties  may include:

• Constipation. Difficulty passing hard, dry stool or the inability to pass stool. This is one of the most common causes of fecal incontinence. Chronic constipation stretches the muscles of the rectum (making them less able to hold stool) and weakens the nerves of the rectum and anus (making them less responsive to the presence of stool in the rectum). Constipation may also cause stool to become stuck in the rectum (fecal impaction). When liquid stool flows around the impacted stool and is involuntarily released through the anus, it is sometimes mistaken for diarrhea, although it is really the result of constipation. When this type of involuntary leakage occurs in children who withhold their stool, it is known as encopresis.
  
  
• Diarrhea. Loose or watery stool. When stool is liquid or watery, it is more difficult to contain in the rectum. Thus, fecal incontinence can occur as a result of diarrhea. Conditions such as inflammatory bowel disease (IBD) (e.g., Crohn’s disease, ulcerative colitis) may cause diarrhea that can lead to fecal incontinence. Irritable bowel syndrome (IBS) can cause both diarrhea and constipation, increasing a patient’s risk of fecal incontinence.
  
  
• Muscle damage. Damage to the anal sphincter muscles can prevent them from tightening enough to keep stool inside the rectum. Muscle damage may be caused by experiences such as vaginal childbirth (especially multiple births) or anal surgery (e.g., hemorrhoid surgery). An episiotomy (incision made to enlarge the vaginal opening) during childbirth may increase the likelihood of sphincter muscle damage that can lead to fecal incontinence. Research also indicates that women who have had numerous vaginal deliveries are more likely to experience fecal incontinence. Hysterectomy (surgical removal of the uterus) may also increase the risk of the condition in women.
  
  In addition, fecal incontinence is more common among older adults than younger age groups, partially because the elderly experience a general muscle weakening that occurs with age.
  
  
• Nerve damage. Problems with nerves that control rectal and anal sphincter activity can result in the inability to sense fullness of the bowel. This may lead to the unexpected release of stool because the sensation that usually precedes and indicates readiness for a bowel movement does not occur. Nerve problems may also prevent sphincter muscles from properly tightening, allowing stool to spill from the rectum.
  
  Nerve damage may be due to a number of conditions or events, which can range from childbirth to stroke. For instance, the use of forceps during delivery may increase the risk of nerve damage that can lead to fecal incontinence. Nerve damage may develop over time due to injury or disease, such as diabetes (the body’s inability to break down blood sugar), multiple sclerosis (an autoimmune disease affecting the central nervous system), and dementia (impairment of brain functioning). Nerves can also become damaged in people with a long-term habit of straining to pass stool.
  
  
• Loss of storage capacity. Scarring of rectal tissue can make rectum walls stiff and unable to stretch adequately enough to hold stool. Rectal surgery, radiation treatment and inflammatory bowel disease (IBD) can all cause rectal scarring. IBD can also make rectal walls irritated and unable to contain stool.
  
  
• Hemorrhoids. May prevent the anal sphincters from closing and cause fecal incontinence.
  
  
• Pelvic floor dysfunction. Problems with the layers of muscles and connective tissue that form the floor of the pelvis and help to maintain continence. Childbirth is the most common cause of pelvic floor dysfunction in women. Other causes of pelvic floor dysfunction include:
  
  
• • Decreased perception of rectal sensation
    
  • Decreased anal canal pressure
    
  • Impaired anal sensation
    
  • Rectal prolapse (protrusion of the rectum through the anus)
    
  • Rectocele (protrusion of the rectum through the vagina)
    
  • Generalized weakness and sagging of the pelvic floor
    
    
• Urinary incontinence. Research shows a link between urinary incontinence (the inability to control the passage of urine) and fecal incontinence in women.
  
  
• Unknown. Sometimes the cause of fecal incontinence cannot be determined (idiopathic). This occurs most commonly in middle-aged or older women.