Many anal and rectal problems are the result of improper function of the muscles, nerves or other structures in the area. These functional problems of the anus and rectum include:

• Fecal incontinence. The inability to control bowel movements. According to the American College of Gastroenterology, more than 5.5 million Americans experience fecal incontinence. This condition generally occurs when the anal sphincter muscles weaken or are damaged, the nerves supplying the sphincter muscles are damaged, or the rectum thickens so that it cannot stretch properly. Diarrhea and fecal impaction may cause brief episodes of fecal incontinence. Persistent fecal incontinence may occur as a symptom of many problems, such as  spinal or anal injuries, anorectal abscess or fistula, rectal prolapse, dementia, radiation therapy or certain  illnesses (e.g. Crohn's disease, multiple sclerosis, diabetes). The sphincter muscles become weaker with age, making this more common in older adults. The external sphincter is also thinner and more susceptible to injury in women.
  
  
• Proctalgia fugax. Severe, episodic pain around the rectum and anus. This pain usually occurs at night and lasts from a few seconds up to 30 minutes. While the cause is not known, spasms in the muscles around the rectum are generally believed to be involved.
  
  
• Levator ani syndrome. Persistent, aching, pressure-oriented pain around the rectum and anus. The pain may be initiated by bowel movements or sitting for long periods of time. It is believed to be caused by spasms in the muscles around the anus.
  
  
• Dyschezia. The inability to properly control the muscles in the pelvis and anus, leading to difficulty in defecating. This may be caused by rectal prolapse, rectocele, failure of the sphincters to relax during defecation (anismus) or a disturbance in pelvic muscle coordination (pelvic floor dyssynergia).