There are two anal sphincters that allow us to control when we want to evacuate stool from the rectum and large bowels. Usually we choose an appropriate setting, typically a toilet, and then pass out stool. However, sometimes stool may be evacuated even before we can reach the toilet. This is seen in severe diarrhea. There are also instances where there may be soiling of the clothing with involuntary leakage of the bowel contents. This is also referred to as anal leakage.
Understanding Anal Leakage
Unlike a bowel movement, anal leakage is where feces is involuntarily passed out either in large quantities or more commonly in small quantities. Anal leakage is the same as fecal incontinence. Sometimes only a feces-tainted fluid is passed out and soils the underwear but solid stools is not passed out. There may even be mucus and blood, depending on the underlying condition that causes anal leakage. It does not only occur in people who are severely ill and in older people. Anal leakage can occur in many different conditions, even in younger people and with conditions that are not considered to be serious or debilitating.
How does anal leakage occur?
There are two anal sphincters, which are circular groups of muscles, that close tightly to prevent feces from being evacuated. One sphincter is under voluntary control while the other is not. When the rectum is filled, signals are sent to the central nervous system which is perceived as an urge to pass stool. Eventually the anal sphincter under involuntary control relaxes the sphincter. When the setting is appropriate, a person can then voluntarily relax the other sphincter and strong contractions then push out the stool through the anus.
In anal leakage, the contents of the bowels passes through the sphincters usually because the sphincters are not closed tightly enough to prevent any leakage. Usually it is watery stool that passes through with ease. The key factor in anal leakage is that a person does not voluntarily choose to defecate and often they are unaware of these small amounts of stool passing out until they can feel the soiling or the odor becomes detectable. Anal leakage can be distressing and embarrassing, and even lead to medical complications.
Causes of Anal Leakage
Anal leakage is due to either a dysfunction of the nerve/muscles of the anal sphincters, increased pressure with the color or inflammation of the anus that impairs its normal functions. Anal leakage may not seem like a serious condition, apart from the discomfort and embarrassment, but this is untrue. It can cause a person significant distress and social isolation. Furthermore some of the causes of anal leakage can be very serious and in some instances even fatal if left untreated.
Diarrhea is among the more common acute causes of anal leakage. It is seen mainly with infectious causes like food poisoning, gastroenteritis and entercolitis. However, anal leakage may also be seen with chronic conditions where diarrhea is either persistent or recurrent. This can occur with conditions such as lactose intolerance or inflammatory bowel disease (IBD). It some instances it can also occur in acute flareups of diarrhea-predominant irritable bowel syndrome (IBS).
Constipation may seem like an unlikely condition for anal leakage to occur. After all, stool is not being evacuated, at least not easily, despite straining. Furthermore the stool is often hard. In severe constipation, the stool accumulates and may become ‘stuck’ in the colon. This is known as fecal impaction. It causes stretching of the colon and rectum and may also weaken it. Fluid stool may seem around the impaction and leak out of the anus.
The anal sphincters are composed of muscles which contract to close the anus or relax to open and allow feces out. If these muscles are diseased or damaged then it may be unable to contract tightly and keep the anus closed. Muscle damage may be seen with surgery like for hemorrhoids (piles) and after childbirth, especially when an episiotomy is performed. Other muscular diseases may also affect these sphincters although these diseases do not specifically affect only the anal sphincter muscles.
The muscles of the anal sphincters are controlled by nerves, as are all muscles in the body. If these nerves become diseased or damaged it can therefore not control the sphincter muscles properly. The sphincters may not be able to close as tightly and liquid stool can seep out. This type of nerve problems may be seen with diabetic neuropathy, spinal cord injury, stroke and multiple sclerosis. Nerve damage may also occur with straining in constipation and childbirth.
The rectum can become diseased in various ways and this can impair its ability to stretch and hold stool. This loss of flexibility is seen when scar tissue forms in the rectal walls making it stiffer than usual. Without being able to stretch, the rectum cannot accommodate large quantities of stool and this may then leak out. This type of stiffening may be see after rectal surgery, with inflammatory bowel disease and radiation damage to the rectum used in the treatment of cancer.
The rectum is supported by a floor of muscles and if this supportive wall weakens, the rectum can protrude through the anus. This is known as rectal prolapse. The last part of the colon passes stool into the rectum, where it is held temporarily until it is evacuated. In rectal prolapse, the fluid contents in the colon can leak out through the protruding rectum. Rectal prolapse is more commonly seen in older women and is also associated with childbirth.
Although anal cancer is not as common as colorectal cancer, it can be very serious. If the cancer damages the muscles or nerves that make up the anal sphincter, it can lead to anal leakage. There may also be blood in the leakage. From all the possible causes, anal cancer is the most serious and potentially life-threatening. It should always be investigated when bloody anal leakage occurs on a regular basis.