What is IBS?
Irritable bowel syndrome (IBS) is a functional bowel disorder meaning that it is due to unknown causes but is not related to any disease process. It is 2 to 3 times more common in women than men in Western nations which is in stark contrast to Asian countries like India where 70% to 80% of IBS sufferers are men. IBS is a condition marked by episodes of abdominal pain with changes in bowel habit broadly labeled as constipation or diarrhea. It is a chronic ailment that can cause severe discomfort and have a wide degree of psychosocial impact but is not life threatening and not associated with an increased risk of more serious diseases like colorectal cancer.
Causes of Irritable Bowel Syndrome
The exact cause of irritable bowel syndrome is unknown. It can be broadly categorized into diarrhea-predominant IBS or constipation-predominant IBS. Many patients, however, may experience diarrhea alternating with constipation. It is believed that IBS is due to a disruption in normal gastrointestinal motility. This is the action of the bowels in propelling food, waste and other substances within in it towards the rectum where it passed out of the anus as feces.
Normally, the muscular bowel walls contract and relax in an orderly pattern to ensure that the contents within it move at a reasonable speed to allow for adequate digestion and nutrient absorption. In IBS this may be affected an be either too slow (constipation-predominant) or too fast (diarrhea-predominant). It seems that this disorders in bowel motility may be associated with the action of serotonin, a hormone that is present in the brain and responsible for moods, but is also found in the bowel wall. Other mechanisms may include some degree of food intolerance and malabsorption that has not as yet been clearly identified. However, these effects of maldigestion and malabsorption may just arise secondary to abnormalities in bowel transit time. Some theories suggest that IBS may also be associated with disruptions in the normal intestinal flora (bowel bacteria).
Certain foods, situations and diseases may exacerbate the condition but these are triggers and not causes. IBS is more likely to be occur in females, start before the age of 35 years and arise in a person with a family history of IBS. It has been postulated that the female hormones may be the reason why irritable bowel syndrome is more common in women but this does not explain the prevalence in men in Asia. IBS does tend to aggravate during pregnancy though. Psychological stress is a strong exacerbating factor and it is believed that IBS could be associated with psychosomatic factors.
Signs and Symptoms
IBS is defined by the presence of abdominal pain and change in bowel habit in the absence of other diseases. The pain appears to be largely due to painful bowel cramps. Bloating, excessive flatulence and less frequently mucus in the stool may also be present. Mucus and blood in the stool, however, needs to be investigated further for conditions like inflammatory bowel disease (IBD) and colorectal cancer. Other functional bowel disorders may also have similar symptoms and should be differentiated from IBS. Diarrhea on its own without abdominal pain is known as functional diarrhea and the same applies to functional constipation. Bloating on its own without pain or changes in bowel habit is known as functional bloating.
There is no definitive treatment for IBS and the focus should be on conservative management through dietary and lifestyle modification. There is no set regimen in this regard and different changes may work for individual patients. However, the focus is on identifying and avoiding trigger factors and stress management. Fiber supplements and probiotics may also be of use in managing IBS. Certain medication may help ease or even resolve the symptoms or reduce the frequency of acute episodes but is not curative. This largely focuses on the use of tricyclic antidepressants and anticholinergics to prevent painful bowel cramps. Other medication such as nerve receptor antagonist may slow down bowel motility and calcium channel activators may increase fluid secretion into the bowel which can be helpful in diarrhea-predominant and constipation-predominant IBS respectively.