What is Irritable Bowel Syndrome?
What is Irritable Bowel Syndrome?
Irritable bowel syndrome (IBS) is a common gastrointestinal disorder, affecting about one in 5 to 10 Americans and reported about 5 times more often in women than men. IBS symptoms may start in childhood or the teenage years, with peak incidence in the third or fourth decade. Commonly associated extra intestinal symptoms include migraine headaches, fibromyalgia, chronic pelvic pain and dysfunctional bladder, suggesting a global smooth muscle dysfunction. Signs and symptoms not seen in irritable bowel syndrome include bloody stools, weight loss, inflammatory arthritis, mouth ulcerations and onset of symptoms after age 50. Individuals with these alarm symptoms may have underlying cancer, structural problems such as diverticulosis, or inflammatory colitis and need to seek medical evaluation immediately.
What causes IBS?
Although the exact cause of IBS is unknown, it is best classed as a functional disorder, because there are no structural, biochemical, or overt inflammatory causes for the disorder. Routine laboratory testing, x-rays and endoscopies are normal. However, sophisticated testing of pain sensation has yielded reproducible evidence that individuals with IBS experience heightened pain when their intestine dilates (such as when gas is present) and also when their colon contracts to evacuate stool. Current research of intestinal motility (peristalsis) is focused on the function of the nerve cells in the gut, as well as their interaction with the brain. Important proteins called neurotransmitters produced by gut derived nerves and the brain; interact in a complex way to control the motor activity of our intestine. This explains why conditions like stress, anxiety, depression, or even happy events like a job promotion or an upcoming wedding may be associated with altered bowel habits and send us running to the restroom! It is important to know that psychological conditions per se do not cause IBS, but that the emotional state of an individual with IBS may have a significant modulating effect on bowel symptoms.
What is Considered Normal Digestion?
Once we swallow our meals, we have no direct or voluntary control over the digestive process. Food moves from the swallowing tube (esophagus) into the stomach within seconds, then is mixed with acid and chemicals (pepsin) and is physically mashed by the powerful contractions of the stomach. The liquefied food (chyme) empties into the small intestine in one to three hours. The majority of digestion occurs in the 27 to 33 feet of small intestine. The chyme is acted upon by pancreatic juice and bile in order to emulsify fat and protein and enzymes in the lining of the intestine act upon sugars, to allow absorption of nutrients and vitamins. Unabsorbed residue enters the large intestine (colon) in about 4 hours and is very watery. Very little digestion or nutrient absorption occurs in the colon; its main function is to absorb about 1 to 1.5 liters of water, such that normal stool should be formed and not watery. Watery stool suggests rapid colon transit, inflammation of the colon lining such that water is not absorbed or altered digestion, with malabsorbtion of nutrients. Passage from the right side of the colon to eventual stool passage is variable, but takes on the average 8 to 48 hours. Thus the average oral to stool passage time should be one to two days. The medical definition of constipation is passage taking longer than 72 hours. This can be measured by swallowing a sitz marker capsule. The capsule coating is dissolved in the acid environment of the stomach, releasing tiny rings plastic rings that can be seen with a standard x-ray. Patients with delayed passage may have the rings hang up at a structural point, such a as tumor, but most often constipated patients just have a slow progression through the colon. The medical definition of diarrhea is passage of more than 200 mls of stool a day.
How would I know if I have IBS and can this be a serious problem?
The characteristic symptoms of IBS include altered bowel passage, low abdominal pain or bloating, which can either be relieved with bowel passage (the release of gas and stool decreased pressure and distention), or pain can be increased with bowel passage due to forceful contractions. Many individuals report a feeling of incomplete defecation, or just passing mucous without stool and the need to return to the bathroom multiple times in order to complete an evacuation. Although each person with IBS will have unique symptoms, there are three main patterns of altered bowel passage: constipation predominant, diarrhea predominant and alternating constipation and diarrhea. Symptoms vary in intensity and frequency, but are recurrent, thus IBS is a chronic disorder. There are also many “silent sufferers,” who learn to live with their discomfort. Studies indicate that only a minority of individuals with IBS ever seek medical help for their condition! IBS is a real disorder however and symptoms can be severe, resulting in work absenteeism, disability, unwarranted narcotic use and marked interference with family and social life. In studies of IBS patients, quality of life can be significantly impaired, thus underscoring the need for accurate diagnosis and treatment.
How is IBS diagnosed?
Although IBS may be accurately diagnosed with a carefully obtained history and physical exam, stool cultures or specific blood tests are oftentimes ordered to exclude other diseases. There are mimics of IBS such as wheat allergy (called celiac spru), thyroid disorders, infections with water-derived pathogens such as giardia, lactose intolerance (sensitivity to the sugar found in milk products) and some rare inflammatory types of colitis that may be indistinguishable from IBS without testing. A total colonoscopy (examination with a fiber optic camera tube) with mucosal biopsy may be necessary to exclude inflammatory causes of diarrhea and colonoscopy or x-rays (barium enema) may be obtained to exclude structural causes for constipation.
What treatments are available for IBS?
The goal of treatment is relief of symptoms and restoration of normal bowel function in order to maximize quality of life. Pain medication use should be discouraged, as the underlying disorder is not adequately treated and in fact may be exacerbated because narcotics commonly worsen constipation and bloating, as well as cause nausea and vomiting. Although used in the past to calm down a spastic colon, sedatives such as Valium and Librium interfere with memory, cause drowsiness and limit the ability to work or drive and so should also be avoided.
Treatment needs to be individualized to the patient's symptoms. With our improved understanding of the underlying pathophysiologic alterations in IBS, we have been able to develop and implement successful therapies. For constipation predominant patients: Prescription medications such as Zelnorm (Tegaserod) work directly on the nerves in the gut to stimulate motility and reduce pain. Stool softeners and osmotic agents (medicines that increase stool water and bulk) may be helpful as well. Conservative measures include providing dietary counseling regarding increasing soluble fiber in the diet, but avoiding insoluble fibers and cruciferous (gas producing) vegetables such as cabbage, broccoli, cauliflower and greens. Avoidance of carbonated beverages may reduce gaseous distention and over the counter simethicone preparations may provide additional relief. Patients with diarrhea predominant symptoms should avoid orbital, a poorly absorbed sugar found in many fruits such as apples, peaches, pears, cherries and prunes, mints and sugarless gum may also contain orbital and many cola beverages contain fructose as a sweetener, which can also exacerbate diarrhea in some individuals. Caffeine increases motility and should be avoided. In some cases, especially those with history of asthma or recurrent sinusitis, food allergy testing may help eliminate dietary triggers. Taking a tablespoon a locally produced honey may induce tolerance to local pollen and can improve symptoms of IBS associated with allergy. Other tips include avoidance of processed foods containing preservatives, especially monosodium glutamate and meat tenderizers. When dining out, pretreatment with over the counter Immodium or prescription medications ( Levsin , Bentyl , Lotronex etc.) may be beneficial. Natural remedies include peppermint oil and caraway, which promote smooth muscle relaxation to reduce painful spasms.
Regardless of the individual pattern of altered stool passage, symptom relief has been successfully achieved with routine exercise, meditation, yoga, relaxation therapies and cognitive behavior therapy. When pain is a major feature of the illness, pain modulators such as serotonin uptake inhibitors ( Prozac, Zoloft, Paxil, Lexapro, Celexa , etc) are most helpful in constipated individuals, while those with pain and diarrhea may benefit the most from tricyclic antidepressants (amitryptyline, nortryptyline, imipramine, trazodone, etc.).
Irritable bowel syndrome is a common disorder, especially in women. Today there are many available traditional and alternative therapies that are effective for symptom relief. If you have altered bowel habits or unexplained abdominal pain, call your doctor for an evaluation; it should be well worth your effort. (Barbara, this last paragraph may be used as a “mini-abstract at the beginning of the article, or as a summary sentence at the end, whichever you choose)
Kristine J. Krueger, MD is an Associate Professor, Gastroenterology & Hepatology, University of Louisville Medical Director, Digestive Health Center, and the University of Louisville Hospital .