Irritable Bowel Syndrome (IBS)
Medically reviewed by C. Fookes, BPharm. Last updated on Mar 28, 2019.
Irritable bowel syndrome (IBS) is a common, complex disorder that affects the large intestine. Symptoms may include abdominal pain, bloating, cramping, gas, and constipation or diarrhea, or both. It is not the same as inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis.
The American College of Gastroenterology defines IBS as "Abdominal discomfort associated with altered bowel habits".
Irritable bowel syndrome may also be called nervous indigestion, spastic colon, intestinal neurosis, functional colitis, irritable colon, mucous colitis, or laxative colitis.
What causes irritable bowel syndrome and who is at risk?
Nobody knows what causes IBS but factors that appear to play a role include:
- Muscle contractions in the intestine
- Abnormalities in the nerves of the digestive system
- Inflammation in the intestines
- Severe infection
- Changes to the microflora (bacteria) in the gut.
Certain risk factors make you more likely to develop IBS. IBS is twice as likely to occur in women than men and more common in people under age 45, usually beginning in adolescence or early adulthood. If you have a family member with the disorder, you are also at higher risk of getting it. Psychological stress, caused by anxiety, depression, a personality or mood disorder, or a history of sexual abuse can bring on IBS.
IBS has also been associated with smoking, a low fiber diet, use of laxatives, or a bout of infectious diarrhea or other cause of temporary bowel inflammation. Hormonal changes may also play a role.
IBS is a persistent condition that requires long-term management.
How is irritable bowel syndrome diagnosed?
IBS is difficult to diagnose, and on average it takes around three years and at least three different doctors before the diagnosis of IBS is arrived at. This is because symptoms of IBS are similar to several other lower abdominal conditions, such as endometriosis, giardiasis, food allergies, inflammatory bowel disease, or ulcerative colitis. Most of these conditions need to be excluded before a definite diagnosis of IBS can be made.
Tests usually reveal no problems. Not all patients require endoscopy, especially if symptoms begin early in life and have been stable. However, patients who have irritable bowel symptoms beginning later in life usually require endoscopy.
Younger patients with persistent diarrhea may require endoscopy to look for inflammatory bowel disease (Crohn's disease or ulcerative colitis). Irritable bowel syndrome, by contrast, is not an inflammatory condition, but the symptoms may be very similar to those of inflammatory bowel disease.
Patients over age 50 should be screened for colon cancer.
What are the symptoms of irritable bowel syndrome?
Only a small number of people with IBS have severe symptoms; most have mild-to-moderate symptoms that can be controlled by managing their diet, lifestyle or stress.
Symptoms can also vary significantly from one person to the next. Even within the same person, symptoms are generally not stable over a lifetime and can change without warning.
Some people are more likely to have constipation (constipation-predominant IBS or IBS-C), others diarrhea (diarrhea-predominant IBS or IBS-D), while a few experience both constipation and diarrhea at different times (mixed IBS).
Most people with IBS have at least two of these symptoms:
- Altered bowel habits - passing feces more or less frequently than normal or periods of constipation and then periods of diarrhea
- Excessive gas
- Mucus mixed in with the feces
- Multiple episodes of stomach discomfort for at least three months of the past year
- Pain or discomfort that lessens after a bowel movement
- Swelling or bloating of the stomach, or a feeling of fullness soon after eating.
Increased stomach gurgling or bowel sounds are also reported frequently by people with IBS.
Call your doctor if:
You have symptoms of irritable bowel syndrome or if you notice a persistent change in your bowel habits.
Irritable bowel syndrome is extremely common, but only a small number of people seek treatment. The goal of treatment is to relieve symptoms.
Diet and IBS
Many people with IBS find gluten-free diets helpful, and avoiding foods like cabbage, beans, and cauliflower may cut down bloating and flatulence. Trials have shown mixed results for people following a low-FODMAP diet (limits foods high in fructose, lactose, fructans, galactans, and polyols). Avoiding substances that stimulate the intestines, such as caffeine, can also help.
Around 30-50% of IBS sufferers relate their symptoms to food allergies or food intolerances. However, trials have found that only 1 in 5 people reacted when given these presumed offending foods in a blinded manner.
Keeping a food diary may help you to work out what foods seem to trigger your IBS. Be prepared to experiment with many different foods, as this is often harder to work out than it seems. Restricted diets are notorious for lacking in certain vital nutrients so talk with a dietician to make sure you are still getting what you need each day. Also be aware that even if you eliminate certain foods, you may still get IBS symptoms. More research is needed investigating the link between diet and IBS.
The relationship between fiber and IBS is not straightforward. There are two types of fiber - soluble and insoluble. Soluble fiber attracts water and turns to a gel during digestion. It is found in foods such as oat bran, barley, nuts, seeds, beans, lentils, peas, some fruits and vegetables, and in psyllium, a common fiber supplement. Research has shown it to be beneficial in IBS, helping to soothe and regulate the digestive tract.
Insoluble fiber is found in foods such as wheat bran, vegetables, and whole grains. It is a powerful digestive stimulant and helps food to pass more quickly through the stomach and intestines. Unfortunately, research has found it not so good for people with IBS. The dilemma is that insoluble fiber is found in a lot of healthy foods, so removing it from your diet altogether is not a good idea, as you would be missing out on a valuable dietary component.
Eating small amounts of insoluble fiber and mixing foods that contain both soluble and insoluble fiber seems to help.
Eating small, regular meals throughout the day is kinder on your digestive system than skipping meals or having massive feeds.
Water is the best liquid you can drink. Alcohol and beverages that contain caffeine stimulate your intestines and can make diarrhea worse. Carbonated drinks just give you more gas!
Probiotics and IBS
Probiotics are "friendly" bacteria that naturally live inside our bodies. Many experts believe a lot of our digestive problems arise when the balance of bacteria inside our gut gets out of balance. Supplements that contain a mixture of Lactobacillus and Bifidobacterium seem to work best for IBS.
Prebiotics are nondigestible food ingredients (usually a type of carbohydrate) that act as food for bacteria. Sometimes you will find a prebiotic mixed with a probiotic (called a symbiotic). Evidence so far hasn't found these as good for IBS, but research is ongoing.
Drug treatment for IBS
Most of the pain experienced in IBS is caused by spasms that occur in the walls of your intestine. Antispasmodics such as hyoscyamine (Anaspaz, Cystospaz, Levsin) and dicyclomine (Bentyl) relieve colicky-type pain and are good for occasional use. However, they do tend to cause side effects such as a dry mouth, drowsiness, and constipation. Peppermint oil capsules are an alternative to antispasmodics. It has a similar effect but without any side effects.
Loperamide (Diamode, Imodium) stops diarrhea, although care must be taken not to overdo the dosage and end up with constipation.
Antidepressants (eg, amitriptyline, doxepin, Lexapro, Celexa) are effective at relieving abdominal pain and providing overall symptom relief in people with IBS. However, side effects such as weight gain, drowsiness, constipation, and sexual dysfunction tend to limit their use for IBS.
Eluxadoline (Virbezi) treats abdominal pain and diarrhea, hallmark symptoms of IBS-D. It is the first in its class and provides a welcome treatment alternative to standard anti-diarrheal medicines. It works on opioid receptors to relieve diarrhea and is classified as a controlled substance. Potentially it is a target for people who abuse prescription medicines or street drugs. Theoretically, there is a risk of psychological dependence.
Plecanatide (Trulance) is approved for the treatment of adults with IBS-C. It changes the balance of sodium within the intestine which causes an influx of water; this helps to soften and loosen stools and increase bowel movements, relieving constipation. In addition, Trulance may help decrease pain and inflammation within the intestines.
Both Linzess and Amitiza soften stools and stimulate bowel movements, so they are effective in people with constipation-predominant IBS, but not so good for people who have diarrhea as their main symptom.
Rifaximin (Xifaxan) is an antibiotic used occasionally in diarrhea-predominant IBS to relieve bloating and reduce overall symptoms.
Alosteron (Lotronex) has some rare, but serious, side effects and can only be prescribed for women suffering with severe, disabling, diarrhea-predominant IBS.
Other Non-drug Treatments
Exercise is a great mood lifter and can help reduce any anxiety you may have about your condition.
A heating pad to place on your stomach when the pain is bad may also help.
Counseling can help you learn to modify your response to stress and mindfulness training teaches you to focus on being in the moment and letting go of worries and distractions. Success has also been reported with biofeedback and progressive relaxation exercises.
Having friends and family that understand your condition is also important. It's far easier to say "I'm feeling really unwell, I can't come out tonight" than to make up excuses for backing out of plans.
If you have chosen your friends wisely, they'll want the best for you. Sharing how you feel with somebody that cares provides a good outlet for your emotions as well.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.