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Irritable Bowel Syndrome (IBS)

  • Medical Author: John P. Cunha, DO, FACOEP
  • Medical Editor: Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)
  • Medical Reviewer: Melissa Conrad Stöppler, MD

Irritable bowel syndrome (IBS) definition and facts

  • Irritable bowel syndrome, or IBS, or spastic colon, is a type of gastrointestinal disorder. IBS symptoms and signs include:
  • The exact cause of irritable bowel syndrome is unknown and may be due to multiple factors.
  • There are different forms of this functional disease. IBS with diarrhea (IBS-D) is characterized by chronic or recurrent diarrhea, while IBS with constipation (IBS-C) is characterized by abdominal pain or discomfort associated with constipation. Some people experience alternating symptoms of diarrhea or constipation.
  • A diagnosis of IBS is based on the duration (at least six months) and frequency of signs and symptoms (at least three times a month). A new blood test may help identify some forms of IBS.
  • There is no known cure for this condition, but there are many treatment options to reduce or eliminate symptoms. Treatment includes dietary modifications, lifestyle changes, and prescription medications.
  • There is no specific diet for IBS, and different people react differently to different foods. It is important for people with IBS to identify foods that trigger their symptoms so they can avoid them. In general, many people with the condition find it helpful to increase dietary fiber, drink plenty of water, avoid soda, and eat smaller meals.
  • It is best to talk to a primary-care physician or a gastroenterologist about the best way to manage IBS symptoms and signs.

What is IBS?

Irritable bowel syndrome is a gastrointestinal disorder characterized by the presence of a cluster of symptoms and signs in adults or children that include cramping, abdominal pain, increased gas, altered bowel habits, food intolerance, and bloating (distention).

Irritable bowel syndrome is a "functional" disorder. This term refers to the changes in the functioning of the digestive system that results in the collection of symptoms referred to as IBS, meaning that it is a problem with the movement (motility) rather than any damage to the tissues of the digestive system.

In the past, irritable bowel syndrome was also called spastic colon or bowel, functional bowel disease, mucous colitis, or nervous colon.

What are the signs and symptoms of IBS?

Irritable bowel syndrome is characterized mostly by abdominal pain and cramping. Other symptoms and signs include:

  • Diarrhea: IBS with diarrhea (IBS-D) can come with sudden urges to have bowel movements and loose stools.
  • Constipation: IBS with constipation (IBS-C) can be accompanied by straining during bowel movements and infrequent stools.
  • Increased gas
  • Abdominal swelling or bloating
  • Abdominal pain or discomfort
  • Cramping pain after eating certain foods
  • Nausea
  • Mucousy or foamy stool
  • Unexplained weight loss
  • Loss of appetite

While not technically a symptom, nearly 70% of people with IBS also experience indigestion.

Symptoms are often relieved by bowel movements. Women with IBS may have more symptoms during their menstrual periods.

What causes IBS?

The exact cause of irritable bowel syndrome is unknown. It is believed to be due to a number of factors, including alteration in the gastrointestinal (GI) tract motility, abnormal nervous system signals, increased sensitivity to pain, and food intolerances. The following are risk factors thought to cause IBS:

  • Abnormal movements of the colon and small intestines (too fast or slow, or too strong)
  • Hypersensitivity to pain from a full bowel or gas
  • Food sensitivities, possibly caused by poor absorption of sugars or acids in food
  • Gastroenteritis ("stomach flu" or "stomach bug"), a viral or bacterial infection of the stomach and intestines, may trigger IBS symptoms
  • Psychological conditions such as anxiety or depression are observed in many people with IBS, though these conditions have not been found to be a direct cause of IBS.
  • Reproductive hormones or neurotransmitters may be off-balance in people with IBS.
  • Small intestinal bacterial overgrowth (SIBO)
  • Genetics is thought to be a possible cause of IBS, but so far, this hereditary link has not been proven.

What are IBS-D (IBS with diarrhea) and IBS-C (IBS with constipation)?

  • IBS-D stands for irritable bowel syndrome with diarrhea. The most common symptoms of IBS-D include:
    • Frequent stools
    • Feeling as if you are unable to completely empty your bowels during bowel movements
    • Nausea.
    • People with IBS-D also may experience signs and symptoms of:
      • Gas
      • Abdominal pain or discomfort
      • Sudden urges to have a bowel movement
      • Loose stools
  • IBS-C stands for irritable bowel syndrome with constipation. The most common symptoms of IBS-C include:
    • Infrequent stools
    • Straining during bowel movements
    • Feeling as if you are unable to completely empty your bowels during bowel movements
    • Feeling as if you need to have a bowel movement but are unable
    • Abdominal pain
    • Bloating
    • Gas

IBS vs. IBD Are the same disease?

While both irritable bowel syndrome and inflammatory bowel disease can have similar symptoms including abdominal pain, diarrhea, and urgent bowel movements; however, IBS is not the same as IBD.

  • IBD is a group of separate diseases that includes ulcerative colitis and Crohn's disease, and is a more severe condition.
  • Irritable bowel syndrome is considered a functional gastrointestinal disorder because there is abnormal bowel function. IBS is a group of symptoms and not a disease in itself, which is why it’s called a ‘syndrome,’ and it is considered less serious than IBD.
  • Irritable bowel syndrome does not cause inflammation like inflammatory bowel disease, and it does not result in permanent damage to the intestines, intestinal bleeding, rectal bleeding, ulcers, or the harmful complications that are often seen with IBD.

IBS vs. SIBO (small intestinal bacterial overgrowth)? Are they the same disease?

Small intestinal bacterial overgrowth (SIBO) is considered one of the factors that may produce signs and symptoms of irritable bowel syndrome (IBS). The medical data from studies done on SIBO are conflicting.

Some studies show an increase in gas production by intestinal bacteria as a cause of the pain and bloating associated with IBS. However, other studies done to determine if SIBO is the cause of IBS and if antibiotic treatment of SIBO is helpful in reducing or eliminating IBS symptoms have not been conclusive.

What tests diagnose IBS?

Irritable bowel syndrome is diagnosed by excluding other GI disorders that can cause similar symptoms. A complete history and physical is taken to determine the duration and frequency of symptoms. To be diagnosed with the condition, the duration of symptoms should be at least six months and should occur at least three times a month.

A doctor may order tests, including blood tests, stool tests, X-rays, or CT scans. There is no specific finding on these tests that can confirm the diagnosis of IBS, however, other problems can be ruled out by performing them.

Irritable bowel syndrome test

Two relatively new blood tests may help diagnose irritable bowel syndrome. One test is for irritable bowel syndrome with diarrhea (IBS-D), and the other is for irritable bowel syndrome with both diarrhea and constipation (irritable bowel syndrome mixed IBS-M). Neither test is able to diagnose irritable bowel syndrome with constipation (IBS-C).

Both blood tests are for anti-CdtB and anti-vinculin antibodies. It is thought that these antibodies develop in some patients after an acute bout of gastroenteritis that is caused by several different, common types of bacteria. The overgrowth of these bacteria in the gut may trigger an immune attack on the patients’ own intestinal tissues (autoimmunity) with the ensuing inflammation and damage to the tissues causing the symptoms of IBS.

The tests may help distinguish between irritable bowel syndrome and inflammatory bowel disease or IBD, a different type of intestinal inflammatory disease that includes Crohn's disease and ulcerative colitis.

The antibody tests seems to be useful in the diagnosis of irritable bowel syndrome with diarrhea IBS-D, but not IBS with constipation (IBS-C). The tests also appear to be specific, and if the antibodies are present, it is highly likely that IBS is present. However, the tests are insensitive, meaning if the antibodies are not present, the patient still may have IBS. Thus, these irritable bowel syndrome tests may be identifying only a subset of patients with IBS, those with post-infectious IBS. Both IBS blood tests have not undergone rigorous testing, and have not yet been approved by the FDA. It is expected to be an expensive test costing $500 to over $1,000.

A doctor also may send the patient to a gastroenterologist (a specialist in the digestive system). Depending on the symptoms, an upper endoscopy and/or colonoscopy may be performed.

What is the treatment for IBS?

Dietary modifications are the first treatments that should be tried to treat IBS. There are several types of foods in particular that often trigger characteristic symptoms and signs.

If dietary modifications and lifestyle changes do not adequately treat the symptoms and signs, a doctor may recommend medical therapies.

What medications are used in the treatment and management of IBS-D and IBS-D?

Medicine for diarrhea

  • Antidiarrheal medications such as loperamide (Imodium), attapulgite (Kaopectate), and diphenoxylate and atropine (Lomotil) can be helpful if loose stools are one of the main signs. Eluxadoline (Viberzi) is a prescription for the treatment of irritable bowel syndrome with diarrhea (IBS-D).
  • For females with IBS who experience severe diarrhea, alosetron (Lotronex) has been used.
  • Rifaximin (Xifaxan) is an antibiotic for the treatment of irritable bowel syndrome with diarrhea (IBS-D) and IBS-related bloating.
  • Bile acid binders including cholestyramine ( (Prevalite), colestipol (Colestid), or colesevelam (Welchol) can help some patients with IBS-D, but can also cause bloating.

Medicine for constipation medication

  • Over-the-counter laxatives such as polyethylene glycol 3350 ( (MiraLax), bisacodyl (Dulcolax), and psyllium seed husks (Metamucil) can help relieve constipation and keep bowel movements regular. Senna laxatives (Senokot, Ex-Lax Gentle Nature) may be taken short-term. Prescription laxatives such as lactulose (Constulose) may also be prescribed.
  • Two drugs specifically used to treat IBS are lubiprostone (Amitiza), a laxative, and linaclotide (Linzess), a constipation medication.
  • SSRI antidepressants fluoxetine (Prozac), citalopram (Celexa), sertraline (Zoloft), paroxetine (Paxil), and escitalopram (Lexapro) may be helpful for those with constipation (IBS-C), but they can trigger IBS attacks in patients with diarrhea (IBS-D).

What other drugs are used in the treatment of IBS symptoms and signs?

  • Antidepressants in low doses, such as tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), may help relieve symptoms associated with IBS.
  • Bismuth subsalicylate (Pepto-Bismol) and magnesium hydroxide (Milk of Magnesia).
  • Antibiotics may be used when small intestinal bacterial overgrowth (SIBO) is suspected.
  • Antianxiety medications such as diazepam (Valium), lorazepam (Ativan), and clonazepam (Klonopin) are occasionally prescribed short-term for people whose anxiety worsens their irritable bowel syndrome symptoms.

What medications are used in the treatment of pain and cramping?

  • Antispasmodics, such as metoclopramide (Reglan), dicyclomine (Bentyl), and hyoscyamine (Levsin), decrease symptoms of pain and cramping.
  • Antidepressants such as amitriptyline (Elavil, Paregoric), doxepin ( (Silenor), desipramine (Norpramin), nortriptyline (Pamelor), and imipramine (Tofranil) may help with abdominal pain but due to side effects are usually reserved for severe cases.

Is there an IBS diet? What are foods to avoid and to eat?

What you eat and how you eat can affect symptom of this condition. While it may not be possible to completely prevent IBS symptoms, you may find that certain foods trigger IBS symptoms. To help figure out which foods cause you symptoms, a doctor may suggest keeping a food diary.

Some foods can help in the prevention of symptoms.

Foods to eat that may provide symptom relief (home remedies and others) for some people:

  • Dietary fiber supplements
  • Water
  • Low-fat foods
  • High-carbohydrate foods (such as whole wheat pasta, brown rice, and whole grain breads)
  • Probiotics (containing Lactobacillus acidophilus a and Bifidobacterium) and prebiotics
  • Some people report kefir or Aloe Vera juice helps symptoms. Talk to a doctor about these home remedies.

A high-fiber diet may help relieve constipation in some cases of IBS, but it may also worsen some symptoms such as bloating and gas. The current recommended daily fiber intake is 20-35 grams daily. Most people fall short of this daily fiber intake and can benefit from a small increase in fiber, but it is best to increase the amount in your diet slowly to reduce gas.

Foods to avoid or limit if you have IBS

  • Dairy products, including milk and cheese (Lactose intolerance symptoms can be similar to IBS symptoms.)
  • Certain vegetables that increase gas (such as cauliflower, broccoli, cabbage, Brussels sprouts) and legumes (such as beans)
  • Fatty or fried foods
  • Alcohol, caffeine, or soda
  • Foods high in sugars
  • Artificial sweeteners
  • Chewing gum
  • Nuts

What is a low FODMAP diet?

A low FODMAP diet may also help relieve symptoms of IBS. FODMAP refers to a group of short-chain carbohydrates (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) that are not well absorbed in the small intestine and are rapidly fermented by bacteria in the gut. These bacteria produce gas, which can contribute to IBS symptoms.

The lists of foods both high and low in FODMAPs are extensive. The International Foundation for Functional Gastrointestinal Disorders, Inc. (IFFGD) has suggestions of foods to eat and foods to avoid if you follow the FODMAP diet for IBS. Talk to your doctor for more information.

What natural and home remedies or other lifestyle changes may help IBS symptoms and signs?

Some lifestyle changes that can also help relieve symptoms are:

What are potential complications of irritable bowel syndrome (IBS)?

In general, there are few complications associated with this functional disease other than the symptoms of the disease itself. If someone has hemorrhoids, the diarrhea and constipation associated with IBS may irritate them. Moreover, a diet that is too strict limits nutrients that could cause problems related to lack of proper nutrition.

The biggest complication of IBS may be on the quality of life. The stress and anxiety as well as the impact on daily activities the condition can cause may be troublesome for patients.

IBS does not lead to colon cancer, rectal bleeding, or inflammatory bowel diseases such as ulcerative colitis.

Is it possible to prevent irritable bowel syndrome (IBS)?

It may not be possible to prevent developing IBS, but you can take steps to prevent symptoms for occurring or worsening. As discussed earlier, dietary and lifestyle changes can help you manage symptoms. To identify food triggers, your doctor may suggest that you keep a food diary and avoid foods that cause symptoms. Manage stress and anxiety, and try cognitive therapy or psychotherapy if needed.

What is the prognosis for a person with irritable bowel syndrome (IBS)?

Irritable bowel syndrome is a chronic disease with symptoms that tend to come and go. The overall prognosis for patients with IBS depends on the severity and frequency of symptoms, and the patient's ability to control these symptoms, whether by diet, lifestyle changes, or medications.

There is no known cure for IBS, but there are many treatment options to reduce or eliminate symptoms. Good communication with a doctor is important to help manage this condition.

Which types of of doctors treat IBS?

A primary-care provider or family-medicine specialist or a child's pediatrician may first diagnose irritable bowel syndrome. You will likely be referred to a gastroenterologist (a specialist in disorders of the digestive system) for further treatment.

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Reviewed on 9/21/2018

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