Irritable bowel syndrome: Types and Symptoms, Causes, Diagnosis and Treatment

Irritable bowel syndrome, or IBS, or spastic colon, is a type of gastrointestinal disorder that affects the large intestine.

Updated: June 16, 2022

Irritable bowel syndrome, or IBS, or spastic colon, is a type of gastrointestinal disorder that affects the large intestine. Signs and symptoms include cramping, abdominal pain, bloating, gas, and diarrhea or constipation, and food intolerance. IBS is a chronic condition that can be controlled by managing diet, lifestyle and stress. Severe symptoms can be treated with medication and counseling.
The exact cause of irritable bowel syndrome is unknown and may be due to multiple factors.
There are different forms of this functional disease which include IBS with diarrhea (IBS-D) which is characterized by chronic or recurrent diarrhea, IBS with constipation (IBS-C) which 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 and frequency of signs and symptoms. A new blood test may help identify some forms of IBS.
There is no known cure for this condition. However, there are many treatment options to reduce or eliminate symptoms which include dietary modifications, lifestyle changes, and prescription medications.
As different people react differently to different foods, there is no specific diet for IBS. It is important for people with IBS to identify foods that trigger their symptoms so they can avoid them. Most of the people with this condition can reduce the symptoms by increasing dietary fiber, drinking plenty of water, avoiding soda, and eating smaller meals.
In case of severe symptoms, it is better to talk to a primary care physician or a gastroenterologist about the best way to manage IBS symptoms and signs.
IBS doesn't cause changes in bowel tissue or increase your risk of colorectal cancer.
Irritable bowel syndrome is a functional disorder which refers to the changes in the functioning of the digestive system. This results in a problem with the movement rather than any damage to the tissues of the digestive system.

Types and Symptoms of IBS:


IBS-D is 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.
  • Gas
  • Abdominal pain or discomfort
  • Sudden urges to have a bowel movement
  • Loose stools


IBS-C is 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

See your doctor in case you experience serious signs and symptoms that include:

  • Weight loss
  • Diarrhea at night
  • Rectal bleeding
  • Iron deficiency anemia
  • Unexplained vomiting
  • Difficulty swallowing
  • Persistent pain that isn't relieved by passing gas or a bowel movement

These may indicate a more serious condition, such as colon cancer.

Causes of Irritable Bowel Syndrome (IBS):

The exact cause of irritable bowel syndrome is unknown. However a number of factors can contribute in development of this disease, including alteration in the gastrointestinal (GI) tract motility, abnormal nervous system signals, increased sensitivity to pain, and food intolerance. The following risk factors are thought to cause IBS:

  • Abnormal movements of the colon and small intestines which could be too fast or slow, or too strong. The walls of the intestines are lined with layers of muscle that contract as they move food through your digestive tract. Contractions that are stronger and last longer than normal can cause gas, bloating and diarrhea. Weak intestinal contractions can slow food passage and lead to hard, dry stools.
  • 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, which is 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. Abnormalities in the nerves in your digestive system may cause you to experience greater than normal discomfort when your abdomen stretches from gas or stool. Poorly coordinated signals between the brain and the intestines can cause your body to overreact to changes that normally occur in the digestive process, resulting in pain, diarrhea or constipation.
  • Small intestinal bacterial overgrowth (SIBO)
  • Genetics is thought to be a possible cause of IBS, but this hereditary link has not been proven so far.
  • Some people with IBS have an increased number of immune system cells in their intestines. This immune system response is associated with pain and diarrhea.
  • Microflora are the good bacteria that reside in the intestines and play a key role in health of a person which might differ in people with IBS from healthy people.

Diagnosis of Irritable Bowel Syndrome (IBS):

There is no specific test to diagnose IBS. However, your doctor will start with a complete medical history, physical exam and tests to rule out other conditions such as GI disorders that can cause similar symptoms.
A complete history and physical examination is done 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. If you have IBS with diarrhea, a gluten intolerance test should be done.
Other problems can be ruled out by performing blood tests, stool tests, X-rays, or CT scans. Imaging tests can include:

Flexible sigmoidoscopy:

The lower part of the colon called sigmoid will be examined by your doctor with a flexible, lighted tube known as sigmoidoscope.


In this procedure a small, flexible tube is used to examine the entire length of the colon.

X-ray or CT scan:

Images of your abdomen and pelvis are produced by these tests that might allow your doctor to rule out other causes of your symptoms, especially if you have abdominal pain. Your doctor might fill your large intestine with a liquid (barium) to make any problems more visible on X-ray. This barium test is sometimes called a lower GI series.
One of these following sets of diagnostic criteria is used for IBS after ruling out other conditions.

Rome criteria:

These criteria include abdominal pain and discomfort lasting on average at least one day a week in the last three months. This should be associated with at least two of these factors:

  • Pain and discomfort are related to defecation,
  • the frequency of defecation is altered,
  • stool consistency is altered.

Manning criteria:

These criteria include

  • pain relieved by passing stool and on having incomplete bowel movements,
  • mucus in the stool
  • changes in stool consistency.

The more symptoms you have, the greater the likelihood of IBS.
Your doctor will also likely assess other signs or symptoms that you have which might indicate another, more serious, condition. These signs and symptoms include:

  • Onset of signs and symptoms after age 50
  • Weight loss
  • Rectal bleeding
  • Fever
  • Nausea or recurrent vomiting
  • Abdominal pain, especially if it is not completely relieved by a bowel movement, or occurs at night
  • Diarrhea that is persistent or awakens you from sleep
  • Anemia related to low iron

If you have these signs or symptoms, or if an initial treatment for IBS doesn't work, you are suggested to do some additional tests.
A stool test and malabsorption test can be done to check for infection or problems with your intestine's ability to take in the nutrients from food respectively.

Laboratory tests can include:

Lactose intolerance tests:

Lactase is an enzyme that helps digest the sugar found in dairy products. If you don't produce lactase, you may have problems similar to those caused by IBS, including abdominal pain, gas and diarrhea. Your doctor may order a breath test or ask you to remove milk and milk products from your diet for several weeks.

Breath test for bacterial overgrowth:

A breath test can determine if you have bacterial overgrowth in your small intestine. Bacterial overgrowth is more common among people who have had bowel surgery or who have diabetes or some other disease that slows down digestion.

Upper endoscopy:

Endoscopy is recommended if celiac disease is suspected. In this procedure a long, flexible tube is inserted down your throat and into the tube connecting your mouth and esophagus. A camera on the end of the tube allows the doctor to inspect your upper digestive tract and obtain a tissue sample or biopsy from your small intestine and fluid to look for overgrowth of bacteria.

Stool tests:

Your stool might be examined for bacteria or parasites, or bile acid, if you have chronic diarrhea.

Anti-CdtB and anti-vinculin antibodies:

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 patient's own intestinal tissues 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). If the antibodies are present, it is highly likely that IBS is present. However, if the antibodies are not present, the patient still may have IBS.

Treatment of Irritable Bowel Syndrome (IBS):

As there is no cure for IBS, treatment of IBS focuses on relieving symptoms. Mild signs and symptoms can often be controlled by managing stress and by making changes in your diet and lifestyle.
Dietary modifications are the first treatments that should be tried to treat IBS. There are several types of foods that often trigger characteristic symptoms and signs of IBS.
Try to:

  • Avoid foods that trigger your symptoms
  • Eat high-fiber foods
  • Drink plenty of fluids
  • Exercise regularly
  • Get enough sleep

Eliminate the following things from your diet:

High-gas foods:

If you experience bloating or gas, you might avoid items such as carbonated and alcoholic beverages, caffeine, raw fruit, and certain vegetables, such as cabbage, broccoli and cauliflower.


Some people with IBS can have improvement in diarrhea symptoms if they stop eating gluten such as wheat, barley and rye even if they don't have celiac disease.


Some people are sensitive to certain carbohydrates such as fructose, fructans, lactose and others, known as FODMAP. FODMAPs are found in certain grains, vegetables, fruits and dairy products. Your IBS symptoms might ease if you follow a strict low-FODMAP diet and then reintroduce foods one at a time. 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.
A dietitian can help you with these diet changes. If your problems are moderate or severe, especially if you have depression or if stress tends to worsen your symptoms, counseling might be suggested by your doctor.
If dietary modifications and lifestyle changes do not adequately treat the symptoms and signs, medical therapies may be recommended by your doctor.

Medicine for diarrhea:

  • Antidiarrheal medications such as loperamide, attapulgite, and diphenoxylate and atropine can be helpful if loose stools are one of the main signs. Eluxadoline is a prescriptional medicine for the treatment of irritable bowel syndrome with diarrhea (IBS-D).
  • Alosetron or Lotronex has been used for females with IBS who experience severe diarrhea.
  • Rifaximin is an antibiotic for the treatment of irritable bowel syndrome with diarrhea (IBS-D) and IBS-related bloating.
  • Bile acid binders including cholestyramine, colestipol, or colesevelam 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 such as Senokot, Ex-Lax Gentle Nature may be taken short-term. Prescription laxatives such as lactulose may also be prescribed.
  • Lubiprostone, a laxative, and linaclotide, a constipation medication are two drugs specifically used to treat IBS.
  • SSRI antidepressants fluoxetine, citalopram, sertraline, paroxetine, and escitalopram may be helpful for those with constipation (IBS-C), but they can trigger IBS attacks in patients with diarrhea (IBS-D).
  • Medications to treat pain and cramping in irritable bowel syndrome (IBS):
  • Antispasmodics, such as metoclopramide, dicyclomine, and hyoscyamine, decrease symptoms of pain and cramping.
  • Antidepressants such as amitriptyline, doxepin, desipramine, nortriptyline, and imipramine may help with abdominal pain but due to side effects are usually reserved for severe cases.

Other medication that may help signs and symptoms of irritable bowel syndrome (IBS):

  • 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, lorazepam, and clonazepam are occasionally prescribed short-term for people whose anxiety worsens their irritable bowel syndrome symptoms.

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