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Irritable Bowel Syndrome (IBS): Classification and Types, Pathophysiology, Etiology, Risk Factors, Symptoms, Signs, Treatment, Investigations

Irritable Bowel Syndrome (IBS) is one of common disorders affecting everyone. It is a chronic gastrointestinal disorder affecting the large intestine (colon). There is no known cause for irritable bowel syndrome. Common symptoms are cramping, pain in the abdomen, bloating, diarrhea as well as constipation. IBS usually doesn’t cause permanent damage to the colon. Symptoms usually improve over the time as patients make lifestyle and dietary changes. Only very few people with IBS continue having symptoms. irritable bowel syndrome never results in inflammation of or changes to bowel tissue, or increase risk of colorectal cancer as is the case with other intestinal diseases such as Ulcerative colitis and Crohn’s disease. IBS can be controlled by managing diet, lifestyle and stress.

Irritable Bowel Syndrome (IBS)

IBS is also known as spastic colon, functional bowel disease, and mucous colitis; however, irritable bowel syndrome is not true “colitis.” Colitis is a separate group of conditions known as inflammatory bowel disease (IBD). IBS occurs more often in women than in men. In half of the cases, it occurs before the age of 35. As the cause of irritable bowel syndrome is unknown, treatment is symptomatic and is focused in helping the patients live a normal life.

Classification and Types of Irritable Bowel Syndrome (IBS)

There Are Basically Three Forms Of Irritable Bowel Syndrome

  • IBS Along With Constipation: Symptoms are pain in stomach as well as discomfort, bloating, irregular bowel movements, or hard stools.
  • Irritable Bowel Syndrome Along With Diarrhea: Symptoms of this type are pain in stomach along with discomfort with an urgent need for bowel movement with extremely frequent bowel movements with loose stools.
  • IBS Along With Alternating Constipation/Diarrhea: There are equal numbers of patients who suffer from each type of IBS and there are some patients who alternate between types with time.

Pathophysiology of Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome is a chronic gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits with no true organic cause. It is the most commonly diagnosed gastrointestinal condition. It is thought that there is some dysfunction in motor and sensory features of digestive tract in patients suffering from IBS with a change in gut motility and secretions due to different stimuli. These stimuli can be environmental or due to certain foods or toxins. This changed reactivity can result in pain along with constipation or diarrhea. There can also be hypersensitivity of gut with increased sensation of visceral type pain; for example, patients with IBS will have pain at a lower pressure when a balloon is distended within lumen of lower colon or rectum as compared to a person who is not suffering from irritable bowel syndrome. This could be related to increased stress reactivity with sensations of afferent signals from enteric nervous system.

Etiology and Risk Factors for Irritable Bowel Syndrome (IBS)

There is no known cause of irritable bowel syndrome. The intestinal walls are lined with layers of muscles. These muscles contract and relax in a coordinated rhythm as the food is moved from the stomach through the intestinal tract to the rectum. If a patient has IBS, the contractions may become stronger and last longer. Food is forced through the intestines more quickly, causing gas, bloating and diarrhea. Sometimes, the opposite can happen. Food passage slows down and stools become hard, lumpy and dry. Disorders in the nervous system or colon may also cause this. There are other factors that also play a role in IBS, e.g. patients with IBS do not have normal serotonin level. Serotonin is generally associated with function of brain but it also has a part to play in digestive system of our body. Sometimes patients with IBS may not have the right balance of good bacteria in the intestine. There are certain triggers for irritable bowel syndrome where some patients react strongly to certain things such as gas or pressure on the intestines to certain foods, medications or emotions.

Risk Factors of Irritable Bowel Syndrome (IBS)

  • Age: IBS symptoms first appear at a young age, generally before the age of 35 in about half of the cases with the disorder.
  • Gender: More women are diagnosed with irritable bowel syndrome than men.
  • Hereditary: People who have a family history of IBS are at increased risk for this condition.

Signs and Symptoms of Irritable Bowel Syndrome (IBS)

Signs and Symptoms of Irritable Bowel Syndrome (IBS)

Different patients exhibit different signs and symptoms of irritable bowel syndrome and they often resemble other medical conditions. There are times when the signs and symptoms accelerate and times when they improve or even disappear completely. If there are persistent changes in bowel habits or symptoms of IBS, they could indicate a potentially serious condition such as an infection or colon cancer, hence immediate medical attention should be sought.

Common Symptoms of Irritable Bowel Syndrome (IBS) are:

  • Abdominal pain
  • Abdominal cramping
  • Bloated or gassy feeling
  • Gas (flatulence)
  • Diarrhea
  • Constipation
  • Sometimes alternating bouts of constipation as well as diarrhea
  • Mucus in stools

Symptoms Indicating a More Serious Condition are:

  • New onset of irritable bowel syndrome symptoms after 50 years of age
  • Loss of weight
  • Bleeding from rectum
  • Anorexia
  • Nausea as well as vomiting
  • Abdominal discomfort, not relieved by bowel movements
  • Persistent diarrhea causing sleep disturbance.

Treatment for Irritable Bowel Syndrome (IBS)

As the cause for IBS is not definitive, the main focus of treatment is on relief of symptoms in order to enable a person to lead a normal life.

  • Lifestyle Changes: Many patients are able to control mild signs or symptoms of IBS successfully by making dietary changes and managing stress appropriately.
  • Fiber Supplements: Fiber supplements like Metamucil along with fluids helps with constipation.
  • Medications for Controlling Diarrhea: OTC medications like Imodium help with diarrhea control.
  • Eliminating Foods High on Products Producing Gas: for people who have bloating and pass huge amounts of gas, then they should avoid carbonated beverages, salads, raw fruits, cauliflower etc.
  • Anticholinergic Drugs: These drugs affect certain activities of autonomic nervous system and promote relief of painful bowel spasms and bouts of diarrhea in people; however, it has a tendency to make the constipation worse.
  • Antidepressant Drugs: When a person is suffering from pain as well as depression then a tricyclic antidepressant or an SSRI is given. If patients have diarrhea as well as abdominal pain but do not have depression, then a lower than usual dose of tricyclic antidepressants can be given.
  • Lubiprostone (Amitiza): Lubiprostone is a chloride channel activator that should be taken twice a day. It helps the patients by increasing fluid secretion in the small intestine to help with the passage of stool. Common side effects of this medicine are nausea, diarrhea and abdominal pain. At present, this drug is prescribed only for those patients who have not benefitted from other treatments.
  • Incorporating Fiber Into the Diet: Patients with irritable bowel syndrome have mixed results to dietary fiber. It helps in decreasing constipation but it also increases gas and cramping. The best way is to slowly increase fiber in diet. Some foods with fiber in them are grains, fruits, and beans. In some cases, patients benefit by limiting dietary fiber and instead taking fiber supplements that causes less gas and bloating.
  • Avoiding Problematic Foods: In some patients certain foods tend to worsen their symptoms. They should avoid these foods. Common foods which can be problematic are: Alcohol, caffeinated beverages, caffeinated medications, dairy products, etc. Foods that might make flatulence symptoms worse are beans, cabbage, cauliflower and broccoli.
  • Eating Smaller Meals: Patients with diarrhea benefit from eating small and frequent meals.
  • Avoiding Dairy Products: Patients who are lactose intolerant should take curd instead of milk. They can also use enzyme products to promote breaking down of lactose.
  • Drinking Fluids Aplenty: Patients suffering from IBS are advised to drink fluids like water liberally. Alcohol and caffeinated beverages needs to be avoided as they tend to stimulate intestines and make diarrhea worse. Carbonated drinks produce gas.
  • Regular Exercise: It is beneficial in relieving depression and helps with stress. It also helps in stimulating the normal contractions of the intestines and generally helps the patients feel better about themselves.

Complementary Treatment Includes:

  • Acupuncture: Some patients benefit with use of acupuncture technique for relaxing muscle spasms and improving bowel functions.
  • Herbals: Peppermint is a naturally found antispasmodic which helps in relaxing smooth muscles in intestines. It may provide short-term relief of irritable bowel syndrome symptoms. Patients should use enteric coated capsule. It may increase heartburn and patients should check with their doctor before taking it.
  • Hypnosis: Hypnosis helps in decreasing abdominal pain and bloating.
  • Probiotic: These are “good-type” bacteria that live in intestines and also are present in certain foods like curd and dietary supplements. Studies have shown that probiotic may help in relieving symptoms of irritable bowel syndrome.
  • Yoga, Massage and Meditation: These are effective ways to relieve stress.

Investigations for Irritable Bowel Syndrome (IBS)

  • Complete medical history and physical exam.
  • Stool tests to look for infections or absorption problems.
  • Flexible sigmoidoscopy examines lower part of colon with a flexible sigmoidoscope.
  • Colonoscopy: A flexible tube is used to examine entire length of colon.
  • CT scan
  • Lactose intolerance tests.
  • Blood tests.


  1. Mayo Clinic. (2021). Irritable bowel syndrome (IBS). https://www.mayoclinic.org/diseases-conditions/irritable-bowel-syndrome/symptoms-causes/syc-20360016
  2. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). (2020). Irritable Bowel Syndrome (IBS). https://www.niddk.nih.gov/health-information/digestive-diseases/irritable-bowel-syndrome
  3. American College of Gastroenterology. (2020). Clinical Guidelines: Irritable Bowel Syndrome. https://gi.org/topics/irritable-bowel-syndrome/
  4. Rao, S. S. (2014). Diagnosis and management of chronic constipation and irritable bowel syndrome with constipation in adults. Postgraduate Medicine, 126(5), 82-93. doi:10.3810/pgm.2014.09.2801

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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 22, 2023

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