Irritable Bowel Syndrome (IBS) is a chronic functional gastrointestinal (GI) disorder characterized by abdominal pain and alteration of bowel habits without a specific organic pathology. IBS is classified into four types depending on stool consistency, IBS-C - IBS with constipation, IBS-D - IBS with diarrhea, IBS-M - Mixed IBS and IBS-U - Unsubtyped IBS.

The exact cause of IBS has yet to be understood, but several factors may play a role, such as brain-gut signal problems, GI motility problems, pain hypersensitivity, GI tract infections, small intestinal bacterial overgrowth, and disruptions in neurotransmitters (body chemicals).

IBS more commonly affects people under the age of 45 and women. Other risk factors include a family history of GI disorders, suffering from abuse during childhood and mental health problems such as anxiety, panic disorder, post-traumatic stress disorder, and depression.

The pathophysiology of IBS is theorized to be a 3-part complex that of altered gastrointestinal (GI) motility, a complex of visceral hyperalgesia and psychopathology. A unifying mechanism for the three parts is still undetermined. Other mechanisms that may cause the production of IBS symptoms include colonic and small bowel inflammation, and alterations in the intestinal biome.

The most common symptoms of IBS include abdominal pain or discomfort and changed bowel habits (diarrhea, constipation or both). Other symptoms may include abdominal bloating, whitish mucus in the stool and the feeling of an incomplete bowel movement.

Diagnosing IBS is usually reliant on ruling out other conditions that may produce similar symptoms. The doctor usually diagnoses IBS based on the patient’s medical history, symptoms, and a physical exam. The doctor may also order further tests such as a blood test or stool test. The patient may also be required to undergo imaging tests such as a flexible sigmoidoscopy, colonoscopy, lower GI series, upper GI endoscopy, or CT scan.

There is currently no known cure for IBS. However, IBS symptoms can be alleviated by suggesting dietary changes such as avoiding high-gas foods, or by taking certain medications such as laxatives or antidiarrheals, and antidepressants, in addition to psychological therapies like stress management.

IBS’s effect on a person’s quality of life is considered as the disease most important complication. It may cause anxiety and stress. IBS does not pose a serious threat to a patient’s physical health, as it does not cause or increase the risk of developing colon cancer, rectal bleeding or inflammatory bowel diseases.

IBS is not a preventable disease. It is a chronic disease whose symptoms may reappear every so often as a result of the lifestyle factors such as diet, stress or other environmental causes.

According to a review published in the journal Clinical Epidemiology, published in New Zealand, the estimated worldwide prevalence of IBS is 11%. The lowest reported prevalence was in South Asia (7.0%) and the highest in South America (21.0%). 

Irritable Bowel Syndrome (IBS) is a functional gastrointestinal (GI) disorder characterized by abdominal pain and alteration of bowel habits without a specific organic pathology. It is a chronic disease.

Alternative names for IBS include adaptive colitis, colonic neurosis, irritable colon syndrome, mucous colitis, spastic colon and unstable colon.

IBS is classified into four types depending on stool consistency

• IBS-C - IBS with constipation

  • lumpy or hard stools not less than 25% of the time

  • watery or loose stools not more than 25% of the time

• IBS-D - IBS with diarrhea

  • watery or loose stools not less than 25% of the time

  • lumpy or hard stools not more than 25% of the time

• IBS-M  - Mixed IBS

  • lumpy or hard stools not less than 25% of the time

  • watery or loose stools not less than 25% of the time

• IBS-U  - Unsubtyped IBS

  • lumpy or hard stools not more than 25% of the time

  • watery or loose stools not more than 25% of the time

The exact etiology of IBS is not understood, but several factors may play a role, including:  

• Brain-Gut Signal Problems: Problems with the signals between the brain and nerves of the gut (small and large intestines) may cause IBS symptoms.

• GI Motility Problems: People with IBS may suffer from abnormal motility in the colon. Fast motility may cause diarrhea and slow motility can lead to constipation. Spasms in the colon may result in abdominal pain.

• Pain Sensitivity: People with IBS are thought to have highly sensitive nerves in the gut, causing pain or discomfort more than normal when stool or gas is in the gut.

• Infections: Some people may develop IBS due to a bacterial infection in the GI tract.

• Small Intestinal Bacterial Overgrowth: An abnormal increase in the number or a change in the type of bacteria in the small intestine. These bacteria may create extra gas and could also instigate diarrhea and weight loss.

• Neurotransmitters: People with IBS have changed levels of neurotransmitters (chemicals that transmit nerve signals) and GI hormones.

• Reproductive hormones: Certain reproductive hormones may worsen IBS problems since post-menopausal women have reduced symptoms than women who are still menstruating. Furthermore, young women with IBS experience exacerbated symptoms during their menstrual periods.

• Food Sensitivity: People who suffer from IBS state that foods rich in carbohydrates, fatty foods, spicy foods, alcohol, and coffee trigger their symptoms. Researchers believe that poor absorption of sugars or bile acids could produce symptoms.

Risk factors for IBS include:

• Young age: IBS is more common in people under 45.

• Female gender: Women are almost twice as likely as men to suffer from IBS.

• Genetics: IBS is found more commonly in people whose family members have a history of GI problems. The impact of family history on the risk of IBS could be linked to genes, to common factors in a family's environment or both.

• Mental Health Problems: Mental health or psychological problems such as anxiety, panic disorder, post-traumatic stress disorder and depression, are commonly found in people with IBS. The link between IBS and mental health is not clear.  In addition, IBS and other GI disorders are present at times in people who have suffered from physical or sexual abuse in the past.

Theories on the pathophysiology of irritable bowel syndrome (IBS) may be seen as a 3-part complex of visceral hyperalgesia, altered gastrointestinal (GI) motility, and psychopathology.

• Visceral hyperalgesia:  This condition is known as abnormally heightened sensitivity to pain in the body organs that lie in cavities, particularly those in the abdominal cavity. IBS is typified by a heightened perception of normal motility and visceral pain. Patients with IBS are more likely to report pain when a balloon is inflated in the distal colon than normal people. This hypersensitivity emerges with fast but not with gradual inflation.

• Altered GI motility: Altered GI motility includes separate irregularities in small and large intestine motility. The electrical impulses generated by the muscles of the colon are comprised of background slow waves with overlaid spike potentials. Impaired motility of the colon in IBS appears as differences in slow-wave frequency and a blunted, late-peaking response of spike potentials after a meal.

Patients who are disposed to diarrhea exhibit these changes more than patients who are disposed to constipation4. Existing theories incorporate these irregularities in motility and hypothesize a general hyperresponsiveness of smooth muscle in the body.

• Psychopathology: Psychopathology is the third part of the complex although a mechanism unifying the 3-part complex has yet to be proven.  The link between psychiatric problems and IBS development is not clearly understood.

Other mechanisms that may cause the production of IBS symptoms include:

• Microscopic inflammation: Microscopic inflammation has been observed in some patients. This is significant since it was previously thought that irritable bowel syndrome has no evident pathologic alterations. Both colonic inflammation and small bowel inflammation have been discovered in a subgroup of patients who suffer from IBS, as well as in patients who develop IBS as a result of infectious enteritis.

• Alterations in the intestinal biome: An increase in the number or change in the type of bacteria in the small and large intestines has been identified as a cause for the symptoms of bloating and distention, common to patients with IBS. This has led to suggested treatments with antibiotics and probiotics (a dairy food or a dietary supplement containing live bacteria).

IBS is a chronic disorder. Its symptoms, however, may be intermittent. The most widespread symptoms of IBS include

• Abdominal pain or discomfort: The abdominal pain or discomfort caused by IBS may feel similar to cramping and may decrease after a bowel movement.

• Changed bowel habits: Changes may involve the frequency of bowel movements and the way the stools look. People with IBS may suffer from constipation, diarrhea, or both.

Other symptoms of IBS may include

• Abdominal bloating

• Feeling of an incomplete bowel movement

• Whitish mucus in the stool

• Flatulence (excessive gas)

• Sexual dysfunction such as dyspareunia (pain during sex) and poor libido

• A lack of energy (lethargy)

• Bladder problems such as nocturia (needing to wake up to urinate at night), and difficulty fully emptying the bladder

• Urine and stool incontinence (lack of voluntary control over urination or defecation)

• Backache

• Dyspepsia (indigestion)

• Heartburn

• Nausea and or vomiting

A diagnosis of IBS is made based on a review of the patient’s medical history, symptoms, and a physical exam. The doctor may also order further tests.

• Medical history: The doctor will inquire about the patient’s symptoms, any recent infections; any family history of GI disorders, any stressful events linked to the beginning of the symptoms and any medication the patient is taking. IBS is suspected if:

• The symptoms have emerged at least three times a month for the past 3 months and the symptoms first appeared at least 6 months ago.

• The abdominal discomfort displays at least two of the subsequent features5,6:

1. It decreases after a bowel movement.

2. A change in the frequency of bowel movements

3. A change in the appearance of the stools.

• Physical Exam: In a physical examination, the doctor looks for signs of abdominal bloating, listens to sounds coming from the abdomen, and checks for tenderness or pain by tapping on the abdomen.

• Blood test: A blood test called CBC is taken to screen for other conditions or problems such as anemia, inflammation, and infection.

• Stool test: A stool test may be used to check for parasites or the presence of blood.

• Flexible sigmoidoscopy: The doctor inserts a flexible, narrow tube that contains a light and a camera through the rectum to look inside the rectum and lower colon. During the sigmoidoscopy, a biopsy may be taken. This procedure is used to identify any problems that might be affecting the lower GI tract such as inflammation or a distal obstruction.

• Colonoscopy: A colonoscopy is used to look inside the rectum and colon. The test will be able to identify any irritated or swollen tissue, polyps, ulcers, and cancer.

• Lower gastrointestinal series: A lower GI series, also called a Barium Enema, is a test where x-rays are used to look at the large intestine. It may help the doctor identify cancerous growths, a fistula (a puncture), diverticula (abnormal pouches in the wall of the colon), polyps (precancerous growths) and ulcers. It may also help the doctor find the reason behind bleeding from the anus, chronic diarrhea, unexplained weight loss, changes in bowel activity and abdominal pain.

•  Upper GI endoscopy: Also called an esophagogastroduodenoscopy. This procedure helps the doctor identify the possible reasons for unexplained symptoms such as dysphagia (trouble swallowing), chest pain or upper abdominal pain that is not heart-related, unexplained weight loss, nonstop vomiting for an unidentified reason, or bleeding in the upper GI tract. A biopsy may be taken during the test, particularly if celiac disease (gluten allergy) is suspected.

• Hydrogen breath test: This test is used to diagnose an excessive growth of bacteria in the small intestine or to screen for carbohydrate intolerance (lactose and/or fructose intolerance).

• CT scan: CT scan and magnetic resonance enterography or wireless capsule endoscopy may be used if the doctor suspects obstructions, tumors, or enteritis (small bowel inflammation).

IBS is a chronic disease that cannot be cured. Treatment involves managing the symptoms through a combination of dietary changes, medication, probiotics, and therapies for mental health problems.

• Dietary changes: These changes can involve:

• Fiber: Patients with diarrhea may find it helpful to avoid foods rich in insoluble fiber such as whole grains, nuts and seeds and the skin of fruits and vegetables. Patients with constipation may find it helpful to increase the amount of water and soluble fiber they consume such as fruits and vegetables without their skin, oats, and rye.

• Avoiding high-gas foods: Including vegetables like cabbage, broccoli and cauliflower, carbonated beverages, and raw fruits.

• Following a gluten-free diet: The diarrheal symptoms improve in some people with IBS when they follow a gluten-free diet, although the scientific evidence is not clear.

• Following a low FODMAP diet: Some patients are affected by types of carbohydrates called FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols). The body doesn’t break down these carbohydrates easily, which means they begin to ferment in the intestines relatively quickly, producing gases which may lead to bloating. FODMAPs are found in some fruits (eg. dried fruits, apples) and vegetables (eg. cauliflower, beans), dairy products and wheat products.

• Avoid caffeine and alcohol.

• Medication: Some people with IBS may take medication to help control their symptoms, such as :

• Fiber supplements to alleviate constipation if increasing fiber consumption in the diet does not help.

• Laxatives to help with constipation.

• Antidiarrheal medication to decrease diarrhea.

• Antispasmodics that help control muscular spasms in the colon and reduce abdominal pain.

• Antidepressants, for example, low doses of tricyclic antidepressants and selective serotonin reuptake inhibitors, relieve symptoms of IBS including abdominal pain. Lubiprostone may be given to people who suffer from IBS-C to relieve constipation and abdominal pain or discomfort.

• Linaclotide may be given to people who suffer from IBS-C to alleviate abdominal pain and increase bowel movements.

• The antibiotic rifaximin may be given to treat an overgrowth of bacteria in the small intestine, thus reducing bloating.

• Coated peppermint oil capsules may help alleviate IBS symptoms.

• Probiotics: Probiotics are live microorganisms (bacteria and yeasts) that are similar to the microorganisms normally found in the GI tract. Some studies determined that taking large enough quantities of probiotics, particularly Bifidobacteria and particular probiotic combinations, could alleviate symptoms of IBS.

• Therapies for mental health problems: Psychological therapies may help reduce symptoms of IBS and can include:

• Managing Stress: Learning methods to decrease stress may alleviate the symptoms of IBS, particularly cramping and pain. The methods include participating in meditation, seeking counseling and support, exercising regularly, such as walking or yoga, avoiding stressful life situations as much as is feasible, and getting enough sleep.

• Talk Therapy: Talk therapy may alleviate stress and reduce symptoms of IBS. Two types of talk therapy are used to treat IBS, cognitive behavioral therapy, and psychodynamic therapy. Cognitive behavioral therapy emphasizes on actions and thoughts. Psychodynamic, or interpersonal, therapy emphasizes how emotions affect symptoms of IBS.

• Gut-Directed Hypnotherapy:  In gut-directed hypnotherapy, hypnosis is used by a therapist to assist the patient in relaxing the muscles in their colon.

• Mindfulness Training: Mindfulness training helps avoid worrying about sensations by focusing the attention on them as they occur.

IBS has few complications. It does not cause or increase the risk of developing colon cancer, rectal bleeding or inflammatory bowel diseases. Diarrhea and constipation from irritable bowel syndrome can exacerbate hemorrhoids in people who already have them.

IBS’s most important complication is considered to be its effect on a person's quality of life.  IBS may cause stress and anxiety, affecting a person's daily life.

IBS is not a preventable disease. It is a chronic disease where the symptoms may reappear from time to time as a result of the lifestyle factors such as diet, stress or other environmental causes. Following the dietary and lifestyle adjustments mentioned above may help prolong the time between episodes of IBS and alleviate its symptoms.

IBS does not present a serious threat to a patient’s physical health and does not increase the risk of developing colon cancer, rectal bleeding or inflammatory bowel diseases. Living with IBS may be challenging as it is a debilitating disease that significantly affects a patient’s quality of life.

A key step in managing the disease and improving a patient’s quality of life involves identifying the trigger factors that are unique to each patient.

According to a review published in the journal Clinical Epidemiology, published in New Zealand, IBS affects an estimated 11% of people worldwide. The lowest reported prevalence was in South Asia (7.0%) and the highest in South America (21.0%).