Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that affects the large intestine. There are different subtypes, depending on the exact symptoms. Two examples include IBS with constipation (IBS-C) and IBS with diarrhea (IBS-D).

The exact cause of IBS is not fully understood, but healthcare professionals believe several factors can contribute to its development.

Some examples include stool passing through the gut too quickly or too slowly, psychological factors including stress, a family history of IBS, and an overactive immune system.

This article looks at the different types of IBS.

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IBS-C is characterized primarily by chronic constipation.

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) states that on the days a person has at least one abnormal bowel movement, more than a quarter of their stools will be hard and lumpy, and less than a quarter will be loose and watery.

The key symptoms of IBS-C include:

  • Abdominal pain and discomfort: Cramping and pain in the lower abdominal area, which is often relieved by a bowel movement. A person may also experience back pain if the constipation is severe.
  • Chronic constipation: Infrequent bowel movements, often less than three times per week. Stools are typically hard, dry, and difficult to pass.
  • Bloating and gas: A feeling of fullness or swelling in the abdomen, accompanied by excessive gas.
  • Straining during bowel movements: Difficulty passing stool, often involving straining or prolonged sitting on the toilet. A person may need to change their body position or press a part of their body to help finish passing stool.
  • Incomplete evacuation: A sensation that not all stool has passed.
  • Mucus in stool: A noticeable amount of mucus in the stool.

In many cases, a person with IBS-C will experience ongoing symptoms. However, for some people, the symptoms may come and go.

Medical professionals identify IBS-D primarily by chronic diarrhea and its associated symptoms.

On the days a person has at least one abnormal bowel movement, more than a quarter of their stool will be loose and watery. Less than a quarter will be hard or lumpy.

Symptoms of IBS-D include:

  • Chronic diarrhea: Frequent, loose, or watery stools. People with IBS-D often experience sudden urges to have a bowel movement. This usually happens during the day. If a person experiences diarrhea that wakes them from their sleep, they can contact a doctor, as this is not typical of IBS-D.
  • Abdominal pain and cramping: Often occurs before a bowel movement and is typically relieved after passing stool.
  • Bloating and gas: Abdominal bloating and a feeling of excessive gas are common.
  • Urgency: A sudden, compelling need to have a bowel movement.
  • Bowel movement frequency: Increase in the number of daily bowel movements.
  • Fecal incontinence: In some cases, the urgency and frequency can lead to incontinence.
  • Mucus in stool: The presence of mucus in the stool is not uncommon.

IBS-M is defined by alternating episodes of constipation and diarrhea, with people experiencing both symptoms over time.

A doctor may diagnose IBS-M if, on the days a person has at least one atypical bowel movement, over a quarter of their stool is hard or lumpy, and over a quarter is loose or watery.

Common symptoms include:

  • abdominal pain and cramping
  • alternating bowel habits between constipation and diarrhea
  • bloating and gas
  • incomplete evacuation
  • mucus in stool
  • urgency

A person may receive an IBS-U diagnosis if they have IBS, but the stool consistency does not match the criteria for the other types of IBS.

For those with IBS-U, less than a quarter of their stool is hard or lumpy, and less than a quarter is loose or watery.

A person may experience symptoms of IBS after an infection or diverticulitis flare-up. Although the exact reason is unclear, a person may experience IBS symptoms after an infection or diverticulitis flare-up due to inflammation.

Post-infectious IBS (PI-IBS)

The development of IBS-like symptoms defines PI-IBS, which occurs after a documented episode of infectious gastroenteritis. The symptoms are similar to those of classic IBS.

The exact mechanism of PI-IBS is not entirely understood, but healthcare professionals believe several factors contribute to its development:

  • Gut wall inflammation: Infection may cause inflammation in the gut wall, affecting its function.
  • Altered gut flora: Infection can disrupt the balance of gut microbiota, leading to symptoms.
  • Immune system changes: Persistent changes in the gut’s immune response post-infection.
  • Neural changes: Changes in the nervous system of the gut following infection.

Antibiotic use may also be a risk factor.

Post-diverticulitis IBS

According to older 2013 research, those with diverticulitis may have an increased risk of developing IBS and other bowel disorders. Diverticulitis refers to the inflammation or infection of one or more diverticula, which are small bulges in the large colon.

The authors suggested calling this post-diverticulitis IBS and theorize that it results from inflammation, similar to PI-IBS.

More research is necessary to confirm whether diverticulitis flare-ups can cause IBS.

Healthcare professionals are still determining what causes IBS. Researchers theorize that there may be a problem with the gut-brain interaction or how the gut and brain work together.

IBS may result from a combination of different problems.

Contributing factors may include:

  • early life events that are stressful or traumatic
  • medical conditions, such as depression, anxiety, or somatic symptom disorder
  • bacterial infections in the digestive tract
  • food intolerance or sensitivities
  • an increase in the amount or type of bacteria in the gut
  • genetics

Diagnosis of the different types of IBS typically involves:

  • Symptom assessment: Using criteria such as the Rome IV guidelines, which focus on the nature and duration of gastrointestinal symptoms.
  • Exclusion of other conditions: A doctor may use other tests, like blood tests, stool tests, and sometimes colonoscopy, to rule out other causes of symptoms such as infections, inflammatory bowel disease, or celiac disease.

Treatment for IBS focuses on relieving symptoms and improving quality of life. There is no one-size-fits-all approach, so a personalized treatment plan is necessary for each person.

Treatment options may include:

  • Dietary changes: A high fiber diet, low FODMAP diet, and adequate hydration can be helpful.
  • Laxatives: A person can use laxatives to relieve constipation in those with IBS-C.
  • Prescription medications: A doctor may prescribe medications such as linaclotide (Linzess) or lubiprostone (Amitiza) to increase fluid secretion in the intestine and help bowel movements. Doctors may also prescribe antidepressants.
  • Probiotics: Probiotics may relieve some symptoms of IBS, including flatulence, stomach pain, bloating, and the urgency of needing a bowel movement.
  • Stress management: People may find techniques such as cognitive behavioral therapy, mindfulness, and relaxation exercises helpful.
  • Physical activity: A 2023 review found that low to moderate intensity exercise may relieve some symptoms of IBS, such as bloating and gas. However, those authors state that there needs to be more quality scientific evidence to support this.
  • Hypnotherapy: Hypnotherapy may help relieve the symptoms of IBS and improve a person’s quality of life and levels of anxiety and depression.

The following are commonly asked questions about IBS.

What does an IBS flare feel like?

An IBS flare-up refers to a period when the symptoms of IBS become more intense or frequent. The experience of an IBS flare can vary greatly from person to person, both in symptoms and severity.

People may experience stomach pain or cramping, bloating, diarrhea, and constipation.

What should a person eat during an IBS flare-up?

The goal is to eat foods that are easy on the digestive system. People can also avoid foods that might trigger or worsen symptoms. During a flare-up, focusing on comfort and easily digestible foods is key.

Doctors often recommend the low FODMAP diet for IBS. FODMAPs are a group of carbohydrates that can cause digestive distress. Foods low in FODMAPs are less likely to trigger symptoms.

Soluble fiber helps regulate bowel movements and can be easier on the gut than insoluble fiber. Easily digestible proteins such as chicken, turkey, fish, and tofu can be good options.

There are four main subtypes of IBS, including IBS-C, IBS-D, IBS-M, and IBS-U. A person may also experience symptoms of IBS after an infection or diverticulitis flare-up.

Each type of IBS shares common features, such as abdominal pain and altered bowel habits. However, they differ in specific symptoms and management strategies, highlighting the need for personalized treatment approaches.