Types Of IBS

Based on the Rome III criteria, IBS may be subtyped according to people’s stool characteristics, which are defined by the Bristol Stool Scale. However, the Rome III criteria are not commonly used in clinical practice.1

Rome III Criteria for Diagnosing IBS1

  1. Onset of symptoms at least 6 months before diagnosis
  2. Recurrent abdominal pain or discomfort for >3 days per month during the previous 3 months
  3. Having at least two of the following features
    • Improvement of symptoms following a bowel movement
    • Association with a change in stool frequency
    • Association with a change in stool form

People may transition between the following subtypes.1

IBS With Constipation (IBS-C)

IBS-C is characterized by the following stool characteristics:1

      • Hard stools more than 25% of the time and loose stools less than 25% of the time
      • Up to 33% of cases
      • More common in women

Approximately 25% of people with IBS-C reported abdominal pain, straining, infrequent stools, bloating and/or gas as their most bothersome symptoms. Gas, bloating, and abdominal pain were reported by constipation sufferers as occurring on average of over 200 times a year.2

IBS With Diarrhea (IBS-D)

IBS-D is characterized by the following stool characteristics:1

      • Loose stools more than 25% of the time and hard stools less than 25% of the time
      • Up to 33% of cases
      • More common in men

The most bothersome IBS symptom reported by 43% of IBS-D sufferers were abdominal pain or discomfort, while 37% reported sudden urges to have bowel movements. People with IBS-D experience symptoms of gas and frequent stools over 200 times a year.2

IBS With Alternating Constipation and Diarrhea (IBS-M)

About 33% of people with IBS categorize themselves as having IBS-M3
IBS-M is characterized by the following stool characteristics:1

      • Both hard and soft stools more than 25% of the time
      • Up to 33% to 50% of cases

This type of IBS can be used to describe people’s IBS symptoms at a specific point in time, but in reality their bowel habits often vary over time. For this reason, some clinicians may prefer to use the term alternating IBS (IBS-A) in place of IBS-M.4

Post-infectious IBS

Symptoms of IBS may occur after an intestinal infection. This type of IBS is usually triggered by something else.1

Post-diverticulitis IBS

Symptoms of diverticulitis are episodic and generally short in duration.1 The symptoms include:1

      • Left-sided abdominal pain
      • Fever
      • Tender inflammatory mass in the left lower portion of the abdominal area

Post-diverticulitis IBS occurs after symptoms of diverticulitis. Therefore, diverticulitis may increase the risk for IBS.1

Alternate Names for IBS

Though less common, IBS may be referred to as spastic colon or irritable colon.5

Written by: Truc Thanh | Last reviewed: June 2016.
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