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The diagnosis of this condition is usually made based on the history. Thus a history of left-sided iliac fossa pain in a 20 year old female, that is relieved by defaecation or the passing of wind, and is exacerbated by 'stress' is likely to be irritable bowel syndrome (IBS). Young patients with chronic symptoms suggestive of IBS, with no sinister features and normal screening investigations e.g. FBC, ESR, CRP, endomysial antibody, can generally be given a positive diagnosis of IBS without the need for further extensive investigation (1). However elderly patients or those with sinister features (e.g. weight loss, anaemia) or recent onset will require more invasive investigation.

A formal diagnostic criteria for IBS has been developed in the form of the Rome II criteria (2):

At least 12 weeks, which need not be consecutive, in the preceeding 12 months of abdominal discomfort or pain that has two of the three features:

  • relieved by defecation, and/or
  • associated with change of frequency of stool and/or
  • associated with change of consistency of stool

The following cumulatively support the diagnosis of IBS:

  • more than three motions per day
  • less than three motions per week
  • hard or lumpy stools
  • loose or watery stools
  • straining during a bowel movement
  • urgency
  • feeling of incomplete emptying
  • passing mucus during a bowel movement
  • abdominal fullness, bloating or swelling


Red flag symptoms that indicate need for colonoscopy in patients with suspected irritable bowel syndrome (3):

  • age > 50 years
  • weight loss
  • occult blood in faeces
  • family history of colorectal cancer



  • there are several other points to consider when making a diagnosis with respect to recurrent abdominal pain:
    • beware false correlations between radiological findings and symptoms. Elderly patient may often have diverticular disease and/or a hiatus hernia. These conditions are often asymptomatic and may not be the cause of a patient's symptoms
    • in female patients, possible gynaecological problems must be excluded
    • a history of recurrent left iliac fossa pain is likely to be irritable bowel syndrome in a 30 year old patient - in an elderly patient other diagnoses such as neoplasia must be considered
    • recurrent right hypochondrial pain may be due to irritable bowel syndrome or gall-bladder disease;
    • the presence of abdominal bruits does not mean that the patient is suffering from ischaemic bowel disease - two different pathologies may be present in the same patient
  • NICE suggest that (4):
    • healthcare professionals should consider assessment for IBS if the person reports having had any of the following symptoms for at least 6 months (rather than 3 months of symptoms noted in the Rome criteria):
      • abdominal pain or discomfort
      • bloating
      • change in bowel habit
    • a diagnosis of IBS should be considered only if the person has abdominal pain or discomfort that is either relieved by defaecation or associated with altered bowel frequency or stool form. This should be accompanied by at least two of the following four symptoms:
      • altered stool passage (straining, urgency, incomplete evacuation)
      • abdominal bloating (more common in women than men), distension, tension or hardness
      • symptoms made worse by eating
      • passage of mucus
    • other features such as lethargy, nausea, backache and bladder symptoms are common in people with IBS, and may be used to support the diagnosis


  1. Prescriber (2000);11 (22): 61-69.
  2. Thompson W.G. et al (1999). Functional bowel disorders and functional abdominal pain. Gut 45 supplement II: II43?II47.
  3. Hatlebakk J.G, Hatlebakk M.V (2004). Diagnostic approach to suspected irritable bowel syndrome. Best Practice & Research Clinical Gastroenterology;18(4):735-746.
  4. NICE (April 2017).Irritable bowel syndrome in adults - diagnosis and management of irritable bowel syndrome in primary care.