• The two underlying mechanisms that cause or significantly contribute to the symptoms of IBS are understood to be altered intestinal motility (abnormal bowel function) and visceral hypersensitivity (increased gut sensitivity). (Abstract links below.)
• Functional findings in irritable bowel syndrome.
• Links to anxiety & depression have been noted. (Abstract links below.)
• Irritable bowel syndrome, anxiety, and depression: what are the links?
• Anxiety but not depression determines health care-seeking behaviour in Chinese patients with dyspepsia and irritable bowel syndrome: a population-based study.
• Irritable bowel syndrome may follow a gut infection, this is known as post-infectious IBS (PI-IBS). (Abstract links below.)
• Is irritable bowel syndrome more common in patients presenting with bacterial gastroenteritis?
• Altered colonic microflora, unusual gut fermentation and irregular breath testing are found in a significant proportion of IBS patients. (Abstract links below.)
• Abnormal colonic fermentation in irritable bowel syndrome.
• Analysis of the Fecal Microbiota of Irritable Bowel Syndrome Patients and Healthy Controls with Real-Time PCR.
• Normalization of lactulose breath testing correlates with symptom improvement in irritable bowel syndrome. a double-blind, randomized, placebo-controlled study.
• Proboitics (friendly bacteria) may alleviate IBS symptoms. (Abstract links below.)
• A probiotic mixture alleviates symptoms in irritable bowel syndrome patients: a controlled 6-month intervention.
• Intestinal microflora and oral bacteriotherapy in irritable bowel syndrome.
• Significant antibiotic use is associated with the onset of IBS. (Abstract links below.)
• Antibiotic use, childhood affluence and irritable bowel syndrome (IBS).
• Antibiotics increase functional abdominal symptoms.
• Carbohydrate malabsorption/intolerance appears to be common among IBS sufferers. (Abstract links below.)
• Sugar malabsorption in functional bowel disease: clinical implications.
• Functional bowel disease: malabsorption and abdominal distress after ingestion of fructose, sorbitol, and fructose-sorbitol mixtures.
• Symptom provocation in irritable bowel syndrome. Effects of differing doses of fructose-sorbitol.
• Low-grade intestinal inflammation has been noted . (Abstract links below.)
• Terminal ileal mucosal mast cells in irritable bowel syndrome.
• Full-thickness biopsy of the jejunum reveals inflammation and enteric neuropathy in irritable bowel syndrome.
• IBS symptom variability and instability. (Abstract links below.)
• A prospective assessment of bowel habit in irritable bowel syndrome in women.
• Clinical patterns over time in irritable bowel syndrome.
• Convincing links between IBS and inflamed bowel disease especially Crohn’s. (Abstract links below.)
• Quality of life in inflammatory bowel disease in remission.
• Identification of a prodromal period in Crohn's disease but not ulcerative colitis.
• Is irritable bowel syndrome a low-grade inflammatory bowel disease?

Although the cause of IBS is unknown, it’s speculated that the disorder may originate from a dysfunction of the so-called ‘brain-gut axis’, which, somehow, may lead to increased gut sensitivity and abnormal function. However, this hypothesis provides no obvious explanation for other, important areas of IBS research, including low-grade intestinal inflammation, carbohydrate malabsorption/intolerance, links between IBS and IBD, abnormal intestinal-flora and why probiotics may alleviate symptoms.

For mainly that reason, the underlying cause of irritable bowel syndrome is unknown. Although, extensive research suggests IBS symptoms emanate from irregular bowel movement (altered intestinal motility) and increased gut sensitivity (visceral hypersensitivity).

As mentioned, IBS is characterized by persistent or intermittent abnormal-bowel symptoms accompanied by abdominal pain (cramping) and usually bloating (a feeling of fullness). The abnormal bowel symptoms are:

• Diarrhoea. Which may be persistent, intermittent or very occasional;
• Constipation. Which, again, may be persistent, intermittent or very occasional.

As a result of varying bowel symptoms, IBS has been categorized into 3 sub-types:

1. C-IBS: constipation-predominant irritable bowel syndrome;
2. A-IBS: alternating between constipation and diarrhoea;
3. D-IBS: diarrhoea-predominant irritable bowel syndrome.

Diagnosis of IBS usually follows the elimination of other – more serious – diseases (such as Crohn’s, Colitis, etc) and/or according to Rome Criteria. Rome Criteria is a set of guidelines used for diagnosis of functional gastrointestinal-disorders including irritable bowel syndrome.

In terms of prevalence, it’s estimated that IBS affects around 10 – 20% of civilized populations.

To summarise, irritable bowel syndrome (IBS) is considered a functional bowel disorder that is characterized by long-standing abnormal bowel habits (constipation and/or diarrhoea) and recurrent abdominal pain.

For more information about IBS, click the following links.

• http://digestive.niddk.nih.gov/ddiseases/pubs/ibs_ez/
• http://www.mayoclinic.com/health/irritable-bowel-syndrome/DS00106
• http://familydoctor.org/112.xml
• http://en.wikipedia.org/wiki/Irritable_bowel_syndrome