1)Background:
IBS: functional abdominal pain (abdominal pain and altered bowel habits in the absence of specific and unique organic pathology)
2)Diagnostic criteria :
6 criteria to distinguish irritable bowel syndrome from organic bowel disease:
-Onset of pain associated with more frequent bowel movements
-Onset of pain associated with looser bowel movements
-Pain relieved by defecation
-Visible abdominal bloating
-Subjective sensation of incomplete evacuation more than 25% of the time
-Mucorrhea more than 25% of the time
Or we can follow the Rome III criteria (recurrent abdominal pain or discomfort at least 3 days per month during the previous 3 months that is associated with 2 or more of the following
Relieved by defecation
Onset associated with a change in stool frequency
Onset associated with a change in stool form or appearance
3)Causes:
Causes related to enteric infection
Central neurohormonal mechanisms
Bloating and distention may also occur from intolerance to dietary fats
Recent elimination and challenge diets have suggested that poorly absorbed short-chain carbohydrates( in the form of fructose and fructants)
4)Imaging studies:
The following selected studies are directed by history:
-Upper GI barium study with small bowel follow-through: Screen for tumor, inflammation, obstruction, and Crohn disease.
-Double-contrast barium enema: Screen for neoplasm and inflammation.
-Gallbladder ultrasonography: Consider this test if the patient has recurrent dyspepsia or characteristic postprandial pain.
-Abdominal CT scan: Screen for tumors, obstruction, and pancreatic disease
(and more workups depends on patient’s history )
5)Treatment:
-Medical care:

Successful management relies on a strong patient-provider relationship.
Reassure the patient that the absence of an organic pathology indicates a normal life expectancy.
Emphasize the expected chronicity of symptoms with periodic exacerbations.
Teach the patient to acknowledge stressors and to use avoidance techniques.

-Diet:

Fiber supplementation may improve symptoms of constipation and diarrhea.
Judicious water intake in patients who predominantly experience constipation is recommended.
Caffeine avoidance may limit anxiety and symptom exacerbation.
Legume avoidance may decrease abdominal bloating.
Lactose and/or fructose should be limited or avoided in patients with these contributing disorders. Take care to supplement calcium in patients limiting lactose intake.

-Medication:

Anticholinergics
Antidiarrheals
Tricyclic Antidepressants
Prokinetics....