Atlas of pathophysiology, 2 Edition

Part II - Disorders

Gastrointestinal Disorders

Irritable Bowel Syndrome

Also referred to as spastic colon or spastic colitis, irritable bowel syndrome (IBS) is marked by a group of GI symptoms often related to stress. About 20% of patients never seek medical attention for this benign condition that has no anatomical abnormality or inflammatory component. It's twice as common in women as in men.

Age Alert

IBS usually begins between ages 20 and 30.


·   Psychological stress (most common)

·   Ingested irritants (coffee, raw fruit, or vegetables)

·   Lactose intolerance

·   Abuse of laxatives

·   Hormonal changes (menstruation)

·   Allergy to certain foods or drugs


IBS appears to reflect motor disturbances of the entire colon in response to stimuli. Some muscles of the small bowel are particularly sensitive to motor abnormalities and distention; others are particularly sensitive to certain foods and drugs. The patient may be hypersensitive to the hormones gastrin and cholecystokinin. The pain of IBS seems to be caused by abnormally strong contractions of the intestinal smooth muscle as it reacts to distention, irritants, or stress.

Signs and symptoms

·   Anxiety

·   Fatigue

·   Depression

·   Nausea and vomiting

·   Crampy lower abdominal pain, occurring during the day and relieved by defecation or passage of flatus

·   Pain that intensifies 1 to 2 hours after a meal

·   Constipation alternating with diarrhea, with one dominant

·   Passage of mucus through the rectum

·   Abdominal distention and bloating

Diagnostic test results

·   Barium enema reveals colon spasm and tubular appearance of descending colon without evidence of cancer and diverticulosis.

·   Sigmoidoscopy or colonoscopy reveals spastic contractions without evidence of colon cancer or inflammatory bowel disease.


·   Stress management measures, including counseling or mild antianxiety agents

·   Identification and avoidance of food irritants

·   Application of heat to abdomen

·   Bulking agents

·   Antispasmodics

·   Possibly, loperamide or alosetron

·   Bowel training (if cause is chronic laxative abuse) to regain muscle control





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