Irritable Bowel Syndrome

Key Features

Essentials of Diagnosis

• Common chronic functional disorder characterized by abdominal pain with alterations in bowel habits

• Symptoms usually begin in late teens to early twenties

• Limited evaluation is intended to exclude organic causes of symptoms

General Considerations

• No definitive diagnostic study

• Idiopathic clinical entity characterized by chronic (> 3 months) abdominal pain or discomfort that occurs in association with altered bowel habits that may be continuous or intermittent

• Abdominal discomfort or pain that has two of the following three features

  • Related to defecation

  • Associated with a change in frequency of stool

  • Associated with a change in appearance of stool (lumpy or hard; loose or watery)

• Other symptoms include

  • Abnormal stool passage (straining, urgency, or feeling of incomplete evacuation)

  • Abdominal bloating or feeling of abdominal distention

  • Other somatic or psychological complaints

Demographics

• Up to 10% of the adult population have symptoms compatible with irritable bowel syndrome, but most never seek medical attention

• Approximately two-thirds of diagnosed patients are women

Clinical Findings

Symptoms and Signs

• Subjective abdominal distention; visible distention not clinically evident

• Abdominal pain, intermittent, crampy, in the lower abdomen, that may be improved or worsened by defecation

• More frequent or less frequent stools with the onset of abdominal pain

• Looser stools or harder stools with the onset of pain

• Constipation, diarrhea, or alternating constipation and diarrhea

• Physical examination usually is normal

• Abdominal tenderness in the lower abdomen is common, but not pronounced

• Bloating, flatulence, and diarrhea may be exacerbated in some patients who eat poorly absorbed, fermentable, monosaccharides and short-chain carbohydrates ("FODMAPS")

Differential Diagnosis

• Inflammatory bowel disease

• Colonic neoplasia

• Celiac disease, bacterial overgrowth, lactase deficiency

• Gynecologic disorders (endometriosis, ovarian cancer)

• Depression and anxiety

• Sexual and physical abuse

• Small bowel bacterial overgrowth (possibly in up to 65% of irritable bowel syndrome patients)

Diagnosis

Physical examination

• Digital rectal examination should be performed in patients with constipation to screen for paradoxical anal squeezing during attempted straining that may suggest pelvic floor dyssynergia

• A pelvic examination is recommended for postmenopausal women with recent onset constipation and lower abdominal pain to screen for gynecologic malignancy

Laboratory Tests

• Complete blood count, erythrocyte sedimentation rate, C-reactive protein

• Serum electrolytes, creatinine, albumin, liver chemistry tests

• Fecal occult blood or fecal immunochemical test

• Thyroid function tests

• Celiac disease serology (IgA tissue transglutaminase [tTG] antibody)

• Stool examination for ova and parasites if diarrhea

• D-[¹⁴C]xylose, glucose or lactulose breath tests to screen for small bowel bacterial overgrowth

Imaging Studies

• Colonoscopy or air-contrast barium enema for patients ...