IRRITABLE BOWEL SYNDROME

Mohamed Abdalaziz, MD • Naureen Rafiq, MD

 BASICS

DESCRIPTION

•  A gastrointestinal disorder characterized by

–  Chronic and/or recurrent abdominal pain or discomfort and alteration in bowel habits

•  May be characterized as diarrhea-predominant or constipation-predominant and may alternate between the two

•  Synonym(s): spastic colon; irritable colon

EPIDEMIOLOGY

Irritable bowel syndrome (IBS) accounts for up to 50% of visits to gastroenterologists:

•  Second only to upper respiratory infection as cause of lost workdays

Prevalence

Pooled estimate of 11% IBS prevalence internationally; ranges from South Asia (7%) to South America (21%) (1)

•  Predominant age: 20 to 39 years

•  If age >50 years, consider other diagnoses.

•  Predominant sex: in the United States, female > male (2:1)

•  More common in low socioeconomic communities

ETIOLOGY AND PATHOPHYSIOLOGY

•  The etiology is unknown, associated with intestinal motility abnormalities and enhanced sensitivity to visceral stimuli.

•  The trigger may be luminal or environmental.

•  Evidence for the role of small intestine bacterial overgrowth (SIBO) in IBS and association with antibiotic therapy is controversial; older age and female gender are predictors of SIBO in IBS patients.

Genetics

Unknown but more common in families of IBS patients

RISK FACTORS

•  Other family members with similar GI disorder

•  History of childhood sexual abuse

•  Sexual/domestic abuse (primarily in women)

•  Depression

•  Gastrointestinal infection

Pregnancy Considerations

No risk to mother or fetus

GENERAL PREVENTION

See “Diet.”

COMMONLY ASSOCIATED CONDITIONS

•  Chronic migraine

•  Fibromyalgia

•  Chronic fatigue syndrome

•  Sleep disorders

•  Psychiatric disorders: major depression, anxiety, somatoform disorders and posttraumatic stress

•  Chronic pelvic pain

•  Temporomandibular joint dysfunction

 DIAGNOSIS

HISTORY

•  Rome III criteria: recurrent pain or discomfort in the abdomen at least 3 days per month over the past 3 months associated with at least two other criteria:

–  Symptoms improve with defecation.

–  Onset is associated with a change in stool frequency.

–  Onset is associated with a change in the form or appearance of the stool.

•  Symptoms can also include:

–  Mucus in stools

–  Constipation, bloating, diarrhea, abdominal distension

–  Upper abdominal discomfort after eating

–  Straining for normal consistency stools

–  Urgency of defecation

–  Feelings of incomplete evacuation

–  Abnormal stool form

–  Nausea, vomiting (rarely)

•  May have history of abuse or depression

•  Patient may note worsening of symptoms with stress or around menses.

•  IBS is unlikely in patients with a history of:

–  Weight loss

–  Bleeding

–  Nocturnal diarrhea

–  Fever

–  Anemia

PHYSICAL EXAM

•  Important to conduct a complete exam to exclude other causes.

•  Vital signs and general exam are typically normal.

•  There is typically an absence of jaundice and organomegaly, but there may be tenderness to palpation.

DIFFERENTIAL DIAGNOSIS

•  Inflammatory bowel disease

•  Lactose intolerance; fructose malabsorption

•  Infections (Giardia lamblia, Entamoeba histolytica, Salmonella, Campylobacter, Yersinia, Clostridium difficile)

•  Celiac sprue

•  Microscopic colitis

•  Laxative abuse

•  Magnesium-containing antacids

•  Hypo-/hyperthyroidism

•  Pancreatic insufficiency

•  Depression

•  Small bowel bacterial overgrowth

•  Somatization

•  Villous adenoma

•  Endocrine tumors

•  Diabetes mellitus

•  Radiation damage to colon or small bowel

DIAGNOSTIC TESTS & INTERPRETATION

•  With a typical history and no warning signs (anemia or weight loss), obtain baseline labs to rule out other causes and begin treatment.

•  In patients who do not respond to treatment, further evaluation with imaging and/or endoscopy is warranted to exclude organic pathology.

Initial Tests (lab, imaging)

Rule out pathology specific to the patient’s symptoms:

•  Diarrhea-predominant: ESR, CBC, tissue transglutaminase, thyroid-stimulating hormone (TSH), and stool for ova and parasites (2)

•  Constipation-predominant: CBC, TSH, electrolytes, calcium (2)

•  Abdominal pain: LFTs and amylase

•  When obtained, abdominal CT scan and ultrasound are generally normal.

•  Consider small bowel series or video capsule endoscopy to rule out Crohn disease (typically normal).

•  Sitz Marker study may be used to evaluate colonic transit in patients with constipation.

Follow-Up Tests & Special Considerations

Consider lactulose breath test to assess for small bowel bacterial overgrowth associated with IBS (2)[C].

Diagnostic Procedures/Other

Sigmoidoscopy/colonoscopy may be used to rule out inflammatory bowel disease or microscopic colitis.

ALERT

Screen all persons >50 for colorectal cancer.

Test Interpretation

None

 TREATMENT

•  Goals: Relieve symptoms and improve quality of life (3).

–  Determine if diarrhea predominant, constipation predominant, or mixed type.

•  Lifestyle modification

–  Exercising 3 to 5 times per week decreases severity (3).

–  Food diary to determine triggers (3)

•  Medications

–  Fiber supplementation (psyllium) increases stool bulk; does not typically relieve abdominal pain; may be used for all types (3)[B]

•  Medications that improve abdominal pain, global symptoms, and symptom severity in all types:

–  Antispasmodics such as hyoscyamine 0.125 to 0.25 mg PO/SL q4h PRN and dicyclomine 20 to 40 mg PO BID can be used for all types but have adverse effects such as dry mouth, dizziness, and blurred vision (3).

–  Probiotics such as Lactobacillus, Bifidobacterium, and Streptococcus (4)[C]

•  Diarrhea predominant

–  Antidiarrheal such as loperamide 4 to 8 mg/day orally divided into once a day to 3 times a day as needed to decrease stool frequency and increase stool consistency; does not help with abdominal pain; may also use diphenoxylate/atropine (3)

–  Antibiotics such as 2-week course of rifaximin improve bloating, pain, and stool consistency (5).

–  Alosetron (Lotronex 0.5 mg orally twice a day), for women with severe symptoms. Associated with ischemic colitis, constipation, and death in a small number of patients.

•  Constipation-predominant

–  Laxatives such as polyethylene glycol (MiraLAX) may improve stool frequency but not pain.

–  Antibiotics such as neomycin and selective chloride channel activators such as lubiprostone (Amitiza) 8 mg twice a day can improve global symptoms and severity (3)[B].

–  Linaclotide (guanylate cyclase-C agonist) has been shown to improve bowel function and reduces abdominal pain and overall severity in adults only (6).

•  Mixed

–  Use medications to match symptoms (3).

•  Treat underlying behavioral issues:

–  Tricyclic antidepressants can help control IBS symptoms in moderate to severe cases.

–  Behavioral therapy helps reduce symptoms (5).

ISSUES FOR REFERRAL

•  Behavioral health referral may help with management of affective or personality disorders.

•  Gastroenterology referral for difficult to control cases

ADDITIONAL TREATMENT

Probiotics use may result in reducing IBS symptoms and decreasing pain and flatulence. There is no difference among Lactobacillus, Streptococcus, Bifidobacterium, and combinations of probiotics.

 ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

The IBS Severity Score is a validated measure to assess the severity of IBS symptoms and can help monitor response to treatment.

IBS Severity Score:

•  How severe has your abdominal pain been over the last 10 days?

•  On how many of the last 10 days did you get pain?

•  How severe has your abdominal distension (bloating, swollen, or tight) been over the last 10 days?

•  How satisfied have you been with your bowel habit (frequency, ease, etc.) over the last 10 days?

•  How much has your IBS been affecting/interfering with your life in general over the last 10 days?

DIET

•  Low FODMAPs diet: This diet contains fermentable oligosaccharides, disaccharides, and monosaccharides, and polyols that are carbohydrates (sugars) found in foods. FODMAPs are osmotic, so they may not be digested or absorbed well and could be fermented upon by bacteria in the intestinal tract when eaten in excess.

•  A low FODMAP diet may help reduce symptoms, which will limit foods high in fructose, lactose, fructans, galactans, and polyols.

–  Increase fiber slowly to avoid excess intestinal gas production.

–  During initial evaluation, consider 2 weeks of lactose-free diet to rule out lactose intolerance.

–  Avoid large meals, fatty foods, and caffeine, which can exacerbate symptoms.

–  A gluten-free diet resolves symptoms for some patients (especially diarrhea predominant IBS) despite negative testing for celiac disease.

PATIENT EDUCATION

IBS is not a psychiatric illness.

PROGNOSIS

•  IBS is a disorder that reduces quality of life. Many patients have behavioral health issues. IBS does not increase mortality (1).

•  Expect recurrences, especially when under stress.

•  Evidence suggests that “symptom shifting” occurs in some patients, whereby resolution of functional bowel symptoms is followed by the development of functional symptoms in another system (1).

REFERENCES

1.  Canavan C, West J, Card T. The epidemiology of irritable bowel syndrome. Clin Epidemiol. 2014;6:71–80.

2.  Reddymasu SC, Sostarich S, McCallum RW. Small intestinal bacterial overgrowth in irritable bowel syndrome: are there any predictors? BMC Gastroenterol. 2010;10:23.

3.  Wilkins T, Pepitone C, Alex B, et al. Diagnosis and management of IBS in adults. Am Fam Physician. 2012;86(5):419–426.

4.  Ciorba MA. A gastroenterologist’s guide to probiotics. Clin Gastroenterol Hepatol. 2012;10(9):960–968.

5.  Schey R, Rao SS. The role of rifaximin therapy in patients with irritable bowel syndrome without constipation. Expert Rev Gastroenterol Hepatol. 2011;5(4):461–464.

6.  Videlock EJ, Cheng V, Cremonini F. Effects of linaclotide in patients with irritable bowel syndrome with constipation or chronic constipation: a meta-analysis. Clin Gastroenterol Hepatol. 2013;11(9):1084.e3–1092.e3.

 SEE ALSO

Algorithm: Diarrhea, Chronic

 CODES

ICD10

•  K58.9 Irritable bowel syndrome without diarrhea

•  K58.0 Irritable bowel syndrome with diarrhea

CLINICAL PEARLS

•  Use Rome III criteria to establish the diagnosis of IBS.

•  Goals of treatment are to relieve symptoms and improve quality of life.

•  If patient does not respond to initial treatment, consider further evaluation (including imaging and/or referral for endoscopy) to exclude organic pathology.