Colitis, Microscopic

Chronic or intermittent watery diarrhea with normal-appearing mucosa at endoscopy

Much more common in women, especially in the fifth to sixth decades

Cause is usually unknown

Several medications have been implicated as etiologic agents, including

• NSAIDs

• Proton pump inhibitors

• Low-dose aspirin

• Selective serotonin reuptake inhibitors

• Angiotensin-converting enzyme inhibitors

• Beta-blockers

• Menopausal estrogen hormone therapy

Diarrhea usually abates within 30 days of stopping the offending medication

Chronic or recurrent diarrhea

May remit spontaneously after many years

A more severe illness may develop in a subset of patients and is characterized by

• Abdominal pain

• Fatigue

• Dehydration

• Weight loss

Serologic testing (IgA tissue transglutaminase antibody [or IgA tTG]) can exclude celiac disease, which may be present in up to 2–9% of patients

Sigmoidoscopy or colonoscopy with biopsy

Histologic evaluation of mucosal biopsies shows chronic inflammation in the lamina propria and increased intraepithelial lymphocytes

Loperamide

• First-line treatment

• Provides symptom improvement in up to 70%

Delayed-release budesonide (Entocort EC)

• 9 mg once daily orally for 6–8 weeks has demonstrated efficacy in controlled studies

• However, clinical relapse is common after cessation of therapy

• Remission is maintained in 75% of patients treated long term with low doses

• In clinical practice, budesonide is tapered to the lowest effective dose for suppressing symptoms (3 mg every other day to 6 mg daily)

5-Aminosalicylates (sulfasalazine, mesalamine) or bile-salt binding agents (cholestyramine, colestipol) may be effective for patients who do not respond to budesonide

Immunosuppressive agents (azathioprine or methotrexate) or anti-TNF agents (infliximab or adalimumab) may be given for refractory or severe symptoms (which occur in < 3% of patients)