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Chronic or intermittent watery diarrhea with normal-appearing mucosa at endoscopy
Two major subtypes: collagenous and lymphocytic
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
β-Blockers
Estrogen hormonal therapy
Diarrhea usually abates within 30 days of stopping the offending medication
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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
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Serologic testing (IgA tissue transglutaminase antibody [or IgA tTG]) can exclude celiac disease, which may be present in 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
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Loperamide
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 orally 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)