What is the recommended treatment for a middle-aged to older adult woman with a history of smoking and autoimmune disorders who has been diagnosed with microscopic colitis, presenting with chronic diarrhea and abdominal pain?

Treatment of Microscopic Colitis

Budesonide is the first-line treatment for microscopic colitis, with strong evidence supporting its use for both induction and maintenance of clinical remission. 1, 2

Initial Management Steps

Medication Review and Discontinuation

• Identify and discontinue potential triggering medications including NSAIDs, proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), and statins when clinically feasible 2, 3, 4
• This patient population (middle-aged to older women with autoimmune disorders and smoking history) has multiple risk factors that align with typical MC presentation 1
• Smoking cessation should be strongly encouraged as tobacco use is a known risk factor 5

Exclude Concurrent Conditions

• Test for bile acid diarrhea, which coexists in 41% of collagenous colitis and 29% of lymphocytic colitis cases 1, 6
• Consider screening for celiac disease, particularly given the association with autoimmune disorders (present in 5-7% of MC cases) 1, 7

Treatment Algorithm by Symptom Severity

Mild Symptoms

• Start with loperamide (antidiarrheal agent) for symptomatic control 1, 8, 3
• However, antidiarrheals appear largely ineffective as monotherapy in this population and should not delay definitive treatment 7

Moderate to Severe Symptoms (Most Patients)

Budesonide is strongly recommended as first-line therapy:

• Induction dose: 9 mg daily for clinical remission 1, 2
• Budesonide demonstrates superior efficacy compared to mesalamine (high-quality evidence) 1, 2
• Reduces clinical relapse risk by 66% (relative risk 0.34,95% CI 0.19-0.6) 2, 6

Alternative First-Line Options (When Budesonide Not Feasible)

The AGA provides conditional recommendations for alternatives when budesonide cannot be used:

• Mesalamine 2-4 g daily (moderate-quality evidence, preferred 5-ASA derivative over sulfasalazine due to fewer adverse effects) 1, 2, 7
• Bismuth subsalicylate (low-quality evidence) 2, 7
• Cholestyramine or colestipol (bile salt-binding agents), particularly useful if concurrent bile acid diarrhea is present 7

Maintenance Therapy

When to Consider Maintenance

• Only offer maintenance therapy to patients who relapse after stopping induction treatment 6
• Approximately one-third of patients achieve spontaneous remission and do not require maintenance 6

Maintenance Dosing Strategy

• Start with budesonide 6 mg daily, then taper to the lowest effective dose 2
• Continue for 6-12 months before attempting discontinuation 2
• Monitor for bone loss with prolonged use; implement osteoporosis prevention and screening strategies 2

Refractory Disease Management

Systemic Corticosteroids

• Prednisolone/prednisone is conditionally recommended only for refractory cases (very low-quality evidence) 1, 2
• Reserve for patients who fail budesonide, mesalamine, and bile salt-binding agents due to significant adverse event risk 1, 7
• May provide only transient symptom improvement 7

Immunomodulators (Rare Cases)

• Consider methotrexate, thiopurines, or biologics (infliximab, adalimumab, vedolizumab) only in exceptional refractory cases 7, 4
• Re-evaluate for other causes of diarrhea including celiac disease, bacterial overgrowth, or chronic infection before escalating therapy 2, 7

Treatments NOT Recommended

The following have insufficient evidence or no benefit:

• Combination cholestyramine plus mesalamine (no superiority over mesalamine alone) 1, 2
• Boswellia serrata (conditional recommendation against use) 1, 2
• Probiotics (conditional recommendation against use) 1, 2

Clinical Pitfalls to Avoid

• Do not delay colonoscopy with biopsies in this demographic (female, age ≥50, autoimmune disease, chronic diarrhea) as these are high-risk features for MC 1
• Biopsies must be taken from right colon (ascending/transverse) and left colon (descending/sigmoid), not just rectum, as rectal biopsies alone miss 34-43% of cases 9
• Do not assume IBS in patients with nocturnal diarrhea, severe watery diarrhea, or recent onset (<12 months), as these suggest MC rather than functional bowel disorder 1, 6
• Recognize that lymphocytic and collagenous colitis cannot be reliably distinguished by symptoms alone and require histologic diagnosis 6

Treatment Goals

The primary objective is symptom relief and quality of life improvement while minimizing drug-related adverse effects 2, recognizing that MC significantly impacts quality of life despite being considered a "benign" disease 5.