What is the recommended workup for suspected lymphocytic colitis in an adult presenting with chronic watery non‑bloody diarrhea?

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Workup for Lymphocytic Colitis

For suspected lymphocytic colitis in an adult with chronic watery non-bloody diarrhea, perform colonoscopy with multiple biopsies from all colonic segments (including descending colon, not just rectosigmoid) to establish the histopathological diagnosis, while simultaneously excluding other causes through targeted testing for celiac disease, infections (particularly Giardia and C. difficile), and medication review. 1, 2, 3

Essential Diagnostic Triad

Lymphocytic colitis is a clinicopathological diagnosis requiring three elements 1:

  • Clinical: Chronic watery (non-bloody) diarrhea (≥3 loose stools/day for >4 weeks)
  • Endoscopic: Normal or near-normal appearing colonic mucosa
  • Histologic: Increased intraepithelial lymphocytes (≥20 per 100 enterocytes) with increased lamina propria inflammation but preserved mucosal architecture

Initial Laboratory Assessment

Before endoscopy, obtain 2, 4:

Blood tests:

  • IgA tissue transglutaminase (IgA-tTG) with total IgA level (to detect celiac disease, present in 3-10% of chronic diarrhea patients)
  • If IgA deficient: IgG-tTG or IgG deaminated gliadin peptides
  • Complete blood count (anemia, elevated WBC)
  • Thyroid function tests (hyperthyroidism)

Stool tests:

  • Giardia antigen testing (ELISA with 92% sensitivity, 98% specificity) 2, 4
  • C. difficile testing (can coexist with lymphocytic colitis and complicate diagnosis) 1, 5
  • Fecal calprotectin or lactoferrin if inflammatory bowel disease is a consideration 4

Endoscopic Evaluation

Perform full colonoscopy (not flexible sigmoidoscopy) with multiple biopsies 3:

  • Obtain biopsies from multiple colonic segments including right colon, transverse colon, descending colon, and rectosigmoid
  • The rectosigmoid alone may miss the diagnosis in some cases
  • Macroscopic appearance is typically normal, which is part of the diagnostic criteria

Critical pitfall: Histology cannot reliably identify bacterial infections, particularly C. difficile, which can present with similar microscopic patterns 1. Clinical correlation is essential.

Medication Review

Immediately review and consider discontinuing potential triggers 3:

  • Nonsteroidal anti-inflammatory drugs (NSAIDs)
  • Proton pump inhibitors (PPIs)
  • Selective serotonin reuptake inhibitors (SSRIs)
  • Other documented triggers: ticlopidine, flutamide, gold salts 6

Medication-induced disease should be suspected and offending agents stopped before initiating specific therapy.

Additional Testing for Refractory Cases

If symptoms persist despite initial management 3, 7:

  • Celiac disease screening is mandatory even if initial serology negative (antibody-negative celiac disease occurs in 6.4-7% of cases) 2
  • Consider duodenal biopsies during upper endoscopy, as >10% of lymphocytic colitis patients show Marsh I villous changes without meeting full celiac disease criteria 7
  • Bile acid diarrhea testing if available (48-hour fecal bile acids or serum FGF-19) 4
  • Cholestyramine trial may be diagnostic and therapeutic if bile acid malabsorption coexists 6

Key Diagnostic Considerations

Distinguish from collagenous colitis: Both present identically clinically; differentiation requires histology showing thickened subepithelial collagen band (>10 μm) in collagenous colitis versus increased intraepithelial lymphocytes in lymphocytic colitis 1, 8.

Association with autoimmune disease: Screen for thyroid disorders and celiac disease, which rank highest among associated conditions 7, 9. Celiac disease is particularly associated with single-episode lymphocytic colitis rather than refractory disease 9.

Focal vs. diffuse infiltrate: Focal lymphoid infiltration strongly predicts coexisting diverticula or polyps and may not represent true lymphocytic colitis 10. Cases without diverticula/polyps and showing diffuse infiltration most closely conform to diagnostic criteria.

Clinical Context

Approximately 1% of patients with chronic diarrhea require colonoscopy 1. The reported prevalence of microscopic colitis ranges from 48-219 per 100,000, with lymphocytic colitis showing no female predominance (unlike collagenous colitis) 3, 11. The condition has high rates of spontaneous remission (nearly 20%) and is not associated with increased colorectal cancer risk or mortality 3, 6.

References

7
Research

A retrospective study on a cohort of patients with lymphocytic colitis.

Revista espanola de enfermedades digestivas, 2010

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