Microscopic colitis is a chronic inflammatory disorder of the gastrointestinal tract, characterized by non-bloody diarrhea. It is a common cause of chronic watery diarrhea in older adults. There are two subtypes of microscopic colitis: collagenous colitis and lymphocytic colitis. The histopathologic features of microscopic colitis are essential for accurate diagnosis and understanding the underlying pathophysiology. In this topic cluster, we will explore the detailed histopathology of microscopic colitis, its diagnostic characteristics, and the implications for patient care.
Normal Histology of the Colon
Before delving into the histopathology of microscopic colitis, it is important to understand the normal histology of the colon. The colon is lined by a single layer of columnar cells called colonocytes. The mucosa also contains goblet cells, which are responsible for mucin production, as well as enteroendocrine cells and absorptive cells. The colonic mucosa is organized into crypts, which are invaginations of the epithelium, and villi, which are finger-like projections that increase the surface area for absorption.
Histopathology of Microscopic Colitis
Collagenous Colitis:
- Increased thickness of the subepithelial collagen band.
- Lymphocytic infiltrate in the lamina propria.
- Surface epithelial injury and flattening.
Lymphocytic Colitis:
- Marked increase in intraepithelial lymphocytes.
- Lymphocytic infiltrate in the lamina propria.
- Surface epithelial injury and flattening.
Both subtypes of microscopic colitis demonstrate chronic inflammation, but the key distinguishing feature is the changes in the subepithelial collagen band in collagenous colitis and the intraepithelial lymphocytosis in lymphocytic colitis.
Diagnostic Characteristics
Microscopic colitis is diagnosed based on histopathologic evaluation of colonic biopsies. Characteristic findings include the presence of the aforementioned histologic features in the absence of features suggestive of other inflammatory bowel diseases such as Crohn's disease or ulcerative colitis. The diagnosis of microscopic colitis requires careful histologic examination and exclusion of other causes of chronic diarrhea.
Impact on Patient Care
The histopathologic findings in microscopic colitis have significant implications for patient care. Accurate diagnosis is crucial for appropriate management, which typically involves the use of medications such as budesonide or mesalamine. Understanding the underlying histologic changes also aids in differentiating microscopic colitis from other causes of chronic diarrhea, guiding clinicians in providing targeted therapy for this condition.
Conclusion
In conclusion, understanding the histopathology of microscopic colitis is essential for accurate diagnosis and appropriate management of this common cause of chronic watery diarrhea. The distinctive histopathologic features of collagenous colitis and lymphocytic colitis, as well as their implications for patient care, highlight the significance of histopathology in gastrointestinal pathology. By recognizing these histologic characteristics, healthcare providers can effectively diagnose and manage patients with microscopic colitis, ultimately improving patient outcomes.