Colonic epithelial lymphocytosis and lymphocytic colitis: descriptive histopathology versus distinct clinicopathologic entities

Microscopic colitis: lymphocytic colitis, collagenous colitis, and beyond

Microscopic colitis (MC) is a chronic inflammatory disease of colon with clinical presentations of chronic, watery, nonbloody diarrhea, and normal or almost normal endoscopic findings. Confirmation of a diagnosis of MC requires microscopic examination on colon biopsy to identify characteristic morphological features, in which 2 main subtypes of MC, lymphocytic colitis (LC) and collagenous colitis (CC), have been described. Although the pathogenesis of MC is still unclear, studies have revealed associations of MC with many risk factors and other diseases such as celiac disease, inflammatory bowel disease, and medication use. Meanwhile, variants of MC, MC incomplete, or MC-like changes in other conditions are still diagnostic dilemmas for pathologists. The goal of this paper is to systemically introduce the clinicopathologic features of MC and focus on unusual features of MC and its associations with other conditions.

Biopsy interpretation of colonic biopsies when inflammatory bowel disease is excluded

The interpretation of colonic biopsies related to inflammatory conditions can be challenging because the colorectal mucosa has a limited repertoire of morphologic responses to various injurious agents. Only few processes have specific diagnostic features, and many of the various histological patterns reflect severity and duration of the disease. Importantly the correlation with endoscopic and clinical information is often cardinal to arrive at a specific diagnosis in many cases.

Optimal approach to obtaining mucosal biopsies for assessment of inflammatory disorders of the gastrointestinal tract

Endoscopic evaluation and mucosal biopsy analysis have assumed important roles in the clinical management of patients with symptoms related to the gastrointestinal tract. Several common inflammatory diseases, including eosinophilic esophagitis, Barrett's esophagus, Helicobacter pylori infection, celiac disease, lymphocytic colitis, collagenous colitis, and inflammatory bowel disease, may display a patchy or discontinuous distribution and, thus, multiple mucosal samples may be required to obtain diagnostic tissue in some cases. Not surprisingly, clinicians and pathologists are increasingly challenged to determine the optimum number of procedures and tissue samples necessary to detect, or exclude, the presence of inflammatory disorders of the gastrointestinal tract. Unfortunately, clinical practice varies widely with respect to tissue sample procurement in the evaluation of these disorders, particularly when the endoscopic appearance of the gastrointestinal mucosa is normal or shows only minimal changes. Guidelines concerning the appropriate number of tissue samples are well established for some diseases, such as Barrett's esophagus and chronic gastritis, but are not clear in other instances. The purpose of this review is to discuss the available literature pertaining to appropriate endoscopic sampling in the assessment of medical diseases of the gastrointestinal tract, and to develop recommendations regarding the clinical evaluation of common gastrointestinal disorders.

Lymphocytic colitis: a clue to bacterial etiology

AIM

To find out the role of bacteria as a possible etiological factor in lymphocytic colitis.

METHODS

Twenty patients with histopathological diagnosis of lymphocytic colitis and 10 normal controls were included in this study. Colonoscopic biopsies were obtained from three sites (hepatic and splenic flexures and rectosigmoid region). Each biopsy was divided into two parts. A fresh part was incubated on special cultures for bacterial growth. The other part was used for the preparation of histologic tissue sections that were examined for the presence of bacteria with the help of Giemsa stain.

RESULTS

Culture of tissue biopsies revealed bacterial growth in 18 out of 20 patients with lymphocytic colitis mostly Escherichia coli (14/18), which was found in all rectosigmoid specimens (14/14), but only in 8/14 and 6/14 of splenic and hepatic flexure specimens respectively. In two of these cases, E coli was associated with proteus. Proteus was found only in one case, Klebsiella in two cases, and Staphylococcus aureus in one case. In the control group, only 2 out of 10 controls showed the growth of E coli in their biopsy cultures. Histopathology showed rod-shaped bacilli in the tissue sections of 12 out of 14 cases with positive E coli in their specimen's culture. None of the controls showed these bacteria in histopathological sections.

CONCLUSION

This preliminary study reports an association between E coli and lymphocytic colitis, based on histological and culture observations. Serotyping and molecular studies are in process to assess the role of E coli in the pathogenesis of lymphocytic colitis.

Atypical forms of microscopic colitis: morphological features and review of the literature

Microscopic colitis is defined as a syndrome of chronic watery diarrhea with a chronic inflammatory cell infiltrate in the colonic mucosa but without significant abnormalities at colonoscopy. It encompasses at least two histopathologic entities (ie, collagenous and lymphocytic colitis). The recognition and characterization of microscopic colitis has markedly changed the approach to the evaluation and management of chronic diarrhea. The histologic features of collagenous and lymphocytic colitis are well known to most pathologists. By considering the clinical history and symptoms, the pathologist should be able to reach the correct diagnosis in most cases. However, the spectrum of morphologic changes associated with watery diarrhea syndrome appears to be broader than originally thought. Morphologic changes more often associated with chronic inflammatory bowel disease or even chronic ischemic or infectious colitis have been noted in patients with clinically established microscopic colitis. The data presented in this article suggest that microscopic colitis is a heterogeneous entity, which includes both classic and "atypical" forms. Problems arise when cases do not fit the usual pattern or lack some of the findings that are expected. Pathologists should be aware of the presence of atypical forms of microscopic colitis.