Lymphocytic and collagenous colitis: an overview of so-called microscopic colitis

The entity of 'microscopic colitis' is being diagnosed with increasing frequency and is a well-established clinicopathological diagnosis that is underpinned by a triad of watery diarrhea, normal results on endoscopy and characteristic microscopic findings. Careful histopathological evaluation and awareness of its numerous associations (especially with drugs and celiac disease) and mimics will lead to the correct diagnosis of microscopic colitis. The etiology of microscopic colitis remains enigmatic and is multifactorial with different elements being more influential in different individuals. Treatment includes antidiarrheal agents and anti-inflammatory drugs (including steroids). The purpose of this article is to provide some clarity on nomenclature, discuss the multitude of conditions that can occur synchronously or metachronously with microscopic colitis and their role in the etiopathogenesis of this condition, provide a detailed review of the pathological aspects of the disease and to briefly discuss treatment trends.

Colonic perforation as a complication of collagenous colitis in a series of 12 patients

OBJECTIVES

The rare complication of colonic perforation in collagenous colitis following colonoscopy or barium enema is reported in this series of 12 patients.

METHODS

Patients with collagenous colitis complicated by perforation were collected from the authors' consultation files between 1992 and 2007. Colectomy and biopsy specimens were reviewed and the corresponding clinical data were analyzed.

RESULTS

The patients ranged in age from 44 to 80 yr, with a female-to-male ratio of 11:1. Perforation occurred during colonoscopy in 2 patients, within 0-5 days following colonoscopy in 8 patients, and during barium enema in 2 patients. The most notable colonoscopic findings were bleeding linear ulcers of the right colon in 9 patients, several of which developed under direct visualization during endoscopy. The perforation culminated in right hemicolectomy in 11 patients. Linear fissuring ulcers were identified in the resections of 8 patients along with features of perforation, including pneumatosis in 4 patients and barium extravasation within the muscularis propria in 2 patients.

CONCLUSIONS

This is the largest published series to date, and the first to uncover several novel clinicopathologic features of perforation in collagenous colitis, including the right colonic predilection (corresponding to disease severity), the association with not only colonoscopy, but also barium enema, the occurrence of recognizable perforation actually developing during the procedure, and a more detailed information on the marked histologic severity of these patients' collagenous colitis. An awareness of this rare but potentially fatal complication of collagenous colitis may facilitate its diagnosis and management.

Pseudomembranous collagenous colitis

The classic clinical and histologic features of collagenous colitis are well characterized; however, the acute or neutrophilic inflammatory changes that may accompany this entity are less well established. In this report of 10 patients, we describe the first series of pseudomembranous collagenous colitis. Because superimposed Clostridium difficile infection was only demonstrated in one patient and no other causes of pseudomembranous colitis were evident in the remaining nine patients, we conclude that pseudomembranes are part of the spectrum of collagenous colitis itself. This case series illustrates the importance of searching for collagenous colitis in the evaluation of pseudomembranous colitis. At the same time, superimposed infectious or ischemic etiologies need to be excluded clinically in any patient with superimposed pseudomembranes. The existence of pseudomembranes in collagenous colitis also lends support to the hypothesis that toxin- and/or ischemia-mediated injury may be involved in the pathogenesis of collagenous colitis.

Inflammatory bowel disease

Although inflammatory bowel disease (IBD) usually presents in adolescents and young adults, both ulcerative colitis and Crohn's disease can also present in older adults. The diagnosis of IBD in the elderly is often difficult and can easily be confused with diverticulitis or ischaemic colitis. The symptoms and complications of IBD in the elderly are similar to those found in younger patients. However, when IBD presents later in life the disease is often less extensive and milder. Older IBD patients are treated with the same medications as younger patients, although the risk for drug toxicity is greater, especially with corticosteroid therapy. Comorbid illness in older patients often has a significant impact on the outcome of medical and surgical therapy for IBD but, in the absence of significant co-morbid disease, most elderly IBD patients can expect a good response to therapy.

Atypical forms of inflammatory bowel disease

Atypical forms of IBD include the microscopic colitides, collagenous and lymphocytic colitis, and two macroscopic colitides, SRUS and diversion colitis. Clinical presentations include chronic, watery diarrhea and intermittant rectal bleeding. Constitutional symptoms are typically absent; laboratory data are often nonspecific. Colonoscopic evaluation and mucosal biopsy are essential in establishing these diagnoses and excluding more classic forms of IBD (i.e., Crohn's disease or idiopathic ulcerative colitis). Prognosis and response to treatment are variable; potential therapeutic options include dietary manipulations, topical or systemic anti-inflammatory agents, and, in refractory cases, surgical intervention.

Interpretation of large intestinal mucosal biopsy specimens

The development of flexible endoscopes has led to a great increase in the examination and mucosal biopsy evaluation of all portions of the large intestine and rectum. Examinations are now performed not only for the determination of diagnosis but also for the monitoring of the course of a wide variety of conditions and for the early detection of complications. This review concentrates on the uses and interpretations of such biopsies in a large number of inflammatory conditions, with special emphasis on the correlations with clinical and functional features. Illustrated are examples of infections, idiopathic inflammatory bowel disease (IBD), vascular disorders, motor and mechanical conditions, toxic and physical reactions, and other inflammatory conditions. Mucosal biopsy specimens also are obtained to identify dysplasia and to evaluate mass lesions, and these subjects are well covered in other articles within this symposium. In patients with chronic disorders multiple examinations are now expected to follow the course of the disease and to detect and correct any complications at an early stage. The exact reasons for the endoscopy and relevant clinical data are essential for the optimal analysis of these mucosal biopsy specimens.