Collagenous, "microscopic," lymphocytic, and other gentler and more subtle forms of colitis

The Watery Diarrhea-Colitis Syndrome

Collagenous and lymphocytic/microscopic colitis represent a distinct histopathologic spectrum of findings, with occasional transition, observed in patients with normal or near-normal colonoscopic findings and chronic watery diarrhea (watery diarrhea- colitis syndrome). Biopsies are characterized by surface epithelial damage, an increased number of chronic inflamatory cells in the lamina propria, intraepithelial lymphocyto sis, intact crypt architecture, and in the cases of collagenous colitis, a thickened subepi thelial collagen layer (SCL). While their precise interrelationship is unclear, as their clinicopathologic similarities far outweigh their differences, it appears reasonable for pathologists and clinicians to consider them conceptually together as part of a syn drome of chronic watery diarrhea and colitis distinct from other forms of chronic inflammatory bowel disease. The etiology and pathogenesis of this syndrome are un clear. Colorectal surface epithelial damage appears to be for the most part responsible for the secretory diarrhea, while the thickened SCL appears to be a variable response to the surface epithelial damage. Why the thickened SCL occurs only in some cases, why it does not occur in other forms of colitis, and whether it functions as a diffusion barrier are unknown. The propensity of the watery diarrhea-colitis syndrome to pref erentially affect middle-aged and elderly women, an association with autoimmune disorders, and clinicopathologic similarities to celiac disease suggest that host immune factors are important. Other dietary factors, medications, or other agents may also play a role, and this is currently under investigation. Small bowel villous atrophy appears to account for the presence of steatorrhea noted in some reports. Definitive diagnosis is facilitated by the procurement of multiple, well-oriented biopsies, prefera bly extending at least into the proximal left colon. A thickened SCL occasionally can only be demonstrated in biopsies from the right colon. An appreciation of the normal variation found in colorectal biopsies and recognition of artifactual thickening of the subepithelial basement membrane in maloriented sections and in relation to bowel preparation will eliminate overdiagnosis of normal biopsies, while the absence of fea tures typical for other forms of inflammatory bowel disease facilitates differential diag nosis. Patients may respond dramatically to therapeutic intervention with drugs often used for ulcerative colitis and Crohn's disease, however, spontaneous remissions are well documented. A colitis-dysplasia-carcinoma sequence has not as yet been docu mented to occur in this patient population. In just over one decade the morphologic features of the watery diarrhea-colitis syndrome have come to be recognized. Hope fully, the next decade of observation and investigation will help to clarify the precise relationship between cases with and without a thickened SCL, as well as the etiology and pathogenesis of the secretory diarrhea. Int J Surg Pathol 1 (1): 65-82, 1993

Advances for improved diagnosis of microscopic colitis in patients with chronic diarrhoea

Microscopic colitis is a generic term that includes 2 main forms, collagenous colitis and lymphocytic colitis, and describes a form of inflammatory bowel disease with a chronic and relapsing course. The incidence of microscopic colitis is between 2 and 8 times higher in women than in men, although age, more than sex, increases the risk of collagenous colitis (odds ratio [OR] 8.3 for age ≥65 vs. <65 and OR 2.8 for women). The main symptom is chronic non-bloody watery diarrhoea. Other common symptoms include abdominal pain (50%-70%), with the result that many patients with microscopic colitis meet criteria for irritable bowel syndrome. Colonoscopy with multiple colonic biopsies is currently recommended, as histological changes are the main characteristic feature. The colonic mucosa is macroscopically normal, although certain minimal endoscopic abnormalities have been described.

Diarrhea in chronic inflammatory bowel diseases

Diarrhea is a common clinical feature of inflammatory bowel diseases and may be accompanied by abdominal pain, urgency, and fecal incontinence. The pathophysiology of diarrhea in these diseases is complex, but defective absorption of salt and water by the inflamed bowel is the most important mechanism involved. In addition to inflammation secondary to the disease, diarrhea may arise from a variety of other conditions. It is important to differentiate the pathophysiologic mechanisms involved in the diarrhea in the individual patient to provide the appropriate therapy. This article reviews microscopic colitis, ulcerative colitis, and Crohn's disease, focusing on diarrhea.

Lymphocytic disorders of the gastrointestinal tract: a review for the practicing pathologist

Increased numbers of intraepithelial lymphocytes (lymphocytosis) can be found in the esophagus, stomach, small intestine, and colon in a variety of clinical circumstances. This review, directed at practicing pathologists, portrays the normal resident lymphocyte population in the mucosa of each segment of the digestive tract and discusses the different situations that may result in quantitative or qualitative alterations of intraepithelial lymphocytes. Esophageal lymphocytosis has not been fully characterized and its clinical significance, if any, awaits definition. Thus, this diagnosis is presently discouraged. In the stomach, it is particularly important to exclude Helicobacter pylori infection and celiac sprue before diagnosing lymphocytic gastritis. Duodenal lymphocytic infiltrates, inextricably tied with alterations of the villous architecture of the mucosa, are often caused by gluten sensitivity. However, similar morphologic changes may be caused by a vast array of other conditions that must be carefully considered and excluded. Lymphocytic and collagenous colitis are most often unexplained, but their frequent association with autoimmune conditions or certain medications deserve a thorough investigation in each case. Using a combination of histologic and clinical clues, a cause for the intraepithelial lymphocytic infiltration can be identified in many instances. As some of the associated conditions are amenable to effective treatment, the importance of diligently seeking such associations before resorting to a diagnosis of primary lymphocytosis is emphasized.

Collagenous and lymphocytic colitis

Collagenous and lymphocytic colitis have been recognized as chronic intestinal inflammatory disorders causing watery diarrhea, which have been recognized in the past three to two decades, respectively. Collagenous colitis is primarily a disorder of middle-aged women and is characterized on biopsy by increased subepithelial collagen as well as increased inflammatory cells in the lamina propria and increased intraepithelial lymphocytes. Key to the correct diagnosis in this condition is recognizing that there are two words in this diagnostic entity, and colitis is, by definition, present. Focusing solely on the collagen band can result in both over- and underdiagnosis. Newer therapeutic options are available in this condition, and patients are now frequently being treated either with budesonide or with high dose bismuth preparations. Whereas collagenous colitis is a tightly coherent clinical pathologic entity, lymphocytic colitis has a more varied clinical picture. Lymphocytic colitis is also seen in middle-aged patients but has a more equal female-to-male ratio. Lymphocytic colitis is defined by increased intraepithelial lymphocytes, with the median being 30 lymphocytes per 100 epithelial cells. There are also an increase in inflammatory cells in the lamina propria, but the increase may be milder than in collagenous colitis and there are usually minimal eosinophils. Although numerous studies have described lymphocytic colitis causing a chronic diarrhea, more recent studies suggest that patients may have a single attack in approximately 60% of cases. Although most cases of lymphocytic colitis are idiopathic, there is a clear association with multiple drugs, celiac disease, and there may be an infectious trigger. Approximately 10% of lymphocytic colitis patients have a positive family history of some type of inflammatory intestinal disease, including ulcerative colitis, Crohn's disease, collagenous colitis, and celiac disease. Therapy in lymphocytic colitis is less well studied, but the same medications are used with success, including budesonide and high dose bismuth.

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.

Diagnosis and management of microscopic colitis syndrome

Microscopic colitis syndrome consists of chronic watery diarrhea, a normal or near-normal gross appearance of the colonic mucosa, and a specific histologic picture described as either lymphocytic colitis or collagenous colitis. The cause of microscopic colitis is unknown, but recent work suggests some immunologic similarities to celiac disease, suggesting that luminal antigens may be important in its pathogenesis. Diarrhea in microscopic colitis seems to be directly related to the extent of inflammation, suggesting that inflammatory mediators are responsible for reduced water absorption by the colon. Microscopic colitis is a frequent diagnosis in patients with chronic diarrhea seen at referral centers. It is often associated with other immune-mediated conditions and frequently is complicated by fecal incontinence. The differential diagnosis is broad, comprising all causes of watery diarrhea. Evaluation is straightforward with the key aspect being review of colon biopsy specimens by an experienced pathologist. Treatment is still being defined: symptomatic management with antidiarrheal agents, 5-aminosalicylate drugs, corticosteroids, especially budesonide, bile acid-binding resins, and bismuth subsalicylate all can be effective. The prognosis is good with no evidence of conversion to classic inflammatory bowel disease or of development of neoplasia over time.

Subepithelial myofibroblasts and tenascin expression in microscopic colitis

AIMS

To assess differences in the pattern of subepithelial myofibroblasts and the expression of tenascin as a marker of extracellular matrix production in collagenous and lymphocytic colitis.

METHODS AND RESULTS

Colorectal biopsies were studied from 122 patients with chronic diarrhoea and normal colonoscopy. The pathological diagnoses were collagenous colitis (n = 35), lymphocytic colitis (n = 37), mild non-specific chronic inflammation (n = 28) and normal mucosa (n = 18). Four cases showed features of collagenous colitis but with collagen bands <10 micro m thick. Normal mucosa from 14 patients without diarrhoea served as healthy control tissue. Immunohistochemical expression of alpha-smooth muscle actin (myofibroblast marker) and tenascin was evaluated in well-orientated sections. The expression of alpha-smooth muscle actin was significantly increased in collagenous colitis compared with all the other groups. Strong tenascin subepithelial expression was seen in all cases of collagenous colitis, including the four without full-blown features. The mean thickness of tenascin bands was greater than that obtained by conventional stains.

CONCLUSIONS

There are clear differences, with respect to extracellular matrix remodelling, between collagenous and lymphocytic colitis. These results support the theory of matrix overproduction in the genesis of collagenous colitis.

Collagenous colitis: a study of the distribution of morphological abnormalities and their histological detection

In collagenous colitis, the literature is conflicting concerning where in the colon the lesions are most likely to be present and most severe. Conflicting data furthermore shed doubt on the sensitivity of the histological detection of the morphological abnormalities and the threshold criteria for diagnosis. We addressed these questions in 56 patients with collagenous colitis. Two hundred ninety-one coded biopsy specimens were analyzed according to six standardized sites from cecum to rectum. Subepithelial collagen deposits were subjectively graded in hematoxylin and eosin (H&E) sections and quantitatively measured in trichrome-stained sections, respectively. Semiquantitative grading was also done for inflammatory changes of the lamina propria and abnormalities of the surface and crypt epithelium. The transverse colon yielded the largest percentage of biopsy specimens (83%) interpreted as diagnostic of collagenous colitis and also had the largest percentage of biopsy specimens with inflammatory changes (98%). Biopsy specimens from both the rectosigmoid and the right colon (ascending and cecum) were significantly less likely to be diagnostic (P<.01). Only 66% of specimens obtained from the rectosigmoid were diagnostic, and 18% of these were interpreted as normal. Subepithelial collagen deposits proved to be significantly thicker in the transverse (median, 46.8 microm; range, 12 to 212.4) and descending (median, 49.2 microm; range, 6 to 230.4) than in the rectosigmoid (median, 33.6 microm; range, 9.6 to 178.8) and right colon (median, 35.4 microm; range, 6 to 140.4), respectively (P<.01). Almost all biopsy specimens (97%) had collagen deposits thicker than 10 microm. However, the subjective interpretation "diagnostic of collagenous colitis" proved to be most consistent with a threshold of 30 microm. Our results indicate that biopsy specimens from at least as proximal as the transverse colon should be obtained to definitely rule out collagenous colitis. Furthermore, it is evident that in a given biopsy specimen, markedly abnormal subepithelial collagen deposition had to be present for an unequivocal histological diagnosis of collagenous colitis.

Guidelines for the initial biopsy diagnosis of suspected chronic idiopathic inflammatory bowel disease. The British Society of Gastroenterology Initiative

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Microscopic colitis is a cause of large bowel diarrhea in Northern India

Chronic diarrhea is a common clinical problem. To determine the possible causes in North India, we studied prospectively 71 patients with chronic diarrhea of the large bowel type. A definite diagnosis could be established in 70 patients. Ulcerative colitis was found in 18 patients, colorectal malignancies in three, colonic polyps in three, and irritable bowel syndrome in 32. In addition, seven patients with seronegative polyarthritis and chronic diarrhea were found to have chronic inflammation of the colon on histology. Two patients had pseudodiarrhea, and no diagnosis could be established in one patient. The remaining five patients with chronic diarrhea showed histologic evidence of chronic colonic inflammation with predominantly mononuclear cell infiltration of the lamina propria and increased intraepithelial lymphocytes, but results of their radiologic and endoscopic studies were normal. These five patients were classified as having microscopic (lymphocytic) colitis. We conclude that the causes of chronic diarrhea in North India patients are similar to a large extent to those seen in Western populations. Microscopic (lymphocytic) colitis is a definite clinicopathologic entity that should be considered in the differential diagnosis of chronic diarrhea.

Microscopic colitis syndrome

The colorectal biopsy specimens from 30 patients with chronic watery diarrhoea but normal endoscopic and radiographic findings were studied by light microscopy, morphometry, immunohistochemistry, and two patients with electron microscopy. The histological changes in the colorectum were originally diagnosed in six patients as lymphocytic colitis and in 24 patients as collagenous colitis. The analysis of the specimens for this study could delineate three distinct groups of microscopic colitis: lymphocytic colitis (six patients), collagenous colitis without lymphocytic attack on the surface epithelium (seven patients), and a mixed form presenting with both thickening of the collagen plate and increased number of intraepithelial lymphocytes (17 patients). No transformation was seen from one type to another during follow up of six patients for four to seven years. Increased numbers of active pericryptal myofibroblasts were found with the electron microscope in one patient with mixed microscopic colitis showing also myofibroblasts entrapped within the collagen layer. Hitherto undescribed flat mucosa of the ileum was found in one patient with lymphocytic colitis and both flat mucosa and thickening of the collagen plate in the ileum were seen in one patient with the mixed form of the disease. In another patient with mixed microscopic colitis, normalisation of the colorectal morphology occurred after temporary loop ileostomy, followed by the reappearance of both diarrhoea, inflammation, and thickening of the collagen plate after the ileostomy was reversed. No association was found between non-steroid anti-inflammatory drug (NSAID) consumption and collagenous or mixed microscopic colitis. The primary cause of microscopic colitis is probably an immunological reaction to luminal antigen/s, perhaps of ileal origin. The engagement of the pericryptal myofibroblasts in the disease process might result in the development of the various forms of microscopic colitis. An inverse relation between intraepithelial lymphocyte count and collagen thickness may indicate that microscopic colitis is a spectral disease.

Collagenous colitis and lymphocytic colitis

Collagenous and lymphocytic colitis are newly recognized causes of chronic watery diarrhea that typically affect middle-aged patients. Although endoscopic studies are normal, inflammatory changes and (in the case of collagenous colitis) collagen deposition occur histologically in the colonic mucosa. The pathogenesis of these disorders remains a mystery, but the possible causes are intriguing. Patients may experience spontaneous remissions and relapses, but treatment with sulfasalazine or prednisone is usually effective for patients with distressing symptoms.

Subepithelial collagen table thickness in colon specimens from patients with microscopic colitis and collagenous colitis

Microscopic colitis and collagenous colitis are similar conditions that are differentiated by the presence or absence of subepithelial collagen table thickening. To better understand the relationship between these two disorders and the role of collagen table thickening in the pathogenesis of diarrhea, colonic mucosal biopsy specimens from 24 patients with microscopic or collagenous colitis and 9 control subjects were analyzed using a computer-assisted morphometric method to evaluate the average thickness of the subepithelial collagen table. The collagen table thickness in colitis patients taken together formed a multimodal rather than a unimodal distribution. There was no tendency for collagen table thickening to increase with age or with duration of symptoms. In general, the types and distribution of inflammatory cells were similar in patients with normal and thickened collagen tables. Stool weight correlated with lamina propria cellularity but not with collagen table thickening. The multimodal distribution of collagen table thickening and the lack of correlation with age, duration of symptoms, or inflammation suggest that microscopic colitis and collagenous colitis are discrete conditions, although the inflammatory changes in the two conditions are similar. Moreover, because stool weight correlates with lamina propria cellularity but not with collagen table thickening, diarrhea probably is caused by the inflammatory changes and not by collagen table thickening per se.

Collagenous colitis: jejunal and colorectal pathology

AIMS

To determine: (1) whether there is an association between collagenous colitis and coeliac disease or lymphocytic colitis; (2) the distribution of lymphocyte subsets and macrophages in the lamina propria and surface epithelial layer in collagenous colitis; and (3) the colorectal distribution of the disease and whether a mucosal biopsy specimen, using a flexible sigmoidoscope, is sufficient to diagnose it.

METHODS

The clinical data and colorectal biopsy specimens from 38 patients with collagenous colitis were studied. In 10, small bowel biopsy specimens were also available for review. Immunostaining of the mucosal lymphoid infiltrate with a panel of relevant antibodies was carried out on formalin fixed tissue in seven cases; in three the phenotyping was performed on fresh biopsy specimens separately frozen or fixed in B5 solution.

RESULTS

Coeliac disease was found in four out of the 10 patients with collagenous colitis who had had a small bowel biopsy, in contrast to the prevalence of the disease in Australia of 1 in 3000. Collagenous colitis did not respond to gluten withdrawal. Five of 29 (17%) of the patients had a mixed pattern of lymphocytic and collagenous colitis. Immunostaining of the lymphoid infiltrate showed that the striking increase in intraepithelial lymphocytes in collagenous colitis was due to an influx of CD8 positive cells. The occurrence and severity of collagenous colitis along the large bowel were independent of the anatomical site, and in more than 90% of cases biopsy specimens from the sigmoid colon or rectum were diagnostic.

CONCLUSIONS

There is a very high incidence of coeliac disease among patients with collagenous colitis so that jejunal biopsy should be an essential part of their investigations, especially if symptoms persist. However, only a minority showed a mixed pattern of lymphocytic and collagenous colitis. The intraepithelial lymphocytes in collagenous colitis are CD8 positive cells. Collagenous colitis can be diagnosed from rectal or sigmoid colon biopsy specimens in more than 90% of cases.