Summary of the mucosal abnormalities associated with collagenous colitis.
Microscopic colitis (MC) are clinical pathologic entities characterized by secretory-like aqueous chronic diarrhea, in its large majority without hematochezia. From the first descriptions of MC, normal endoscopic and radiological findings have been a pathognomonic feature. It is thought that up to 20% of adults with chronic diarrhea who have an endoscopically normal colonoscopy may have MC.
Most common MC are collagenous colitis and lymphocytic colitis. They are two morphologically distinct entities of MC. They are similar in presentation but differ histologically. Endoscopic biopsy is required for the diagnosis of MC. As there are usually no mucosal abnormalities, the biopsies taken must be random. However, several authors have described different mucosal abnormalities related to the MC, most of them related to collagenous colitis.
Our aims were to review the medical literature and to describe the mucosal patterns and mucosal abnormalities that have been associated with the microscopic colitis, especially those related to the collagenous colitis.
A MEDLINE search (1966-December 2010), was done using the terms "Colitis, Microscopic"[Mesh] or "Colitis, Collagenous"[Mesh] or "Colitis, Lymphocytic"[Mesh] and "Endoscopy, Digestive System"[Mesh] or "Endoscopy, Gastrointestinal"[Mesh] or "Colonoscopy"[Mesh] to find relevant articles. The search was carried out without restrictions or limits. The selection process of the articles was done independently by both authors. Agreement was measured using kappa coefficient (k). First, relevant studies were selected by the title (k 0.80, CI95% 0.63-0.97) and differences were resolved by consensus. Then, the fulltexts of selected articles were read.
2. Role of endoscopy in microscopic colitis
Endoscopy is essential for the diagnosis of microscopic colitis. The diagnosis of microscopic colitis is based on mucosal biopsies taken during colonoscopy at the appropriate sites. It is essential to take colonic biopsies when endoscopic examinations are carried out in the clinical context of chronic diarrhea, even if the functional nature of the diarrhea is suspected. By definition, the colonic mucosa has an endoscopically normal appearance in microscopic colitis. However, some authors have reported endoscopic abnormalities and mucosal patterns in patients with MC (see below).
2.1. Colorectal biopsy samples: where and how much?
Histological abnormalities in MC are generally pancolonic as they can be distributed throughout the colon as well as limited to the right colon. In collagenous colitis, thickening of the subepitelial collagen band is in some cases more marked in the proximal colon than in the distal colon. The two endoscopically normal sites in which biopsies should be taken for optimal diagnosis of MC are the ascending colon and the sigmoid colon. Three to four biopsies should be taken per site.
3. Mucosal patterns and mucosal lesions associated to microscopic colitis
In the colonoscopy, the colonic mucosa has usually a normal aspect or it can present minimum and unspecific abnormalities such as erythema patches, edema or alterations in the vascular pattern.
In our search, we found several case reports and case series of endoscopic findings that would suggest the presence of this type of colitis, most of the findings related to collagenous colitis. In Table 1 there is a summary of the different endoscopic manifestations of the collagenous colitis and the authors of these findings.
|Richieri ||mucosal tears|
|Katsinelos ||multiple red spots|
|Sato ||spindle network pattern|
|Cruz−Correa ||mucosal tears|
|Buchman ||pseudomembranous collagenous colitis|
|Koulaouzidis ||mucosal tears and scars|
|Tysk ||mucosal tears, longitudinal mucosal lacerations|
|Smith ||mucosal tears on insufflattion, colonic perforation|
|Allende ||bleeding linear ulcers, colonic perforations|
|Hashimoto ||linear ulcers, scar−like areas; crowded vascularity of the colonic mucosa and dilated, circling or winding blood capillaries|
|Dunzendorfer ||mucosal tears|
|Umeno ||linear mucosal defects|
|Couto ||scars; mucosal tears, superficial lacerations or ‘‘cat scratches’’ enhanced with air insufflation during colonoscopy|
|Hashimoto ||mucosa similar to ischemic colitis|
|Cimmino ||colorectal mosaic pattern|
|Nomura ||linear mucosal defects|
3.1. Mucosal tears
Mucosal tears were the most frequent endoscopic findings in our search. The terms “linear mucosal defects” have been used by several authors to describe mucosal tears and sharp longitudinal ulcers (characteristic colonoscopic findings in patients with collagenous colitis).
In 2006, Koulaouzidis
In the same year, Curl Tysk
In 2008, Hashimoto
In 2009, Couto
3.1.1. Drugs associated with mucosal tears
3.1.2. Risk of colonic perforation in patients with collagenous colitis
Several authors have suggested that patients with collagenous colitis have an increased risk of colonic perforation during the colonoscopy procedure. Most of them agree that the mucosal tears might be the initial lesion of the perforations.
In 2010, Hussain
3.2. Other mucosal abnormalities
In 1997, Katsinelos
In 1998, Sato
In 2004, Alan Lewis Buchman
In 2008, Hashimoto
In 2009, Hashimoto
In 2010, Cimmino
4. The future of endoscopy in microscopic colitis
Endomicroscopy is a newly developed endoscopic modality, which allows in vivo microscopy of the mucosal layer in about 1000-times magnification with subcellular resolution during ongoing gastrointestinal endoscopy. This technique enables subsurface imaging of living tissue during ongoing endoscopy and allows confocal microscopy in addition to standard video endoscopy.
The term microscopic colitis includes the collagenous colitis and the lymphocitic colitis, both entities are characterized by chronic diarrhea and normal colonoscopy, and the diagnosis is confirmed by biopsies taken at random. In recent years, abnormalities in the mucosa, mainly related with collagenous colitis, have been described. In Table 1 we summaries the mucosal patterns and the endoscopic manifestations which have been associated with collagenous colitis. Most of the reports mentioned the mucosal tears as the most frequent abnormality. Scars following mucosal lacerations were also a frequent finding. The risk of colonic perforations seems to be slightly higher in patients with collagenous colitis during colonoscopy. The main reason appears to be the lacerations done during air insufflations in the procedure. Other endoscopics findings were blood vessels alterations, pseudomembranes and mosaic pattern.
Several mucosal patterns and mucosal abnormalities have been reported in association with collagenous colitis. Knowledge of these endoscopic manifestations of the collagenous colitis could help to a better understanding of this disease and to target the colonic biopsies.
We want to thank Dr. Curl Tysk, Dr. Eiki Nomura and Dr. Alan Lewis Buchman for providing us the pictures and photos of their endoscopic findings. They have been very kind.