AbstractBackgroundIntestinal fibrosis (IF) is commonly identified on histopathology of intestinal biopsy specimens (IBSp) from cats with chronic inflammatory enteropathy (CIE) however, its clinical relevance is unknown.ObjectivesCharacterize and determine the clinical relevance of IF in cats with CIE.AnimalsSixty‐five client‐owned cats diagnosed with CIE after gastrointestinal histopathology from a single referral hospital in the United Kingdom.MethodsMedical records were retrospectively searched for cases of CIE on the basis of histopathology of IBSp. The IBSp from eligible cats were re‐reviewed by a single board‐certified veterinary pathologist for inclusion. Masson's trichrome (MT) stain and immunohistochemical labeling using antivimentin and anticollagen I antibodies to identify IF. For each case, various variables at the time of diagnostic investigation were recorded and referring veterinarians were contacted for follow‐up information.ResultsMucosal fibrosis was identified in 51% of duodenal and 76% of colonic hematoxylin and eosin (HE)‐stained IBSp. Vimentin labeling and MT staining identified additional cases of IF in 65% and 58% of the duodenal biopsy specimens, respectively. Vimentin labeling detected IF in 79% of the colonic biopsy specimens. Positive vimentin labeling and MT staining of the colonic mucosa were associated with decreased likelihood of attaining clinical remission and increased risk of death because of CIE (P< .05).Conclusions and Clinical ImportanceAdditional stains at initial histopathologic examination of IBSp allow for better identification of IF compared to routine HE staining. Identification of IF in colonic biopsy specimens by vimentin immunolabeling and MT staining may provide prognostic information in cats with CIE.