The aim of this study was to assess the degree of correlation between the intensity of clinical symptoms and the macroscopic and histopathological evaluation of the small intestinal mucous membrane in dogs. The results point to a statistically significant correlation between the values of the CIBDAI index and the histopathological assessment of the duodenum mucous membrane in patients with minor and moderate intensity of the disease. The lowest correlation coefficient was obtained for the indicator comparing macroscopic and histopathological evaluations. A positive correlation between the CIBDAI score and the histopathological index offers a base for applying it in the monitoring and treatment of mild, moderate and severe cases of canine inflammatory bowel disease.