A grading system for lymphocytic plasmacytic colitis in dogs.

Colonic mucosal samples were obtained every 4 weeks for 13 months from 6 clinically normal dogs and from 47 dogs with a clinical diagnosis of chronic inflammatory bowel disease. All samples were graded on a scale of 0-5, based upon the quantity of lymphocytes and plasma cells in the lamina propria, epithelial changes, and the presence of ulcers and erosions. A grade of less than or equal to 2.0 was considered normal and was assigned to 77 of 78 samples from clinically normal dogs and 28 of 48 samples from dogs with diarrhea. A transient increase in cellularity was noted in 1 sample from 1 control dog. Nineteen dogs with clinical disease had obvious histologic abnormalities. The grading scheme described provides the pathologist with an objective criterion for the microscopic evaluation of colonic mucosal samples obtained by endoscopic techniques and offers clinicians a method of assessing the dog's progress and response to therapy.