Concordance of the Histopathologic Diagnosis of Concurrent Duodenal and Ileal Biopsy Specimens in Dogs

SIMPLE SUMMARY: Canine chronic inflammatory enteropathy (CIE) is a gastrointestinal (GI) inflammatory condition that requires histopathology of intestinal biopsies for definitive diagnosis. This can be performed endoscopically or surgically; with the former being more common as it is less invasive. In recent years, research has identified that different types of inflammatory disease and histologic severity can exist at different locations within the GI tract, known as discordance. There is a lack of understanding of the clinical impact of lesion oversight in dogs with discordant biopsies between locations. Therefore, current recommendations are to procure endoscopic biopsies from both the upper intestinal (stomach and duodenum) and lower small intestinal tract (ileum) when possible. The rate of discordance between different GI locations has not been assessed in dogs with non-inflammatory enteropathies, i.e., neoplastic etiology, nor compared between endoscopic and surgically collected biopsy specimens. Here, we report that the rate of discordance between the duodenum and ileum in CIE is similar between endoscopic biopsy and surgical biopsy specimens and confirm that discordance between upper and lower GI biopsies exist for small-cell lymphoma. There were no clinicopathologic variables that were correlated with discordance. We conclude that for all dogs with chronic GI signs, concurrent duodenal and ileal biopsies should be performed. ABSTRACT: Histopathologic discordance between gastrointestinal (GI) locations in canine chronic inflammatory enteropathy (CIE) has prompted recommendations to biopsy both the duodenum and ileum, while further evaluation is required for non-CIE. We aimed to determine the concordance of histopathologic diagnosis between duodenal and ileal endoscopic or full-thickness biopsy specimens for all dogs with CIE and GI neoplasia and to assess the association between histopathologic discordance between GI locations with clinicopathologic variables. Seventy-nine dogs were eligible, with endoscopic (74) or full-thickness (5) biopsy specimens. Clinicopathological data were recorded for all dogs. Concordance of histopathologic diagnosis was retrospectively assessed for concurrent duodenal and ileal biopsy specimens by a single board-certified veterinary pathologist using the modified World Small Animal Veterinary Association (WSAVA) Gastrointestinal Standardization Group guidelines. Sixty-seven dogs were diagnosed with CIE and 5 with enteric-associated T-cell lymphoma-2 (EATL-2). Concordance of histologic diagnosis between duodenal and ileal sites was similar between endoscopic (73.0%) and full-thickness (80.0%) biopsy groups. For the CIE cases, lymphoplasmacytic enteritis had the highest concordance (73.0%) and eosinophilic enteritis the least (16.7%). Of the 5 neoplastic cases, 5/5 (100%) were present at the duodenum but only 3/5 (60%) in the ileum. No clinicopathologic variables demonstrated a statistically significant association with discordance. We conclude that the level of discordance necessitates concurrent biopsy of both duodenum and ileum in all dogs with chronic GI signs. The rate of EATL-2 was lower than rates reported for cats.