Ultrasonographic appearance of the major duodenal papilla in dogs without evidence of hepatobiliary, pancreatic, or gastrointestinal tract disease

OBJECTIVE To determine the ultrasonographic appearance of the major duodenal papilla (MDP) in dogs without evidence of hepatobiliary, pancreatic, or gastrointestinal tract disease.ANIMALS 40 adult client-owned dogs examined because of conditions that did not include hepatobiliary, pancreatic, or gastrointestinal tract disease. PROCEDURES Ultrasonographic examination of the MDP was performed. Each MDP was measured in 3 planes. Intraobserver reliability of measurements was determined, and associations between MDP dimensions and characteristics of the dogs were investigated. Histologic examination of longitudinal sections of the MDP was performed for 1 dog to compare the ultrasonographic and histologic appearance. RESULTS The MDP appeared as a layered structure with a hyperechoic outer layer, hypoechoic middle layer, and hyperechoic inner layer that corresponded to the duodenal serosa, duodenal muscularis, and duodenal submucosa, respectively. Layers visible during ultrasonographic examinations were consistent with layers identified histologically. Intraobserver reliability was substantial for each plane of measurement. Mean ± SD length, width, and height of the MDP were 15.2 ± 3.5 mm, 6.3 ± 1.6 mm, and 4.3 ± 1.0 mm, respectively. An increase in body weight of dogs was significantly associated with increased values for all measurements. CONCLUSIONS AND CLINICAL RELEVANCE The ultrasonographic appearance and approximate dimensions of the MDP of dogs without evidence of hepatobiliary, pancreatic, or gastrointestinal tract disease were determined. Additional studies are needed to evaluate possible ultrasonographic lesions of the MDP in dogs with hepatobiliary, pancreatic, or intestinal diseases and to investigate clinical implications of these lesions with regard to diagnosis and prognosis.