Projection-Dependent Variability of Intestinal Diameter Measurements Between Right Lateral and Ventrodorsal Abdominal Radiographs in Dogs

Abdominal radiography is widely used for evaluating gastrointestinal disease in dogs, and intestinal diameter measurements play a key role in differentiating ileus, obstruction, and colonic distension. This study aimed to determine whether small and large intestinal diameter measurements differ between right lateral (RL) and ventrodorsal (VD) abdominal radiographs in dogs. Thirty-four client-owned dogs presenting with gastrointestinal signs underwent orthogonal abdominal radiography. Minimum, mean, and maximum diameters of the small and large intestines were measured on both projections. Wilcoxon signed-rank test, Bland–Altman analysis and Passing–Bablok regression were used to evaluate differences and agreement between projections. No significant differences were identified between RL and VD projections for small intestinal diameters (p > .05), and agreement analyses demonstrated minimal bias with narrow limits of agreement, indicating projection independence. In contrast, large intestinal diameters were significantly greater on VD projections (p < .05) and showed consistent negative bias on RL views, reflecting predictable projection-dependent variation. Despite this positional effect, linear relationships between projections remained preserved. These findings indicate that small intestinal diameter measurements are interchangeable between projections, whereas large intestinal measurements are influenced by patient positioning. Awareness of projection-related variability may improve interpretation and standardization of abdominal radiographic assessment in dogs with gastrointestinal disease