Ability of ultrasonography to predict the presence and location of histologic lesions in the small intestine of cats

BACKGROUND: Diagnosis of infiltrative small intestinal (SI) disease in cats is challenging, and debate continues regarding optimal biopsy techniques. Ultrasonography may facilitate selection of biopsy type and location. HYPOTHESIS/OBJECTIVES: Assess ability of ultrasonography to predict histologic lesions by SI segment and tissue layer. ANIMALS: One‐hundred sixty‐nine cats that had abdominal ultrasonography and full‐thickness SI biopsies performed. METHODS: Ultrasonographic images and full‐thickness biopsy samples were retrospectively reviewed, and each SI wall layer evaluated for lesions according to published standards. RESULTS: Ultrasonographic SI lesions were present in 132 cats (63 duodenum; 115 jejunum; 71 ileum). Samples were obtained at laparotomy (60) or necropsy (109). Ultrasonographic abnormalities had high positive predictive value (PPV) for histologic lesions (duodenum, 82.0%; 95% confidence interval [CI], 68.6‐91.4; jejunum, 91.0%; 95% CI, 81.5‐96.6; ileum, 88.1%; 95% CI, 74.4‐96.0), but poor negative predictive value (duodenum, 27.1%; 95% CI, 17.2‐39.1; jejunum, 27.3%; 95% CI, 10.7‐50.2; ileum, 40.4%; 95% CI, 26.4‐55.7). The ability of ultrasonography to predict histologic lesions in this population, which had high disease prevalence (SI histologic lesions in 78.1% of cats) was high for mucosal lesions (PPV, 72.7%‐100%) but low for submucosal or muscularis lesions (PPV, 18.9%‐57.1%). CONCLUSIONS AND CLINICAL IMPORTANCE: In a population with high disease prevalence, most cats with SI mucosal ultrasonographic lesions will have mucosal histologic lesions. Small intestinal submucosal and muscularis ultrasonographic lesions are not predictive of histologic disease in those layers, suggesting that full‐thickness biopsy may not be essential in these cats. Ultrasonography may help guide decisions about biopsy type in individual cats.