CT vs. Ultrasound in Diagnosing Canine Biliary Disease: Which Wins?

Comparison of Abdominal Computed Tomography to Ultrasonography in the Diagnosis of Biliary Disease in Dogs with Acute Abdominal Signs

Shanna M. Marroquin, Alison M. Lee, Marc A. Seitz, Robert W. Wills, Kimberly Ann Woodruff

Background
Biliary diseases in dogs, although relatively uncommon, can be life-threatening and present with nonspecific clinical signs such as vomiting, anorexia, jaundice, and abdominal pain. Imaging is critical for timely diagnosis and treatment planning. While ultrasonography (US) has traditionally been the preferred imaging modality due to its accessibility and cost, it has limitations such as operator dependency and limited visibility in some patients. Computed tomography (CT) offers potential advantages including improved visualization and reproducibility, but its comparative diagnostic value for biliary diseases in dogs had not been fully investigated.

Methods
This prospective, observational study evaluated 35 client-owned dogs presenting with acute abdominal signs and suspected biliary disease. All dogs underwent both abdominal US and dual-phase contrast-enhanced abdominal CT within 24 hours. The imaging studies were interpreted by two blinded reviewers using standardized protocols. Final clinical diagnoses were established based on comprehensive clinical data, imaging, cytology, and histopathology when available. Agreement between imaging modalities and final diagnoses was assessed using intraclass correlation coefficients (ICCs) and logistic regression analysis.

Results
Out of 35 dogs, 28 had confirmed biliary disease. CT demonstrated a higher diagnostic accuracy (97.1%) compared to US (82.9%). CT identified all cases of cholelithiasis, while US missed 8 of them. Both modalities equally identified gallbladder mucoceles and a gallbladder wall mass with perfect agreement (ICC = 1.0). Moderate to good agreement was observed for cholecystitis and gallbladder wall edema. US struggled with common bile duct visualization, identifying it in only 51.4% of cases compared to 100% with CT. CT also detected more intrahepatic bile duct dilations and choleliths, especially small or mineralized ones.

Limitations
The study's small sample size limits generalizability, and not all patients underwent histopathologic confirmation. There were minor procedural inconsistencies, including variations in sedation and timing between imaging modalities. Additionally, some ultrasound exams were incomplete or of suboptimal quality, and bile was not sampled in all cases, which may have led to underdiagnosis of certain conditions.

Conclusions
CT and US both show good diagnostic performance for biliary disease in dogs with acute abdominal signs. CT may serve as a suitable alternative to US, especially when rapid imaging is needed or sonographic expertise is unavailable. CT is particularly superior in identifying cholelithiasis and visualizing biliary ductal structures. These findings support broader integration of CT into emergency diagnostics for canine biliary disease.

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