Computed tomography-derived liver volume is not detectably lower in dogs with histopathologic findings compatible with primary hypoplasia of the portal vein.

OBJECTIVE: To compare CT-derived liver volume and noncontrast attenuation variables between dogs with histopathologic findings compatible with primary hypoplasia of the portal vein (PHPV) and dogs without liver disease. METHODS: Medical records were retrospectively reviewed for dogs with abdominal CT and liver histopathology compatible with PHPV. Controls were 121 dogs without liver disease from a published CT reference cohort and were not matched by breed, age, sex, or body weight. Liver volume was evaluated with allometric regression of log-transformed liver volume on log-transformed body weight and group. A body weight-restricted sensitivity analysis was performed. RESULTS: 26 dogs with PHPV-compatible histopathology and 121 controls were analyzed. Affected dogs were substantially lighter than controls (median body weight, 2.13 vs 38.0 kg). In the primary allometric model, the adjusted geometric mean ratio for liver volume in affected dogs versus controls was 0.887 (95% CI, 0.751 to 1.047; P = .156). The body weight-restricted sensitivity analysis was similar (0.923; 95% CI, 0.769 to 1.107; P = .377). Noncontrast hepatic attenuation did not differ significantly between groups, and qualitative CT abnormalities were uncommon. CONCLUSIONS: After allometric adjustment, CT-derived liver volume was not detectably lower in dogs with PHPV-compatible histopathology. This finding should be interpreted cautiously because groups differed substantially in body weight and closely body weight-matched controls were unavailable. CLINICAL RELEVANCE: These findings do not support using absence of CT-detectable microhepatia to exclude PHPV. Computed tomography volumetry should be interpreted with body size, vascular imaging, clinical findings, and histopathology, especially when controls are not closely matched by body weight.