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

Absence of CT-detectable microhepatia cannot reliably exclude primary hypoplasia of the portal vein in dogs.

This retrospective study investigated whether CT-derived liver volume is reduced in dogs with histopathologically confirmed primary hypoplasia of the portal vein (PHPV), a condition associated with microscopic portosystemic shunting and hepatic underdevelopment. Twenty-six dogs with PHPV-compatible histopathology were compared to 121 control dogs without liver disease using allometric regression of log-transformed liver volume on log-transformed body weight. A critical limitation was the substantial body weight disparity between groups (median 2.13 kg vs. 38.0 kg), as affected dogs were predominantly small breeds. After allometric adjustment, the geometric mean ratio for liver volume in PHPV-affected dogs versus controls was 0.887 (95% CI, 0.751–1.047; P = .156), indicating no statistically significant reduction. A body weight-restricted sensitivity analysis yielded similar results (0.923; 95% CI, 0.769–1.107; P = .377). Noncontrast hepatic attenuation did not differ significantly between groups, and qualitative CT abnormalities were uncommon in PHPV dogs. The authors caution that the lack of closely body weight-matched controls limits interpretive confidence. Clinically, these findings suggest that the absence of CT-detectable microhepatia should not be used to exclude PHPV. CT volumetry must be interpreted in conjunction with body size, vascular imaging, clinical signs, and histopathology. This study underscores the diagnostic complexity of PHPV and highlights the need for well-matched control populations in future imaging studies evaluating hepatic size in small-breed dogs.

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