When Liver Looks Like Lung: A CT Perspective on Rare Diaphragmatic Hernias in Dogs

Radiographic and Computed Tomographic Features of Caval Foramen Hernias of the Liver in 7 Dogs: Mimicking Lung Nodules

Jaehwan Kim, Soyoung Kim, Jieun Jo, Seungjun Lee, Kidong Eom

Background
Caval foramen hernias are a rare subtype of diaphragmatic hernias where the liver herniates through the caval foramen at the central tendon of the diaphragm. These hernias can compress adjacent thoracic structures, such as the caudal vena cava (CVC), and are rarely reported or characterized in veterinary literature. Misdiagnoses as lung or thoracic masses are common due to their imaging resemblance, necessitating clearer diagnostic criteria.

Methods
This retrospective study reviewed medical records and CT images of 7 dogs from three veterinary centers diagnosed with caval foramen hernias between 2012 and 2015. CT scans were performed under anesthesia using standard protocols. Radiographs and CT images were assessed by radiologists for hernia characteristics, including defect size, involved liver lobe, CVC compression, hepatic vein dilation, and biliary involvement.

Results
Radiographically, 6 of 7 dogs showed dome-shaped, broad-based caudal mediastinal lesions suggestive of masses. CT revealed right lateral liver lobe herniation in 6 dogs and right medial in 1, with all cases showing CVC compression. Hepatic vein dilation was seen in 5 dogs, and biliary tract involvement in 1. Most hernias were partial, but one case involved complete liver lobe herniation. Defect sizes ranged between 8.8–17.1 mm. Hernias often mimicked pulmonary nodules, leading to initial misdiagnosis in 4 dogs.

Limitations
The small sample size limits generalizability and statistical analysis. Most dogs were senior and asymptomatic, complicating the assessment of clinical relevance. Lack of hemodynamic data and surgical/histological confirmation in most cases also limits the evaluation of clinical impact. Only one dog underwent surgery, and no long-term follow-up data were available.

Conclusions
Caval foramen hernias, though rare, should be considered in the differential diagnosis for dome-shaped caudal thoracic lesions on lateral radiographs, particularly in small-breed dogs. CT is essential for accurate diagnosis and surgical planning, as hernias can compress the CVC and lead to complications such as hepatic vein congestion or Budd-Chiari-like syndrome, even when small. Greater awareness and more case documentation are needed to better define the clinical implications.

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