Congenital interruption of the caudal vena cava in a Bulldog with diversion of flow into the azygous vein

The patient, a neutered female adult Bulldog of unknown exact age was presented for investigation of skin problems, keratoconjunctivitis and lethargy.  As part of the investigation routine abdominal ultrasonography was performed.  However, routine things are not always routine……

The caudal vena cava is…….unusual…..

Following the cava forwards things become more bizarre:

Flow from the cava is diverted through a much smaller shunt vessel which courses dorsally towards the azygous vein.

This phenomenon is not unknown:

Congenital interruption of the portal vein and caudal vena cava in dogs: six case reports and a review of the literature.

https://www.ncbi.nlm.nih.gov/pubmed/9605232

Although, in human medicine, this anomaly is associated with increased risk of deep vein thrombosis, in dogs it appears to be exclusively an incidental finding.

The present dog also exhibits a double vena cava caudal to the renal veins: not uncommon in cats but less frequent in dogs.