Anatomy of Extrahepatic Portosystemic Shunts in Dogs as Determined by Computed Tomography Angiography

Abstract

Congenital extrahepatic portosystemic shunts are anomalous vessels joining portal and systemic venous circulation. These shunts are often diagnosed sonographically, but computed tomography (CT) angiography produces high-resolution images that give a more comprehensive overview of the abnormal portal anatomy. CT angiography was performed on 25 dogs subsequently proven to have an extrahepatic portosystemic shunt. The anatomy of each shunt and portal tributary vessels was assessed. Three-dimensional images of each shunt type were created to aid understanding of shunt morphology. Maximal diameter of the extrahepatic portosystemic shunt and portal vein cranial and caudal to shunt origin was measured. Six general shunt types were identified: splenocaval, splenoazygos, splenophrenic, right gastric-caval, right gastric-caval with a caudal shunt loop, and right gastric-azygos with a caudal shunt loop. Slight variations of tributary vessels were seen within some shunt classes, but were likely clinically insignificant. Two shunt types had large anastomosing loops whose identification would be important if surgical correction were attempted. A portal vein could not be identified cranial to the shunt origin in two dogs. In conclusion, CT angiography provides an excellent overview of extrahepatic portosystemic shunt anatomy, including small tributary vessels and loops. With minor variations, most canine extrahepatic portosystemic shunts will likely be one of six general morphologies.

Surgical correction of a splenophrenic shunt in a dog: a case report

“…In this earlier study, an extrahepatic portosystemic shunt, draining into the caudal vena cava cranial to the phrenicoabdominal vein and caudal to the liver was the most common type, occurring in approximately 48% of all extrahepatic portosystemic shunt cases, followed by the shunt type, which drained into the azygos vein (36%) (Nelson and Nelson 2011). The type, which drained into the caudal vena cava cranial to the liver along the diaphragm, occurred least often, in 16% of cases (Nelson and Nelson 2011). In embryology, congenial extrahepatic portosystemic shunts are believed to result from abnormal communications between the vitelline and cardinal venous systems (Broome et al 2004).…”

“…Extrahepatic shunts are typically single vessels and arise from the portal vein or a major tributary including left gastric, gastroduodenal, splenic, cranial mesenteric, and caudal mesenteric veins, and drain into the caudal vena cava cranial to the phrenicoabdominal vein (Tobias 2003;Mehl et al 2005). In a report from 2011, six general conformations of an extrahepatic portosystemic shunt were identified using CTA: a splenocaval shunt arising from the splenic vein and terminating in the caudal vena cava caudal to the liver, a splenophrenic shunt arising from the splenic vein and terminating in the caudal vena cava cranial to the liver along the diaphragm, a splenoazygos shunt arising from the splenic vein and terminating in the azygos vein, a right gastric caval shunt extending along the lesser curvature of the stomach and inserting on the caudal vena cava, a right gastric azygos shunt with a caudal loop arising from the gastroduodenal vein and terminating in the azygos vein, and a right gastric caval shunt with a caudal loop extending from the gastroduodenal vein and terminating in the caudal vena cava (Nelson and Nelson 2011). In this earlier study, an extrahepatic portosystemic shunt, draining into the caudal vena cava cranial to the phrenicoabdominal vein and caudal to the liver was the most common type, occurring in approximately 48% of all extrahepatic portosystemic shunt cases, followed by the shunt type, which drained into the azygos vein (36%) (Nelson and Nelson 2011).…”

“…Treatments usually include medical therapy to stabilise the patients, followed by surgical attenuation of the anomalous vessel (Broome et al 2004;Doran et al 2008;Worley and Holt 2008). Although a study of the anatomy of different types of extrahepatic portosystemic shunts has been reported in dogs, to the authors' knowledge, there is a lack of information on clinical presentation, treatment, and postoperative results in a specific type of extrahepatic portosystemic shunt, such as a splenophrenic shunt (Nelson and Nelson 2011). The purpose of this case report was to describe the clinical presentation, diagnosis, and successful surgical management of a splenophrenic shunt in a dog.…”

“…Extrahepatic portosystemic shunts are mostly portocaval, originating from the portal vein and draining into the caudal vena cava, followed by portoazygos, branching from the portal vein to the azygos or left hemiazygos vein (Broome et al 2004;Windsor 2007). Extrahepatic portosystemic shunts can be characterised into different types such as splenocaval, splenophrenic, splenoazygos, double right gastric azygos, right gastric caval, and double right gastric caval, depending on exact shunt location or morphology (Nelson and Nelson 2011). Treatments usually include medical therapy to stabilise the patients, followed by surgical attenuation of the anomalous vessel (Broome et al 2004;Doran et al 2008;Worley and Holt 2008).…”

Unusual haemodynamics in two dogs and two cats with portosystemic shunt - implications for distinguishing between congenital and acquired conditions

“…Abnormal venous porto-caval connections are widely described in small animal veterinary literature, with majority of cases reported in dogs (Lamb, 1996;Bertolini et al, 2006;Bertolini, 2010aBertolini, , 2010bBruehschwein et al, 2010;Nelson and Nelson, 2011;Fukushima et al, 2014). These vascular anomalies are divided in two main categories according to their origin: congenital PSS (CPSS) deriving from embryogenetic errors in the development of vitelline and cardinal venous systems (Ferrell et al, 2003), and acquired PSS (APSS) deriving from recanalization of pre-existing, vestigial embryonic vascular connections between portal and caval systems as a consequence of portal hypertension (PH) (Fossum, 2002;Szatmari et al, 2004;Bertolini, 2010a).…”