Comparison of^99mTcO₄⁻Trans‐Splenic Portal Scintigraphy with Per‐Rectal Portal Scintigraphy for Diagnosis of Portosystemic Shunts in Dogs

Abstract

TSPS provides information about shunt number and location, which allows improved surgical planning. Because it requires significantly less radionuclide, TSPS improves safety, allows for more comprehensive patient care, and earlier surgical intervention.

Determination of Porto‐Azygos Shunt Anatomy in Dogs by Computed Tomography Angiography

“…Based on Poiseuille's law, there might be more resistance to blood flow in porto‐azygos shunts than in porto‐caval shunts, since the diameter of the azygos vein is smaller than that of the caudal vena cava . Moreover, porto‐azygos shunts can be partially compressed by the diaphragm during respiration and by gastric distension after eating, which can result in temporary improved hepatic perfusion through the normal portal vasculature . Furthermore, the blood that flows through a porto‐azygos shunt that inserts in the thorax, could be assumed to travel a greater distance than through most porto‐caval shunts, adding to the resistance of the flow .…”

Distribution of extrahepatic congenital portosystemic shunt morphology in predisposed dog breeds

“…In porto-azygous shunts, probably less blood bypasses the liver in comparison with portocaval shunts, because the receiving azygos vein has a smaller diameter and therefore more resistance than the abdominal vena cava. Another explanation reported for the later onset of clinical signs in these dogs could be that respiration causes diaphragmatic compression during which the shunt is intermittently closed [16]. Therefore it can be expected that liver functions are better and hepatic encephalopathy less pronounced in dogs with porto-azygous shunts.…”

“…In general, dogs with porto-azygous shunts show milder clinical signs [16]. It is not known whether these different shunt types (portocaval and port-azygos) have a different genetic background.…”

“…Based on the higher number of portocaval shunts (89%) compared to porto-azygous shunts reported in previous studies [8], an increased amount of portocaval shunts is to be expected in our study. The milder clinical signs in dogs with a porto-azygous shunt [16] could cause a later onset of clinical signs. Therefore we could expect a later age at diagnosis of dogs with this type of shunt within our study population.…”

Insight into congenital absence of the portal vein: Is it rare?

“…Conventional angiography is not good for children, although it is fairly safe [49,110] . Rectal portal scintigraphy plays an important part in suspected abnormalities of portal circulation and is precise to quantitate portosystemic shunts and valuable for clinical diagnosis [111] . During performing this kind of examination, shunt indexes (SI) are calculated, relative portal hemodynamics can be observed noninvasively, and portal collateral circulation can be detected as well [112] .…”