Multiple acquired portosystemic shunts (MAPSS) in dogs due to portal hypertension are not necessarily accompanied by hepatofugal flow in the normal tributaries of the portal vein
This is an issue I used to wonder about. When you see acquired shunts running, for example, from splenic to left renal veins….should flow in the gastrosplenic vein also be hepatofugal? That is, does blood flowing down the mesenteric vein from the guts continue into the main portal vein or does it all get diverted into the splenic vein?
I think the answer to that question depends on the severity of portal hypertension.
In this dog, below, all of the portal vein tributaries are somewhat dilated: reflecting portal hypertension but flow in all of the tributaries in close approximation (gastroduodenal and its tributary R gastric veins; gastrosplenic and its tributary L gastric) remains hepatopetal.
Tortuous shunt vessels alongside the caudal cava
The cranial part of the portal vein as seen from the right side: flow in the R gastric vein runs up into the gastroduodenal and thence into the portal vein.
The caudal part of the portal vein as seen from the right side. Flow in the gastrosplenic vein remains hepatopetal (into the portal vein) despite the fact that there is shunting from the splenic vein into the left renal vein in addition.
In other dogs with MAPSS, gastrosplenic vein flow is hepatofugal.
View of the cava at the level of the entry of the L renal vein: as seen from the right side. A shunt vessel joins the L renal vein just before it enters the cava (typical morphology for splenic-to-L-renal shunt via the remnant of the testicular/ovarian vein)
In this dog it appears that almost all the blood flowing down the mesenteric vein is diverted as hepatofugal flow through the gastrosplenic vein. Indeed flow in the main portal vein (originating from the gastroduodenal vein) is also hepatofugal.
