Portosystemic Shunts
A portosystemic shunt is the
most common congenital liver anomaly. This condition is known also,
as a portacaval shunt and portosystemic vascular shunt. Most often
this condition is the result of blood flowing through the portal vein directly
into the systemic vascular system; bypassing the liver.
This bypass of the liver,
is a normal condition during fetal development. The bypass should,
however, close off shortly after birth.
Alternately a shunt can
occur by the vein passing through the liver without allowing blood to flow
into the organ.
The liver serves numerous
functions which include: participation in carbohydrate, fat and protein
metabolism; temperature regulation, circulatory regulation, the detoxification
and excretion of unneeded substances, storage of nutrients, and certain
body defense activities.
As a normal part of the
digestive process, a dog's intestines are bathed in blood. The blood
absorbs the proteins, minerals and their by-products (ammonia being one).
This laden blood is carried by the portal vein to the liver. Within
the liver the blood is detoxified and sent to the vena cava, which then
carries the blood to the heart, and onward via the circulatory system.
In the case of a dog with
a portosystemic shunt; a portion or all (depending on severity of the defect)
of the blood does not go through detoxification. The result is a
poisoning of the body's tissues and cells. This poisoning can impact
the body in numerous ways, ranging from poor weight gain, excessive sleepiness,
vomiting, blindness, and/or seizures - to name only a few possible presentations
of this condition.
There are several tools
available to the veterinarian to aid in the diagnosis of this condition.
Among these tools is urine analysis by cystocentisis, x-rays, ultrasound
and rectal portal scintigraphy.
Care of a portosystemic
shunt can only be through surgery. Dependent upon the severity, location
of the shunt, and health of the liver; surgical success varies from case
to case.
Medical management is available
in the event of inoperable shunts. Long-term medical management can
be difficult, expensive, and impractical. Again, the prognosis has
to be evaluated case by case.
Success in the treatment
of portosystemic shunts relies heavily upon early diagnosis, and immediate
treatment.
Through responsible breeding,
it is hoped, that this condition can be drastically reduced; with the ultimate
goal of elimination within a bloodline.
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