Most people ask, "What in the world is a liver shunt?" It is a deadly disease

This is a very complex matter but we will try to make this article simple to understand and will try to explain what a shunt is in the easiest way possible.

A portosystemic shunt is an extra pathway between the hepatic venous system and the arterial circulation which needs to have shut down immediately after birth. In the uterus, the foetus is fed via the mother's umbilical vein which leads to the left side of the heart, completely opposite to the normal circulatory route which would mean the venous blood went to the right side of the heart and thence to the lungs to be oxygenated.

To correct this difference, a shunt opens up in the foetus to bypass blood from the left side of the heart into the arterial system. When this shunt does not automatically shut down after birth, the blood supply to the liver is compromised and this leads to poor or non-existent development of the liver.

In young dogs the compromised blood flow will result in abnormal neurological patterns, and failure to thrive in comparison to their siblings. However that is not to say that its siblings won't have the same condition, when it may simply be one or other of the siblings has a shunt that isn't completely closed off.

Diagnosis is confirmed by blood test and liver function tests, which will show compromised liver function, and is also dependent upon behaviour patterning. Depending on the results it is possible to offer surgery to some dogs if they are healthy enough for surgery and the liver is strong enough, and although the surgery is tricky, because success depends on the tension it is possible to close or partly close the shunt with a ligature which will give the dog an extra lease of life. The surgeon will partly close the shunt if the liver has not gained sufficient strength to cope with normal arterial flow, and he will need to take extreme care in ensuring that the partially occluded shunt is wide enough to let arterial blood through and yet narrow enough to avoid damaging the liver with a pressure it's not yet ready for.

Angiography is another possible diagnostic tool, and involves slipping an X-ray opaque tiny-bored catheter into the circulatory system by the shunt to determine its path and patency. Using image intensifier X rays the catheter can be moved and be seen in screen so that the surgeon can see where the occlusions are and where the shunt is.

Where surgery is not performed. in most cases the dog may be able to function properly with only part of a liver but the demands put on it as the dog develops are too much and he will most probably die at around 2 or 3 years old.

signs

Liver Shunts

Signs of portosystemic shunts include poor weight gain, sensitivity to sedatives (especially diazepam), depression, head pressing (pushing the head against a solid object), seizures, weakness, salivation, vomiting, poor appetite, increased drinking and urinating, balance problems and frequent urinary tract disease or early onset of bladder stones. If the signs of problems increase dramatically after eating this is a strong supportive sign of a portosystemic shunt.

Animals that are showing signs of liver disease should have a complete blood count, serum  chemistry screen, and urinalysis performed. If the test results are suggestive of a liver disorder, the animal's bile acids should be measured. Bile acids are considered to be the most sensitive screening test for portosystemic shunts. Two (2) blood samples are drawn, the first after a twelve (12) hour fast, the second sample is drawn 2 hours after a high protein meal. Elevation of bile acids (especially the second sample) is highly suggestive of a portosystemic shunt (rather than any other cause of liver disease). These patients should have the diagnosis of PSS confirmed. Diagnostic tests include radiographs, ultrasonography and intravenous portovenography. Portovenography involves anesthetizing the patient, injecting radio opaque dye intravenously, and taking radiographs of the liver as the dye is circulating through the liver vasculature.

It is possible for surgery to correct the shunt. If the problem is extra hepatic it is quite a simple operation. Veterinarians have had great success with this type. The intra hepatic type of problem is another story. The surgery is quite extensive and usually requires two surgeries and several days in the hospital. The veterinary surgeon first has to go into the liver to find a suitable vein (i.e., large enough) to reconnect. This part of the surgery takes quite a bit of time and current protocol is to find the vein, sew everything back up, let the dog recover for a few days and then go back in and connect the vein. So far only limited success has been achieved with this type of surgery. Management plays a critical role in the long term maintenance of affected animals, regardless of surgical intervention. Either a low-protein diet or a no-protein diet is usually recommended. The results of this are not entirely pleasant. These dogs are never quite 100% healthy. Portosystemic shunts (PSS) are the result of abnormal vascular connections between the portal vein and the systemic circulation. The portal vein should connect the gastrointestinal tract with the liver. Figure 1. is an illustration of correct anatomy.

Correct or normal placement of the portal vein allows blood from the intestinal tract to flow directly to the liver. The liver then performs its function of metabolism and detoxification. The cleansed blood then returns to the heart and is pumped to the rest of the body.

Figure 1. Correct Portal Vein Anatomy

Shunts can be present at birth or acquired later in life as a result of disease process. Approximately 75% of shunts are present at birth. They are the result of anatomical anomalies or failure of fetal vessels to close after birth. Shunts are classified by their location: the extrahepatic shunt is outside the liver and the intrahepatic shunt is inside the liver.

Figure 2. Extrahepatic Shunt             Figure 3. Intrahepatic Shunt

web site that may be of help    http://www.vetinfo4dogs.com/dshunt.html

http://lbah.com/liver.htm http://www.thedca.org/liver-working.html

the article below is a more indepth article regarding puppies, in the womb and after being born

This much-discussed disorder is most commonly the result of improper fetal development of the circulatory system. To thoroughly understand liver shunts, it is important to have an understanding of the development of blood vessels in the fetus. The fetus, through the placenta, umbilical vein and artery, is connected to the mother's circulatory system (bloodstream). Therefore, the liquid portion of the blood of the fetus can move into the mother's bloodstream, but the cells cannot. The mother's liver then performs the important liver functions, such as eliminating wastes, for the fetus. The mother's liver is necessary for this, since the fetal liver is just developing and is not yet capable of many functions including removing metabolic wastes from the fetal bloodstream, storing minerals, and enzyme production. Because the fetal liver is underdeveloped, the fetus possesses blood vessels which transport blood around the developing liver rather than to and through it. This is necessary, since the small developing fetal liver cannot filter or handle the full quantity of blood that needs to be filtered. When the fetus is born, the placenta, umbilical vein and artery (jointly referred to as the umbilical cord) are severed and are no longer functional. Once the umbilical cord is cut at birth, there is no longer this connection between the mother and the just-born puppy. At this point, the puppy must rely on his own liver functions and not that of his mother.

At or about the time of birthing (whelping), the blood vessels within the fetus, which allowed blood to bypass the developing fetal liver, must close. Once these vessels close, the puppy's blood is forced to pass through the puppy's now developed liver. If these fetal vessels fail to close, then blood is allowed to abnormally be shunted around the liver, hence the name liver shunt. When blood is shunted around the liver rather than to and through it, the liver is not able to filter all of the blood, and therefore, toxic metabolic wastes such as ammonia are not adequately removed from the bloodstream. The degree to which blood is shunted around the liver is dependent on the extent to which shunting vessels persist. Liver shunts may be large allowing much blood to bypass the liver, or they may be partially closed allowing only small amounts of blood to shunt around the liver. The extent of blood shunting varies with every dog.

The above information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinary physician for confirmation of any diagnosis. Your pets life may depend on it.

©CHERISTAR POMERANIANS. All rights reserved. No part of this web site may be reproduced without the prior permission of CHERISTAR POMERANIANS. Opinions and views expressed within this website are not necessarily those of CHERISTAR POMERANIANS  Every effort has been made to ensure the accuracy of this website. If there are any errors or you have any comments or suggestions please send details to  us.

Disclaimer:Cheristar Pomeranians is not responsible for any purchases made through the adverts or links shown on this web site. When purchasing a puppy through a breeder who is a member of this site it is your responsibility to ensure that all paperwork etc., is to your satisfaction.