Sharon A. Center, DVM
Diplomate - American College of
Veterinary Internal Medicine
Professor of Medicine
Donations
Biewer Yorkshire Terrier National Club feels not only should we be taking an active role in the Liver Shunt Study that Dr. Centers is heading, but BYTNC feels that we should be taking an active role in raising funds for this research as well. We will be hosting various fundraisers, auctions and taking donations. Please watch our news page for upcoming events if you would like to participate or you can make your donations with donation button provided below. There is never a donation to small or too large. Thank you.
Samples are being solicited from dogs affiliated with informative pedigrees (3 generation pedigrees, multiple offspring per parent pair) in which dogs are available for bile acid testing and DNA sampling. Each dog will need to have paired serum bile acid measurements (a sample before a routine meal, a sample 2-hrs after a routine meal) for phenotype designation. All Biewers are welcome to participate including known affected subjects (dogs with high bile acid concentrations attributable to PSVA/MVD) and non-affected individuals. Information is kept strictly confidential. Individuals interested in participating are welcome to contact Dr. Center via her email (sac6@cornell.edu) providing your name, phone number, and a general description of your pedigree and availability of dogs for testing.
The BYTNC contacted Dr. Sharon Center at Cornell University on April 1st, 2008 and we have been asked to coordinate the participation of the Biewer breed in the clinical study being conducted on the genotyping of Portosystemic shunt (portosystemic vascular anomaly (PSVA) also known as Liver Shunt)/ microvascular dysplasia (MVD). Dr Center developed the bile acid test to determine the presence of PSVA and MVD in dogs and is working to identify DNA markers that may enable development of a genetic test for the PSVA/MVD trait. Linkage between the PSVA/MVD trait and a common chromosomal region has been demonstrated in several breeds. This AKC supported project is entering the phase of fine gene mapping using single nucleotide polymorphisms (SNPs). Inclusion of more breeds in the study will help narrow the DNA region requiring fine mapping. We hope that everyone will participate, regardless of affiliation, to expand the breed-wide data regarding this trait. Participation of the Biewer breed should be viewed as a proactive step towards eventual eradication of this heartbreaking birth defect.
PORTAL SHUNT (LIVER SHUNT)
This condition is often referred to as a "liver shunt" but the current favored term appears to be portosystemic shunt. These have also been referred to by more exact terms since there are specific types of shunts that vary slightly.
.
There are three shunt types: intrahepatic, extrahepatic, or microvascular. The most common is Portosystemic shunt (PSS) occurs in many dog breeds the Biewer Yorkshire is one. It is an abnormal flow of blood between the liver and the body. Since the liver is responsible for detoxifying the body, metabolizing nutrients and eliminating drugs, the blood bypassing the liver can cause indications of a possible PSS which might include, but are not limited to, neurobehavioral abnormalities, anorexia, hypoglycemia, intermittent gastrointestinal symptoms, urinary tract problems, drug intolerance, unthriftiness and stunted growth.
.
Signs of PSS usually appear before two years of age, but later onset has been recorded. If an animal has a confirmed PSS,
corrective surgery can be helpful in the long-term management of these animals. Dietary manipulation is also important in
maintaining PSS animals. Mode of inheritance has not been established.
.
Symptoms:
Most shunts cause recognizable by the time a dog is a young adult but once in a while one is diagnosed at a later time in
life. Since the severity of the condition can vary widely depending on how much blood flow is diverted past the liver it is possible for a lot of variation in clinical signs & time of onset for the signs to occur. Often, this condition is recognized after a puppy fails to grow, making an early diagnosis pretty common.
Signs of portosystemic shunts include:
* poor weight gain
* sensitivity to sedatives (especially diazepam)
* depression
* pushing the head against a solid object
* seizures
* weakness
* salivation
* vomiting
* poor appetite
* increased drinking and urinating
* balance problems
* frequent urinary tract disease or early onset of bladder stones.
* If these signs increase dramatically after eating, it is a strong
supportive sign of a portosystemic shunt.
Most dogs will be diagnosed with port-systemic shunts under one year of age, but dogs as old as eight have been diagnosed with the condition. Animals are usually stunted, thin, depressed, have trouble gaining weight, and are usually characterized by the owners as chronic "poor doers". In most affected dogs there will be some degree of behavioral signs ranging from listlessness, apathy, or depression to more severe signs of circling, head pressing, stupor, drooling, blindness, or convulsions, some leading to coma.
.
These behavioral changes are due to an accumulation of toxins (especially ammonia) that affect the brain causing a condition called Hepatic Encephalopathy. These toxins are most abundant in the blood stream following the dog eating, especially a high protein meal, and may remain high for hours afterward. Not all dogs with the shunt will show this meal associated behavioral change, but in 25% of the affected dogs that do, the diagnosis becomes clearer. A high percent of affected animals show an intolerance to anesthetics or tranquilizers, and will show increased recovery times following use of these products. Even anti-convulsants used to control seizures may be potentially dangerous if allowed to concentrate in a dog with functional shunt.
.
Approximately 75% of affected individuals will show digestive system symptoms including poor appetite, ascites, vomiting, drooling, diarrhea, or occasionally deranged appetite (eating paper, etc.).Urinary system symptoms may include increased thirst and urination, & in a majority of porto-systemic shunt cases, there will be crystals or stones formed in the urinary tract. These crystals will be either uric acid or ammonium urate (ammonium biurate or thorn-apple crystals.). There can be bladder stones formed or crystals may be noted on the hair around the prepuce or vulva.
