The Scottish Terrier is one of over 74 breeds of purebred dogs reported to produce the genetic defect of congenital portosystemic shunt. Currently our STCA Health Survey reports a carrier frequency of 4.7%. This is a rare condition and not a widespread problem in the Scottish Terrier at this time. Unfortunately genetic disorders in dogs can spread rapidly. Two factors, in particular, influence the spread of a genetic disease: 1.) a lack of understanding about the disease and its symptoms and 2.) the widespread use of carrier dogs or bitches, well respected in the area of conformation, for breeding purposes. Much is still unknown about portosystemic shunt and its mode of inheritance. Because PSS is thought to be a polygenic disease, the parents may not contribute equally to the traits responsible for affected puppies and the carrier offspring may only inherit a piece of the carrier parent's traits. A percentage of puppies produced by carrier parents will also be carriers. The purpose of this article is to deal with factor 1.) - the disease, portosystemic shunt, recognition of its symptoms, methods of arriving at a diagnosis and options for treatment.

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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

Typically, smaller dogs, such as the Yorkshire Terrier, Maltese, Cairn Terrier and Scottish Terrier have extrahepatic shunts and larger dogs such as Golden Retrievers and Irish Wolfhounds have intrahepatic shunts. Size exceptions have been noted within the intrahepatic classification of shunt. Extrahepatic shunts occur more frequently than intrahepatic shunts. Additionally, another phenomenon called microvascular dysplasia (MVD), a series of small intrahepatic shunts appear to be highly prevalent among Cairn Terriers. Hepatic microvascular dysplasia is thought to be a related disease to PSS that the Cairn Terrier carries. Research scientists are not of one mind about this phenomenon. A Cairn Terrier research project was undertaken by Thomas Schermerhorn, Sharon A. Center, Nathan L. Dykes, Peter H. Rowland, A. E. Yeager, H. N. Erb, Karen Oberhansley and Michael Bonda. They published an article in the Journal of Veterinary Internal Medicine, Vol. 10, No. 4 (July-August) 1996: pp 219-230. The article's title is "Characterization of Hepatoportal Microvascular Dysplasia in a Kindred of Cairn Terriers." This article is more technical than practical for our particular discussion. Within the article is a description of anatomical changes in livers of PSS Cairns and description of anatomical liver changes of MVD Cairns. MVD Cairns can appear to be healthy and they can go undiagnosed throughout their lives. If they are undetected, they often remain in the breeding population. The role of MVD Cairns in the spread of PSS isn't known. At this time we do not know if the MVD phenomenon occurs in our Scottish Terrier population.

The differentiation of congenital and acquired shunts is important to this discussion. Acquired shunts are not hereditary in nature. They are a result of progressive liver disease. Dogs suffering from cirrhosis, hepatitis or congestive heart failure can have increased pressure inside their livers. This pressure causes embryonic vessels that normally have no function after birth to open. Often this involves a number of vessels not the one or two seen in congenital shunts. The presence of shunts in an autopsy of an older dog does not mean this dog carries the genetic traits for portosystemic shunt. It requires further examination of liver tissue. Careful examination of the dog's medical history and a study of liver tissue should reveal the origin of this dog's shunt.

There are multiple symptoms associated with this disease and the number and severity of symptoms depends on how much blood bypasses the liver. Symptoms are most often seen at a young age. The typical PSS dog is purebred and under one year of age. Dogs as old as eight and ten years have been discovered to have PSS. Although recorded, this is not the norm. Affected dogs can be small in stature, unthrifty and sometimes anorexic. Coat and skin condition are poor. They develop urinary tract infections at an unusually young age. The cause of the urinary tract infection is ammonium urate crystals. These crystals are formed by excessive ammonia and uric acid in the urine. PSS puppies do not react well to sedatives or anesthesia. The liver cannot metabolize these agents to help eliminate them from the dog's body. The sedatives are shunted back to the heart and returned to the body's circulation. PSS dogs can be subject to bouts of lethargy and depression. Dogs with severe shunts develop additional central nervous system signs like hyperactivity, circling behavior, disorientation, severe aggression, weakness, excessive salivation, staggering, temporary blindness, seizures and even coma. Vomiting and diarrhea are present in 2/3 of the cases of PSS. All of the PSS symptoms are affected by the consumption and digestion of protein rich foods. These foods produce ammonia, gamma-aminobutyric acid, natural benzodiazepines and mercaptains during the process of digestion. These chemicals are potential neurotoxins.

As the author of this piece my intention is to present information for other breeders and owners to use if necessary. Opinion and emotion can obstruct this purpose, but observation of fellow breeders can be helpful. During the course of research on this disease I spoke to Yorkshire Terrier breeders, Cairn breeders and Scottie breeders. One scenario was repeated to me several times. It mirrored my personal experience. This narrative is anecdotal and not intended to imply that all cases follow this pattern.

A litter of puppies is born and progresses normally. By six weeks of age the puppies are completely weaned and all appears to be well. During the next four to eight weeks the puppies increase their consumption of protein rich puppy food. At this stage of life the introduction of vaccines becomes the next step in the successful raising of the litter. Between six weeks and fourteen weeks most puppies are given three to four sets of vaccinations. Some are combination vaccines and others are individual vaccines. (As a breeder I have never experienced puppies with a vaccine reaction but, I have read the articles concerning the possibility of adverse vaccine reaction especially with combination shots.)

One night my litter was healthy. The next day one puppy, Holly, was wobbly, disoriented and clearly in distress. The outside pen was checked for leaves or other foreign material the puppy could have ingested. Electric cords were checked in the den. All the cords had been raised out of the puppies' reach. We checked Holly for bites or a possible bee sting. Truthfully, it was too early in the season for bees in Massachusetts. Next her temperature was taken. It was normal. Nothing external appeared to have happened to this nine-week-old puppy. Why was she suddenly so sick? Off we went to the veterinarian.

Dr. Cindy Shaefer had seen Holly and her sisters for a routine vaccination and checkup the week before. Dr. Shaefer ordered blood work on Holly and examined her. Nothing specific was found. Later in the day Holly was almost normal in behavior. Then later at night her behavior was nothing less than bizarre and she staggered like a drunken sailor. By morning she was again nearly normal. The blood chemistry results were all within normal range and the blood count showed no sign of infection. For two days this erratic pattern of close to normal behavior and periodic staggering accompanied by rages or vacant staring persisted. Then Holly had a mild seizure. We consulted a veterinary neurologist. He found her symptoms, at the time of examination, unremarkable. She became worse and the seizures and behavior changes occurred more frequently. At the second visit to the neurologist he stated two possible causes for Holly's illness vaccine reaction or possible brain malformation. Some other breeders have reported the initial concern by veterinarians about vaccines.

Neurological tests like MRI and a spinal tap were discussed as possible options for determining the cause of Holly's illness. The first logical course of action was a bile acid test, a simple inexpensive blood test. The neurologist did not strongly believe that Holly was a PSS puppy; however, the test would rule out shunt and tell us if Holly could tolerate Phenobarbital for her seizures. The bile acid test detects diminished liver function. Dogs on seizure medication and older dogs with liver failure symptoms often require bile acid tests to monitor their health status.

For the young dog high bile acid results indicate a need for a PSS work up. This test is an effective screening test. It does not provide definitive diagnosis. Rather, it tells you if more testing in this area is needed. Breeders in other breeds report spending thousands of dollars on sophisticated neurological tests only to find that the simple fifty dollar test, the bile acid test, provides them with a direction for diagnosis of their sick puppies.

The full text of this article contains additional information concerning the diagnosis of PSS in the Scottish Terrier. It also includes information about: 
     a. Screening test: bile acid test;
     b. Diagnostic tests: ultrasound, scintigraphy, surgery and necropsy;
     c. Medical treatment;
     d. What should Scottie breeders know and
     e. References used for this article.

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This article is the copyrighted material of the author, The Bagpiper, and ScottiePhile. It was originally printed in The Bagpiper. It may not be distributed or reprinted without the permission of the author or ScottiePhile. This article represents general knowledge and is not intended to replace veterinary diagnosis or treatment. You may reach the author at eowyn236@earthlink.net.