When she was 7 months old, Olive, a Portuguese Water Dog, went into a coma during her spay surgery. She was transferred to an all-night veterinary hospital, where her guardian, Hannah, wondered what could have happened – why her healthy young dog of only a few months would go into a coma during a routine surgery like spaying. Olive’s blood work revealed a problem with her enzyme levels: Olive’s liver was not functioning properly. But, after receiving fluids and care from the hospital, Olive finally came out of her coma at 5 o’clock the next morning. Thrilled that Olive was conscious, Hannah took her home to the family to recuperate. A couple of weeks passed, and with Olive on antibiotics all seemed well. Then, Olive became very lethargic. She stopped eating her food and was constantly drinking water. Hannah noticed that she was growing, but not very quickly. Olive also had started bumping into things. After a trip to the veterinarian, Hannah learned that Olive’s enzyme levels were still off. This fact, followed by copious online research about Olive’s other behaviors, led Hannah to believe that Olive had an intrahepatic shunt.
What Is a Liver Shunt?
One of the liver’s primary functions is to remove toxins from the blood. A liver shunt is an abnormal blood vessel that allows blood to bypass the liver instead of passing through it. Shunts can either be within the liver (called intrahepatic) or outside the liver (extrahepatic). They can be congenital (present at birth) or acquired secondary to chronic liver disease.
Olive
In fetuses, a shunt is always present, so that the mother’s liver can do the work of cleaning the blood of toxins – as the fetus’s liver does not yet work. Usually the shunt closes soon after birth and the newborn’s liver takes over, filtering out toxins from the blood flow.
Sometimes, however, the shunt does not close properly, and a congenital shunt is formed, allowing unfiltered, contaminated blood to reach general circulation without being filtered through the liver. Toxins can build up in the bloodstream or kidneys. In addition, under normal circumstances, food is broken down or digested in the intestines and then absorbed into the portal bloodstream, which is carried through the liver. When a shunt is present, this flow is diverted; therefore, the pet lacks the necessary materials to help him grow and to give him a ready energy source.
While extrahepatic shunts are more commonly seen in small-breed dogs such as the Yorkshire Terrier, Havanese or Maltese Terrier, intrahepatic shunts occur more frequently in large-breed dogs. They are often reported in Labrador Retrievers, Irish Wolfhounds, Australian Shepherds, Australian Cattle Dogs, Samoyeds and Old English Sheepdogs. The incidence of shunts in the general dog population is 0.18 percent; it is a 36 times higher incidence in Yorkshire Terriers.
Clinical Signs
Shunts can be seen at any age, although congenital shunts are usually diagnosed before the pet is 1 or 2. Some common clinical signs of a shunt include the following:
- Intermittent anorexia
- Abnormal behavior after eating
- Neurologic dysfunction such as head-pressing, circling, pacing or unresponsiveness
- Episodes of apparent blindness
- Excessive salivation
- Pica (eating foreign material)
- Seizures
- Poor weight gain
- Small stature, stunted growth, poor muscle development
- Excessive sleeping, lethargy
- Excessive water consumption, excessive urination
- Straining to urinate due to bladder stone formation
- Poor recovery after surgery
Through her research, Hannah identified and reached out to specialists with expertise in shunts, and eventually connected with Margo Mehl, DVM, Diplomate, American College of Veterinary Surgeons.
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