Hepatotoxins in Dogs
The liver is the largest gland in the body, and one of the most important organs for the overall health of the body. It serves many vital functions, like production of bile (the fluid substance that helps in fat digestion), production of albumin (a protein present in blood plasma), and more importantly, the detoxification of chemicals and drugs that pass through the body.
Hepatotoxins are toxic substance that can damage the liver. Some toxins are known for having properties that can bring about liver damage and that almost always lead to liver toxicity. However, an individual dog may be more likely to develop liver toxicity symptoms that are related to a particular drug than another dog might under seemingly similar circumstances. This type of reaction is called an "idiosyncratic reaction" and can sometimes lead to unpredictable injury.
In comparison to other organs, the liver is more susceptible to adverse toxicity reactions due to its location and to its central role in the metabolism of toxic chemicals and drugs. Liver toxicity is most commonly associated with adverse drug reactions.
The severity of the liver toxicity is also determined by age, nutritional status, concurrent diseases, hereditary factors, other drugs being used, and previous exposure to the same or similar drugs. The extent of the liver injury also depends on drug concentration, duration and frequency of drug exposure, and current liver health status.
Dog breeds including Dalmatians, Dobermans, Samoyeds, Labrador retrievers, German shepherd dogs, and herding breeds show increased vulnerability to certain drugs. Though liver toxicity can occur in dogs of any age, young dogs are more susceptible to adverse drug reactions and liver damage due to their immature liver metabolism functionality and excretory functions.
Symptoms and Types
Symptoms can vary depending on the duration of drug exposure and the type of toxin. The following symptoms may be observed in dogs with liver toxicity:
Loss of appetite
Jaundice (often progressive)
Fluid in the abdominal cavity (ascites) - this symptom is often indicative of advanced disease
Petechia (minute red or purple spots on the surface of the skin as the result of tiny hemorrhages of blood vessels in the skin)
Ecchymosis (the escape of blood from ruptured blood vessels into the surrounding tissue, forming a purple or black-and-blue spot on the skin)
You will need to give a detailed history of your dog’s health, onset and nature of symptoms, and possible conditions that might have led to this condition, such as prior health condition, any medications your dog has been on, etc. Your veterinarian will perform a thorough physical exam to evaluate all of your dog’s body systems and to evaluate your dog’s overall health.
Routine laboratory tests include a complete blood count, biochemistry profile, and urinalysis. These test results should allow your veterinarian to make an initial diagnosis. The biochemistry profile will reveal abnormally high levels of liver enzymes due to liver injury if toxicity is present.
Creatine kinase, an enzyme in the tissues, will show increased levels in the blood in cases with severe muscle damage, and as certain chemicals are toxic to the muscles, its levels are also determined in animals with liver toxicity. In patients with liver toxicity, the blood protein albumin may also show increased levels. The urinalysis may indicate high levels of glucose (sugar) in the urine if kidney damage is also present.
Because the liver also performs a pivotal role in blood clotting, in cases of liver damage the normal blood clotting functions may be disturbed. For this reason your veterinarian will likely order a complete blood clotting profile test for your dog.
Abdominal X-rays and ultrasonography may be used to evaluate the size of the liver along with the extent of damage. Your veterinarian may also need to take a sample of liver tissue for a liver biopsy in order to confirm the diagnosis and estimate the level of damage. Your veterinarian will require three to five days to assess a realistic prognosis of liver damage in your dog, so that you will have some ideas on how you will want to progress with available treatments.
Treatment and Care
In case of advanced liver damage, your dog will need to be hospitalized for intensive therapy. Intravenous fluid therapy is required for patients with deficient body fluids to maintain hydration status. In case of abnormal blood clotting functions, your dog will be given fresh whole blood or fresh frozen plasma (a normal fluid component of blood).
Oxygen will be given to improve the delivery of oxygen to liver tissue, and urine output will be monitored to access the normal functions of the kidneys. In case of low blood sugar, intravenous fluids containing sugar will be administered. Antibiotics can be given to protect your dog against infections, and vitamins are also given for maintaining the liver’s metabolism functions. Intensive care is usually required for at least 3-10 days for initial stabilization.
Living and Management
Liver damage is a serious health problem, and you will need to provide your dog with a quiet and comfortable environment so that your dog can recover and properly rest. Patients with liver damage usually have a low body temperature, so you will need to keep your dog in a warm environment to prevent further aggravation of normal body functions.
Special dietary support is generally prescribed for these patients, as a supportive and well-balanced nutritional diet is essential for energy levels and a successful recovery. If your dog is not able to eat, your veterinarian will use a stomach tube to feed the dog until it is able to start eating on its own. Your veterinarian will demonstrate the proper use and cleaning of the feeding tube for home care.
Follow-up evaluations of your dog will include laboratory tests to evaluate the current liver functions and efficacy of ongoing treatment. Other than the drugs that have been prescribed by your veterinarian, do not give your dog any medications during or after the recovery period, unless you have been specifically advised to do so by your veterinarian. The already damaged liver will be very vulnerable for some time after treatment, and will need to be treated with great care. Failure of this organ leads to certain death.
Prognosis is highly variable and depends on the extent of the initial liver damage. In some patients liver damage is permanent and may lead to complete liver failure.