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Causes of Enlarged Liver in Dogs

Enlarged Liver in Dogs

If your vet has found a large liver in your dog, you may be wondering what may be some causes of enlarged liver in dogs. The liver is an organ that carries out many important functions and some of the most important tasks involve detoxifying chemicals and metabolizing drugs. When a dog's liver enlarges, it may have an impact on many bodily functions and therefore it's important to thoroughly investigate the underlying cause. Liver enlargement in dogs may be sign of a primary condition mainly affecting the liver, or it may develop secondary to other medical conditions.

 effects of steroids on the dog's liver.

Enlarged Liver in Dogs 

Liver disorders in dogs are sometimes tricky to diagnose because the liver is a very resilient organ that tends to compensate quite well. This means, that signs of trouble may not manifest right away. For instance, there may be problems with the liver, yet the dog's liver enzymes values may actually show normal on a chemistry profile.

A dog's liver varies in size but generally it varies from being 1.3 to 6.0 percent of the dog's body weight. In neonate puppies it tends to occupy a large portion of their abdominal cavity but as the dog matures, it's mass tends to decline. However, in older dogs liver enlargement is a common finding. What contributes to the liver's overall size is ultimately the blood flowing to it.

An enlarged liver in dogs, medically known as hepatomegaly, is often first detected through an x-ray. While this is a first good step, the best next step so to better detect the underlying cause of an enlarged liver in dogs is having the dog undergo an ultrasound.

An ultrasound is a non-invasive diagnostic tool that doesn't usually require sedation or anesthesia and it allows the vet to not only visualize the liver but also the rest of the dog's belly. An ultrasound can therefore provide valuable information. In some cases, the vet may request an ultrasound along with a a diagnostic sampling of the liver and this would require sedation.

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Cushing's Disease 

Sometimes, as mentioned, the enlarged liver develops secondary to some underlying issue. One such case is when dogs are suffering from a medical condition known as Cushing's disease. Also known as "hyperadrenocorticism" Cushing's disease is a condition that results from the excessive production of cortisone. Affected dogs typically drink excessively and develop a voracious appetite.

Cushing's disease may affect the liver and cause enlargement due to fat depositing there diffusely something known as hepatic lipidosis. The damage can eventually lead to liver failure.

According to veterinarians Dr. Johanna Cooper and Cynthia R.L. Webster, it is estimated than in 85 percent of cases, dogs with Cushing's disease will show mild to moderate increases in the total serum ALP content in their blood chemistry profiles.

Cushing's disease is diagnosed with what's known as an ATCH stimulation test, with cortisol levels taken over the course of 12 hours. If this condition is diagnosed and there is therefore hepatic lipidosis, there is unfortunately no way to reverse the damage to the liver, explains veterinarian Dr. B J Hughes. 

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Dog Liver Infection

The liver, as many other organs, can be susceptible to infection, medically known as "hepatitis." The liver infection can be caused by viruses and bacteria. As mentioned earlier, sometimes liver problems may not show up in bloodwork and this can be one of such cases: the dog's blood work can show normal values and yet the dog may have a liver infection. However, usually liver infections cause some changes in the dog's liver enzymes.

Identifying the offending organism causing the infection can be tricky at times. Usually, it would require an ultrasound with biopsy but not always this test is fool proof, explains veterinarian Dr. Christian K.

If your dog has an enlarged liver because of a liver infection, your vet may prescribe medications such as liver friendly antibiotics and supplements such as Denosyl (SAMe), Denamarin or Milk thistle to help the liver recover.

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Dog Liver Cancer

Sadly, in some cases, an enlarged liver may be a sign of liver cancer affecting one or more lobes of the liver. Liver cancer in dogs may originate primarily from the liver or the liver cancer may occur secondary to another cancer through a process that's known as "metastasis."

Liver cancer is a common finding in older dogs. It may often stem from a cancer of the spleen that has spread to the dog's liver. Spleen cancer (hemangiosarcoma) is particularly common in elderly golden retrievers.

Generally, liver cancer in the early stages can be quite tricky to pick up on an x-ray. If the vet suspects liver cancer, he or she will request an ultrasound with biopsy of the liver and surgery may be suggested.

Other Causes

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There are several other potential causes for liver enlargement in dogs. In some cases, an enlarged liver can be a sign of heart failure. Basically, what happens is that the dog's heart enlarges and is therefore no longer able to pump blood as it should. The blood therefore accumulates in the dog's blood vessels and abdomen which leads to the liver becoming enlarged. Dogs with heart failure will suffer from coughing, exercise intolerance and collapsing. Heart failure may occur secondary to heartworm disease.

Ehrlichiosis, a tick-borne disease, may also cause liver enlargement in dogs. What happens in this case is that the dog's immune system is activated to fight the disease and the immunity network in the dog's liver will pull out abnormal and infected cells contributing to an increases in its size, explains veterinarian Dr. Ralston. On top of the liver, the dog's lymph nodes and spleen may also enlarge.

Other possible causes include diabetes, several cancers that metastatize to the liver (spleen cancer, cancer of lymphocytes), chronic liver disease, blocked blood flow to the liver and use of drugs toxic to the liver. 

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