The Liver and Its Functions

The liver is located in the upper right-hand portion of the abdominal cavity, beneath the diaphragm, and on top of the stomach, right kidney, and intestines.

Shaped like a cone, the liver is a dark reddish-brown organ that weighs about 3 pounds.

There are 2 distinct sources that supply blood to the liver, including the following:

• Oxygenated blood flows in from the hepatic artery
• Nutrient-rich blood flows in from the hepatic portal vein

Functions of the liver

The liver regulates most chemical levels in the blood and excretes a product called bile. This helps carry away waste products from the liver. All the blood leaving the stomach and intestines passes through the liver. The liver processes this blood and breaks down, balances, and creates the nutrients and also metabolizes drugs into forms that are easier to use for the rest of the body?or that are nontoxic. More than 500 vital functions have been identified with the liver. Some of the more well-known functions include the following:

• Production of bile, which helps carry away waste and break down fats in the small intestine during digestion
• Production of certain proteins for blood plasma
• Production of cholesterol and special proteins to help carry fats through the body
• Conversion of excess glucose into glycogen for storage (glycogen can later be converted back to glucose for energy) and to balance and make glucose as needed?
• Regulation of blood levels of amino acids, which form the building blocks of proteins
• Processing of hemoglobin for use of its iron content (the liver stores iron)
• Conversion of poisonous ammonia to urea (urea is an end product of protein metabolism and is excreted in the urine)
• Clearing the blood of drugs and other poisonous substances
• Regulating blood clotting
• Resisting infections by making immune factors and removing bacteria from the bloodstream
• Clearance of bilirubin, also from red blood cells. If there is an accumulation of bilirubin, the skin and eyes turn yellow.?

When the liver has broken down harmful substances, its by-products are excreted into the bile or blood. Bile by-products enter the intestine and leave the body in the form of feces. Blood by-products are filtered out by the kidneys, and leave the body in the form of urine.

What Causes Liver Problems

Sometimes liver disease can happen as a result of aging. Sometimes it's genetic. But it can also be brought on by infection or trauma to the area. Some diseases and?medications?can hurt your dog's liver.

Other causes of liver disease may include:

• Some plants and herbs such as ragwort, certain mushrooms, and blue-green algae
• Leptospirosis, a bacterial?disease dogs can get?through direct contact with urine from infected animals or through water, soil, or food contaminated with their urine
• Molds that grow on corn
• Untreated heartworms
• Diabetes
• Issues with the?pancreas
• Use of painkillers
• Fatty foods

Common Disorders of the Canine Liver

Vessel Abnormalities: In young dogs, one of the most common liver disorders is a birth defect called the congenital portosystemic shunt. In these cases, a blood vessel is present that bypasses the liver, causing a buildup of toxins that the liver would normally take care of. Congenital portosystemic shunts are suspected in young dogs who have stunted growth, develop seizures, or seem disoriented.

In older dogs, we more commonly see acquired shunts, which develop when there is a blood pressure back up in the liver due to hypertension or cirrhosis. In an effort to get around the “jammed” region, new vessels grow to bypass the blocked area, but they also bypass the liver cells themselves.

Treatment depends on the anatomy of the shunt. If it consists of one large vessel outside of the liver, as is more common with congenital shunts in small breed dogs, surgery can be very successful. Shunts inside the liver or those consisting of multiple vessels may not be surgically repairable, and in those cases, the patient has to be managed with a low protein diet and medications to help reduce the number of toxins in the blood. In these cases, the liver problem isn’t cured, but instead, the emphasis is placed on controlling the symptoms.

Endocrine Diseases: Certain diseases that affect the endocrine glands can lead to liver problems. Diabetes mellitus, hyperadrenocorticism (Cushing’s disease), and hyperthyroidism can all cause impaired liver function because of their effects on the organ. In these cases, treating the underlying endocrine disease is the most important component of improving liver function.

Infectious diseases: Because the entire blood volume passes through the liver, it is especially susceptible to a variety of infectious diseases. The liver can be infected by bacteria, viruses, parasites, or fungi.

The most common viral disease associated with the canine liver is infectious canine hepatitis, which can cause inflammation and scarring. This is a vaccine-preventable disease.

Leptospirosis is a bacterial infection that can lead to liver disease, though many people associate it more with kidney disease. Dogs are infected with leptospirosis through contaminated water sources, and the disease can be spread to humans.

Leptospirosis is diagnosed by blood test or tissue biopsy. While it can be challenging to diagnose due to the wide variety of nonspecific clinical signs, the bacterial infection can be cleared with early treatment. Secondary liver and kidney damage may be permanent. Commercial vaccines for leptospirosis are available for at-risk dogs.

Coccidioidomycosis and histoplasmosis are the most common fungal causes of liver disease. Dogs are exposed to spores in the environment. These fungal infections can be difficult to clear and often require months of treatment with anti-fungal medications. Because of the difficulty in treating the fungal disease of the liver, the long-term prognosis is guarded.

Liver masses: Dogs are susceptible to several types of liver masses. Liver cysts can be present from birth or acquired with age. Though often benign, large or growing cysts can cause symptoms of liver disease. Surgical excision is usually curative.

Liver cancer: Cancer of the liver comes in two main forms—primary tumors, which originate in the liver, and secondary or metastatic tumors, which means they spread from another area in the body. Primary tumors are less common than metastatic ones. Depending on the type of cancer, location, and the number of masses, treatments may include surgery, chemotherapy, radiation, or a combination.