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Disorders of the Liver and Gallbladder in Dogs


Disorders of the Liver and Gallbladder in Dogs

Postby admin » Sun Nov 22, 2015 5:27 pm

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The liver is an organ that performs numerous functions. It has a large storage capacity and functional reserve and is capable of regenerating. These properties provide some protection against permanent damage. However, the liver is also susceptible to injury because of its role in metabolizing, detoxifying, and storing various toxic compounds.

Signs that a dog has liver disease can vary and include loss of appetite, vomiting, stomach ulceration, diarrhea, seizures or other neurologic problems, fever, blood clotting problems, jaundice (a yellow tinge noticeable in the skin, mucous membranes, and eyes), fluid collection in the abdomen, excessive urination and thirst, changes in liver size, and weight loss. Gastrointestinal bleeding can be seen in animals with liver disease due to ulcers or problems with blood clotting. The veterinarian's understanding of the potential causes of each of these signs helps him or her to diagnose illness and provide appropriate treatment.

A variety of blood tests can be useful in detecting and diagnosing liver disease. X‑rays and ultrasonography can help your veterinarian determine liver size and find irregularities, gallstones, and diseases of the gallbladder. Aspiration or biopsy procedures can be used to obtain samples for bacterial culture, cell and tissue analysis, and, when appropriate, toxicologic analysis. Other, less common tests, such as nuclear scintigraphy, may be used in some cases to identify portosystemic shunts (see Digestive Disorders of Dogs: Portosystemic Shunts and Other Vessel Abnormalities) and other blood vessel abnormalities.

The liver, gallbladder, and pancreas of a dog

Early treatment is critical for dogs with acute liver failure. Your veterinarian will prescribe specific treatment if an underlying cause be identified. In cases of longterm or end-stage liver disease, and in cases of acute liver disease when no under-lying cause has been identified, supportive treatment is directed at slowing progression of disease and minimizing complications.

The diet usually recommended for dogs with liver disease includes adequate calorie intake, with the bulk of energy supplied by carbohydrates (20 to 40% of the diet) in the form of complex carbohydrates such as rice and pasta. A diet higher in soluble fiber may be recommended because the fermentation of fiber in the large intestine decreases ammonia production and absorption and reduces the chances of hepatic encephalopathy. Protein restriction is usually required only for dogs that are at risk of developing hepatic encephalopathy. Follow the specific advice provided by your veterinarian. Dogs that refuse to eat may require tube feeding.

Functions of the Liver
Metabolizes fats, carbohydrates, and proteins
Metabolizes drugs (inactivates or makes it easier for the body to excrete them)
Stores and metabolizes vitamins
Stores minerals, glycogen, and triglycerides
Manufactures proteins needed for various body functions, such as blood clotting
Produces bile acids needed for digestion
Detoxifies harmful products manufactured within the body (such as ammonia) or consumed by the animal (such as poisons)
Prescribed vitamin and mineral supplements may include zinc, B vitamins, and vitamin C. Zinc may help to protect the liver by preventing the absorption of copper from the gut. Low potassium levels and decreased levels of B vitamins are common complications with liver disease, and supplementation is often recommended. Vitamin C deficiency has been reported in dogs with liver disease, and supplementation may be beneficial. Injections of vitamin K are sometimes given to dogs with bleeding tendencies.

Complications of Liver Disease
The liver has multiple functions, including removing many toxins from the bloodstream and producing blood clotting proteins. When it is not working properly, many other organs can be affected.

Hepatic Encephalopathy
Hepatic encephalopathy, a syndrome of neurologic problems caused by poor liver function, is seen in a number of liver diseases. While the development of this condition is not completely understood, failure of the liver to clear poisons from the bloodstream and changes in amino acid metabolism caused by the liver disease may act together to cause this disorder. Signs of hepatic encephalopathy include circling, head pressing, aimless wandering, weakness, poor coordination, blindness, excessive drooling, aggression, dementia, seizures, and coma.

Treatment of hepatic encephalopathy is aimed at providing supportive care and rapidly reducing the poisons being produced by the colon. Affected dogs are usually comatose or semicomatose and should not be fed until their status improves. Treatment is likely to include intravenous fluids to correct dehydration and electrolyte (salt) imbalances. Enemas may be used to cleanse the intestines of ammonia and other poisons, and to introduce nutrients that help decrease poison production. Once the dog has been stabilized, treatment is aimed at preventing recurrence. A protein-restricted diet may be prescribed.

Ascites is a condition in which fluid collects in the abdomen. In patients with liver disease, ascites is caused by a combination of high blood pressure in the liver and an imbalance in sodium and water metabolism. The first step in the control of ascites is restriction of sodium in the dog's diet. However, sodium-restricted diets alone are often not sufficient, and diuretics (medications that promote loss of fluid by the kidneys) may also be needed. If ascites interferes with breathing, fluid can be removed from the abdomen using a long needle in a process called abdominocentesis. Periodic abdominocentesis can also be used if ascites does not respond to treatment with medication.

Clotting Defects
Clotting problems can be treated using transfusions of blood or plasma to provide the necessary clotting factors. Heparin and vitamin K can also be administered to aid in clotting. Your veterinarian will prescribe the treatment most appropriate for your pet, its overall condition, and blood type.

Bacterial Infections
Dogs with acute liver failure and long-standing liver disease are susceptible to bacterial infections. Your veterinarian will be alert to this possibility because signs of the liver disease itself (for example, fever or low blood sugar) can be similar to those of infection. One or more antibiotics may be necessary to adequately treat the types of bacteria associated with the infection.

Fibrosis, the formation of fibrous scar tissue in the liver, can eventually lead to liver cirrhosis. Cirrhosis is a serious disease that disrupts liver function. However, fibrosis can sometimes be reversed or reduced by the use of appropriate medications. Your veterinarian can determine which, if any, of the available medications would be beneficial for your pet.

Portosystemic Shunts and Other Vessel Abnormalities
Portosystemic shunts have already been described as a congenital (inborn) defect (see Digestive Disorders of Dogs: Liver). However, in some cases they can develop as a part of illness. In these instances they are called acquired shunts. They can be caused by high blood pressure in the vessels entering the liver. The diseased liver can be thought of as resisting blood flow into the organ. In this case, new blood vessels open to bypass the liver and connect to the blood system of the rest of the body, where the blood pressure is lower. It is as if the blood system were finding a detour around a traffic jam. Acquired shunts are usually seen in older animals and are more frequent in dogs than in cats.

Signs of an acquired shunt include excessive thirst, vomiting, and diarrhea. Fluid accumulation in the abdomen (ascites) is common. Laboratory tests can identify abnormalities associated with the underlying liver disease. Medical treatment of the disease, along with placing a band around the caudal vena cava to slightly raise the blood pressure outside the liver and reduce shunting, can result in a favorable outlook for some dogs with this condition.

Poisons Affecting the Liver
Because of the liver's function in metabolizing drugs, some drugs have been associated with liver dysfunction in dogs. The specific signs and effects depend on the the drug and dosage. In many cases your veterinarian will be aware of the potential for liver disease when prescribing these drugs and will monitor your dog for any signs of decreased or altered function.

Other substances that are toxic to the liver include heavy metals, certain herbicides, fungicides, insecticides, rodent poisons, aflatoxins (produced by mold), amanita mushrooms, and blue-green algae. These can cause life-threatening liver damage.

If your dog has had an accidental overdose of a medication, has had an adverse reaction to a medication (even at the prescribed dose), or has eaten a poison, a veterinarian should be consulted immediately. If necessary, the veterinarian can take steps to minimize absorption of the drug or poison. Depending on the situation, the veterinarian may induce vomiting, administer activated charcoal, pump the animal's stomach, and/or administer an appropriate antitoxin. (see Poisoning: Introduction to Poisoning)

Infectious Diseases of the Liver
Several types of infections may affect the liver, including viral, bacterial, fungal, and parasitic diseases.

Viral diseases of dogs associated with liver dysfunction include infectious canine hepatitis, canine acidophil hepatitis, and canine herpesvirus. Infectious canine hepatitis (see Disorders Affecting Multiple Body Systems of Dogs: Infectious Canine Hepatitis) can cause longterm inflammation and scarring of the liver in addition to causing death of liver tissue. Canine acidophil hepatitis and canine herpesvirus are uncommon.

Leptospirosis (see Disorders Affecting Multiple Body Systems of Dogs: Leptospirosis in Dogs) is a bacterial infection, caused by Leptospira interrogans, that can cause liver disease. The diagnosis is usually made with a blood test and identification of the organism in body tissue samples obtained by biopsy. Treatment includes supportive care and treatment with penicillin or other appropriate antibiotics. Special precautions are recommended when handling dogs suspected of leptospirosis, because this organism may also infect humans.

The most common fungal infections associated with liver dysfunction are coccidioidomycosis and histoplasmosis (see Disorders Affecting Multiple Body Systems of Dogs: Fungal Infections in Dogs). Signs of liver dysfunction include fluid accumulation in the abdomen (ascites), jaundice, and an enlarged liver. Histoplasmosis is generally treated with a prescription antifungal drug. Depending on the level of illness, the outlook for recovery may be poor. In some cases, coccidioidomycosis can be treated with the longterm (6 to 12 months) use of antifungal medications. However, relapses do sometimes occur.

Toxoplasmosis (see Disorders Affecting Multiple Body Systems of Dogs: Toxoplasmosis in Dogs) is a parasitic disease that can kill liver cells and cause sudden liver failure. Jaundice, fever, lethargy, vomiting, and diarrhea are seen in addition to signs of central nervous system or eye involvement. Liver disease associated with toxoplasmosis in dogs is most often seen in young dogs. A high percentage of dogs with toxoplasmosis are also infected with canine distemper virus. The disease is sudden in onset and rapidly fatal. Diagnosis can be difficult. Treatment usually involves appropriate antibiotics. The outlook for recovery depends on the severity of the illness.

Canine Chronic Hepatitis
Chronic hepatitis is a longterm inflammation of the liver. It is more common in dogs than in cats. Several breeds of dogs are predisposed to this condition, including Bedlington Terriers, Cocker Spaniels, Doberman Pinschers, Skye Terriers, Standard Poodles, and West Highland White Terriers. Although the cause can be determined in some cases of chronic hepatitis, in many cases the cause remains unknown. Copper accumulation is often seen in chronic hepatitis of Bedlington Terriers, West Highland White Terriers, Doberman Pinschers, Skye Terriers, and Cocker Spaniels. Other conditions that have been associated with chronic hepatitis include viral infection (such as infectious canine hepatitis), leptospirosis, and drug toxicity.

Depending on the signs, the cause (if known), and the breed and history of the dog, your veterinarian will determine the appropriate plan for treating and managing chronic hepatitis.

Endocrine Diseases Affecting the Liver
Several diseases involving the endocrine glands can cause liver problems in dogs. These diseases include diabetes mellitus (see Hormonal Disorders of Dogs: Diabetes Mellitus), Cushing's disease (see Hormonal Disorders of Dogs: Cushing's Disease), and hyperthyroidism (see Hormonal Disorders of Dogs: Hyperthyroidism).

Dogs with diabetes mellitus have an increased risk of developing fatty degeneration of the liver because diabetes mellitus increases the metabolism and mobilization of lipids. Lipids include any of a group of water-soluble fats and fatlike chemical substances that are sources of fuel for the body. However, when too many lipids are deposited in the liver, the function of the organ is impaired. Insulin replacement may or may not correct this storage problem.

Dogs with hyperadrenocorticism are likely to develop changes in the liver similar to those seen in overdoses of cortico-steroids. These problems are controlled when the underlying disorder is treated.

Liver Cysts and Nodular Hyperplasia
Liver cysts can be acquired (usually single cysts) or present at birth (usually multiple cysts). Congenital polycystic disease of the liver has been reported in Cairn Terriers and West Highland White Terriers. Occasionally, the cysts can become large and cause abdominal swelling and other signs such as lethargy, vomiting, and excessive thirst. Your veterinarian may be able to feel masses in the abdomen that usually are not painful. Fluid may accumulate in the abdomen. The problem can be identified using x-rays or ultrasonography, although a definitive diagnosis is made by biopsy. Surgical removal of the cysts usually cures the condition.

Nodular hyperplasia is a nonspreading, age-related condition in dogs. It does not usually cause disease or affect liver function. If it is detected, a biopsy may be needed to distinguish these changes from those caused by hepatocellular carcinoma, a form of cancer.

Cancers of the Liver
Tumors that originate in the liver (called primary tumors) are less common than those caused by spread from another part in the body. Primary tumors are most often seen in animals more than 10 years old. These tumors can be either malignant or benign and may spread (metastasize) to other locations such as the lymph nodes, abdominal wall, and lungs.

Cancers that can spread to the liver include pancreatic cancer, mammary (breast) cancer, and several others. Metastatic tumors usually occur at multiple sites.

Signs can include excessive urination and thirst, vomiting, weight loss, jaundice, bleeding problems, hepatic encephalopathy (see Digestive Disorders of Dogs: Hepatic Encephalopathy), enlarged liver, and fluid accumulation in the abdomen. Seizures may develop because of hepatic encephalopathy, low blood sugar, or the spread of cancer to the brain. An abdominal tumor may be found by your veterinarian during an examination. A biopsy is often needed for a definitive diagnosis. If a single liver lobe is involved, surgical removal of the involved lobe is often recommended. Chemotherapy may be effective for some other cancer types. The outlook is poor for primary liver tumors that involve multiple lobes because an effective treatment is not yet available.

Other Liver Diseases
Several other noninfectious chronic diseases may also affect the liver.

Glycogen Storage Disease
Glycogen is a form of stored sugar found in animals. It is converted to glucose when the body needs energy. Glycogen storage diseases are caused by a deficiency of certain enzymes and result in failure of glycogen to be released from cells. When this occurs, glycogen accumulates within the liver and other organs and is unavailable for conversion to glucose. Signs of this disorder include an enlarged liver, retarded growth, and weakness due to low blood sugar levels. Analysis of samples of liver, muscle, or skin is needed for diagnosis. Treatment is based on signs of illness and includes frequent small meals of high-carbohydrate food. The outlook in most cases is poor, and most dogs with these diseases die at a young age.

Hepatic Amyloidosis
Amyloid is a protein that is not folded into the correct shape. The misfolded protein causes damage by displacing normal cells. Amyloidosis is an inherited disease of Chinese Shar-Peis; however, the liver is not always affected. Although some dogs may show no signs, typical signs include loss of appetite, excessive thirst and urination, vomiting, jaundice, and an enlarged liver. Affected animals may collapse and have pale mucous membranes due to rupture of the liver and subsequent internal bleeding. Diagnosis is made by identifying amyloid deposits in liver biopsy samples. Drugs are available that may slow the progression of amyloidosis, but the outlook is poor, especially if the diagnosis is made late in the disease.

Idiopathic Liver Fibrosis
Liver fibrosis in young dogs that is not associated with any underlying inflammatory conditions is referred to as idiopathic hepatic (liver) fibrosis. Fibrosis is accumulation of tough scar tissue that replaces normal liver tissue. Affected dogs are usually less than 2 years of age. Signs include fluid accumulation in the abdomen (ascites) and hepatic encephalopathy (see Digestive Disorders of Dogs: Hepatic Encephalopathy). Other signs include weight loss, vomiting, and diarrhea. X‑rays of the liver show a decrease in size, and abnormalities of the blood vessels between the intestines and liver can be identified by ultrasound. Treatment to manage signs of illness, particularly hepatic encephalopathy and ascites, is usual.

Diseases of the Gallbladder and Bile Duct
The liver secretes bile, a substance that assists with digestion and absorption of fats and with elimination of certain waste products from the body. Bile is stored in the gallbladder and is released into the duodenum through the bile duct.

Jaundice (a yellow tinge noticeable in the skin, mucous membranes, and eyes) is often the main sign of diseases of the gallbladder and bile duct. An exception is cancer of the gallbladder, which may not cause jaundice.

Obstruction of the Bile Duct
Obstruction of the bile duct is most often caused by pancreatic disease. Pancreatic swelling, inflammation, or fibrosis can cause compression of the bile duct. Diagnosis is based on laboratory tests, x‑rays, and ultrasonographic evidence of pancreatic disease. Treatment of pancreatitis will often relieve the obstruction. If this is not successful, surgery may be necessary to connect the gallbladder directly to the intestine. If gallstones are the cause of obstruction, the gallbladder may need to be removed. Cancer of the pancreas, bile ducts, liver, intestines, and lymph nodes can also cause obstruction. A biopsy is needed to confirm the diagnosis. When cancer is present, surgery can provide some relief but is not a cure.

Inflammation of the Gallbladder (Cholecystitis)
Inflammation of the gallbladder (cholecystitis) is usually caused by bacterial infections that start in the intestines and either travel up the common bile duct or are spread through the blood. In some cases, the wall of the gallbladder is damaged, and bile leaks into the abdomen causing severe abdominal infection and inflammation, which can be fatal. Loss of appetite, abdominal pain, jaundice, fever, and vomiting are common signs. The dog may be in a state of shock due to abdominal inflammation.

The inflammation can also spread to the surrounding branches of the bile duct and the liver. Diagnosis can be confirmed by biopsy for bacterial cultures and tissue analysis. Treatment usually consists of removal of the gallbladder and appropriate antibiotic medication to treat infection. The outlook is good if appropriate antibiotics are started early but is less favorable if diagnosis and treatment are delayed.

Gallstones rarely cause disease. When it does occur, disease is usually seen in older, female, small-breed dogs. Signs include vomiting, jaundice, abdominal pain, and fever. Treatment consists of removal of the stones and appropriate antibiotics.

Rupture of the Gallbladder or Bile Duct
Rupture of the gallbladder or bile duct is most often due to gallstone obstruction, inflammation of the gallbladder, or blunt trauma. Rupture of the bile duct may also occur as a result of cancer or certain parasites. Rupture leads to leakage of bile into the abdomen, causing a serious condition called bile peritonitis, which may be fatal if the rupture is not repaired. Treatment includes surgery, which consists of tying off the bile duct, removing the gallbladder, or connecting the gallbladder with the small intestine.
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