hepatic encephalopathy | acute hepatic failure | chronic hepatic failure and cirrhosis | cholestatic hepatobiliary disease | drug/toxin injury | infectious liver disease | infectious canine hepatitis (ich) | canine herpesvirus (chv) | leptospirosis | hepatic abscesses | cholangiohepatitis complex | chronic hepatitis | copper accumulation | neoplasia | portosystemic shunts (pss)
Introduction: In order to understand diseases of the liver, it is important to have some knowledge of the normal function of this complicated organ. The liver is important in keeping the body’s metabolism and function in balance. It has been estimated that the liver is responsible for over 1,500 essential processes on a biochemical level. The failure of any of these biochemical functions could lead to death of the animal.
Some of the main functions of the liver include proper handling of carbohydrates (sugars, starches), lipids (fats, cholesterol, bile acids), and proteins. Some of the important proteins produced by the liver include blood clotting factors, urea (used by the kidney to help with the body’s water preservation), and albumin (the main protein in the blood which helps maintain the proper fluid volume in the heart and blood vessels). Essential vitamins and minerals are produced, stored, or altered by the liver for proper use in the body. The liver aids in the functions of the immune system and the endocrine system. The liver also plays a role in maintaining healthy blood cells. Bile acids are produced and stored in the liver and gallbladder and are used in the digestive tract to help breakdown food.
One very important function of the liver is its role as the body’s filter from the digestive tract. The entire digestive tract contains bacteria and food in various stages of breakdown. Nutrients are absorbed into the blood through tiny capillaries from the stomach and intestines. Blood from the digestive tract may be thought of as "dirty," since it is so close to a source of potential contamination— millions of bacteria and possibly harmful substances taken into the body through the mouth. From here, the blood enters the liver’s portal blood system, a second bed of capillaries where the liver can "detoxify" any harmful substances and acts as the first line of defense against invading bacteria from the digestive tract. This function of the liver as a filter from the stomach and intestines becomes very important in the understanding of many diseases of the liver.
Hepatic Encephalopathy: A specific condition called hepatic
encephalopathy (HE) often develops with diseases in which the liver’s function
as a filter fails. "Hepatic encephalopathy" actually means disease of the brain
associated with the liver. HE occurs when toxic by-products usually filtered by
the liver arrive at high levels in the brain via the bloodstream. These
by-products of digestion, especially ammonia, cause hallucination-like symptoms
to occur in the brain along with circling or pacing around a room, aggression,
blindness that seems to come and go, and "head pressing," or standing with the
head lowered and pressed into a corner or against a wall.
Hepatic encephalopathy seems to correlate with the specific types of proteins which make up an animal’s diet. Some types of protein are more likely to lead to HE than others. In dogs, meat proteins seem to be the worst types for animals prone to hepatic encephalopathy. In people, the proteins found in red blood cells are particularly likely to cause HE. Bleeding ulcers in people with liver diseases are more likely to lead to symptoms of HE than in dogs, but if enough blood is lost from an ulcer and digested back into the body, any animal can suffer a similar problem. Proteins from a vegetable or dairy source are less likely to cause problems in patients with liver disease.
The liver has a tremendous ability for regeneration and functional reserve. It is able to tolerate an injury and insult better than most organs without failing (although sickness may be very apparent in the body) and can repair itself remarkably well following damage. These are wonderful features of a vital organ, but can also make it difficult to recognize when a serious disease of the liver is present.
Introduction: Sudden failure of the liver occurs when approximately 75% of the liver tissue is severely damaged or becomes damaged over a period of time. This quantity of damage exceeds the liver’s functional reserve and leads to clinical signs of liver failure.
Some of the causes of acute liver failure include:
Clinical Signs: Clinical signs of acute liver failure are usually dramatic, but often not specific. Lack of appetite, dehydration, vomiting, diarrhea, depression, and increased urine output, sometimes accompanied by increased water intake are common signs. Jaundice or icterus (yellowness to the gums and white of the eye) may or may not be present, but is a more specific indicator of liver disease than the other mentioned clinical signs, especially if the patient is not anemic. Signs of hepatic encephalopathy are often noticed and may be quite dramatic, with severe depression and disorientation. The patient is generally found to be in good body condition. Sometimes, the abdomen may appear swollen as the liver becomes enlarged. In the most severe cases, the animal may experience hemophilia (bleeding tendencies due to a loss of blood-clotting ability). Widespread damage to the liver that is not immediately life-threatening may lead to chronic liver failure if there remains too little healthy tissue to regenerate.
Diagnosis: Diagnosis of acute liver failure is accomplished with a variety of tests. Physical examination by a veterinarian, followed by routine CBC, serum chemistry panel, and urinalysis are generally performed first. An increase in the liver enzyme alanine aminotransferase (ALT) is the laboratory value most consistent with acute failure of the liver, and may be elevated many times above the normal levels. Increases in the other liver enzymes (ALP and AST) are also commonly noted as well as an increase in serum bilirubin. Serum bile acid testing is generally recommended with any liver disease. Radiographs and ultrasound of the abdomen are usually recommended to visualize the changes within and around the liver and nearby organs. For a complete diagnosis to be made, a liver biopsy must be obtained, either through ultrasound-guided technique or surgery. If the animal has clotting problems, however, a liver biopsy may be too risky.
Treatment: The typical treatment of sudden liver failure centers around aggressive supportive care and eliminating the cause of the failure, if possible. Discontinuing any drug which has potentially caused the liver to fail is essential. Antidotes for acetaminophen poisoning, such as N-acetylcysteine, may be offered if that particular drug is to blame. Fluid therapy and rapid correction of the blood acid-base balance and dissolved salt levels (sodium, potassium, chloride) must be initiated as soon as possible. If hepatic encephalopathy is present, this concern must be specifically treated by reducing ammonia levels in the bloodstream. Special enemas and oral medications can be given to help reduce ammonia levels in the blood. Antibiotics are selected specifically for their ability to remove ammonia-producing bacteria from the colon. Diet therapy is started as soon as possible. Diets restricted in meat proteins are very important in recovery and are usually fed initially in small amounts, several times daily. Treatment may continue for weeks to months and can even be indefinite in some cases in order to prevent recurrence of the liver failure.
Prognosis: Prognosis for recovery depends on how severe the injury to the liver has been, on the ability to remove any contributing cause of the disease, and on the general health of the animal. Older patients in poor body condition may experience failure of multiple organs even with a relatively moderate injury to the liver, whereas, a younger patient in good health that experiences the same injury to the liver may be able to fully recover with proper treatment.
Chronic Hepatic Failure and Cirrhosis
Introduction: Long-term gradual injury to the liver will lead to chronic liver failure and cirrhosis. Cirrhosis is a term used to describe excessive scar tissue formation with repeated attempts by the liver to regenerate itself. The end result is permanent and irreversible disfigurement of the organ structure and loss of liver function.
Causes: Early scar tissue formation is common in any situation where the liver becomes inflamed or irritated and generally can be reversed if the cause is removed. Cirrhosis results only when long-term constant injury occurs, such as repeated use of damaging drugs such as anticonvulsants, chronic accumulation of heavy metals such as copper, certain liver infections, or long-term deprivation of oxygen which occurs with some types of heart failure. One of the more common causes of chronic liver disease leading to failure is termed "idiopathic," meaning the actual cause of the damage is unknown. Idiopathic chronic hepatitis is thought by some to be a result of gradual, constant damage by the body’s own immune system.
Once cirrhosis begins to disorganize the structure of the liver, it is very common for the organ’s blood supply to re-route itself, often resulting in portosystemic shunting (see discussion later in this article). The change in blood flow through the liver also leads to lack of oxygen and cell death, worsening the cirrhosis. The pattern becomes a vicious cycle. Removing the initial cause of damage at this point may slow down the progression to complete liver failure, but the problem is considered irreversible and incurable.
Diagnosis: Diagnosis of chronic liver disease and cirrhosis follow much the same outline as for acute hepatic failure. Physical examination, bloodwork, serum bile acid testing, abdominal radiographs and ultrasound are helpful in making a preliminary diagnosis. Liver biopsy and histopathology are the only ways to completely make a diagnosis of cirrhosis, however.
Treatment: Treatment of cirrhosis is mainly supportive since there is no cure for a liver in this condition. Controlling the unpleasant associated problems with cirrhosis can be accomplished initially with a variety of medications: antibiotics for secondary infections, diuretics or dietary modification to control fluid retention in the body, antacids to help treat ulcers of the stomach and intestines, and specific therapy for hepatic encephalopathy. Sometimes treatment of the underlying cause can be helpful at this point (but not curative), such as suppressing the immune system with cases of idiopathic chronic hepatitis or changing the drug regimen for dogs receiving anticonvulsant medication.
Prognosis: The long-term prognosis for chronic hepatic failure and cirrhosis is poor.
Cholestatic Hepatobiliary Disease
Introduction: Cholestasis is a term referring to the blockage of bile. Bile is the digestive fluid produced by the liver and normally excreted into the upper small intestine to help digest food. Bile ranges in color from yellow to dark green to brown and is often seen when an animal vomits. Bile-tinged vomit does help a veterinarian know that at least some bile is being normally excreted by the liver into the small intestine and that the connection from the stomach into the small intestine is open. Some diseases cause a blockage of normal excretion of bile into the small intestine. Harmful waste products normally removed from the body through bile then tend to back up into the liver and other body systems. One of these products that can be measured in the bloodstream is bilirubin, a breakdown product of dead and dying red blood cells. Increased levels of bilirubin in the bloodstream give a yellow tinge to the skin and other tissues of the body. This condition is called "jaundice" or "icterus." While icterus is not a specific pinpoint of liver disease, there are not many other disorders in the body which can cause this yellowing of the tissues to occur.
Causes: Most of the time cholestasis is caused by inflammation to the bile ducts and tubes through which bile flows. A variety of diseases can cause this type of inflammation, most of which require a biopsy of the liver to specifically diagnose. Bloodwork, serum bile acid testing, abdominal radiographs, and ultrasound of the liver can all be helpful tools in pinpointing the specific problem which has led to blockage of bile flow. Treatment and prognosis of cholestatic liver disease depends on the specific cause. If the specific disease can be identified and proper treatment initiated, the outcome is often favorable.
Introduction: One of the primary functions of the liver is to "metabolize" or alter in some way any foreign substance which enters the body. Any such substance which is taken orally, whether it be some type of medication or the animal’s normal diet is broken down by the digestive tract and absorbed into the bloodstream. All blood from the digestive tract enters the liver before it can proceed to any other part of the body. Many of the foreign substances consumed by a pet have been shown to cause irritation or damage to liver cells. Most of the time, the irritation is mild and will never become a problem to the animal. Occasionally, a drug or toxin may be encountered that causes significant damage to the liver and leads to disease or even organ failure and potentially death. A list of drugs commonly used in veterinary medicine which have been shown to cause some degree of liver damage in dogs is included below:
A list of toxins which are known to cause liver damage in dogs is also included:
Diagnosis: Diagnosis of drug-induced liver injury is generally identified through the animal’s medical history, physical examination by a veterinarian, and routine bloodwork showing liver enzyme levels. Discontinuing the use of the damaging drug is the most effective treatment, followed by any supportive care that may be needed. Most of the time, the outcome is very favorable for drug-induced liver injury. If the drug or toxin has caused enough damage to lead to failure of the liver, aggressive supportive care, usually with hospitalization of the animal is advised. A favorable outcome in these cases is questionable.
Introduction: A variety of viruses, bacteria, and fungi routinely cause liver disease in dogs. Some of the most important of these are listed in the following information:
Infectious Canine Hepatitis (ICH) - Please see page F360
ICH is caused by canine adenovirus-1 which specifically targets liver tissue in dogs. Prior to development of an effective vaccine, ICH was much more common than it is today. Vaccination against this disease is routine in any standard immunization protocol. The "A
2" in DA2PP stands for adenovirus-2, a very close relative of canine adenovirus-1. It has been found and proven through years of use that vaccination against adenovirus-2 also protects the dog against adenovirus-1. The virus causes the sudden death of large numbers of liver cells and subsequent liver failure in dogs with no immunity; in dogs with low immunity, it can cause long-term liver inflammation leading to cirrhosis and eventual liver failure. Dogs with high immunity can effectively fight off the virus, preventing any damage to the liver. The virus also targets tissues in the eye, leading to possible blindness. Often the eye takes on a bluish appearance from leakage of fluid into the cornea, which is why this disease has been nicknamed "blue eye." Treatment of ICH primarily consists of supportive care, but a positive outcome is doubtful in many cases.Canine Herpesvirus (CHV) - Please see page F105
Canine herpesvirus infection in puppies between 1 and 3 weeks of age causes fatal liver failure as well as failure of many other organs. Puppies usually acquire this disease from their mother as they pass through the birth canal. They may also become infected through nasal or vaginal secretions after birth.
Once one puppy is infected, it spreads the virus among its littermates. The virus takes 4-7 days to start causing problems, which rapidly develop into a fatal disease. This virus is one major cause of "fading puppy syndrome" which tends to affect multiple puppies in a litter. No vaccine exists for prevention of canine herpesvirus. Tissue hemorrhage is commonly seen with bruising of the skin and gums. Death usually occurs in puppies less than 3 weeks of age. If a puppy is infected between 3 and 5 weeks of age, the puppy has a better chance of survival. Most often the diagnosis is made through a necropsy of a deceased puppy. Littermates of the deceased puppy can then be treated for CHV with intraperitoneal injections (given directly into the abdomen) of serum from a dog known to have survived herpesvirus infection. This treatment may be helpful in making the disease less severe for affected puppies. Female dogs which have lost entire litters of puppies to herpesvirus infection may still be able to successfully have healthy litters in the future if she provides sufficient antibody protection through her colostrum. However, this possibility is not certain and a risk is taken when breeding a dog known to have been infected with CHV.
Since no vaccination exists for protection against canine herpesvirus, the best prevention of this disease is to refrain from breeding to any dog (male or female) known to have been infected at any time in the past. There is no known treatment for CHV in adult dogs that may shed the virus through their reproductive tracts. Fortunately, the prevalence of this infection tends to be rather low (less than 20%) among the dog population as a whole.
Leptospirosis - Please see page F468
Canine leptospirosis is a bacterial infection that primarily affects the kidneys and liver. Different types of the Leptospira family of bacteria are responsible for varying degrees of illness. Some types cause kidney disease only, with little to no liver involvement. When the liver is affected by leptospirosis, it generally swells, causing cholestasis (see previous information). Tissues become jaundiced (yellow) as a result of bile backup. Diagnosis of leptospirosis is made through serology. Treatment consists of aggressive supportive care and antibiotic therapy. For the most part, treatment of leptospirosis focuses more on the kidneys than on the liver because those animals that die from this infection usually succumb to renal failure. Vaccination against certain strains of leptospirosis is recommended as a preventative measure for dogs living in areas where this disease prevails. Other preventative measures include strict kennel sanitation, isolation of infected animals, rodent control, and limiting access to marshy or muddy ponds, stagnant water, heavily irrigated areas, and wildlife.
Causes: Abscesses can form in the liver through a variety of ways. In puppies, infection of the umbilical cord/stump can travel directly to the liver through a vein that connects the navel to the liver. This vein disappears as a puppy matures.
Older dogs may acquire bacterial infections of the liver through the bloodstream from other areas of the body, or through a direct puncture or stab wound into the liver. Sometimes the bile ducts themselves become infected and bacteria can then travel up into the liver, usually causing swelling and cholestasis (see previous information) as it progresses. The liver’s blood supply is complicated and easily affected by inflammation or other diseases of the body. If the liver cells begin to suffer from a lack of oxygen because of low blood pressure in the vessels which feed the liver, bacteria will thrive and begin to destroy those weakened cells. To some degree, bacteria are always present in the blood from the digestive tract and in the liver itself as it cleans and filters the material received from the stomach and intestines. Any weakening of the liver’s defenses can easily lead to bacterial growth and abscess formation. Any disease that causes suppression of the immune system in general, such as diabetes mellitus and Cushing’s disease, can also set up the proper conditions for developing a liver abscess. Staphylococcus bacteria are responsible for most liver abscesses in dogs. E.coli, Salmonella, and Clostridium species have also been found in hepatic abscesses.
Clinical Signs: Dogs with liver abscesses exhibit a variety of clinical signs, most often including vomiting, lethargy, and anorexia. Sometimes jaundice is present if the abscess has caused cholestasis. A veterinarian may find tenderness of the abdomen and enlargement of the liver on a physical examination. Leakage of fluid into the abdomen and fever may also be found. If a liver abscess breaks open and leaks pus and contamination into the abdomen, the dog may rapidly go into shock and die.
Diagnosis: Sometimes it is very difficult to diagnose a liver abscess. These infections can be hidden deep within the organ and often do not show up on an x-ray of the abdomen. Ultrasound of the liver is very helpful at finding abscesses within the liver. Surgical exploration of the abdomen is also a common method used to diagnose liver infections and abscesses. Bloodwork usually shows a high white blood cell count and increases in liver enzymes. These findings are not consistent, however. Surprisingly, liver enzymes may be normal in the face of a liver abscess. Aspiration of fluid from the abdomen may show white blood cells are present when examining the fluid using a microscopic. If bacteria are also seen, either within the white blood cells or free in the fluid, a condition called "septic abdomen" is present and emergency surgery is usually warranted.
Treatment: Treatment of hepatic abscesses consists of correction of fluid imbalances in the body, appropriate treatment with antibiotics, and surgical drainage or removal of the abscess. If the underlying disease which led to the abscess in the first place can be corrected, and if the abscess is appropriately treated, the prognosis for full recovery is fairly good.
Systemic Fungal Infections
Fungal infections that affect entire body systems will often affect the liver. This is especially true in cases of histoplasmosis or coccidiomycosis. Abdominal swelling with excess fluid, swelling of the liver, and jaundice are usually noted. Most of the time other body systems are affected. For example, since these fungal organisms tend to be inhaled from the environment the respiratory tract is often involved. With special staining by a pathologist, a biopsy of liver or other body tissue can help diagnose these infections. Treatment is supportive with specific anti-fungal medications given to eliminate the organism.
Introduction:
Cholangiohepatitis is a disorder specifically affecting the bile ducts and surrounding liver cells. Since this disease is very uncommon in dogs, the discussion here will be brief.Causes: Cholangiohepatitis occurs when inflammation and sometimes bacterial infection occur around bile ducts. The duct tissue becomes inflamed and can eventually result in severe scar tissue formation and permanent blockage of the bile ducts. Cholestasis and inflammation of the surrounding liver cells (hepatitis) develop as a result. The actual cause of the original inflammation is usually not known. When bacteria are involved, they are usually suspected to have arrived from the intestines. Sterile inflammation can occur in the absence of any infection at all. Once cholestasis occurs, progressive bacterial infection which penetrates deeper and deeper into the liver can result as a secondary complication. Gall bladder stones can occur if the bile remains stagnant for long enough to solidify.
Clinical Signs: Dogs with cholangiohepatitis may experience lethargy, lack of appetite, vomiting, weight loss, fever, dehydration, and jaundice.
Diagnosis: A preliminary diagnosis of this condition can be obtained through bloodwork combined with imaging tests such as radiographs and ultrasound examination. For a certain diagnosis to be made, a liver biopsy with histopathology is generally required. Abdominal surgery or laparoscopy is often recommended for obtaining a biopsy sample so that the liver and surrounding tissue can be carefully inspected. Biopsy specimens for histopathology as well as bacterial culture should be obtained.
Treatment: Treatment of cholangiohepatitis may take weeks to months. Supportive care, such as fluid therapy, nutritional support, and vitamin supplementation, is often essential. Long-term antibiotics are selected based on culture results, if possible. Corticosteroids are sometimes used to relieve the inflammation in the ducts and allow bile to flow properly again. Corticosteroids should be used with caution, however, since they weaken the immune system, making the patient more susceptible to bacterial infection.
Prognosis: Prognosis for this condition is variable and unpredictable. Some dogs which recover may experience recurrences throughout their lives.
Introduction: Canine chronic hepatitis is a broad title that covers several types of inflammatory liver disease occurring in dogs. Most of these diseases are breed-specific and tend to worsen with age in susceptible individuals. Diagnosis of chronic hepatitis depends on a liver biopsy. However, biopsies cannot always reveal the cause of the inflammation. In fact, few of the known categories of canine chronic hepatitis have any known cause. Copper accumulation in the liver is one of the few well-known causes of canine chronic hepatitis. Bedlington terriers, West Highland White terriers, Skye terriers, and Doberman pinschers are known to experience differing degrees of chronic hepatitis associated with copper accumulation. American and English cocker spaniels tend to have a higher than expected rate of chronic hepatitis and liver failure, but the underlying cause is unknown in these breeds. Any dog breed may be affected with chronic hepatitis and liver failure, however.
Introduction: Copper is present in small quantities in the diet of all mammals. Certain dog breeds have a heritable tendency to store excessive amounts of copper in the liver. With time, these copper deposits can cause significant injury to the liver, leading to organ failure and cirrhosis. Bedlington terriers are the most prone to copper-induced liver failure, and it has been proven to be a recessive genetic trait. This is a significant problem in the United States, where as many as two-thirds of the breed may be affected or carry the problem gene. Prior to breeding any Bedlington terrier, it is recommended that a liver biopsy be performed at one year of age or older to screen for this genetic disease. A liver registry has been formed for certification of Bedlington terriers that are unaffected by genetic copper-associated liver disease (Canine Liver Registry, Veterinary Medical Data Base, 1235 SCC-A, Purdue University, West Lafayette, Indiana 47907-1235). Other breeds which have been shown to experience copper-associated liver damage include West Highland white terriers, Skye terriers, and Doberman pinschers.
Clinical Signs: Clinical signs of copper accumulation are similar to those seen in chronic hepatitis of any cause and can include loss of appetite, decreased energy levels, weight loss, vomiting, diarrhea, swollen abdomen, and jaundice. Occasionally, copper may be released in large quantities from dying liver cells directly into the bloodstream and can lead to the destruction of red blood cells (hemolytic anemia). Sometimes the disease may be present in a dog’s liver without causing any apparent clinical signs at all.
Diagnosis: Diagnosis of copper storage disease is best made with a biopsy of the liver. The concentration of copper in the liver tissue can be measured and compared with normal values. Other diagnostic tests that can be helpful include routine bloodwork, bile acid testing, ultrasound and radiographs of the liver, and surgical exploration of the abdomen.
Treatment: Treatment of copper-associated liver disease includes the use of products such as zinc which help prevent absorption of copper into the body from the digestive tract. Strict adherence to a low-copper diet is also important in preventing accumulation of copper in the liver, but it is of little value once the disease has become advanced. Other drugs, such as D-penicillamine, help the body excrete copper through the urinary tract. Blood transfusions may be necessary to treat hemolytic anemia. With the proper lifelong treatment, some dogs affected with copper accumulation in the liver may have long, relatively healthy lives. If treatment of this condition is stopped, the disease begins to progress again toward liver failure. Once hepatic failure has begun, appropriate supportive care should be initiated.
Introduction: Less than 2% of all cancerous disease in dogs begins in the liver. However, because the liver is a common site for the spread of other cancer types, liver cancer is a relatively common disease. Some of the more common types of cancer that spread to the liver include lymphosarcoma, hemangiosarcoma, malignant mammary gland cancers, malignant tumors from the digestive tract, pancreatic cancers, and mast cell tumors. Primary liver cancer in dogs includes hepatocellular carcinoma (most common type), hepatocellular adenoma (sometimes called hepatoma), and bile duct carcinoma.
Clinical Signs: Signs of liver cancer include lethargy, weight loss, decreased appetite, vomiting, and sometimes jaundice. These clinical signs are typical of most other liver diseases and are not specific to cancer. Knowledge of tumors in other parts of the body, such as mammary gland cancer, may help cast suspicion on a metastatic liver cancer if suggestive clinical signs are seen.
Diagnosis: Diagnosis of liver cancer requires biopsy, just as for other types of cancer. One possible exception to the traditional biopsy for diagnosis of liver cancer is lymphosarcoma, which may be tentatively diagnosed with a good cytology sample. Both biopsy and cytology samples may be obtained from the liver during an ultrasound procedure. Laparoscopy and surgical exploration of the abdomen for obtaining a biopsy sample have the advantage in that the doctor can observe closely for hemorrhage following the procedure. Bleeding tendencies are rather common if the liver is in failure and are a risk factor to be considered when planning a biopsy.
Treatment: Treatment of liver cancer depends on the type of cancer present and on whether the liver is in failure or not. The benign hepatocellular adenoma often grows on a stalk attached to the liver. While they can become extremely large, they can be successfully removed with surgery and the pet will often have a survival rate of more than two years. Hepatocellular carcinomas are more serious, but may be treated with surgery if the tumor is confined to a portion of the liver. Some varieties of this cancer spread throughout the entire liver and cannot be successfully treated with surgery. Metastasis is also fairly common with hepatocellular carcinomas. They can spread to the abdominal wall, surrounding lymph nodes, and the lungs. Bile duct carcinomas are more common in female dogs and start from gallbladder tissue or the bile ducts leading through the liver to the small intestine. Close to 90% of these cancers have already spread to body wall, lymph nodes, or the lungs by the time the disease is diagnosed. This type of cancer can be removed surgically if it is relatively confined and has not spread to other organs or areas. In general, primary liver cancer tends to respond quite poorly to traditional chemotherapy protocols.
Treatment of metastatic liver cancer depends on the type of cancer that has spread to the liver. Proper treatment of the primary tumor and management of the secondary spread to the liver may be somewhat successful for many types of cancer, depending on the responsiveness to surgery and chemotherapy. Prognosis for patients with liver cancer depends greatly on the type of cancer. Malignant cancers affecting the liver, whether primary or from secondary spread, are usually given a guarded prognosis at best.
Introduction: Many diseases can create high blood pressure within the vessels leading into the liver. Inflammation and swelling of liver cells can impede normal blood flow through the liver, called portal hypertension. Blood pressure increases before it reaches the liver’s capillary beds and can create alternate routes to bypass the liver and thus avoid the areas of resistance. However, in doing this, the body creates a way for blood from the digestive tract to reach the heart without passing through the liver first. When a route is created wherein blood bypasses the liver, it is called a portosystemic shunt. This blood has not been treated or cleaned by the body’s natural filter and contains potentially harmful or toxic substances. The heart then pumps this blood throughout the body. Hepatic encephalopathy is the usual result when enough untreated blood is allowed into the body’s general circulation. Portosystemic shunts can also occur as birth defects, especially in small pure-bred dogs. Yorkshire terriers, miniature schnauzers, and Cairn terriers are among those breeds known to be predisposed to this problem. Male dogs affected with a portosystemic shunt from birth are often noted to retain a testicle (usually the right), a condition known as cryptorchidism.
Clinical Signs: Most dogs with congenital portosystemic shunts begin to exhibit problems by the time they are six months old, although some dogs may not begin to show clinical signs until they are several years old. Early clinical signs are usually non-specific and include lack of appetite, listlessness, depression, and vomiting. Signs of hepatic encephalopathy may then become apparent with drunken walking (ataxia), pacing, circling, seizures, disorientation, excessive salivation, and profound weakness that may come and go. At times the puppy may appear normal as the clinical signs come and go. Eating a protein-rich diet may bring on or worsen the typical signs of hepatic encephalopathy. Growing animals with PSS tend to be smaller than their normal littermates. Puppies with PSS also tend to be extremely sensitive to tranquilizers or anesthesia and may take an extremely long time to awaken. Animals that acquire portosystemic shunts later in life will sometimes show clinical signs of hepatic encephalopathy early on, but may also exhibit signs of general liver disease. Sometimes failure of the liver will occur by the time the shunt is sufficiently large enough to begin causing problems.
Diagnosis: Diagnosis of a portosystemic shunt requires some in-depth testing. Physical examination and bloodwork, along with the pet’s medical history may give suspicion to PSS. Serum bile acid testing can be extremely helpful in supporting a diagnosis. However, in order to pinpoint this disease exactly, it is generally necessary to physically observe the actual shunt. This can be done with ultrasound examination in some cases; however, the abnormal blood vessel is not always easily found using ultrasound. Specialized contrast radiography can also be used where dye is injected into the liver’s portal blood system. Then a series of radiographs are taken to show the flow of blood through (or around) the liver as it reaches the heart. Surgical exploration of the abdomen is also an appropriate method of diagnosing a portosystemic shunt.
Treatment: Treatment of this condition is achieved both medically and, in some cases, surgically. Specific antibiotics, fluid therapy, low-protein diets, special enemas, and medications for reducing the amount of ammonia in the bloodstream are all helpful in controlling the clinical signs associated with portosystemic shunts. Surgery can be an option for treatment if the shunt consists of a single blood vessel and the patient is in relatively good health. This is more likely with a congenital shunt than with a shunt acquired later in life. Because the operation is complicated and the recovery period is critical, this surgery should be performed at a specialty hospital. Closing off the entire shunt all at once is generally not possible because it causes an overload of blood through the normal vessels in the liver resulting in life-threatening complications. Either partial closure of the shunt or gradual complete closure over time are preferred. With successful surgical repair of a portosystemic shunt, the prognosis for this condition may be excellent if the animal regains full liver function. In some cases, medical management of this condition can result in a good quality of life for years after the problem is diagnosed.