Overview of Ascites in Dogs
Ascites is the abnormal accumulation of fluid in the abdominal cavity. The volume of the fluid can be quite subtle, or it may be significant, causing distention of the abdomen. In dogs, ascites has many causes, most of which can be very serious. Ascites is caused by the leakage of fluid into the abdomen from blood vessels, lymphatics, internal organs or abdominal masses.
Causes of Canine Ascites
Hypoalbuminemia or a decrease in the blood albumin level
Severe liver disease
Right sided heart failure
Peritonitis or inflammation of the inner lining of the abdomen
Diseases of lymphatics
Obstruction of the hepatic vein or caudal (lower) vena cava causing compromises in blood circulation
What to Watch For
Breathing difficulty or increased respiratory effort
Diagnosis of Ascites in Dogs
Certain diagnostic tests must be performed for a definitive diagnosis of the underlying cause of ascites. The following tests should be considered:
A complete history and physical exam should always be performed
Complete blood test (CBC)
Chest and abdominal x-rays
Abdominocentesis or peritoneal lavage with fluid analysis and culture. This involves sampling of the fluid from the abdomen for analysis and cultured if infection is suspected
Based on the results of these initial tests, further diagnostics might include:
Bile acid measurements
Abdominal ultrasound and ultrasound guided biopsies
Endoscopy (a fiber optic scope that is placed through the mouth and into the stomach and small bowel. The mucosa can be visualized and biopsies obtained)
Treatment of Ascites in Dogs
An accurate diagnosis is needed for proper therapy. Pending a definitive diagnosis, certain treatments may be appropriate:
Therapeutic abdominocentesis (removing a larger amount of fluid from the abdomen) if the amount of abdominal distention is compromising the animal’s ability to breath
Diuretics to promote fluid excretion
Oxygen therapy if the animal is in respiratory distress
Intravenous fluids in cases of shock or dehydration
Transfusions of blood products
Antibiotic therapy if infection is suspected
Keep your dog calm and minimize stress. Make sure your pet stays warm and provide fresh water if your pet wants to drink. Seek veterinary care immediately if your pet is having trouble breathing or is extremely weak.
In-depth Information on Ascites in Dogs
Ascites, itself, usually does not cause a problem, but the primary disease process causing the ascites can be a serious condition. Ascites is usually produced slowly and in small amounts; however, if a large amount of fluid is produced, or rapidly produced, an emergency situation may exist. Large amounts of free fluid in the abdomen may compress the diaphragm, leading to respiratory compromise and difficulty breathing. Fortunately, this is a rare occurrence.
Another potential emergency situation is the rapid onset of ascites. If the ascites develops quickly, it is often associated with profound weakness or shock. The loss of intravascular (within the blood vessels) blood volume may lead to acute anemia and shock as fluid leaves the blood vessels and moves freely into the abdominal cavity. The most common cause of such an event is the rupture of a blood vessel within the abdominal cavity. Bleeding tumors within the abdomen or traumatic injury are likely causes.
Most of the time, the fluid buildup is more gradual and an emergency situation is not present. Any amount of ascites is a significant finding, however, and steps should be taken to find a diagnosis. Ascites has many different causes and establishing a diagnosis is usually not difficult. A good physical exam, basic blood tests and evaluation of the ascitic fluid often lead to the diagnosis, or they provide a direction upon which further diagnostics need to be done.
Hypoalbuminemia is a decrease in serum albumin levels. Albumin is available through the diet, but it is also produced in the liver. The kidney functions to maintain albumin concentration in the plasma by preventing its excretion in the urine. Normal gastrointestinal function is needed for proper absorption. Albumin is responsible for much of the colloidal osmotic pressure of the blood, and thus is an important factor in regulating the exchange of water between the plasma and the interstitial compartment (space between the cells). Decreases in the albumin level (usually under 1.5 gm/dl) lead to a pressure gradient that causes fluid to leak out of the blood vessels, producing ascites.
Protein-losing nephropathy. Disease of the kidney’s glomerulus (filtration system) may produce a condition where protein is excreted through the urine resulting in very low plasma albumin levels. This may be caused by infectious, immune, neoplastic or idiopathic (unknown etiology) mechanisms.
Gastrointestinal diseases that prevents the absorption of albumin. If albumin is not being absorbed, low blood levels are to be expected. Some diseases causing this include gastrointestinal lymphoma, inflammatory bowel disease and intestinal lymphangiectasia.
Severe liver disease may cause ascites by decreased albumin production or by increased resistance to blood flow within the liver. Severe hepatitis and liver cirrhosis are examples.
Obstruction of blood flow within the abdomen can result in ascites. This obstruction may cause a leakage of fluid from the veins or lymphatics and into the peritoneal (abdominal) cavity depending on the location.
Obstruction of the blood flow from the liver to the heart (hepatic venous outflow obstruction) may cause a more chronic ascites. This occurs in right-sided heart failure, as the heart cannot handle the venous blood return from the liver.
Right sided heart failure. This may be caused by primary cardiac disease, pulmonary disease or severe heartworm infestation.
Abdominal masses. Tumors, abscesses or cysts may cause ascites by several mechanisms. They may rupture, causing acute ascites. Hemangiosarcoma is the most common tumor to potentially rupture and bleed. Other masses may compress or cause obstruction of vessels and lymphatics causing a more chronic and slower buildup of ascites.
Trauma. Rupture of the spleen may cause leakage of blood; rupture of the gall bladder may cause leakage of bile, a bile peritonitis; injury to the urinary tract (kidney, ureter, bladder, or urethra) may cause leakage of urine, resulting in a uroabdomen (urine within the abdomen).
Peritonitis is inflammation of the inner lining of the abdomen. This inflammation can produce fluid in varying amounts with very specific characteristics. Acute pancreatitis is a potential cause. Peritonitis can also occur in cases of bowel (stomach, small and large intestines) compromise or perforation, necessitating emergency surgical intervention.
Bleeding disorders caused by a variety of conditions (poisoning, metabolic, inherited, cancer) might result in a bloody ascites.
Diseases of the lymphatics may cause lymph fluid to form in the abdomen. Ruptured lymphatics due to tumors, trauma or idiopathic (unknown etiology) conditions are the usual causes.
A complete history and physical examination is very important in determining the diagnostic aids of choice. Proper evaluation will determine the depth of the diagnostics needed.
Abdominocentesis is the sampling of the ascites using a needle and syringe. The fluid obtained is then submitted to a laboratory for fluid analysis. This may be the single most important diagnostic test when evaluating an animal with ascites because specific diseases have specific fluid analysis characteristics. Ascitic fluid is divided into three different categories based on the fluid’s cell count and protein concentration.
Transudates are fluids of low cell count (under 1500cells/mcl) and low protein concentration (under 2.5g/dl). Examples of transudates include those caused by: hypoproteinemia, liver disease, some tumors and obstruction of lymphatic drainage.
Modified transudates are fluids with higher cell counts (1000 to 7000 cells/mcl) and protein concentration (2.5 to 7.5g/dl). Examples of modified transudates include ascites caused by: congestive heart failure, abdominal tumors, obstruction of the hepatic vein or thoracic caudal vena cava and some liver diseases.
Exudates are fluids with the highest cell counts (over 7,000 cells/mcl) and protein concentrations (usually over 3.0g/dl). Examples include: bleeding conditions, tumors, bacterial infections caused by bowel compromise, chyloabdomen (lymph fluid in the abdomen), urine and bile leakage and pancreatitis.
A pathologist also examines the cell types microscopically. Different types of cell populations represent different disease processes, and cytologic evaluation is a valuable aid in establishing a correct diagnosis.
CBC. The CBC evaluates the red and white blood cell lines. Elevations and morphology changes in the white blood cell line may indicate peritonitis. Decreases in the red cells are indicative of anemia. Acute blood loss or chronic debilitating diseases are potential causes of the anemia. Platelet (blood cells required for proper clotting) counts are assessed. Significant decreases may lead to intra-abdominal hemorrhage.
A biochemical profile evaluates several body systems. A decrease in serum albumin (hypoalbuminemia) would be noted. Decreased kidney function is assessed with increases in blood urea nitrogen (BUN) and creatinine. Liver disease is evaluated by elevations in ALT, AST and ALKP enzymes. Decreases in BUN, albumin, cholesterol and occasionally blood glucose might indicate decreased liver functional capability.
A urinalysis completes the assessment of kidney function. Urinary protein loss (proteinuria) may be noted, and a follow up urine protein creatinine ratio might be recommended to confirm and quantify significant urinary protein loss.
Chest x-rays evaluate the heart and lungs for evidence of cardiopulmonary disease. Cardiac enlargement or fluid in the chest may suggest right-sided heart failure. Masses near the diaphragm compressing the caudal vena cava may also be visualized. Abdominal x-rays may be useful in evaluating liver and kidney size as well as visualizing some abdominal masses. Unfortunately, if there is a significant amount of ascites, the abdominal structures are often obscured by the nature of the fluid.
A bile acid measurement is a specific test of liver function. If the ascites is due to liver disease the bile acids are generally highly elevated.
Serum lipase measurements test for pancreatic inflammation. Pancreatitis, pancreatic cancer and pancreatic abscesses may all cause elevations.
An abdominal ultrasound is an excellent test for evaluating abdominal organs when ascites is present. Generally, the fluid in the abdomen enhances the images, providing for greater detail. This allows for visualization of abdominal masses and evaluation of the liver, kidneys, spleen and pancreas. If indicated, abnormalities may be biopsied for definitive diagnosis.
If heart disease is suspected, an echocardiogram is indicated. The heart valves and heart muscle are visualized, and cardiac function may be assessed. Congestive heart failure has many causes, and an echocardiogram is the diagnostic test that provides the best information on the prognosis and treatment of the disease.
Endoscopy is a good, relatively noninvasive, method of assessing small bowel disease. The inner lining of the stomach and duodenum can be visualized and biopsied. Intestinal neoplasia, inflammatory bowel disease and intestinal lymphangiectasia may be a cause of a protein losing enteropathy (losing protein through the gastrointestinal system).
One or more of the diagnostic tests described above may be recommended by your veterinarian. In the meantime, treatment of the symptoms might be needed, especially if the problem is severe. The following nonspecific (symptomatic) treatments may be applicable to some, but not all, pets with ascites. These treatments may reduce severity of symptoms or provide relief for your pet. However, nonspecific therapy is not a substitute for definite treatment of the underlying disease responsible for your pet’s condition.
The most important aspect of treating ascites is to determine how quickly the ascites has developed, and the clinical condition of your pet. If the ascites has developed slowly, and your pet is fairly strong, then emergency treatment is generally not required. If the ascitic fluid has developed rapidly, it is often associated with weakness and emergency care is indicated. Appropriate treatment pending a diagnosis of the primary cause of the ascites may include:
Therapeutic abdominocentesis. If there is a large amount of fluid in the abdomen it may be compressing the diaphragm, which leads to difficulty breathing. A needle is inserted into the abdominal wall and fluid drained to relieve the pressure, making breathing easier and your pet more comfortable. Once your pet is breathing more comfortably, the needle is withdrawn. All the fluid is not removed, however, because losing too much fluid from the body may lead to shifts in fluid homeostasis and shock.
Diuretics are medications given to promote the removal of fluid from the body. Fluid is excreted as urine production is increased. Diuretics are most effective in removing fluid from tissue rather than from a body cavity; thus they have limited effect on removing ascitic fluid from the abdomen. Furosemide (Lasix) is most commonly used.
Animals in respiratory distress often require oxygen for stabilization. Oxygen may be provided by an oxygen mask, nasal oxygen canola or an oxygen cage. Usually, once some fluid has been removed from the abdomen, the oxygen is no longer required.
A rapid onset of ascites might require intravenous fluid support to maintain tissue perfusion and treat an animal in shock. If the animal has a low total protein (due to a low blood albumin level), fluid support with colloids (fluids that increase the oncotic pressure of plasma) may be given to slow the production of the ascites.
Transfusions with blood, or blood products, might be required if the ascites is due to bleeding within the abdomen. If transfusions are needed, the animal is usually very weak and has a falling hematocrit (a blood test that measures anemia).
If infection is suspected, intravenous antibiotics are given pending definitive diagnosis. Ascites caused by infection is a situation requiring emergency surgery.