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Overview of Canine Abdominal Distension
Abdominal distension is an abnormal enlargement of the abdominal cavity. This term is usually reserved for abdominal enlargement due to causes other than simple obesity.
In dogs, one cause of abdominal distension is fluid accumulation. The types of fluids include blood from internal hemorrhage (bleeding), urine from a tear in the urinary tract, exudate (cellular fluids similar to pus) from infection as with feline infectious peritonitis, and transudates (clear fluids), that are leaked from vessels.
Another cause of abdominal distension is enlargement of any abdominal organ including the liver, kidneys, or spleen. Distension of the stomach with air (“bloating“) or fluid or distension of the uterus (womb) during pregnancy, can result in abdominal distension.
Tumors within the abdomen can also cause abdominal distension. The tumor may be malignant (an invasive cancer), or benign, (abnormal but not spreading to other tissues). Tumors can involve any of the abdominal organs, including the intestines or lymph nodes (glands).
Loss of abdominal muscle tone, with or without significant weight gain, also can lead to abdominal distension.
Pressure from the abdomen pushing into the chest may make breathing more difficult and pressure within the abdomen may decrease the appetite. NOTE: It is important to recognize abdominal distension because it can be a symptom of potentially life-threatening diseases and should be investigated thoroughly.
What to Watch For
- Sudden abdominal enlargement. Treat this as a medical emergency especially if associated with vomiting, retching, sudden weakness or collapse.
- Distension that occurs over days to weeks. This requires prompt medical attention.
- Slowly developing abdominal enlargement. This should be investigated if it is accompanied by loss of muscle or fat in other regions of the body, decreased appetite, vomiting or diarrhea, changes in urinary or bowel habits, or a diminished activity level.
Diagnosis of Abdominal Distension in Dogs
Veterinary care should include diagnostic tests to determine the cause of the abdominal distension and provide information on which to base recommendations for treatment. Diagnostic tests that your veterinarian may wish to perform include:
- A complete medical history and physical examination
- Abdominal radiographs (X-rays)
- Abdominal ultrasonography
- Abdominocentesis (the removal of fluid from the abdomen using a needle)
- Thoracic radiographs (chest X-rays)
- Blood tests such as biochemistry analysis, a complete blood count (CBC), a PCV (packed cell volume) and TP (total protein)
- Other specific tests, like liver function, evaluation for feline coronavirus exposure or biopsy of affected tissues or organs
Treatment of Abdominal Distension in Dogs
Treatment for abdominal distension is dependent upon the underlying cause (diagnosis). Treatment may include:
- Abdominocentesis or drainage of fluid from the abdomen. If fluid distension causes pressure on the diaphragm (the muscular membrane separating the chest and abdomen) and impairs breathing, fluid may be drained from the abdomen with a needle. Fluid accumulation that does not interfere with breathing is not routinely removed.
- Diuretic administration. Certain types of fluid accumulation can be lessened with diuretic administration, which increases urination.
- Surgery. Some causes of abdominal enlargement, including ruptured abdominal organs, must be treated surgically.
If you notice abdominal distension and your dog is acting sick, call your veterinarian. If abdominal distension is associated with vomiting, wretching or collapse, call your veterinarian immediately. These symptoms can be life-threatening.
In-depth Information on Abdominal Distension in Dogs
The abdominal cavity contains vital organs such as the stomach and intestines, liver, spleen, pancreas, kidneys and urinary bladder. It also contains numerous blood vessels, lymph vessels and lymph nodes are also present in the abdominal cavity and is lined with a thin, specialized membrane (the peritoneum) that contains the contents within a sterile environment.
Causes of Abdominal Distension in Dogs
Abdominal distension can be caused by fat accumulation, fluid accumulation in the peritoneal space, enlargement of abdominal organs or weakness of the abdominal muscles. The fluids that cause abdominal distension can be blood, urine, exudate, transudate or any combination of these.
Causes of these different fluid types are listed below:
Blood can fill the abdomen because of trauma, erosion of blood vessels, failure to form blood clots normally, or tumors causing organs to rupture.
Urine can fill the abdomen and cause distension. Rupture of the urinary tract is generally the result of trauma (such as being hit by a car).
Exudates are thick, cellular fluids. These fluids often result from infection within the abdominal cavity. Dogs may develop exudate in response to bacterial infection as a result of a penetrating injury or a tear in the gastrointestinal tract. This can occur in dogs with a string-type foreign body that “saws” its way through the intestine. Exudates may also accompany cancers of the abdomen (neoplastic effusion) or result from obstruction to drainage of lymphatic fluid (chylous effusion). Lymphatic fluids are fluids that surround cells and are collected and transported by lymph vessels into the bloodstream.
Transudates are clear fluids, without many cells or much protein, resulting from pressure blocking normal blood flow or from decreases in the protein (albumin), which holds water in the blood. Examples of processes likely to produce transudates include:
- Right-sided heart failure, in which blood “backs up” in the vessels because it cannot enter the heart easily, and some liquid from the blood is forced out of the vessels. Congenital heart disease, heart muscle disease (cardiomyopathy), arrhythmia (abnormal electrical activity of the heart), and diseases of the pericardium are also potential causes of right-sided heart failure in dogs. However, heart failure is a very uncommon cause of abdominal fluid accumulation in dogs.
- Cirrhosis, or fibrosis of the liver, also causes changes in pressure to the blood vessels within the abdomen. In addition, cirrhosis results in liver failure. When the liver fails, it does not produce normal amounts of albumin (blood protein).
- Loss of albumin through the kidneys (or the gastrointestinal tract (lymphangectasia or protein loosing enteropathy) can lead to very low albumin levels. When albumin levels are too low, liquid is not held within the blood and can leak out into the abdomen. This situation is very uncommon in dogs.
Enlargement of any abdominal organ can cause distension. Enlargement of the liver, kidneys or spleen may be due to obstructions of fluid flow (either blood flow or urine flow) or infiltration with cells (cancer or leukemia cells or inflammatory blood cells).
Other causes of abdominal distension that are not caused by fluid accumulation include:
- Distension of the stomach caused by air (bloat) or distension of the uterus (womb) during pregnancy
- Tumors within the abdomen, which can be malignant (invasive cancer) or benign, and may involve any of the abdominal organs, including intestines or glands
- Loss of abdominal muscle tone with or without significant weight gain
Diagnostic tests are needed to recognize abdominal distention and exclude other diseases. These tests may include:
- A complete medical history and physical examination. Expect to answer questions regarding your dog’s environment, dietary and elimination habits, the progression of symptoms and any other changes from the norm. Your veterinarian will likely be able to tell from physical examination if the swollen abdomen is the result of fluid or a solid mass.
- Abdominal radiographs (X-rays) can show enlargement of abdominal organs and large tumors. Radiographs may not be requested if the abdomen is full of fluid, because fluid obscures the picture.
- Abdominocentesis is the removal of fluid from the abdomen and may be both therapeutic and diagnostic. The fluid can be analyzed by chemical methods and viewed under a microscope to determine what type of fluid it is (blood, urine, exudate, transudate or a mixture) and thereby determine which causes are most likely.
- Abdominal ultrasonography, in which a probe is held against the abdomen after clipping the hair, allows sound waves to produce a picture of the abdominal contents. Unlike radiographs, ultrasound works well when fluid is present. Yet another advantage of ultrasound over radiographs is that ultrasound allows visualization of the inside of the organs, rather than simply viewing the organ silhouette. Your veterinarian may request that a specialist perform this test.
- Thoracic radiographs (chest X-rays,) may be requested to look for the spread of cancers or to evaluate the heart. Heart failure is an important cause of abdominal fluid accumulation.
- A complete blood count (CBC,) may provide evidence of infection or anemia (deficiency of red blood cells).
- Biochemical analysis of the blood can provide clues to the underlying cause of fluid accumulation and allow assessment of organ function.
- Urinalysis can detect protein loss through the kidneys (one potential cause of abdominal fluid buildup,) and provide clues to both kidney and liver function.
- Biopsies, obtained at surgery or with a needle, may be recommended if tumor or organ enlargement is detected.
On an individual basis, additional diagnostic tests may be needed to determine and/or diagnose other medical problems or to understand the overall impact abdominal distention may have on your dog. These include:
- Bile acid measurements involve analyzing a blood sample obtained after fasting (usually 12 hours) and then giving the animal food. Eating causes bile to be released from the gallbladder but bile should be reabsorbed by the intestines and removed from the blood by the liver. Elevated blood bile acid levels suggest liver disease or abnormal circulation to the liver.
- Urine protein quantification can be done by collecting all urine for 24 hours and measuring the protein content, or an estimate of protein can be made from a one-time urine measurement. Urinary protein loss can lead to abdominal fluid accumulation. This test is rarely done in dogs.
- Biopsies of the intestines obtained either at surgery or with endoscopy, may be recommended if a very low albumin level is believed to be present due to loss of this protein through the intestines. Endoscopy involves passing a fiberoptic tube down the mouth of an anesthetized patient, and examining and/or taking a biopsy of the inner lining of the stomach and part of the intestine. An endoscopy cannot show the entire length of the intestine, nor can biopsies be taken from every layer of the intestines. Often, a specialist will perform this test.
- Echocardiography uses ultrasound to examine the heart and its valves and the entrance of the caudal vena cava (the large vein that drains the abdomen). This test is similar to abdominal ultrasonography. Infrequently in dogs, heart failure can cause abdominal fluid accumulation. A specialist usually performs this test.
- Bacterial cultures of any abdominal fluid may be performed to help determine the cause of fluid accumulation and to help pick the best possible antibiotics to treat infection.
- Intravenous pyelography (IVP,) involves injection of a dye into the veins, followed by radiographs of the kidneys. This test may be indicated if a very enlarged kidney is found to be the cause of the abdominal distension. Kidneys can become very enlarged if urine flow is blocked, if tumors are present or in certain hereditary diseases in which fluid-filled cavities (cysts,) form within the kidney tissue.
- Various specific tests may be performed to look for infectious diseases.
Exact treatment requires establishment of a diagnosis. Abdominal swelling in itself is seldom a threat to life, so symptomatic (nonspecific) treatments are often not indicated. However, severe abdominal distention can place pressure on the chest and interfere with comfortable breathing. The following is a list of potential nonspecific (symptomatic) treatments that may be applicable. These treatments cannot be a substitute for more definite treatment.
- Abdominocentesis, the removal of abdominal fluid through the placement of a needle, is primarily used as a diagnostic aid but can also relieve pressure from excess fluid accumulation.
- Certain types of fluid accumulation can be lessened with diuretic administration, which increases urination. Unfortunately, diuretics often fail to greatly reduce abdominal fluid accumulation.
- Some causes of abdominal enlargement, including ruptured or twisted abdominal organs can be life threatening conditions, and must be treated immediately with surgery. See your veterinarian as soon as possible.
Follow-up Care for Dogs with Abdominal Distension
Optimal treatment and follow-up for your dog requires a combination of home and professional veterinary care. Specific recommendations will be dependent upon the underlying cause of the abdominal distension.
- Administer prescribed medication(s) as directed by your veterinarian. Be certain to alert your veterinarian if you are experiencing problems treating your dog.
- Monitor your dog. You may be requested to either weigh your dog or measure abdominal girth with a tape measure. Note changes in appetite, thirst, elimination behaviors, including the frequency of urination. Also note changes in attitude, including increased or decreased activity levels.