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Written by Vet Evidence Based

Fluid In Abdomen In Dogs: What Causes It? And How Can It Be Treated?

Margarita Boyd
Written by: Dr. Margarita Boyd, BVSc MRCVS
Ascites in dogs is an abnormal build-up of fluid in the abdomen. This condition is also known as abdominal effusion. Check here what creates this condition.

The abdomen, which is commonly called the belly, is the area of the dog’s body that contains the digestive organs such as the intestines and kidneys.

This area can fill with abnormal fluid and cause problems for the dog. The medical terms used for fluid in a dog’s abdomen are ascites or abdominal effusion.

The buildup of abnormal fluid in the belly can make your dog feel very sick, with signs of vomiting, weakness, and discomfort. There are many different underlying causes of this serious condition in dogs, and each one requires specific treatment.

In this article, we will find out more about this serious condition and what causes it, as well as teaching you how to spot the symptoms of fluid in the abdomen in dogs.

What Is Ascites?

Ascites is the build-up of abnormal fluid between the organs in the abdomen. Over time, the fluid can build up to cause the dog’s belly to become distended.

Depending on the underlying cause this can happen slowly over weeks, or happen rapidly over a few hours. (1)

When the fluid builds up, it starts to cause problems. It puts pressure on the dog’s diaphragm, making it difficult for the dog to breathe. The fluid also puts pressure on the abdominal organs and blood vessels, making the dog feel lethargic and uncomfortable.

What Are The Signs Of Fluid In The Abdomen?

The signs will vary depending on the underlying cause and the amount and type of fluid in the dog’s tummy.

If a dog only has a small amount of fluid in the abdomen, the signs may be mild, but if the fluid builds up the dog’s abdomen will appear much larger than normal and the signs will be more severe.

Common symptoms of fluid in the abdomen include:

  • Lethargy
  • Decreased appetite
  • Vomiting
  • Tummy appears swollen and round
  • Weight gain
  • Weakness
  • Uncomfortable when lying down
  • Painful or uncomfortable when tummy felt
  • Difficulty breathing or panting
  • Collapse

What Causes Fluid In The Abdomen?

There are lots of different underlying causes that could be behind a build-up of fluid in your dog’s abdomen. All of them are serious, emergency conditions which need veterinary attention as soon as possible.

1. Right-Sided Heart Failure

A dog’s heart can be divided into two sides: right and left. The right side receives blood from the organs, pumps it to the lungs to pick up oxygen where it returns to the left side of the heart, before being pumped around the body to deliver the oxygen.

If a dog has right-sided heart failure, the right side of the heart struggles to pump blood to the lungs to pick up oxygen.

This causes a backlog of blood in the veins and a build-up of fluid between the organs in the abdomen.

2. Hemoabdomen

Hemoabdomen is the term used to describe blood in the abdomen. There shouldn’t be any free blood in your dog’s belly, and if there is then it is due to internal bleeding.

This can quickly lead to anemia (low red blood cell count), collapse and even death if not treated!

The internal bleeding can come from one of the organs (e.g. spleen or liver), a blood vessel or the abdominal muscles.

It can be caused by trauma, like getting hit by a car, a tumor in the abdomen, blood clotting disorders, ingestion of rat poison or a complication following abdominal surgery.

3. Abdominal Cancer

Abdominal cancer is a common cause of ascites. Some tumors can block the normal flow of lymph or blood within the vessels of the abdomen, causing an abnormal fluid build-up. Other types of tumors produce abnormal fluid or cause damage to blood vessels to cause an internal bleed.

4. Peritonitis

Peritonitis is an inflammation of the lining of the abdominal wall(peritoneum). It can be caused by a bacterial infection that has entered through the blood, a traumatic injury to the body wall, or due to a hole in the intestines.

This causes a build-up of inflammatory fluid in the abdomen, as the body tries to fight off the infection. This condition can quickly become life-threatening for your dog.

5. Ruptured Bladder

If the bladder is ruptured, then urine will leak into the abdomen. Usually, it is caused by a trauma (e.g. the dog getting hit by a car), but can also be caused by things such as a urinary blockage or cancer.

The waste products that are normally filtered by the kidneys and removed in the urine are suddenly pouring into the dog’s belly, where they cause lots of irritation and possible infection.

6. Liver Disease

Ascites is a common clinical sign in chronic liver disease. It usually means the liver is really struggling to carry out its normal functions.

Fluid can build up in the abdomen due to abnormal water retention, decreased protein production by the liver or increased resistance to blood flow in the liver. (2)

7. Protein-Losing Enteropathy

Protein-losing enteropathy (PLE) is a condition where protein is abnormally lost through the intestines into the dog’s stools.

This causes low levels of protein in the dog’s blood, which then causes fluid to move out of the blood vessels into spaces such as the abdomen or lungs. (3)

Many diseases can cause PLE in the dog including inflammatory bowel disease, intestinal cancer, fungal infections or intestinal parasites.

How Is Fluid In The Abdomen Diagnosed?

A veterinarian will ask questions as part of taking a clinical history. They will ask you questions about your dog’s current problem, such as when the dog’s abdomen became enlarged?

What other symptoms your dog is showing? Was the dog involved in a trauma/car accident? They will usually ask questions about your dog’s appetite, diet and exercise, and previous medical problems too.

The information you give the veterinarian is really important, as it will help give them clues for what has caused your dog’s problem.
The vet will also complete a full physical examination of your dog.

During the physical exam, your vet will check things like your dog’s heart and lungs, the color of the dog’s gums for signs of anemia or jaundice (a sign of liver disease), and your dog’s temperature. They will also palpate (feel) your dog’s abdomen to check for signs of pain, gas or excess fluid.

Following the clinical history and physical examination, the vet will usually recommend further tests to confirm or reach a diagnosis and to check the overall health of the dog. Which tests are recommended depends on the dog’s signs and the suspected underlying condition.

1. Blood Tests

Two of the most common blood tests are:

  • A complete blood count checks the different cells in the blood, such as the red blood cells, white blood cells, and platelets. A low red blood cell count, is a sign of anemia which could be a sign of an internal bleed or a chronic disease. An increased white blood cell count could be a sign of infection, inflammation or a tumor.
  • Serum biochemistry checks the general health of the body’s organs, checking for kidney or liver disease. It also checks the levels of glucose (sugar), proteins, fats and electrolytes in the blood.

2. Urinalysis

A urinalysis checks for signs of blood, infection, sugar or protein in the urine. The urine can also be checked for abnormal cells such as tumor cells or bladder crystals.

A urinalysis is an important way to check the kidneys are working ok, and to check if the dog has diabetes.

3. X-ray

X-rays are a great way to check the dog’s bones. If the dog was involved in a road traffic accident, x-rays will be needed to check for any broken or dislocated bones.

An abdominal x-ray can check the internal organs, checking for abdominal fluid, abdominal tumors or foreign bodies (e.g. something the dog has swallowed which he shouldn’t have, such as toys). X-rays can also check if the heart is enlarged or if there are fluid or tumors in the lungs.

4. Ultrasound

Ultrasound is the best way to confirm if there is fluid in the abdomen, as it provides a real-time moving picture.

The vet can assess the internal organs for signs of disease or cancer. Ultrasound can also be used to diagnose certain causes of ascites, such as heart failure or a ruptured bladder. (4)

5. Abdominocentesis

Abdominocentesis involves taking a small sample of the fluid which has built up in the abdomen, bypassing a small sterile needle through the body wall.

The fluid can then be analyzed to check for bacterial infection (peritonitis), urine (ruptured bladder), blood (internal bleed), proteins (PLE), or tumor cells.

5. Biopsy Or Fine Needle Aspirate

A biopsy involves taking a small sample of tissue so that it can be analyzed in the lab to check for signs of disease or cancer. Biopsies of the intestines may be needed to diagnose PLE or certain cancers.

Biopsies can be collected via endoscopy (a small camera inserted into the intestines via the mouth), during surgery or a “keyhole” surgery of the abdomen.

A fine needle aspirate collects a smaller sample of cells or liquid using a needle and syringe.

Aspirates of internal organs can be taken by passing the needle through the body wall, with the vet using ultrasound as a guide.

What Are The Treatment Options?

The treatment will vary depending on the underlying cause of ascites. If the dog’s abdomen is very distended with fluid and the dog is in a lot of discomforts, then some of the fluid may be removed (via a needle and syringe) to make him more comfortable while further tests or treatment is carried out.

1. Surgery

Surgery may be needed to stop an internal bleed, to close a ruptured bladder, or to remove an abdominal tumor.

2. Medications

The type of medication needed will depend on the underlying condition. For example, heart failure may require medication to help remove excess fluid from the lungs and abdomen (diuretics e.g. furosemide) or to help the heart muscles pump better (e.g. pimobendan).

Fluid build-up due to a bacterial infection or peritonitis will require antibiotics.

Blood clotting disorders will require the dog to receive whole blood, plasma clotting factors or vitamin K to help the blood clot. Dogs with liver disease may require supportive therapy, antibiotics, a change in diet and medications to support the liver.

The treatment of PLE depends on the underlying cause but may involve a diet change, anti-inflammatory medications (e.g. prednisolone) and vitamin B12 injections.

3. Blood Transfusion

If a dog is severely anemic (low level of red blood cells), due to an internal bleed or a clotting disorder, then he will require a blood transfusion.

Follow Up Care

Most dogs with fluid in the abdomen will need to be hospitalized while they are treated. Depending on the underlying cause they may require a course of pain relief medication, antibiotics, anti-sickness medications or a specialized diet as they recover.

Once they are stable, they may be allowed to go home with some medication. Usually, they will require regular check-ups, which may include blood tests and ultrasound scans.

Some causes of fluid in the abdomen such as heart failure, liver disease or PLE will need life long management and treatment. (5)

Conclusion

Many different conditions can cause a dog’s abdomen to become distended with fluid. Your veterinarian may suspect ascites after carrying out a physical examination, but usually, further tests such as blood samples, x-rays, and ultrasound are needed to figure out what has caused the build-up of fluid.

The treatment may involve emergency surgery or some medications, and your dog will often need to be hospitalized while he is treated.

If you notice that your dog’s belly is bigger than normal then he needs to be taken to a veterinary clinic as soon as possible, as fluid in the abdomen is usually caused by a serious and potentially life-threatening condition!