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15 Potential Causes of Abdominal Enlargement in Dogs

A free-ranging pregnant dog.

A free-ranging pregnant dog.

What is Distended Abdomen in Dogs?

The term abdominal enlargement in dogs (or abdominal distension) is used to describe the circumstance in which a dog's belly appears to bulge or be larger in certain areas. The enlargement can take place as a result of a variety of factors.

  • An accumulation of air, fat, or fluids.
  • The presence of masses or tumors.
  • Enlarged organs.

While some forms of abdominal enlargement in dogs are obvious, not all forms of abdominal enlargement are easily detected by dog owners. It takes many years of hands-on experience for veterinarians to palpate the abdomen and detect slight abnormalities such as enlarged organs.

If you notice abdominal enlargement/distention, see your vet. Your vet will likely start with a physical exam and part of that will entail palpating your dog's abdomen. Your dog's abdomen will be inspected for distention, asymmetry (one side different from the other), the presence of fluid or gas, enlargement of organs such as the spleen, liver, or kidneys, the distention of the stomach, intestines, or bladder, the presence of masses, and the enlargement of the dog's bladder or uterus.

The Anatomy of a Dog

The Anatomy of a Dog

A Look at Abdominal Organ Anatomy in Dogs

Your dog's abdomen, also less formally known as the stomach, belly, or tummy, refers to the section of the body found sandwiched in between the thorax (chest area) and the pelvis (the bony structure nearby the base of the spine to which the hind limbs attach).

Because a dog's abdomen houses various vital internal organs, the abdominal area is often referred to as an abdominal cavity. A dog's abdominal cavity contains several hollow organs of the digestive tract including the dog's stomach, small intestine, and colon (also known as the large intestine).

Other organs found in the dog's abdomen include the liver, gallbladder, pancreas, spleen (located just behind the liver, in the mid-abdomen), kidneys, and adrenal glands. It remains under debate whether a dog's bladder, prostate gland, uterus, and ovaries would fall under the category of abdominal organs or pelvic organs.

These vital organs are enclosed by strong abdominal muscles and protected by the vertebral column on top; some organs are also protected by the ribs.

If your puppy or dog has a swollen abdomen, see your vet to play it safe.

If your puppy or dog has a swollen abdomen, see your vet to play it safe.

15 Potential Causes of Abdominal Enlargement in Dogs

Here is a list of some potential causes of abdominal enlargement in dogs. Some of these are relatively benign conditions, while others may be suggestive of a disease process of dysfunction and are worthy of being looked at by a veterinarian. This is a limited list, and there may be several more causes not mentioned here.

1. Weight Gain

In this case, the enlargement is due to the presence of extra fat. Weight gain is often seen in dogs who are fed caloric foods in abundance and in dogs who do not exercise enough. Dietary changes along with an exercise regimen can often help.

Certain medical conditions may cause weight gain in dogs as well. Examples include diabetes and thyroid disease.

2. Pregnancy in Female Dogs

In this case, the abdominal enlargement is due to the presence of developing puppies. Generally, around week 5 or 6, the belly will start to enlarge and the mom dog will start to gain weight.

Puppies are carried in the mom dog's uterus which is found in the back half of the belly, nearby the bladder. As the puppies develop, the uterus expands. As the end of pregnancy nears, all the puppies will be quite large and the abdomen may appear enlarged near the stomach and edge of the ribcage.

Pregnancy in intact female dogs can be detected by a veterinarian via gentle palpation of the abdomen at about a month after breeding.

3. Presence of Intestinal Parasites

Dogs with heavy parasite loads may develop a potbellied appearance. Puppies are notorious for having this appearance when young. In puppies, the most common parasite known for causing a potbelly is roundworm. Fortunately, the problem is easy to resolve. After a fecal test testing positive for parasites, the vet can select the most appropriate dewormer that will kill the exact type of parasites found.

4. Enlargement of Organs

An abdominal mass may sometimes be detected by a vet upon physical examination, and this can be suggestive of liver tumors. Abdominal distension (ascites) may also be seen. An enlarged liver may also take place when a dog is in heart failure.

Normally, abdominal enlargement due to enlarged tumors won't be obvious. It often takes an experienced vet to gently palpate any enlarged organs. Sometimes, for example, an enlarged spleen is difficult to feel even for an experienced veterinarian.

5. Gastrointestinal Issues

Distension of the abdomen after eating (postprandial) may be due to gastric retention disorders, explains Dr. Jennifer E. Stokes a board-certified veterinarian specializing in internal medicine.

What may cause such retention? The presence of a tumor may be slowing down the normal emptying of the stomach leading to gas building up in the stomach. Perhaps, the nerves of the dog's intestinal tract are not working as they should.

Other possible GI issues causing a swollen abdomen in dogs include organ torsion (stomach, spleen, intestinal tract), infection of the membrane lining the cavity of the abdomen (peritonitis), foreign body obstruction, and abdominal organ trauma.

Sometimes, eating certain foods may cause a bout of pancreatitis in dogs. Pancreatitis is the inflammation of the pancreas, which may cause a dog's stomach to hurt and become hard or distended. A distended belly can sometimes also form from a lot of gas-forming due to a bout of colitis.

6. A Case of Ascites

Sometimes, a dog's abdomen is enlarged when there are fluids accumulating inside the abdominal cavity. Gently pressing on the abdomen may generate at times a "wave" that looks like fluid. The fluids may accumulate as a result of malfunctioning organs such as the heart (as it happens with congestive heart failure, especially in dogs with a history of a heart murmur) or the liver.

7. Presence of Blood

Blood may flow within the abdominal cavity as a complication from surgery, underlying bleeding disorders, exposure to rat poison, bleeding masses, and penetrating trauma to the abdomen causing direct injury to abdominal organs (car accident, dog bite).

8. A Urinary Problem

When a dog's bladder ruptures, it may fill the abdomen with urine as a result of significant trauma such as being hit by a car. Another possible cause of abdominal/pelvic swelling includes a urinary blockage.

9. Intestinal Lymphoma

Lymphoma is a type of cancer capable of attacking almost any system. In the case of intestinal lymphoma, this cancer will block the lymphatic system leading to the leaking of fluids into the abdomen. This type of cancer may be detected on ultrasound where enlarged lymph nodes may be seen.

10. Presence of Masses

Several types of cancer may affect the organs found in the dog's abdomen and superficial masses may be found too. Sometimes benign or malignant skin masses may cause localized enlargement of certain areas of the abdomen.

Lipomas are benign masses often found just under the skin and are usually movable. They are often found in the dog's abdominal area. A fine-needle aspiration can help determine where a skin mass on the abdomen is cancerous or not. Generally, these benign growths are only removed if they are interfering with a dog's ability to walk/move.

11. Cancer of the Spleen

Spleen cancer in dogs (hemangiosarcoma) may produce acute swelling of the abdomen, abdominal pain, labored breathing pale gums, and a distended abdomen. The swelling of the abdomen takes place when the spleen ruptures causing blood to fill up space in the abdomen. The tricky part about these tumors is that you often can't know whether they're benign or cancerous until the vet removes the entire spleen and has a pathologist look at it.

When spleen cancers enlarge, they may sometimes put pressure on the dog's stomach and intestines, causing discomfort and lack of appetite.

12. Presence of Air

When a dog's abdomen fills with air, it may lead to a life-threatening complication known as GDV. Deep-chested dogs are typically predisposed to this condition. The stomach basically fills up with air and twists on itself cutting blood supply and causing shock.

GDV typically causes dogs to make frequent attempts to vomit, assume a hunched-up posture, become restless, and their stomach becomes distended and tight like a drum causing a thumping sound when patted with fingers. If you suspect bloat in your dog, please see an emergency vet at once.

13. Low Thyroid Levels

When the dog's thyroid gland becomes sluggish and stops producing sufficient amounts of thyroid hormones, affected dogs may start gaining weight. Other symptoms include bilateral hair loss, dry coat, or seborrhea. Skin and hair problems are usually first seen by the tail area, base of the ears, and lateral lumbar regions.

14. A Case of Excess Cortisol

Cushing's disease takes place when the dog's cortisol levels are too high. This condition requires specific testing that is not routinely carried out: a dexamethasone suppression and/or ACTH stimulation test.

Affected dogs (a good 90 to 95 percent) tend to gradually develop a potbellied or pendulous appearance of their abdomen. This potbelly is believed to be the result of the increased weight of abdominal contents due to the redistribution of fat from various storage areas to the abdomen along with a decrease in muscle strength (muscle wasting). The increased size and weight of the liver as a result of excess cortisol may also play a role in the pot-bellied appearance.

On top of a pot-bellied appearance, dogs with Cushing's may develop increased drinking, increased urination, panting, and a dull coat.

15. A Uterine Infection

A uterine infection, medically known as pyometra, affects only intact female dogs (not spayed). This is a life-threatening condition. An intact female dog acting sick, showing decreased appetite, and displaying an enlarged abdomen/pelvic area may be suffering from a distended uterus. See your vet at once to play it safe.


  • Textbook of Veterinary Internal Medicine Expert Consult: Expert Consult, ... 7e(2 Volume Set) by Stephen J. Ettinger DVM DACVIM
  • Withrow and MacEwen's Small Animal Clinical Oncology - 5th Edition
  • VCA Animal Hospitals, Testing for Abdominal Enlargement in Dogs
  • Author's own experience as a former veterinary assistant for AAHA-accredited animal hospitals.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2018 Adrienne Farricelli


Adrienne Farricelli (author) on September 07, 2019:

Cricket, thanks for stopping back. If your sick dog brought you to this page on abdominal enlargement in dogs, I hope with the help of your vet that you're able to pinpoint the problem and that your dog makes a speedy recovery!

Cricket K. on September 04, 2019:

Hi, thanks so much for this for the time you took to research and compile. This was a great help in answering my questions.

Suhail Zubaid aka Clark Kent from Mississauga, ON on May 20, 2018:

Hi Adrienne,

This was a very medically inclined article that I found informative. I know a Labrador, a friend of our K2, died due to abdominal enlargement caused by some disease that I was not able to find from the neighbour.


Clive Williams from Jamaica on May 12, 2018:

Good Listing here.