Sudden Weight Gain in Dogs: Why Has My Dog Expanded in Front of My Eyes?

I believe that every time you use the word sudden when describing your dog’s symptoms, you should figure that the urgency of treatment is equal to the speed of onset. Sudden is a synonym for acute.

Obesity is a real epidemic, but no dog goes to bed skinny and wakes up fat.

When it appears that they do, something is seriously amiss.

Sudden Weight Gain in Dogs: Why Has My Dog Expanded in Front of My Eyes?

Some conditions can cause your dog to gain weight or look like they did relatively quickly, such as underactive thyroid or Cushing’s disease. But that doesn’t happen overnight either. So none of these things should be ignored, but they don’t constitute an emergency.

Acute onset

If it happens acutely, you’re not looking at weight gain but distention or swelling.

In large breed dogs, a common cause of a sudden expansion of the abdomen–and a mother of all emergencies–is GDV, gastric dilatation-volvulus, also referred to as bloat. While there is a difference between bloat and GDV, the former can quickly turn into the latter. The abdomen will be visibly enlarged. Your dog might be retching without anything coming out, having difficulty breathing, and acting distressed. GDV is extremely painful and can quickly become deadly.

If your dog has symptoms like these, call your veterinarian immediately.

Enlarged appearance

Blood or fluid accumulation in the abdomen will also make the belly look enlarged.

A splenic tumor, for example, whether benign or cancerous, can rupture and bleed into the abdomen. Your dog may also act lethargic, weak, and have pale mucous membranes. This, too, is an emergency.

Excess fluid in the abdomen can be a common side-effect of some types of heart disease, liver disease,  or low blood protein levels that lead to fluid leaking out of the blood vessels.

Other potential serious causes of an enlarged abdomen can be swelling or enlargement of vital organs, infection of the abdomen (peritonitis), a ruptured bladder, or a large abdominal tumor.

Symptoms that can come with it may include lethargy, weakness, loss of appetite, vomiting, signs of discomfort, and pain.

Severe intestinal parasite infestation can cause fluid build-up.

When you observe these things, you know you have a very ill dog on your hands.

Other body areas can swell up, such as legs with heart failure or swelling of the face or legs with lymphoma.

Even something as deceptively as benign as an allergic reaction with severe swelling can become an emergency in a hurry.

Related articles:
Swelling in Dogs

Further reading:
7 Medical Causes Behind Weight Gain

Categories: Sudden weight gainSymptoms

Tags: :

Jana Rade edited by Dr. Joanna Paul BSc BVSc

I am a graphic designer, dog health advocate, writer, and author. Jasmine, the Rottweiler of my life, was the largest female from her litter. We thought we were getting a healthy dog. Getting a puppy from a backyard breeder was our first mistake. Countless veterinary visits without a diagnosis or useful treatment later, I realized that I had to take Jasmine's health care in my own hands. I learned the hard way that merely seeing a vet is not always enough. There is more to finding a good vet than finding the closest clinic down the street. And, sadly, there is more to advocating for your dog's health than visiting a veterinarian. It should be enough, but it often is not. With Jasmine, it took five years to get a diagnosis. Unfortunately, other problems had snowballed for that in the meantime. Jasmine's health challenges became a crash course in understanding dog health issues and how to go about getting a proper diagnosis and treatment. I had to learn, and I had to learn fast. Helping others through my challenges and experience has become my mission and Jasmine's legacy. I now try to help people how to recognize and understand signs of illness in their dogs, how to work with their veterinarian, and when to seek a second opinion. My goal is to save others the steep curve of having to learn things the hard way as I did. That is the mission behind my blog and behind my writing. That is why I wrote Symptoms to Watch for in Your Dog, which has turned out being an award-winning guide to dog owners. What I'm trying to share encompasses 20 years of experience. Dr. Joanna Paul BSc BVSc is our wonderful sponsor and has been kind to edit and fact-check my important articles.

  1. Ah…the extended belly…sadly, my Bandit passed with this which instinctively I recognized as a spleenic tumor as her older brother years earlier passed from it when they went in to do a splenectomy and found him full of cancer and an orange size tumor – hemangiosarcoma. As always – important info and I will be sharing.

  2. One of my dogs has heart disease. Thanks for sharing this information. I will keep a close eye on her abdomen.

  3. As a pet owner I know that a sudden weight loss should set alarm bells ringing but I did not know the kind of reasons this could happen. Good grief! I am going to share this because lives could be at stake.

  4. Wow! I hadn’t given much thought to an allergic reaction causing the appearance of weight gain with your dog. I know that can happen with humans, I just never equated it with dogs. That was silly on my part. Great post and very educational as always! I’m sharing this one with my dog parents.

Share your thoughts