Enlarged Spleen in Dogs: Causes, Symptoms & Treatment Options

Published by Dr. Sarah Wooten
3 min read

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Splenomegaly is the official medical term for an enlarged spleen in dogs and humans and it is a common condition that can affect dogs of all ages, sizes, breeds and genders. However, it tends to be more commonly diagnosed in middle-aged dogs. Read on to learn more about the spleen and how splenomegaly can affect your dog.

All About the Dog Spleen

Just like humans, dogs have lymphatic systems that filter their blood, remove damaged red blood cells and balance the fluids in their body. The spleen is the largest organ in the lymphatic system. In dogs, the spleen lives in the abdominal cavity, snuggled up under the rib cage on the left side of the abdomen alongside the stomach.

A normal, healthy spleen looks like a small, purple, soft and squishy boomerang. Its many blood vessels attach it to the liver and the stomach, and the blood supply of these three organs is closely tied together.

The spleen has two main functions: removing old red blood cells and helping the immune system fight off infections. Both of these functions are very important to keeping your dog healthy. Thankfully, if your dog ever has to have their spleen removed, the body has protective mechanisms in place to ensure these functions can be carried out by other organs in the body.

Causes of an Enlarged Spleen in a Dog

Splenomegaly in dogs can occur for multiple reasons, including:

The main concern with enlarged spleens is that they are at an increased risk for injury and rupture, which can cause massive and potentially life-threatening abdominal bleeding in a dog, according to Wag!. Although there is no way to completely prevent an enlarged spleen, having your dog checked out yearly by a veterinarian can help you catch any problems early on.


The signs of an enlarged spleen in dogs depend on how big the spleen becomes. Also, if the spleen is ruptured and bleeding and then how much, how fast, or how long the spleen has been bleeding. All of these factors will significantly impact how sick your dog acts. Symptoms of an acutely ruptured and actively bleeding spleen can include:

  • Sudden lethargy
  • Pale gums
  • Appetite loss
  • Enlarged, potbelly abdomen
  • Sudden weakness or collapse
  • Racing heart rate
  • Panting

Dog spleens that are damaged from an injury or cancer may not be easily noticeable, and they can bleed small amounts over a long period of time. Dogs with a damaged spleen may look and behave completely normal even if they are slightly anemic, meaning they have a lower than normal red blood cell count.

If your dog has cancer, an infection or inflammatory bowel disease, they may also experience symptoms associated with these conditions, such as fever, weight loss, vomiting and diarrhea.

Diagnosing an Enlarged Spleen

Oftentimes, an enlarged dog spleen isn't obvious by just looking at your pup. A vet will use physical exam findings and laboratory testing to diagnose splenomegaly.

If your dog's spleen is enlarged, a vet can often feel the enlarged organ with their hands using a technique called abdominal palpation. Abdominal palpation, along with the rest of the physical exam, will clue your vet in about what to do next. If they suspect an enlarged spleen, it's likely that they'll recommend blood testing, abdominal radiographs (X-ray imaging) and/or abdominal ultrasound scans. An enlarged spleen, tumors of the spleen and any bleeding can easily be seen on X-ray and abdominal ultrasound.

Your vet may also want to examine your dog further using tests such as evaluating samples of spleen tissue under a microscope, collecting and testing fluid from their abodmen, or advanced imaging techniques, such as a CT scan or ultrasound of the heart, to look for evidence of cancer. They may also consider testing for certain blood-borne infections depending on where you live.

Treatment Options

Splenomegaly treatment in dogs depends on the cause of the enlargement and if there is active, life-threatening blood loss.

If a dog's spleen is enlarged and is heavily bleeding due to traumatic injury or a bleeding tumor, your dog may be at risk of life-threatening blood loss. In this scenario, surgical removal of the spleen needs to happen immediately to offer your dog the best chance of survival. Fortunately, most dogs can live long, normal, healthy happy lives without spleens. If your dog has lost a lot of blood, they may require a blood transfusion. Additional consultation with an oncologist for follow-up cancer care is recommended if your dog has a malignant tumor of the spleen, such as in cases of hemangiosarcoma.

If your dog's spleen is enlarged due to another condition, such as hepatitis, blood loss from a tick-borne infection or hookworm anemia, or other inflammatory or infectious conditions, they'll receive treatment that's aimed at addressing their specific disease condition. That's because once underlying conditions are resolved, a dog's spleen often returns to normal size.

But what if your dog's spleen is bleeding very little or intermittently bleeding? What happens if you don't treat it? In these cases, it is best to solicit and follow the recommendations of your local veterinarian as every dog is different. Don't be afraid to ask questions — your vet is there to help you make the best decisions for your dog and your situation.

In any case, the best thing you can do is not panic if your dog is diagnosed with an enlarged spleen. By working closely with your vet, you can ensure that your dog gets the treatment they need to feel their very best.

Contributor Bio

Dr. Sarah Wooten

Dr. Sarah Wooten

A 2002 graduate of UC Davis School of Veterinary Medicine and certified veterinary journalist, Dr. Sarah Wooten has 16 years experience in small animal veterinary practice, is a well known international speaker and writer in the veterinary and animal health care spaces, and is passionate about helping pet parents learn how to care better for their fur friends.