Reviewed by Dr. Fiona Lee
Admit it: You've probably never given your dog's spleen a second thought. But this oblong organ plays a key role in your pup's body. The spleen helps remove aging red blood cells from circulation, prevent the spread of infection and support the immune system.1
When the spleen becomes enlarged—a condition called splenomegaly—it can be a sign of underlying health problems. Understanding the causes, symptoms and treatment options for an enlarged spleen in dogs can help you manage the condition.2
What Is the Spleen and Where Is It Located?
The spleen is an oblong organ that sits just below your dog's stomach. It's made up of two main types of tissue: red pulp and white pulp.2
Red pulp handles several important jobs:2
- Filters blood
- Removes damaged or aging blood cells
- Produces new leukocytes, platelets and red blood cells
- Aids in metabolism
- Recycles iron
- Produces and stores immune cells
- Monitors the immune system for invaders, like blood cells with infectious organisms
Your dog's spleen also acts as a reservoir, storing up to 20% of their red blood cell mass and 30% of their platelets. When needed—like during injury or stress—it can release these reserves back into circulation.2
What Happens When a Dog's Spleen Is Enlarged?
“Splenomegaly" might sound intimidating—and in many cases, it's a sign that something is wrong. While an enlarged spleen isn't rare in dogs, it's usually a symptom of an underlying condition that needs attention.
Dogs of all ages and breeds can develop splenomegaly, but it's seen more often in older dogs and medium to large breeds like German Shepherds, Golden Retrievers, Labrador Retrievers and Standard Poodles.
Not only can splenomegaly cause symptoms like lethargy, loss of appetite, abdominal swelling and vomiting, but an enlarged spleen can also press against nearby organs—particularly the stomach. This pressure may contribute to gastric torsion (bloat), a life-threatening condition where the stomach twists on itself. Additionally, because an enlarged spleen becomes more fragile and prone to tearing, it's at greater risk of rupture.3
The spleen has a large number of blood vessels, and there can be extensive bleeding if the spleen is ruptured. A ruptured spleen, called a splenic hemorrhage, is a medical emergency.3
If your dog's spleen ruptures, it can cause internal bleeding into the abdominal cavity—the space between the organs—not into the stomach. This can lead to rapid blood loss, shock and anemia. Without emergency treatment, it can be fatal. Seek immediate veterinary care if your dog shows signs like weakness, collapse, or a swollen and bloated abdomen.4
An enlarged dog spleen due to illness or infection could return to normal size with treatment.3
Causes of an Enlarged Spleen in Dogs
There are several possible reasons for splenomegaly in dogs:3
- Cancer
- Abdominal trauma or injuries
- Tumors
- Liver infections (hepatitis)
- Severe stomach or intestinal inflammation
- Tick-borne diseases
- Blood infections
Symptoms of an Enlarged Spleen
Enlarged spleens are more common in older dogs, and in some cases, dogs may show little to no symptoms—at least at first.2 When symptoms do appear, they can vary depending on the underlying cause of the enlargement.
There are four primary types of splenomegaly, each with different root causes:
- Inflammatory splenomegaly: Triggered by infections—bacterial, viral, fungal or protozoal.
- Hyperplastic (reactive) splenomegaly: Caused by immune system stimulation, red blood cell destruction (as seen in autoimmune diseases) or low oxygen levels.
- Congestive splenomegaly: Results from poor blood flow due to conditions like right-sided heart failure, splenic torsion, liver disease, or even certain anesthetic agents.
- Infiltrative splenomegaly: Happens when abnormal cells or substances invade the spleen, such as with tumors, cancers or storage disorders. This can be diffuse or nodular.
When symptoms are present, they may include:2
- Lethargy
- Lack of appetite
- Vomiting
- Weight loss
- Abdominal swelling or discomfort
- Pale gums1
- Irregular heart rate (arrhythmia)
- Sudden collapse (in severe cases)
If your dog shows any of these signs, it's important to schedule a veterinary exam right away. Early diagnosis can make a big difference in treatment outcomes.
Diagnosing an Enlarged Spleen
To diagnose an enlarged spleen, your vet will review your dog's medical history and perform a thorough physical exam. In some cases, the spleen can be felt during the exam if it's significantly enlarged. However, imaging—like X-rays or ultrasound—is often needed to confirm the diagnosis and check for possible causes, such as tumors or cancer.3
Your vet may also run additional tests, including a complete blood count (CBC), blood chemistry panel and urinalysis, to help identify what's behind the splenomegaly.3
Treatment Options for an Enlarged Spleen
Treatment for an enlarged spleen depends on the underlying cause. If a viral or bacterial infection is to blame, your vet may prescribe medications to resolve the issue. In more serious cases—such as cancer, tumors or trauma—surgical removal of the spleen (a procedure called a splenectomy) may be necessary.3
Splenectomy is a major surgery. The incision usually heals within two weeks, but full recovery can take up to a month. After surgery, your vet will likely send your dog home with an e-collar (cone) to prevent them from bothering the stitches, along with pain medication and possibly antibiotics to reduce the risk of infection. Strict rest and limited activity is important during recovery to avoid complications like incision reopening.5
While there's no guaranteed way to prevent splenomegaly—especially when it's caused by cancer—there are a few steps you can take to support your dog's overall health:3
- Keep up with parasite prevention.
- Stay current on routine vaccinations.
- Schedule regular wellness exams so your vet can catch potential issues early.
Caring for a Dog With an Enlarged Spleen
Caring for a dog with splenomegaly—or one recovering from spleen removal—requires close monitoring and supportive care. After a splenectomy, dogs may experience short-term issues such as digestive weakness, nausea, diarrhea or constipation.6 Weight loss can also occur, especially if their appetite remains low during recovery. These symptoms are usually temporary and can often be managed with medications and a bland or vet-recommended diet.
Keeping your dog calm and rested during recovery is key. Follow your vet's post-op instructions carefully, including any activity restrictions, medications and incision care.
What to feed a dog with an enlarged spleen
Feed your dog easily digestible, nutrient-rich foods that support their digestive process and organ function. Skip raw diets, which can have higher levels of bacteria, and opt for freeze-dried or dehydrated diets, cooked fresh foods, or regular canned or kibble diets.6
Supplements to stimulate the lymphatic system, support the immune system and aid elimination could help. Options include:6
- Astragalus
- Burdock root
- Calendula
- Digestive enzymes
- Phytoplankton
- Probiotics
- Spirulina
- Walnut
How to keep your dog comfortable
After a splenectomy, your dog will need plenty of rest. It's important to minimize their activity and avoid any rough play during the recovery period. Keeping them calm helps prevent complications like incision reopening or internal bleeding.5
If your dog's enlarged spleen was caused by cancer, your vet may recommend ongoing monitoring through follow-up blood tests, X-rays or ultrasounds to track their progress and catch any changes early.5
Pets Best Is Here To Help
An enlarged spleen in dogs can be a serious medical condition, so it's important to seek care from a veterinarian to get an accurate diagnosis and treatment. Pets Best knows that your dog's health is a top priority, and protecting them with dog insurance may help you keep them stay safe and healthy.
Pets Best dog insurance plans are customizable, and a network of veterinary experts is always available through our 24/7 Pet Helpline to answer questions and help you get the best care for dogs with enlarged spleens.
Sources/ Citations
- “Splenic Masses in Dogs (Splenectomy)," Wendy Brooks (7/2024), Veterinary Partner, https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4951872
- “Top 5 Causes of Splenomegaly in Dogs," Todd Archer and Alyssa Sullivant (4/2018), Clinician's Brief, https://www.cliniciansbrief.com/article/top-5-causes-splenomegaly-dogs
- “Enlarged Spleen in Dogs," Jamie Lovejoy (3/2024), PetMD, https://www.petmd.com/dog/conditions/cardiovascular/enlarged-spleen-dogs
- “Splenic Hemorrhage in Dogs," Hannah Hollinger (9/2021), Wag! https://wagwalking.com/condition/splenic-hemorrhage
- “Splenectomy in Dogs," Hannah Hollinger (2/2024), Wag! https://wagwalking.com/treatment/splenectomy
- “Splenectomy in Dogs: Support Your Dog Without a Spleen," Rita Hogan, (5/2022), Dogs Naturally, https://www.dogsnaturallymagazine.com/dog-splenectomy/