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Causes of Dog Leg Swelling

Leg Swelling in Dogs

Dog leg swelling is a symptom that requires investigation by a veterinarian. There can be several causes of swollen legs in dogs and some of them may be quite serious. The onset of leg swelling often tends to occur suddenly, leaving dog owners wondering about what may have caused it. Seeing the vet should be the best first step in finding the underlying cause. If your dog's leg or legs are swollen, collect as much information as possible pertaining the happening and report to your vet.

dog leg swelling

Causes of Dog Leg Swelling 

There are several causes of dog leg swelling, some of them may involve a localized problem with the leg, other may be more systemic (involving even distant organs which may cause leg swelling as a secondary problem.)

The medical term for swelling deriving from leaking of fluid between cells/tissues is edema, and when it affects the legs, it is often referred to as "peripheral edema." Due to gravity, the swelling often tends to settle into the lower parts of the legs.

One thing dog owners should be aware of is what's known as "pitting edema." Pitting edema is a medical term used to depict swelling which, when pressure is applied with a finger to the skin, it leaves an indentation. Any time pitting edema is noticed, it's very important to have the dog examined as soon as possible.

Pitting edema may be caused by several worrisome conditions, such as infections, cancer and lymph node disorders, bleeding disorders or blood vessel disorders.

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In the case of dog leg swelling, unless the cause is pretty obvious, the vet may want to have an x-ray of the swollen leg done and at least some blood work. Further tests may involve an abdominal ultrasound and/or heart ultrasound.

Dog Leg Swelling from Heart Problems

Clogged arteries leading to heart disease is mostly seen in humans.

Clogged arteries leading to heart disease is mostly seen in humans.

Swollen legs in dogs may occur secondary to some type of heart problem. In this case, the leg swelling occurs as a result of the heart not working well as it's supposed to.

When the heart works well, blood circulates throughout the dog's body delivering oxygen-rich blood to all tissues. When the heart though is not working well, blood circulation is impaired and it ends up pooling in the veins of the legs, causing edema.

Congestive heart failure is a condition where the heart is no longer able to pump hard and fast enough to deliver blood efficiently throughout the whole body.

This causes fluid retention in the lungs and other parts of the body. Affected dogs usually have a history of coughing, trouble breathing and exercise intolerance. Heart failure can be commonly found in older dogs and dogs with advanced heartworm disease may develop heart failure. Cranial cava obstruction is a heart problem that can cause swelling of the dog's front legs and neck.

Often the vet can detect a heart problem by listening for a heart murmur with a stethoscope, but not all forms of heart disease develop a detectable murmur. An echocardiogram (heart ultrasound) may be necessary.

Dog Leg Swelling from Lymph Nodes

dog watermelon

When dog leg swelling occurs as a result of the lymphatic system it is known as lymphedema. The dog's lymphatic system is essential for keeping his body healthy. It effectively sweeps away any bacteria, viruses and waste products that are then sent to the lymph nodes where lymphocytes, (special infection-fighting cells), drain these lymphatic waste fluids and flush them out of the dog's body.

Lymphedema takes place when the dog's lymph nodes cannot drain as they should. There are chances that the the lymph node system may be obstructed for some reason. Causes may be various and may include trauma and infections, but also cancer.

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For instance, should there be a cancerous growth blocking the dog's lymphatic vessels, as it may happen when there is a tumor growing near a lymph node or lymph vessel, lymphedema may result. The tumor may therefore enlarge to such an extent as to block the flow of the lymph fluid.

Lymphoma is a cancer of the lymph nodes which is know to cause return of the lymphatic fluid to be impaired. Lymphoma can be diagnosed through a lymph node biopsy. Abdominal masses affecting lymph nodes may also cause leg swelling.

An inflammation or infection affecting the lymph nodes can also restrict the flow of fluids. Prednisone may be prescribed by the vet to help reduce the inflammation.

Dog bone cancer is more common in the front legs.

Dog bone cancer is more common in the front legs.

Dog Leg Swelling from Problems in Leg

Not all leg swelling is due to edema, and therefore from fluid leaking, in some cases, it may be simply due to cells and tissue swelling (cellulitis).

Leg swelling may be simply due to localized allergies, inflammation or infections. If the swelling is affecting just a part of the dog's leg, it can be a growth in the skin like some sort of tumor, lipoma or cyst. Such growths may need to be aspirated with a needle to know more about them.

In some cases, if the swelling is limited to a leg and it is localized, there may be chances it is caused from some sort of trauma or a bite. The bite/sting may come from a bug, spider, scorpion or even a snake. Not always you will be able to see the bite, so just because there is no bite wound, doesn't by exclusion mean your dog wasn't stung or bitten.

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Another possibility for leg swelling is that the dog has a bacterial or fungal infection. A dog may sustain an injury, for example a broken toenail and a secondary bacterial or fungal infection sets in from contamination such as contact with soil. Antibiotics may work for bacterial infections, but won't work for fungal disease which require anti-fungal products.

Some mild or quite severe orthopedic problems may be a cause of limb swelling in dogs. A sprain may be a culprit. When degenerative joint disease develops acute inflammation, this can cause some swelling. Sadly, leg swelling affecting only one leg can also be due to bone cancer.

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Other Possible Causes

Liver disease can be also a culprit for leg swelling in dogs. The liver makes a special protein that is known as albumin. Albumin has many roles in the dog's body, and one of them is to keep the concentration of blood inside of blood vessels high enough so that fluid doesn't leak out.

Should the dog's levels of albumin decrease, the water in blood plasma will end up leaking out, which leads to swelling. The swelling may be seen in the legs and abdomen (ascites).

Chronic portal hypertension, which is high blood pressure in the portal vein to the dog's liver may cause rear leg swelling of both legs and ascites.

Some tick-borne disease (Lymes disease, rickettsia disease) may cause swollen legs in dogs. For example, Lyme disease may be a culprit. Not all affected dogs develop symptoms when infected.

Symptoms tend to develop around 2 to 5 months following infection and may include fever, swollen lymph nodes, joint swelling, and shifting leg limping, explains veterinarian Dr. Joey. Tick-borne diseases are treated with antifungal drugs such as doxycycline.

Other possible causes for leg swelling include vasculitis, systemic allergic reactions, a clot in the leg causing blood back flow, inflammation of a vein, inflammation of arteries and more.

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