Hygroma in Dogs

Due to the repetitive trauma of lying on hard surfaces, your dog may develop a hygroma. A hygroma is a soft, swelling under his skin filled with fluid over a pressure point or bony prominence. Hygromas are treatable with the course of treatment depending on the size and severity of the hygroma and whether there are additional issues like ulceration or infection.

A hygroma is a noninfectious, inflammatory response to trauma presenting as a soft, subcutaneous swelling filled with fluid, typically over a pressure point or bony prominence.

Should your dog have a hygroma, you will notice a soft subcutaneous swelling filled with fluid (yellow to red in color) over a pressure point or bony prominence. Hygromas vary in size, but can grow to two inches in diameter, and are often developed on the olecranon of the elbow. With a hygroma, your dog will typically show no signs of systemic illness and will not exhibit pain when touched. Hygromas are often bilateral. If the hygroma has been present for a significant length of time, severe inflammation may occur, along with:

• Ulceration
• Infection
• Abscesses
• Granulomas
• Fistulas
• Tissue erosion

Should a hygroma become infected, it may be painful and warm to the touch.

Types 

While there are not different types of hygromas, it is important to note that hygromas can be complicated with comedones and furunculosis. Also, follicular cysts or calcinosis cutis circumscripta may develop at the sites of the hygromas in some dogs.

A hygroma is caused by repeated trauma. Lying on hard surfaces (such as pavement) may produce an inflammatory response in your dog, which will lead to a dense-walled, fluid-filled cavity and the development of a soft, fluid-filled swelling. The swelling will typically be found over pressure points, particularly of the arm and leg joints. A hygroma is more likely to occur in larger breeds of dogs, where more weight is put on the bony area, as well as those that are more sedentary (for example after recovering from surgery, or in the dog’s elderly years).

Your veterinarian will conduct a physical examination of your dog. You will want to let your veterinarian know when you first noticed the swelling on your dog, as well as whether you have noticed any changes in your dog’s behavior. Your veterinarian may choose to conduct a biopsy to confirm diagnosis, particularly if lesions look unusual.

When viewing a hygroma macroscopically, it can be seen that it is separated from the skin. It will show a tough, dense wall and be filled with fluid that can be somewhere between yellow and red in color. The color is dependent upon the degree of trauma associated with the hygroma, leading to a larger or smaller amount of red cells. The lining of the sac will appear pale and can be smooth or rough.

Hygromas do not always need treatment. Oftentimes, we just monitor them.

When hygromas are small, protective padding (bandaging the area and soft bedding) may lead to their being resolved. If that is not successful, the hygroma can be treated with aseptic needle aspiration and corrective housing. It is important that your dog have soft bedding or padding over pressure points in order to prevent additional trauma. After about three weeks a protective callus should have formed. 

Should your dog have chronic hygromas, surgical drainage, flushing and Penrose drains may be recommended. Three weeks after surgical drainage the drained lesions should be dry; bandages can be removed at six weeks. Should lesions develop, small ones can be treated with laser therapy. If your dog experiences severe ulceration he may need extensive drainage, surgical removal or skin grafts. 

There is a chance that your dog’s condition will not respond to treatment. Should that be the case, your veterinarian will likely recommend a skin biopsy to determine the best way to proceed with treatment.

Your veterinarian will discuss with you the need for follow-up appointments, which will depend upon your dog’s condition. You will want to provide a padded environment for your dog in order to avoid repeated trauma, complications with the wound or recurrence of the hygroma. 

Infection is not uncommon after aspiration, drainage, and reconstruction. You will want to work closely with your veterinarian to ensure your dog is healing well and that any infections developed are treated promptly.