Hygroma in Dogs

A hygroma, or "false bursa," is an acquired non-epithelial-lined, fibrous sac filled with serous fluid that develops over a bony prominence or pressure point. Hygromas are a common problem in dogs, as well as in horses, but they can occur in any species.

Hygromas frequently affect large- and giant-breed dogs (eg, Irish Wolfhound, German Shepherd Dog, Great Dane, Mastiff, Newfoundland, Saint Bernard). The typical age of onset is adolescence (6–18 months of age); however, hygromas are also common in older dogs with elbow osteoarthritis.

Uncomplicated hygroma, elbow, dog

Image

Courtesy of Dr. Kevin Winkler.

The pathogenesis of hygromas is believed to involve repetitive trauma. The trauma could be the result of impaired ambulation or excessive time spent in recumbency on hard surfaces. Trauma produces an inflammatory response in which a dermal callus and pocket of serous fluid form to cushion the affected area; however, lack of healing owing to repeated traumatization leads to eventual walling off of the fluid-filled cavity by a dense fibrous capsule.

Trauma-related hygromas, dog

Image

Courtesy of Dr. Peter Muir.

Hygromas can be uncomplicated or associated with complications such as ulceration or infection.

Hygroma, chronic inflammation, dog

Image

Courtesy of Dr. Karen A. Moriello.

The characteristic clinical finding of hygroma is a soft, fluctuant, fluid-filled, painless swelling over a pressure point, especially the olecranon or tarsus (see uncomplicated and trauma-related hygroma images).

If a hygroma is long-standing, severe inflammation can develop (see chronic inflammation image), and ulcers, infections, abscesses, granulomas, and fistulas can occur. The hygroma contains a clear, yellow to red fluid.

Hygroma management, protective elbow padding, dog

Image

Courtesy of Dr. Kevin Winkler.

Hygromas can also become complicated with comedones and furunculosis. Some dogs develop follicular cysts or calcinosis cutis circumscripta at hygroma sites. Severe lesions can develop into decubital ulcers.

Diagnosis of hygroma is typically straightforward and based on physical examination. Radiography or ultrasonography can be useful to help confirm an extra-articular location of the lesion. Differential diagnoses include a true cyst, callus, infectious dermatitis, and benign or malignant neoplasia.

There is no ideal treatment to resolve elbow hygromas. If diagnosed early and still small, hygromas can be managed medically with specialized bandaging techniques or via aseptic needle aspiration, followed by corrective housing. Soft bedding works well for some dogs. Dogs that lie on only hard surfaces can wear padding over pressure points to prevent further trauma (see elbow padding image).

For larger or chronic hygroma lesions, complete excision of all affected tissue is ideal. However, the rate of complications, including dehiscence of the repair, is high. For this reason, a variety of skin grafting techniques have been used.

An alternative to complete removal of a hygroma involves drainage, wound flushing, and the placement of Penrose drains for chronic hygromas. Active drainage with closed-suction drains has also been reported to be helpful.

Smaller lesions can be treated with laser therapy or extracorporeal shock wave therapy. Laser therapy has been reported to decrease inflammation and edema and help stimulate healing (1).

Intrahygromal corticosteroids are not recommended; infection has been reported as a complication.

Bacterial culture and susceptibility testing are indicated before the use of antimicrobials to treat hygromas.

A skin biopsy of atypical hygroma lesions or lesions that do not respond to conservative medical therapy is recommended.

Also see Carpal Hygroma in Horses.