Auricular Hematomas in Animals

Auricular hematomas (also called aural hematomas) are small-to-large, fluid-filled swellings that develop on the concave surface of the pinna in dogs, cats, pigs, horses, and sheep. The pathogenesis of the lesions is unknown; however, trauma from head shaking or ear scratching in response to pruritus from otitis externa is almost always involved.

In dogs, auricular hematomas have been observed in cases of atopic dermatitis and food allergy in which the ear canals are the primary sites of allergic inflammation, pruritus, and secondary infection.

In pigs, sarcoptic mange (mite infestation), pediculosis (lice infestation), and meal in the ears (from overhead feeders) have been implicated as causes of head shaking that can lead to auricular hematomas. Bites from other pigs also can also cause hematomas on the ears.

Auricular hematomas are rare in horses and seem to be secondary to pruritus and atopic dermatitis. They are also rare in sheep but have been associated with Otobius megnini (spinous ear tick) infestation.

Treatment of auricular hematomas in dogs and cats requires control of the underlying cause of pruritus (eg, bacterial, yeast, or mixed otitis externa) and management of atopic dermatitis.

Various surgical techniques have been developed to manage aural hematomas. Most techniques involve evacuation of the hematoma (draining fluid or removing fibrous debris) followed by placement of sutures with or without drains to decrease the likelihood of recurrence by eliminating dead space and by promoting formation of scar tissue.

One technique used in dogs and cats involves using a 4- or 6-mm punch biopsy instrument to create multiple drainage holes on the concave surface of the pinna overlying the hematoma, taking care to avoid vessels. Holes are created approximately 0.5–1 cm apart in a staggered dot pattern. With a nonadherent pad on the concave pinnal surface, a simple interrupted suture is placed coming out each hole and tacking down the adjacent skin (ie, the suture goes through-and-through all pinnal layers, including the skin on both sides), and a square knot is tied on the concave aspect over the pad. The sutures are left in place for at least 3 weeks so the skin will scar down to the cartilage. The fenestrations are left to heal by second intention (1, 2).

Another technique involves making a vertically oriented incision (linear or S-shaped) on the convex surface of the pinna spanning the entire length overlying the hematoma. Multiple rows of staggered, through-and-through sutures are placed parallel to the long axis to compress the pinna. Knots are tied over a nonadherent pad on the convex side of the ear. The longitudinal orientation of the sutures and incision on the concave pinnal surface minimize ligation of the auricular blood supply. The sutures are left in place for at least 3 weeks (3).

Some clinicians elect a surgical approach to allow drainage, flushing of the pocket, and placement of several mattress sutures to eliminate the pocket. Another surgical approach, using a polycaprolactone splint, has been tried in dogs and cats (4).

Some clinicians opt for drainage and glucocorticoid instillation. Drainage is best achieved with a butterfly catheter or an IV catheter. Glucocorticoids are instilled to fill the cavity without causing skin distention. Options include triamcinolone (1–10 mg instilled every 7 days for 1–3 weeks), methylprednisolone (10–40 mg instilled every 7 days for 1–3 weeks), and dexamethasone (0.2–0.4 mg diluted in saline, instilled every 24 hours for 1–5 days [5]).

Many dermatologists manage auricular hematomas medically with an anti-inflammatory dose of prednisolone (1 mg/kg, PO, every 24 hours for 14 days, followed by a taper to 0.5 mg/kg, PO, every 24 hours for another 14 days), while treating any underlying otitis externa (6).

Scarring and crinkling of the pinna (cauliflower ear) can be the outcome despite any form of surgical or medical treatment. However, this result is most likely to occur with nonsurgical therapeutic options.