While structurally much simpler than the other components of a cat’s hearing apparatus, the pinna—the fleshy, visible portion of the outer ear—is an essential part of the feline auditory system. A thin, funnel-shaped, mobile structure, supported internally by cartilage and tiny muscles that give the ear its shape, the pinna serves to collect sound waves from the external environment, concentrate them, and channel them into the depths of the auditory canal—the middle and inner ears. Although normally a sturdy structure, protected on both the front and back surfaces by a layer of tough skin, the pinna—directly exposed as it is to the outside world—is subject to various traumas that can lead to a swelling called aural hematoma.

The swelling can be caused by, for example, blunt trauma to the skull or by deep wounds to the ears that a cat may sustain in fights with other animals. The most frequent cause, however, is the trauma that a cat may inflict upon itself by persistently and furiously scratching at its own ears to relieve the relentless itching stemming from otitis externa, an infection of the external ear canal. Otitis externa may result from a yeast or bacterial infection or the invasion of parasites within the ear canal. A relatively common source of such obsessive scratching, according to James Flanders, DVM, associate professor of surgery at Cornell University’s College of Veterinary Medicine, is otitis externa stemming from the proliferation of ear mites within the outer ear. “A cat with otitis externa,” says Dr. Flanders, “may scratch its head frequently and, in the process, rupture blood vessels inside the pinna. The blood has nowhere to go, so it accumulates—and the pinna can start to look like a big, swollen balloon. This swelling, of course, will be very uncomfortable for the cat, so the animal may traumatize the ear even more by scratching at it.”

If an aural hematoma goes untreated, he notes, the condition will be increasingly uncomfortable for an affected cat. “A hematoma can spontaneously resolve,” says Dr. Flanders, “but that can take weeks, and by the time the ear heals, it will tend to be deformed. The cartilage will take on an odd, bumpy shape—and the cat is apt to end up with a permanent cauliflower ear.”

Treatment for an aural hematoma ranges from needle aspiration of the blood and any clots that have accumulated in the pinna to surgical drainage. Surgery is preferable, since needle aspiration is usually only a temporary fix. Dr. Flanders describes the typical surgery as follows: “We anesthetize the cat, make an incision on the inside of the pinna, drain the accumulated blood from the pinna, and then suture the inside and outside of the earflap together, so that the inner skin is pressed flat against the outer skin. By doing this, the space where blood could accumulate in the future is obliterated.”

The stitches will be removed within two to three weeks following surgery, after which, says Dr. Flanders, the cat will look “perfectly normal.” The surgical approach to treating aural hematoma is commonly taken, he notes, and most veterinarians are well-equipped to perform it. Of course, any underlying infections or parasite infestations must be addressed as well.