Cases- Working at the veterinary hospital, I have been seeing lop bunny rabbits presented for ear base mass once every month. It is one of the most common abscessations seen in rabbits. Lop rabbits are predisposed to this sort of problem, due to the ear canal conformation and orientation which reduces aeration and ventilation. Ear discharge and bacteria easily accumulate around the angle of the vertical and horizontal ear canal which they form a nidus of infection and abscessation ensues. An abscess is a collection of pus consisting of bacteria and white blood cells in a capsule. Rabbit abscesses are caseous and thick compared to other animals. It is as thick as cheese or toothpaste. Some owners may note there is a swelling at the base of the ear pinna and some may report excessive head shaking or ear scratching of the affected ear. A portion of the affected rabbits may have stinky ear discharge oozing out of the ear canal. They can scratch themselves to bleed as the infection can be irritating. If the ear base abscess is locally invasive, surrounding nerves can be affected that rabbits will show facial paralysis- facial asymmetry, lack of blinking reflex, dry eye, corneal ulceration, tear overflow etc. Some severely affected rabbits may show head tilt signs towards the affected ear side. During physical examination, first I check for the presence of any firm and soft tissue swelling over bilateral ear base. Many of them are big enough to be palpated. The size of the abscess ranges from a “maltesers-” to grape-size. Second, an otoscope is used to examine the presence of purulent exudate in the ear canal. In the mean time, ear canal stenosis, inflammation can be visualized. Most of the ear base abscesses are not responding to oral antibiotics and topical ear medications as the abscess capsule is too thick which prevents the penetration of medications into the centre to tackle the infection. Due to the fact that there is a relative high recurrence rate, a new surgical techniquelateral ear canal resection is advised. This surgical procedure is to shorten the length of the ear canal and remove the abscess embedded in the cartilage en bloc. This can facilitate aeration, drainage and ear medicating. Overall, the humidity and temperature of the ear canal micro-environment are modified leading to a decrease of infection. Surgically, the rabbit patient is placed in lateral recumbency under general anaesthesia, clipped around the ear base and aseptically prepared. The ear canal is reconstructed by resecting a rectangular portion of skin, ear cartilage. The edge of the skin and ear canal are sutured with absorbable 4-0 suture in a simple interrupted pattern. This surgery requires a good knowledge of the rabbit skull anatomy as there are few important structures nearby- auricular veins, arteries, facial nerves- which may be sacrificed during surgery if abscessation is getting too deep. Possible complications would be haemorrhage, facial paralysis etc. Antibiotics and analgesics are used postoperatively. The surgical wound may become covered with bloody crusts and ear discharge that regular cleaning with antiseptic is recommended. Sutures are removed in 3 weeks time. Normally, recovery can take up to one to two months. Prognosis depends on the severity and size of the ear base abscess. It is advised the sooner the operation done the better the prognosis as they tend to be smaller and easier to be resected en bloc and less traumatized. This new surgical technique is way better than previous lancing and drainage technique since it reduces the recurrence rate. Have a look of your rabbit ear base, if he or she is a lop bunny. Please pay special attention to the ears as they are predisposed to chronic ear infection and ear base abscess. If you can feel lumpiness or anything suspicious, take him or her to your rabbit veterinarian for a detailed examination and figure out the best treatment as soon as possible. |
