What is Choanal Atresia?
This birth defect affects approximately 1% to 4% of foals and is a common cause of stillborn neonates. If the foal is born with a unilateral (partial) choanal atresia, it is not as serious as bilateral (complete) choanal atresia, but it is still a dangerous condition that will need treatment. The foal will have trouble breathing and will need treatment by a veterinarian to remove the membrane as soon as possible. In some cases, unilateral choanal atresia may go unnoticed until the horse gets a bit older and has difficulties in breathing or exercising. The condition may be overlooked or mistaken for a nasal infection or nasal polyps.
Choanal atresia in horses is an obstruction of one or both of the nostrils at birth. This happens when the bucconasal membrane that is supposed to separate the mouth and nose during fetal development is still there when the foal is born. This may be unilateral (only one nostril) or bilateral (covering both nostrils). Both of these are serious but bilateral choanal atresia is a life-threatening emergency and has to be treated immediately after birth or the foal will die of suffocation. A tracheotomy will be done by making a small incision in the neck and inserting a tube so the foal is able to breathe until the condition can be repaired by an equine veterinarian.
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Symptoms of Choanal Atresia in Horses
The symptoms are obvious if the choanal atresia is bilateral, but if it is unilateral you may not notice it at first.
- Unable to stand
- No breath sounds
- Blue tinted mucous membranes
- Rapid heart rate
- Heavy breathing
- Rapid heart rate and breathing
- Inability to exercise
- Unilateral (partial) choanal atresia is the blockage of only one nostril by the bucconasal membrane.
- Bilateral (complete) choanal atresia is the blockage of both nostrils by the bucconasal membrane.
Causes of Choanal Atresia in Horses
- The cause is unknown, but it is a congenital birth defect that is seen more in Standardbred foals than other types
- The bucconasal membrane that is supposed to separate the mouth and nose during fetal development remains
- This may be unilateral (only one nostril)
- The condition may also be bilateral (covering both nostrils)
Diagnosis of Choanal Atresia in Horses
Diagnosing bilateral choanal atresia is done immediately at birth because the foal will not be able to breathe. If the veterinarian is not there to place a tracheostomy tube, you may be able to make a small incision in the membrane yourself while the veterinarian gives you instructions over the phone. However, do not try to do this if you are unable to get an equine veterinarian to instruct you over the phone because you could make things worse. When the veterinarian arrives or when you get to the emergency equine clinic, the diagnosis can be made in the same way as diagnosing unilateral choanal atresia.
To diagnose unilateral choanal atresia in horses, the veterinarian will need to perform a physical examination first, which includes heart rate, breath sounds, blood pressure, and weight. Diagnostic tests that may be done include a complete blood count (CBC) and blood chemistry panel to determine the levels of red and white blood cells, platelets, and to assess organ (heart, liver, kidney) function. After the bloodwork is done, the veterinarian will need to perform some imaging such as x-rays, CT scan, and ultrasound to see what is causing the obstruction. To confirm the choanal atresia, the veterinarian will use a long flexible tube with a lighted camera on it placed into the sinus canal.
Treatment of Choanal Atresia in Horses
Treating choanal atresia depends on whether it is unilateral or bilateral. With unilateral choanal atresia, the veterinarian has more options than with bilateral because your horse is able to breathe from one nostril.
Incising the bucconasal membrane may be done in the case of unilateral choanal atresia. This is performed with the use of a video endoscope, which is just an endoscope that has a video camera attached that lets the veterinarian see what is going on in real time.
If laser ablation is not acceptable or if your horse has bilateral choanal atresia, 2-6 stents will be placed into the nasal cavity to keep it from collapsing after the membrane is removed. Postoperative stricture is common and must be accounted for with by inserting a short nasotracheal tube to keep it open. The tube will be sutured into the nostril and will remain there for six to eight weeks for the best outcome.
Recovery of Choanal Atresia in Horses
You must continue to monitor the surgical area and clean the area every day. The veterinarian may prescribe steroids for pain and swelling. Be sure to check the sutures daily to make sure they are holding the tube in place and call your veterinarian if you have any questions or concerns.