Subcutaneous emphysema (or subcutaneous air sac emphysema) in a young chick.
Normally, a chicken's air sacs are thin-walled structures connected to the lungs. If one of these air sacs ruptures because of trauma, excessive strain, disease, or occasionally without an obvious cause, air can escape into the tissues beneath the skin instead of remaining within the respiratory system.
The affected bird typically develops:
A soft, swollen area under the skin that feels like an inflated balloon.
Swelling most commonly on the neck, breast, back, or under the wings.
Little or no pain when the swelling is touched.
In severe cases, difficulty moving or breathing if a large amount of air accumulates.
Common causes include:
Flying into an object or other trauma.
Being startled and struggling violently.
Respiratory infections that weaken the air sacs.
Rarely, congenital weakness or spontaneous rupture.
Treatment depends on the severity:
Mild cases often resolve on their own if the bird is kept calm and the air sac heals.
More severe cases may require a veterinarian or experienced poultry keeper to release the trapped air using a sterile needle or a small skin incision. Because the air sac leak can persist, the procedure sometimes has to be repeated until the tear seals.
If an underlying respiratory infection is present, that also needs to be treated.
Although it can look alarming, many chickens recover completely if the underlying cause is addressed and infection is prevented.
