Balloon syndrome is a rare condition in hedgehogs in which gas is trapped under the skin as a result of injury or infection, causing the animal to inflate. It is akin to surgical emphysema seen in humans, although somewhat more profound in hedgehogs due to their tissue structure. The British Hedgehog Preservation Society describes the symptoms as: "Hedgehog has blown up appearance, subcutaneous emphysema".
Reported incidents
In 2017 the BBC reported a case in which a male hedgehog was "almost twice its natural size, literally blown up like a beach ball with incredibly taut skin". The head vet at Stapeley's Wildlife Hospital, Bev Panto, said, "In my career I have seen three or four of these cases and they are very strange every time and quite shocking... When you first see them they appear to be very big hedgehogs but when you pick them up they feel so light because they are mostly air". She added that the condition was unique to hedgehogs because they have significant space under their skin as a result of their ability to curl up. A similar case had been reported in 2013.
Causes and treatment
The British Hedgehog Preservation Society advises that: "There is no single cause for this condition. The air can be removed by incising or aspirating through the skin over the back. Antibiotic cover should be given. This may be associated with lung/chest wall damage or a small external wound acting like a valve or a clostridium type infection". Incisions in the affected parts of the hedgehog will allow the trapped air to escape, but these must remain open until after the animal's lungs have healed to prevent recurrence of the syndrome. In July 2017Live Science reported Romain Pizzi, the specialist wildlife veterinary surgeon at the Scottish Society for the Prevention of Cruelty to Animals, saying that, "Hedgehogs have a little windpipe that runs from their mouth and nose to their lungs, and at the top of this windpipe is the glottis, which opens and closes as hedgehogs breathe.... If a hedgehog is struck when that glottis is open, air simply flows out of the lungs and out of the body. But if the glottis is closed when the animal is struck, that air has nowhereto go, and the lung tissue can rupture. It's like a balloon popping.... This trauma can also cause damage to the muscles in between a hedgehog's ribs". Live Science added that "the ruptures in the lungs and rib muscles 'act like a one-way valve,' so air can flow out of the lungs and into the body cavity—but not back in. So, with each breath the hedgehog takes, a bit of air leaks out, causing the hedgehog to inflate itself.... Pizzi noted that the tissue under a hedgehog's skin isn't designed to be filled with air, so it's not one big open compartment. Instead, there is a lot of connective tissue under the skin, sectioning areas off into little compartments of air. Though it's called balloon syndrome, in most cases the hedgehogs 'puff up more like Bubble Wrap,' he said".
