Disclaimer: This blog is for educational purposes and cases described are not from any one animal. Please be warned that this blog contains pictures from real animal post mortems and graphic descriptions of disease.
This was a case with a couple of twists. It started with a dog whose skin felt just a little strange. He came to his vet, and it sounded as though his chest and front leg was covered in bubble-wrap, crackling when touched. This is how air trapped under the skin (tissue emphysema) feels. Tissue emphysema commonly happens after traumatic injuries, where outside air is forced through wounds under the skin, or alternatively, can escape from the lungs after chest injuries.
Hidden under the dog’s fur, there were indeed several shallow wounds. X-rays revealed three air rifle bullets lodged in the dog’s foreleg, ribcage, and abdomen. The vet operated and retrieved the bullet from the abdomen.
During surgery, everything seemed fairly ok. Air rifles are classed as ‘low velocity’ guns, meaning the bullets travel under a thousand feet per second (unlike high velocity bullets which travel over 2500 feet a second). The surgeon checked carefully, and it seemed that the bullet hadn’t directly entered the intestines or any organs.
But then, shortly afterwards, things took a negative turn. The dog developed a fever, rapid, unstable breathing, and dependent oedema – signs of sepsis, or blood poisoning. Unfortunately, this carries a poor prognosis and high chance of suffering, and he was euthanised on humane grounds.
Bullets cause damage by cavitation; tissues in the bullet path balloon and stretch, tear, and then finally contract. Because of this, tissue damage is not necessarily confined to the direct bullet path.
Tissue cavitation creates a negative pressure that sucks hair and contaminants into the bullet wound. In the post mortem, it became clear that damage extended far beyond the bullet’s path. It seems that even though the bullet hadn’t penetrated the intestines, it had damaged them. Faecal material leaking from the guts was combined with debris sucked into the wounds, setting up a huge infection in the abdomen, chest, and tracking under the skin. The chest, abdomen and subcutaneous layers were filled with litres of watery, red fluid – oedema and blood, a result of massive inflammation due to infection.
Sadly, as pathologists we can find out how an animal died, but in some cases we cannot fathom why.