By Karen Rosenthal, DVM, MS
I have two female, 8-month-old rats (they’re sisters). Today, when I came home from college, I got them out and realized that one of my rat’s feet had swollen to about three times the normal size. I then realized that it had been bleeding, as there is a blood stain on the tail and there are cuts on the foot itself. I can’t see any bones that are dislodged. The color is slightly purplish, like a bruise maybe? She is unable to walk on it and is limping. When I have touched it gently, she hasn’t cared and she hasn’t squeaked, but if she puts too much pressure on it, she does squeak. I have separated the two rats and placed the injured one into a smaller cage and removed all of the shelves and stairs. I only left her with a lot of bedding, food and water. She is resting her foot and licking it quite a lot. I’m not sure what she has done. They could’ve been fighting. Is this injury serious?
When a limb is swollen, there are only a few reasons for that to occur. The skin covers the limb or foot as if it is a closed container, like a balloon. As you put more air into a balloon, it will get bigger. When more “stuff” gets under the skin, the skin gets bigger. The “stuff” is usually either more liquid or more tissue or even a foreign object.
More liquid could be pus, as can happen with an infection. Or more liquid can be free blood, as with a bruise due to broken blood vessels. Inflammation, you hear that word a lot, means that cells and fluid have invaded a space and that is another cause for swelling.
More tissue causing a swelling can be a mass, like cancer. Or more tissue can be a bone that is broken and out of its place under the skin. If a very sharp piece of bedding punctured the skin, causing inflammation, the area can be swollen both from the foreign object and fluid that comes with inflammation.
A finite number of things will cause the swelling. The important thing now is to figure out which one is the culprit.
Depending on how you have the cage set up for your rats, an accident on an exercise wheel is a common cause of injury leading to either a broken bone or damage to soft tissue. Both of these things can lead to what you are describing. A bite from a cagemate, as you suspect could be the cause, also could lead to inflammation, infection and broken bones.
The only way to know for certain is to visit your veterinarian. It will not take your vet long to decide what is causing this problem and how best to treat it. If nothing else, your rat is likely in some pain due to this swelling and some pain medication will go a long way to helping your rat feel better and recover faster.