Guinea pig sneezing blood?!

Question
I have a female guinea pig that I recently adopted from another owner. One day I picked her up and she chattered at me (which isn't unusual, she is very unsocialized) and then she sneezed blood everywhere so I rushed her to a vet who looked at her and since she has clear eyes, normal lung sounds, no signs of injury, and is behaving normally he diagnosed it as a simple nosebleed but it must have happened again last night because I went to wash out her pigaloo and there was blood splattered all over the inside of the pigaloo. What could be causing the bloody sneezes. She lives alone (she had a cage mate but they have a divider down the middle of the cage as they have started fighting), her eyes are still clear, she sneezes once in a while but not excessively, she is not having any breathing problems, she is eating and drinking normally, and she has normal poo and pee. Thanks so much for your time.

Answer

Cavy skull and teeth  

Cavy skull and inside   My first thought is that she has a broken tooth. Cavy incisor teeth grow way up inside of the head just below their nose. They're much longer than the part we see when we open the mouth. Blood doesn't just happen without trauma. It flows through vessels and arteries unless there's a break through tissues somehow.

A "simple" nose bleed in humans happens because a small vessel or capillary got dry enough from lack of humidity, or had enough inside pressure from high blood pressure to break, thus bleeding through the nose. It can also happen from picking your nose. Guinea pigs don't do that.

This first picture show you what a cavy skull looks like. The part of the upper teeth we actually see is only about half of what you see in the picture. The nasal passages are just above the teeth. I've seen pigs who for unknown reasons had a tooth growing out of the nasal opening. It was probably early trauma from a bang to the front of the face, causing the undeveloped incisor to deviate from its normal growth path.

If there is some kind of trauma to the root or other part of the tooth it would begin to make it's way into the nasal soft tissue tissue thus causing bleeding. I suspect that's what's happening. It may not be visibly seen without an xray.

In the second picture you can see two small holes just in front of the molars and a larger hole just at the back of the molars. When we have post nasal drip that larger hole is where it drips down into the throat. If there's a broken tooth or injury into the nasal passage, blood can drip down into the throat - OR you can sneeze it out of your nose.

If your pig is eating okay and there isn't an abundance of blood or frequent enough to cause a significant blood loss I suspect it will resolve itself in a short time. Most probably the reason it looked like there was more blood in the igloo is because the particles of mucus and/or blood are small enough and spread far enough with a sneeze to be hidden in the bedding. Sneezing inside the igloo contained it as it ended up all over the inside of it.

I hope the pictures help you get a better idea of how the anatomy is built and works. Please keep me posted as to how she does. Hopefully this will resolve quickly and you can rest easy again.