Gut problem with my chin?

Hey, im new to this and i really need help i dont where else to turn to... I’m desperate so if anyone has any kind of advice it is very welcome.
So my chin has been acting up for about two weeks now. Btw she is 13 years old, but this started very suddenly so i think the age is not the reason. She stoped moving around as much, sleeping in the corner and started eating less then before. Last week i noticed that she hadn’t pooped for a day or so. Naturally i freaked out, called a vet...

Gut problem with my chin?