Have Cat Questions? Ask a Cat Vet Online.
Your cat has two glands located at 10 and 2 (like a clock) beneath the tail. These glands secrete a smelly substance that looks like gel when they poop. You might be seeing these secretions.
If your cat seems troubled by it, you can see the vet and have the glands expressed.
Let me know if you still have questions.
If you are seeing lethargy and a lack of appetite, you should be very worried. Any time that a cat won't eat for more than 48 hours, you are in serious trouble. Their liver can fail and then the cat can die. It is called hepatic lipidosis where the liver thinks it is being starved and starts "grabbing" fat cells...and actually ends up killing the liver.
I suggest that you see the vet first thing for a full exam and possibly bloodwork to find out what's going on.