These glands are normally filled with fluid. These are also called scent glands, because dogs of both genders release super small amounts of the liquid when meeting another dog; it's how the communicate. In fact, it's rather interesting, because they can tell a lot about each other by doing this. It lets the other know the dog's gender, health status and even his/her mood (if he/she wants to play or isn't in the mood to socialize, etc.) Also, some may be released in tiny amounts when having a bowel movement, particularly one that is hard and large.
Some dogs never have a problem with them...But most dogs do experience an issue once in a while...And some dogs need to have them checked on a routine basis.
What happens, is that sometimes the fluid in those glands builds up. This makes the skin stretch and in turn it can cause itching or discomfort. And this is one of the most common reasons why a Maltipoo would keep licking their butt area. Since they can't really use a paw to scratch the area, they have to use their tongue.
It sounds like that is what your Maltipoo is doing right now.
Another way that dogs deal with this issue is that they will do what is called "Scooting"...An owner will notice that they rub their bottom on the floor or on the grass and this is often done right after a bowel movement has been pushed out.
Owners who do not know about Maltipoo anal glands
will something think that their dog is actually wiping their behind after a bowel movement. It really looks like that is what they are doing, but it is just a scratching method like the licking.