Could be blockage, could be parasites, could be ovulation/eggs it could be a lot of things. We need more history. How long has it been since she's ate? Passed a stool? Is she drinking? You can dry soaking her to hydrate her which could help her pass a stool if it's not a serious blockage.
You're welcome
You can also try spraying down the sides of her tank and/or humid hide with a spray bottle.. some geckos prefer to get their water that way instead of a cup. Especially if it's a younger gecko. How old is the gecko? Is it an import or from a breeder?
Soaking is easy. Put it in a cup/container filled with 1/8" to 1/4" water (depending on how big your gecko is) filled with luke warm clean fresh water and let it sit in there about fifteen minutes once a day. Always observe the gecko in case it gets tired/weak and problems arise. The idea is to allow the water to soak into the vent area. If it's dehydrated this can help it pass a stool.
Calcium powder will not cause impaction. Too large of crickets could cause the problem. Parasites are treated with oral medicine usually through a fecal sample. If it won't give you a stool sample to check, you can still take the gecko to the vet for an exam where the Dr. can observe and look for other clues such as MBD, calcium deficiency etc. and treat from there.
I would start with a soak first and go from there.. unless you see other obvious signs such as not being able to walk properly, sleeping all the time and non-active when handled etc.
Good luck
Many Thanks!
I started the soaking yesterday. I do spray down the tank twice daily for humidity. Do you recommend going to a reptile vet or do most vets handle geckos? I got the gecko from a friend of mine who bred it. It is about 3 years old. She/he is still seems normal activity wise and is eating, but w/ not passing any fecal matter and the distended belly I am concerned. Many thanks again!