My mom has not urinated in 30 hours. Looking for some advice.

She is not eating and drinking. You are correct that her output (which is likely quite dark if any due to concentration of urine) will be almost nil. Same with bowel movements.

These are all things that you should be discussing with Hospice. That's what they are there for. Ask for other signs to the approaching of the end, such as cooling and mottled extremities.

I am grateful your Mom has Hospice care support, and I am so sorry for your coming loss.

As the body starts shutting down all your moms organs and bodily functions will as well.
If hospice is concerned about your mom not peeing they can put in a catheter to drain her bladder. And hospice can also give your mom a shot in her arm of Relistor that will make her poop in about 15-20 minutes. So talk to her hospice nurse to see what they feel needs to be done.
The most important thing now is to just keep your mom as comfortable and pain free as possible as she transitions from this life to the next.
And leave nothing left unsaid.
God bless you.

Her body maybe shutting down. Another sign is the skin starts breaking down. Looks like bedsores but the are called Kennedy sores.

The nurse should be available 24/7 by phone.

Is she showing any others sign of deterioration? Like anxiety or agitation? Agree with moondancer, ask the hospice nurse. Good advice.

What does the hospice nurse say?