It could be anal glands (and they could even be infected) but that smell is MUCH worse than urine.

If the cat is heavy and unable to clean herself in the rear end area, the urine could be accumulating and causing a form of "diaper rash".


And the theory about diarrhea is also valid.

A urinary tract infection could also cause soreness, especially if she needs to go a LOT.

The veet visit is your best bet.

Good luck, keep us updated.