Hi again, and thanks for your very helpful reply.
Because Sweetness is a senior kitty, she is more prone to develop various medical conditions like diabetes, hyperthyroidism, liver and kidney issues. In addition, if she is a medium-haired tabby, she may have a large hairball from self-grooming, that has mixed with hard, dry stool and caused an intestinal obstruction. This would cause her to not be able to defecate and also lose her appetite.
If she's not eating, her stomach is empty and an empty stomach produces excess acid which then causes nausea, so this could be the reason for throwing up bile. You can try to give her 1/4 of a 10mg. Pepcid AC (Famotidine is the generic) every 12 hours to quell the nausea and decrease the stomach acid or acid reflux, if it's coming up into her throat.
She should urinate, if you gave her the sub-Q fluids, but you have to wait for the fluids to be absorbed by her body.
It's possible she has an oral/dental problem, so try to check the inside of her mouth for anything stuck on the roof of her mouth, between teeth, between teeth and gums, under tongue or any redness/gum swelling, indicating an abscessed tooth or gum infection. This may be a cause for her not wanting to eat or drink, if her mouth is in pain.
If you have any live or dried plants or flowers in the house, she could have nibbled on a toxic one or she could have ingested a non-food item, causing an intestinal obstruction and inappetance. She also could have been bitten or stung by a venomous insect, spider or snake, depending on your location. Feel all over her body for any bites, swellings or pain response. Feel if her belly is hard.
When a cat of this age begins to exhibit the symptoms you describe, There's not much to be done at home, so your next best step would be to bring her to her vet, or if they are not open now, bring her to an ER vet center for evaluation, diagnosis and treatment.
I hope all will be well with your Sweetness and please let me know how she's doing. Also, please let me know what the vet tells you. Thanks!
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