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Cat Dehydration and Kidney Damage
elizabeth_1 posted:
How long can a cat go without water before damage to the nephrons in the kidneys occurs?

My cat had surgery on Wednesday and when I picked him up Thursday afternoon, the receptionist casually informed be that he refused to eat or drink anything after the surgery, which means he hadn't had any fluids since Tuesday morning--so he'd been without fluids almost 60 hours.

He did not receive IV fluids during the surgery because although I had requested them (because I was concerned about lack of renal perfusion during surgery) and they added them to the estimate, they decided not to give them to him because his pre-anesthetic screen was normal.

If, say, 10% of his nephrons were destroyed due to lack of fluids for 60 hours and blood pressure drop during surgery, would there be any way for me to know? Would a urine specific gravity test detect a small amount of kidney damage, or does kidney damage have to be severe before any test will pick it up?
elizabeth_1 responded:
By the way, when he got home from the surgery, he drank out of his water bowl for a really long time...and normally he doesn't drink out of his water bowl at all because he gets water from his food.

Obviously, he was really dehydrated...or his kidneys are already in the early stages of disease.
Drew Weigner, DVM, ABVP responded:
This depends primarily on your cat's kidney function. If he has normal kidneys (like most young cats,) he can go at least three days before getting dehydrated. If his kidneys are already compromised (like most geriatric cats) he can get dehydrated within 24 hours. Whether any kidney damage occurred in your cat is difficult to say but if he wasn't dehydrated when you got him home, kidney damage is unlikely. Unfortunately, the fact that he drank so long when he got home does not necessarily mean he was dehydrated. The vast majority of kidney tests won't become elevated until almost 75% of nephrons are lost. While it is possible to measure glomerular filtration rate (GFR) it's not accurate enough to detect a 10% difference in functional nephrons. The good news is that if your cat is back to normal, he's unlikely to have suffered permanent kidney damage.

Drew Weigner, DVM, ABVP
The Cat Doctor
Board Certified in Feline Practice
elizabeth_1 replied to Drew Weigner, DVM, ABVP's response:
Thank you for the information. He is mostly back to normal but he is sleeping a more than usual and his appetite is a little low (he's eating about 1/2-2/3 what he normally eats). I'm thinking his appetite will be better once he is done with the antibiotic

The small, slow-growing tumor on his head turned out to be a fibrosarcoma, so now I'm more worried about that than his kidneys.


William Draper, DVM, better known as "Dr. Will," is a well-known small animal practitioner in the Atlanta, GA area. He grew up in Inglewood,...More

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