What her kidneys were doing for her
Four jobs, four consequences
Filtering waste is the job everyone knows about. The kidneys do four more things that matter just as much once they start failing, and each one explains a symptom you'll meet later.
| What healthy kidneys do | What she loses as function goes | The word your vet will use |
|---|---|---|
1 They clear waste productsCreatinine, urea, and a long list of others. | When they build up, she feels nauseated, dull and off her food. That's what uremia means, and it's most of why a kidney cat feels bad. | Uremia |
2 They concentrate urineHealthy kidneys pull water back out and send it home. | Damaged ones can't, so she loses water constantly and drinks more to keep up. That's the drinking and the bigger clumps in the box. | Thirst, and big clumps |
3 They balance mineralsPhosphorus and potassium especially. | Phosphorus climbing is what makes her feel ill. Potassium leaking out is what makes her weak. | Phosphorus, potassium |
4 They make a hormone for red blood cellsA signal to the bone marrow to make more. | As that signal fades, she becomes anemic and tires easily. That's a later-stage problem and it's treatable. | Anemia |
Why she looked perfectly well until last week
Kidneys are built with enormous spare capacity. A cat can lose something in the region of two thirds of her total kidney function before her blood values move outside the normal range at all. She spent that whole period compensating, quietly and effectively, by drinking more and passing more urine. Nothing grows kidney tissue back, but how she feels and how fast she loses the rest can both be changed, and that is what the rest of the care is for.
You don't need to memorize this table. It's here so that when your vet mentions phosphorus or potassium or anemia later on, you'll know which of the four jobs they're talking about.