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How to help my 18-year-old cat with kidney disease and hyperthyroidism?

Updated On September 23rd, 2025

Pet's info: Cat | American Shorthair | Female | spayed | 18 years and 8 months old | 4.5 lbs

[I asked this question before BUT the vet response thought I mixed the levels up. I did not!] Our 18 year old cat had a blood test with SDMA of 34, BUN 20.9 mmol/L, and cretanine of 173 (normal range 80-221). We believe she has CRF but we don't know what stage it's in? Her free t4 was also high at 47.7 (thyroid). What can we do to help that is non-invasive to help her quality and duration of life? She is a picky eater and will not eat wet foods. What is her realistic life expectancy?

2 Answers

Most Helpful Answer

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Answered By Jacqueline Nobles, DVM, DACVECC

Veterinarian, Board-Certified Emergency/Critical Care Specialist

Published on March 20th, 2017

Hello, I am sorry I misunderstood your question earlier. I hope this response helps you. In order to stage renal failure, we need to know the urine specific gravity, blood pressure, and urine protein to creatinine ratio. Based on the values you provided, she has chronic kidney disease but I cannot stage it without further information. If the free T4 was elevated that is consistent with hyperthyroidism which often masks underlying kidney disease. Therefore, her kidney disease could be worse than we suspect based on the info you provided above. Realistically, she has two diseases and fortunately both are treatable. Ultimately, the prognosis depends on response to therapy. It is not uncommon for some patients to do well for a few years with appropriate therapy and kidney diet. Prior to treating her hyperthyroidism, her kidney disease should be treated (at home) with subcutaneous fluid therapy, antibiotics to cover for an underlying kidney infection, and vitamin B12 supplementation. After she feels better and begins eating consistently, discuss treatment for hyperthyroidism.

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    Answered By Megan, DVM, CVA

    Veterinarian

    Published on July 6th, 2017

    Poor Shiba! 19 years old! Wow! You're doing an awesome job taking care of her. Unfortunately when they have a high thyroid and kidney disease, it makes this complicated. When you treat the hyperthyroidism, it can make the kidney disease worse because it essentially decreases their metabolism and therefore decrease the amount of blood going through the kidneys so therefore the kidneys don't filter out the toxins as well. BUT if you don't treat the hyperthyroidism then the heart can become in large and they can develop heart disease. I would talk to your vet about potentially starting a very low dose of medicine for her thyroid while simultaneously closely monitor her kidney values. If they start to increase, y'all may want to also discuss starting her on a subcutaneous fluid regimen at home to help flush out her kidneys. these cases can be difficult to manage but it is possible. I hope this helps!

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