Possible Risk Factors for Kidney Disease in Cats

Chronic kidney disease (CKD) is a common and important cause of illness in older cats. It is a frustrating disease for many reasons, especially the lack of a clear understanding of what causes CKD and the absence of a proven effective strategy for preventing it. Many theories have been advanced for what causes CKD, but the existing evidence is not conclusive for any of them.

Particularly popular among alternative medicine advocates is the notion that commercial diets and vaccines are important causes. The role of diet is not at all well-established. There are some studies suggesting that certain vaccines can induce the formation of antibodies against proteins in the kidneys of cats, but this has not yet been linked to actual disease. A new study evaluating risk factors for CKD in cats adds both some useful data and also some confusion to the subject.

Finch, N.C., Syme, H.M. and Elliott, J. (2016), Risk Factors for Development of Chronic Kidney Disease in Cats. Journal of Veterinary Internal Medicine, 30: 602–610.

This study involved signing up a large number of cats in the U.K. and collecting data about many aspects of their life and health. These cats were then followed over time, and differences between those who developed CKD and those who didn’t were evaluated. The results can’t be taken as proof that these differences are or are not direct causes of CKD, but it can help to identify potential risk factors.

Many different factors were evaluated, though of course the number of potentially relevant variables is enormous, so many were not evaluated which might still be important. As is common in this sort of study, most factors tested did not appear to differ statistically between the groups while a few did. The type of statistical significance testing used has come under growing criticism, with the major organization representing statisticians recently producing an unprecedented position statement suggesting this strategy be abandoned as misleading. This complicates interpretation of this and most other scientific studies employing this method. The results are presented in the two tables below.

Finch 2016 Table 1 finch 2016 table 3

The first shows statistically significant differences in 3 of 12 variables compared, with more cats developing kidney diseases being predominantly outdoors, vaccinated every 1-2 years (as opposed to >/= 3 years or never), and having moderate to severe dental diseases. The second table shows the results of linear regression analysis intended to confirm statistical association between some of these variables and kidney disease. This analysis found statistically significant differences in 4 of 16 variables, with the risk of kidney disease being greater with increased age, vaccination more often than every 3 years, and moderate or severe dental disease. In this analysis, being predominantly outdoors did not reach statistical significance as a risk factor.

The association between vaccination and kidney disease in this study will undoubtedly fuel opposition to vaccination of cats among some owners and veterinarians. It is an important observation since it does suggest that vaccination may be a risk factor for this common disease. However, even if this is true, it suggests that the current vaccination guidelines, which include vaccinating no more than every three years and considering even fewer vaccinations in cats who are indoors only and not exposed to vaccine-preventable disease, are probably sufficient to eliminate or dramatically reduce this risk.

Unfortunately, no additional information about which vaccines might play a role and which components in those vaccines might increase the risk of kidney disease is available in this study. Until the potential association between vaccination and kidney disease is confirmed and a specific understanding of the causal relationships involved in available, the only reasonable response to the possible risk is to adhere to current vaccination guidelines. More radical action, as is likely to be advocated by anti-vaccine advocates, is not justifiable and will likely only increase the risk of preventable infectious disease without protecting cats from kidney disease.

The other variables associated with kidney disease in this study were dental disease, age, and possibly outdoor lifestyle. Because dental disease is a chronic infectious and inflammatory condition, it is quite plausible that this disease might increase the risk of kidney problems and other health conditions. This emphasizes the importance of good oral hygiene for cats. Age has long been associated with kidney disease, and confirming this does not provide much in the way of actions we can take to reduce kidney disease risk. Finally, the finding that predominantly outdoor living may increase kidney disease risk is interesting, but it would certainly need to be confirmed before we could confidently include this risk among the many known to be associated with letting cat roam freely outside.

The failure to find associations between some variables and kidney disease is also worth considering. No association was seen, for example, between diet and kidney disease. It is often claimed that commercial diets, particularly dry kibble, increases kidney disease risk. However, in this study at least, such an association was not supported.

As always, there are a number of limitations to this study that require us to interpret the findings with caution. The use of p-values, and the risk of evaluating many factors and drawing conclusions about the few that show a significant association has already been mentioned.

The other most significant concern is that almost half (43%) of the cats initially enrolled in the study dropped out, and no information about their development of kidney disease is available. If these cats differ in any way from the cats who were followed up, this could completely change the results of the study. Additionally, of the cats who were followed to the end of the study, only 27 developed kidney disease, which is a pretty tiny sample for this kind of epidemiologic survey. By comparison, several similar studies in humans have included between 4000 and 9000 individuals.

There are a number of other ways in which the cats in this study might not fairly represent other populations at risk for kidney disease. Most were from urban areas in the U.K., and there may be significant genetic and environmental differences between these cats and other populations, such as suburban or rural cats in the U.S. Also, much of the information about diet and vaccination was obtained from owners and was limited in detail and reliability. All of these factors influence the extent to which these results can be generalized.

Overall, this study highlights a few variables that might or might not influence the risk of kidney disease. Further study will be necessary to confirm both the positive and negative findings and elucidate the details of any real risk factors to allow meaningful action to be taken to reduce the risk of this common and serious disease.

 

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9 Responses to Possible Risk Factors for Kidney Disease in Cats

  1. Shawna says:

    Very interesting! Was there any kind of relationship between wet or dry food being fed?

  2. skeptvet says:

    No, they did not find any association between type of diet and kidney disease.

  3. Lisa says:

    Specifically, which vaccinations were identified as contributory to kidney disease? And, what about the rabies vaccination?

  4. skeptvet says:

    You can read the full study, since it is open access. They did not collect any data on specific vaccines.

  5. Cathy lowder says:

    Is there any link between vaccinations and accute kidney failure? I have a cat that was fine and got a clean bill of health from the vet along with annual vaccinations. The next week she died of kidney failure.

  6. skeptvet says:

    This has not been reported as an effect of vaccines. Unfortunately, the occurrence of one thing (vaccination) shortly before another kidney failure) often turns out not to be a reliable way of deciding if the one caused the other because so many other potential risks factors exist that we don’t know about or pay attention to.

  7. Donna C says:

    Our 8 year old female kitty went in for a routine visit 3/23/19, weighing 5.50 lbs. given the 3 year rabies vaccine. Zoetis Lot 282272 and Profender dewormer medium. We were told she lost 3 lbs from the last visit a year before, recommending some blood work. She never was her self after that vet appt. She was hardly eating or taking her treats which she loved so much when I shake the treat bag. She would stay in one area, not around us as much or other cats. She still went outdoors but not active like she always was. We took her back to the vet on 3/30 and were told she had a mouth infection. This was just one week after her routine visit and the 3 year rabies vaccine. We were given an antibiotic to give her by mouth. She was given fluids that day from an IV. We did the blood work cause Vet said it could be kidneys, feline aids, not sure..so the vet called me that evening to tell me my Kitty has Chronic Kidney Disease! I was shocked cause she was completely fine and herself before that first vet visit. Only 8 years old! The Veraflox oral antibiotic wasn’t going so well so I brought her back for the antibiotic injection Convenia on 4/1. I was also sent home with fluids in an IV to give her regularly. Kitty bounced back a bit after the antibiotic injection. She still wasn’t her normal self. She was eating but not much. She did want comforting and would sleep on my bed pillow most of the day. She still went outside. Eventually as some weeks went by, Kitty was deteriorating rapidly.. skinny .. loosing fur. Hiding in different areas. Not coming right away when called, hanging out in litter box. On 4/25, I went back to the Vet for more fluids. The Vet had called me once after the kidney disease diagnoses and said in voicemail she would call back the following Monday but never did. I called to follow up and to have her call me, she never did. When I went back to pick up fluids, I asked receptionist to please have her call me cause she hasn’t yet after a few attempts. Still no call! Kitty got worse and worse… dwindled down to nearly nothing. This past week, she was still eating very little, taking her treats but only up to 5/14/19. On 5/15 she went out ( we have a cat flap), We have 2 other older male cats. We open the cat flap in the morning and get all cats in before dark and than close flap. On that Wednesday 5/15, I couldn’t find her.. I kept calling her, shaking the treats. I figure she went out in back woods somewhere to die. Than.. she appeared in the yard looking up. I was up on the deck. I ran out to get her and brought her in. She wouldn’t eat and ran downstairs to walk out basement. She went into the boiler room and stayed there in an unusual spot. The next morning she was in the walk out basements bathroom, just comfortable on the throw carpet. We put some food, treats, and litter box there. That later afternoon when I returned home from work..found her in boiler room but curled up in back of heating system.. she was ok but just relaxed. A few hours later she had moved but not very far and there was wet under her so I figured she couldn’t make it to her litter box. I picked her up and brought her outside on deck and this was the first time I saw she couldn’t walk.. she stood up and tried to walk but her back end and legs couldn’t do it and she laid back down.. I brought her back in after 10 minutes cause she enjoys the outside. I tried to see if she would eat or drink.. nothing. I took her to her favorite cat tower located in the dining room where 12 foot slider shows entire outside view. She went inside one of the open cubby’s in the tower. This was Thursday night 5/16/19. I stayed by her till 2am, petting her and talking to her, she was purring. there was a full moon peering down on us through the glass. I felt this was the end for her. I was heartbroken. The next day 5/17, I brought the cat tower and her outside on the deck. The sun had come out and the birds were chirping. When I spoke, her tail would move. The other 2 male cats were around. One of them came and hung out nearby on deck railing. When dark set in.. I brought Kitty in her cat tower into dining room overlooking the outside view. She passed a few hours after with me by her side petting her and talking to her. We made a beautiful grave site for her in the backyard next to the woods. There happened to be a wild flower there already growing. I am completely devastated by what happened to our Kitty. It’s quiet here now without her and her 2 male cat buddies are feeling it. She was the life of the cat family here. We are all heartbroken and just want answers to how this happened so suddenly.

  8. skeptvet says:

    I’m sorry for your loss, and for the poor communication you seem to have had from your vet. Unfortunately, I don’t think there are “answers” that will make any of this better. Kidney disease is common, and it probably has multiple causes that vary from individual to individual. There are often treatments that can help, but unlike people we don’t put cats through dialysis and kidney transplants because the cost and the suffering to the cat simply don’t make sense for most people. Kidney disease also doesn’t show symptoms until very late, so it probably didn’t happen “suddenly,” it’s just that there’s no way to know it is happening without blood and urine tests.

    In any case, I doubt there is any information that will ease your loss. I imagine only time.

  9. Donna C says:

    Thank you for your response.
    I truly believe if a blood test was done first before the 3 year rabies shot, we would have known she had kidney disease. At that point, no need for a 3 year vaccine. I feel her body couldn’t handle the vaccine while going through kidney disease. Apparently she wasn’t a healthy cat since the onset of kidney disease. I think she went complete downhill after that shot. That’s my observation..

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