High Creatinine, Low BUN?

10thomer

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Hi all - I'm a bit stumped and would like help understanding my cat's blood and urinalysis results. So my cat is a 5 y.o. domestic short hair who has had upper tract IBD all his life. We took a lot of time to find a food that works for him and his sister (who has lower tract IBD), and finally settled on Blue Buffalo Wilderness Mature Chicken Recipe Canned food with a daily snack of half a can Wellness Core Signature Selects Skipjack Tuna & Shrimp. He has been on this wet food-only diet for a couple of years now.

A couple of months ago, he started throwing up intermittently, maybe once every 3-4 days, so we took him to the vet and they ran a routine blood test and urinalysis. Much to our surprise, while his BUN was normal, his SDMA was 15 and his creatinine was 2.3. He also had +1 protein in urine and seemed to be dehydrated. Our vet was surprised and scheduled him for an ultrasound, and his kidneys looked totally normal - the only abnormality was that his upper GI tract was inflamed (not surprising considering IBD). He was scheduled for a second test about 2 months later, and this time his BUN was still normal, his SDMA was unable to be detected, but his creatinine was 2.6. This was dismaying to me, as I had been mixing water into his wet food, hoping that he was just dehydrated during his first test. I've attached his latest blood and urinalysis results for reference.

I have a couple of questions, it would be helpful if someone could answer even one of them:
1. Are these unusual lab test results for a young cat who's a healthy weight and is a bit on the muscular side? His vet is also confused so this is making me anxious
2. Can high-protein foods cause results like this? Is the Blue Buffalo food perhaps too hard on his kidneys?
3. He has had gabapentin before each visit. Can gabapentin sometimes cause these wacky lab results?
4. Could this be anything else besides reduced renal function? Wouldn't his kidneys look weird on the ultrasound if his kidneys were having problems?

Thanks so much for any amount of insight you can provide me with!

Blood 1.PNG Blood 2.PNG Chemistry 1.PNG Urinalysis 1.PNG Urinalysis 2.PNG
 
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10thomer

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Maybe this will help? Looking for the links with info about elevated BUN/crea in raw fed cats It's about raw diets but may also apply to high protein canned diets.
Thanks for sharing this with me! Unfortunately, they linked to a study that showed that cats who were fed a high protein diet generally have lower creatinine levels


Not sure why this is happening to my little boy :(
 

Maurey

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IANAV, just in human research, but here are my two cents.

Are these unusual lab test results for a young cat who's a healthy weight and is a bit on the muscular side? His vet is also confused so this is making me anxious
IMO, it’s unusual. If your vet seems confused, perhaps it’s time to request a referral to a specialist. You want internal medicine or endocrinology.

Can high-protein foods cause results like this? Is the Blue Buffalo food perhaps too hard on his kidneys?
Could this be anything else besides reduced renal function? Wouldn't his kidneys look weird on the ultrasound if his kidneys were having problems?
High protein diets should not be hard on the kidneys of an obligate carnivore, as that is their biologically appropriate diet, so I wouldn’t worry about that. Also, the conventional wisdom is that a low BUM to creatinine ratio (I.e. low bum, high creatinine) can indicate either a diet too low in protein (though this is generally seen in humans), severe muscle injury (rhabdomyelosis, again more common in humans but known to happen in cats), or SIADH (syndrome of inappropriate antidiuretic hormone secretion, this is a rare condition in cats, more common in humans). Generally, the typical cause of this ratio in cats is indicators of starvation/malnutrition (unlikely in your case), liver or kidney issues, or pregnancy. I’d talk to your vet about ruling out liver and kidney issues before tackling the idea he might have some rare disorder like SIADH — think horses, not zebras, after all. Especially considering there is some link between renal insufficiency and IBD, though this has only been explored in humans, to my knowledge.

In early stages, renal disruptions may not be visible on an ultrasound.


He has had gabapentin before each visit. Can gabapentin sometimes cause these wacky lab results?
Gabapentin is expelled exclusively through the kidneys. If he’s been to the vet a lot, it could definitely be causing at least some of these results, it’s hard to say. if you’re keeping within the correct dosages, and aren’t medicating daily, it’s not super likely to have exclusively caused the results, unless your kitty was already predisposed to renal issues genetically.
 
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10thomer

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IANAV, just in human research, but here are my two cents.



IMO, it’s unusual. If your vet seems confused, perhaps it’s time to request a referral to a specialist. You want internal medicine or endocrinology.



High protein diets should not be hard on the kidneys of an obligate carnivore, as that is their biologically appropriate diet, so I wouldn’t worry about that. Also, the conventional wisdom is that a low BUM to creatinine ratio (I.e. low bum, high creatinine) can indicate either a diet too low in protein (though this is generally seen in humans), severe muscle injury (rhabdomyelosis, again more common in humans but known to happen in cats), or SIADH (syndrome of inappropriate antidiuretic hormone secretion, this is a rare condition in cats, more common in humans). Generally, the typical cause of this ratio in cats is indicators of starvation/malnutrition (unlikely in your case), liver or kidney issues, or pregnancy. I’d talk to your vet about ruling out liver and kidney issues before tackling the idea he might have some rare disorder like SIADH — think horses, not zebras, after all. Especially considering there is some link between renal insufficiency and IBD, though this has only been explored in humans, to my knowledge.

In early stages, renal disruptions may not be visible on an ultrasound.



Gabapentin is expelled exclusively through the kidneys. If he’s been to the vet a lot, it could definitely be causing at least some of these results, it’s hard to say. if you’re keeping within the correct dosages, and aren’t medicating daily, it’s not super likely to have exclusively caused the results, unless your kitty was already predisposed to renal issues genetically.
Thank you so much for the detailed response! I'm also in research, but I'm focused on in vitro biochem so all of the unusual results here are really stumping me because I'm used to more straightforward data hah. He has an appointment with an internal medicine specialist on Monday so I'll definitely post an update in case this thread ends up being useful for anyone else.

So the new thing that I learned after speaking to a third vet about his issue is that his urine specific gravity was quite low during his first test (1.019) but had improved on his latest test (1.030). So it's likely that he has some sort of kidney injury that he may be recovering from. I'm worried that dehydration caused by regular vomiting stressed his kidneys and now that I'm mixing water into his wet food and have gotten his vomiting under control that his kidneys' are regaining their ability to concentrate his urine. Still doesn't explain the increased creatinine and the fact that his BUN has been normal this whole time *sigh*. I'm just really hoping that it was an acute stress rather than the start of chronic kidney disease, which I feel like would be unusual for such a young cat but as you mentioned, there is some data suggesting a link between renal insufficiency and IBD so it's maybe not impossible.

I read a couple of case studies about how gabapentin may have caused some myopathy and/or renal stress in human patients, so I'm going to keep him off of it during his specialist appointment even though I know it's super unlikely it's causing this. I just wonder if this looks so bizarre because it's a multifactorial issue because I can't find one reason why this all would be happening.
 

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Thank you so much for the detailed response! I'm also in research, but I'm focused on in vitro biochem so all of the unusual results here are really stumping me because I'm used to more straightforward data hah. He has an appointment with an internal medicine specialist on Monday so I'll definitely post an update in case this thread ends up being useful for anyone else.
Here's hoping you hear back something positive (and less confusing!)

So the new thing that I learned after speaking to a third vet about his issue is that his urine specific gravity was quite low during his first test (1.019) but had improved on his latest test (1.030). So it's likely that he has some sort of kidney injury that he may be recovering from. I'm worried that dehydration caused by regular vomiting stressed his kidneys and now that I'm mixing water into his wet food and have gotten his vomiting under control that his kidneys' are regaining their ability to concentrate his urine.
It does sound quite possible that he's recovering from whatever caused his results (and initially caused the vomiting, presumably). I'm assuming you know, but just in case, urine specific gravity is essentially a factor used to assess whether urine is dilute or not based on urine concentration as compared to water, which is the baseline 1. Low urine specific gravity means the urine is dilute, which can be a sign of just drinking more than usual or kidney damage. Fortunately, his readings are improving, and he never got into the true risk zone (unless he was assessed as dehydrated at the time of taking the sample), considering there's a huge range in usg readings in healthy animals.

Still doesn't explain the increased creatinine and the fact that his BUN has been normal this whole time *sigh*. I'm just really hoping that it was an acute stress rather than the start of chronic kidney disease, which I feel like would be unusual for such a young cat but as you mentioned, there is some data suggesting a link between renal insufficiency and IBD so it's maybe not impossible.
Stress can sadly cause a lot of things in cats, so it's theoretically quite possible. Regardless, here's hoping he just had a relatively minor health hiccough, rather than anything like kidney disease.

read a couple of case studies about how gabapentin may have caused some myopathy and/or renal stress in human patients, so I'm going to keep him off of it during his specialist appointment even though I know it's super unlikely it's causing this. I just wonder if this looks so bizarre because it's a multifactorial issue because I can't find one reason why this all would be happening.
It's definitely possible, but rare. Might be worth asking the vet when you get there about your concerns, or see if you could call in advance? They might want to get initial readings on him on gabapentin vs off.
 

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1. Jamie is now about 4 and at 2 had a high BUN and creatinine reading. This is probably more typical, so your vet's confusion might not be from incompetence. Having said that, I am a huge believer in referrals to specialists once anything becomes confusing, complicated, or risky.
2. Jamie eats a high protein diet, which I am trying to deal with, and prefers fish over anything else. He does eat cat food, not raw or human. Applaws is the current favorite. I am trying to deal with the protein/phosphorous issue.
3. I have never used gabapentin with Jamie although by the time he gets to the vet he is in a state and they have had to knock him out in order to do one of the ultrasounds. Conscious or not did not vary the consistency of the reading. Ultrasound showed nothing.
4. We have ruled out hyperthyroidism and diabetes, neither of which he was even close to having. The next test will be an echocardiogram.

We have considered that he is an outlier, among other things. I personally have had lifelong low white blood cells and high bilirubin and have not dropped dead yet; that sort of thing. I completely sympathize with your frustration and concern for your cat.
 
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10thomer

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Thanks to everyone for the insights and kind words! We just finished up at the internal medicine specialist annnnnnnnnnd... unfortunately she suspects that he has both IBD and CKD as a 5 y.o. cat. Not the response that I was hoping for, and if this is true then I have absolutely terrible luck picking out kitties.

She conducted another blood test so we'll have the results of those soon. She also did a vitamin test to ensure that he's absorbing vitamins properly given that his IBD might hinder this process. She recommended getting an endoscopy/biopsy to potentially rule out some type of GI cancer but that seems a little extreme to me right now.

She just didn't really seem concerned about treating his potential CKD right now which I thought was weird? She also wasn't concerned that his BUN was normal while his creatinine has been elevated - she said something to the tune of BUN being more variable than creatinine but this still seems suspicious to me. She said his last urinalysis was unremarkable so she did not rerun that.

Overall she thinks that he's a very healthy looking cat, at a good weight for his size (he's very long) and he has good muscle development. No signs of cardiac or respiratory issues.

Another update is that I started feeding my cat at the same time of day during which he used to vomit bile (saw something about bilious vomiting syndrome and I was like... eh why not see if this works) and his vomiting has totally stopped and he's acting normal again.

I guess I'm still confused and pretty dissatisfied with the internal medicine specialist so far. Like, what are the chances I've got a 5 y.o. cat with 2 generally geriatric chronic conditions? I feel pretty defeated. I'll post his lab results when I get them in case this thread ends up being useful for anyone in the future.
 

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She also wasn't concerned that his BUN was normal while his creatinine has been elevated - she said something to the tune of BUN being more variable than creatinine but this still seems suspicious to me.
BUN is indeed more variable and not used to diagnose kidney disease or the lack of it alone. Like, BUN can go high just by some dehydration, or high protein diet/food. Where I live vets ask cats to fast for 8 hours prior to the blood test for that reason. They say "Otherwise we won't be sure if something is high because of the food or something else we need to check."

Of course I can't say what "normal BUN to high creatinine" means in your case.

what are the chances I've got a 5 y.o. cat with 2 generally geriatric chronic conditions?
If I were you I would ask the vet if there is kidney disease what makes them think it's Chronic Kidney Disease and not Acute Kidney Disease. Acute is usually reversible.

There's AskVet on Reddit. They have very strict rules and diagnosis guessing is against their rules so most questions end up getting not answered. But if you upload the test results on imgur and share it there and say you have already seen a speciliast, they might at least hopefully tell you if any other test would help in your case. If not, still good to have the test results saved on imgur. Ask Veterinary Related Questions • r/AskVet
 
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10thomer

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Would you be able to talk with a university veterinary medicine department?
I'm located in NYC so I assume there should be some good university vet departments in the city.... If things still keep not making sense I'll definitely talk to my vet about having him see a university specialist. Thanks so much for the suggestion!
 
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10thomer

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BUN is indeed more variable and not used to diagnose kidney disease or the lack of it alone. Like, BUN can go high just by some dehydration, or high protein diet/food. Where I live vets ask cats to fast for 8 hours prior to the blood test for that reason. They say "Otherwise we won't be sure if something is high because of the food or something else we need to check."

Of course I can't say what "normal BUN to high creatinine" means in your case.


If I were you I would ask the vet if there is kidney disease what makes them think it's Chronic Kidney Disease and not Acute Kidney Disease. Acute is usually reversible.

There's AskVet on Reddit. They have very strict rules and diagnosis guessing is against their rules so most questions end up getting not answered. But if you upload the test results on imgur and share it there and say you have already seen a speciliast, they might at least hopefully tell you if any other test would help in your case. If not, still good to have the test results saved on imgur. Ask Veterinary Related Questions • r/AskVet
Yeah, from what I've read BUN can go up for reasons other than kidney issues, but it is generally high when creatinine is high. I asked the specialist this and I remember her skirting around the question.

So what made her think it was chronic instead of acute is he had a blood test performed in 2019 in his medical records where apparently his creatinine was 2.0. This wasn't flagged to me at the time because the general consensus was that this was in a normal range for a cat, but now it's perceived to be a high value. But once again, his BUN was totally normal in this test...

I did post a while back on r/AskVet but the answer was pretty unhelpful, this forum is much more helpful in terms of acquiring insights but you're right, I'll come back with the results from the specialist and see if they're more comfortable commenting on it! Thanks so much for your response.
 

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Please keep us updated when you're able! Hopefully you're able to get to the bottom of this, and your lovely boy continues to feel better!
 
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10thomer

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ANy update?
Still nothing from the vet :( I think the specialist has to communicate with my local vet who then has to call me so there are several steps where the process could be delayed. I also haven't been proactive in reaching out because I'm afraid of getting more bad news about his creatinine levels...

In terms of how the boy is doing right now, as I mentioned earlier, I started feeding him his normal food at the same time when he was throwing up every day, and he still hasn't thrown up since I started that feeding schedule. He also seems a bit more comfortable and energetic. Such a weird thing, it looks like bilious vomiting syndrome but I'm not sure what it is or what caused it in the first place....

The Cornell Vet school suggestion is a good one - once I hear back from the vet and if things are still confusing I'll reach out to them.
 
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10thomer

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Update for anyone still following this thread! The specialist finally got back to me (I guess she had a typo in my original email address....) and the good news is that his creatinine value has actually decreased a bit from his second test (2.3)! BUN is still normal. All other blood work looks great and he's absorbing vitamin B12 properly.

The maybe not great news (but not as bad as him definitely having CKD?) is that she believes he has chronic pancreatitis because his fPL was 2x reference interval. It doesn't seem like there's much to do here besides control his vomiting and watch his appetite according to her email? And I've gotten his vomiting under control with his new feeding schedule so I'm not sure how worried I should be about starting some sort of treatment regimen. I'll call her and discuss further, of course but wanted to see if anyone had any thoughts on this forum too.

Does anyone have anything to share regarding experiences with chronic pancreatitis in cats?
 
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