How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Dr. Michael Salkin Your Own Question
Dr. Michael Salkin
Dr. Michael Salkin, Veterinarian
Category: Cat
Satisfied Customers: 33258
Experience:  University of California at Davis graduate veterinarian with 45 years of experience.
Type Your Cat Question Here...
Dr. Michael Salkin is online now

My cat had a blood test (pre-op dental) that showed bun

This answer was rated:

My cat had a blood test (pre-op for a dental) that showed bun levels of 18 (UK) and crea levels of 3. On the basis of that test, a diagnosis of kidney disease was made. Should there not have been further investigation into that uria level? A urine analysis, maybe an ultrasound and perhaps further chemical testing on the blood? His left kidney is enlarged, but the vets didn't think that was much of an issue. From what I have read, the left kidney could be enlarged because it is performing some of the function of the right kidney because the right kidney is blocked in some way (with stones or, possibly, with tumours). He is a dry food cat (a good 90% of his diet is dry food) and I believe kidney stones are more likely in cats with dry food diets. Is it not possible that that uria level of 18 is not simply down to kidney stones in that right kidney?

Aloha! You're speaking with Dr. Michael Salkin
Can you clarify for me, please, which units were used for the BUN and creatinine? A BUN of 18 mmol/L (UK) = 50 mg/dL (USA). A creatinine of 3 umol/L (UK) = 265 mg/dL (USA) which isn't possible. It looks as if international units were used for the BUN yet common units were used for the creatinine.

In any event, to answer you directly when clarifying kidney disease not only is a urinalysis necessary but also a hematocrit/packed cell volume, serum sodium, potassium, phosphorus and calcium, and blood pressure measurement. Abdominal radiographs and/or ultrasound may further elucidate the cause of or factor contributing to kidney disease (e.g., obstructing or partially obstructing nephrololiths (kidney stones) or ureteroliths (ureteral stones), renal neoplasia, and pyelectasia(changes in the renal pelvis often seen concommitant with pyelonephritis). It's best to have a complete blood count and serum biochemistry profile performed because elevations in the BUN and creatinine can occur due to pre-renal (disorders outside the kidneys affecting the kidneys), renal, and post-renal (obstruction) disease. Please note that alterations of the shape and size of the kidneys are common and may not indicate disease.

Please respond with further questions or concerns if you wish.

Customer: replied 3 years ago.

I suspect international units and common units were used as I was told the creatinine levels were not bad at all, but the BUN levels were a bit above a normal range.

I noticed a change in shape of the left kidney around the time he started to have problems chewing and I thought nothing of it until the dental pre-op bloods showed the levels they did and I was told this was kidney disease.

Is it not possible that the right kidney has some nephrololiths and the left kidney has enlarged as it takes up some of the function lost by that right kidney? And, subsequently, reduced the overall ability of the kidneys to process out uria, resulting in a slightly higher than normal level of uria in the blood?

Thank you. Yes, that makes the most sense. The normal BUN range in mmol/L is 6.4 - 14.6. The normal creatinine range in mg/dL is 0.7-2.2. 18 and 3, respectively would suggest less than 25% of normal functioning renal tissue remains if primary renal disease exists. This can't be known by peforming a BUN and creatinine only. Without a urinalysis I have no way of knowing if excessive proteinuria (protein in the urine) exists and then if there's a need for Simentra. I have no way of knowing if a phosphate binder is necessary if a serum phosphorus level isn't peformed. I don't know if dietary protein restriction is necessary.

How did you notice the shape of the left kidney? It's certainly possible that nephroliths exist - they're relatively common - but one kidney can compensate for the other secondary to a host of diseases in the compromised kidney. Yes, the BUN is usually mildly elevated when one kidney isn't functioning properly.

Please continue our conversation if you wish.
Customer: replied 3 years ago.

At one point, his weight had dropped to 3.69kg (8.13lb). I opted to give him whatever food he would eat. As a result he had 2 weeks eating lots and lots of chicken. After those 2 weeks his weight increased to 4.1kg (9.03lb). He then had another blood test. That test showed BUN levels had increased to 24 and the creatinine levels had remained around 3.

I was told that a high protein diet could raise the BUN level. As his weight was at a good level, I made changes. I started using a phosphate binding powder and continued to use Simentra. His food intake was still largely normal (at this point, he was still having trouble chewing - even after having four teeth removed in a dental operation) and not specialist renal food.

After 2 weeks (and this takes us up to Monday this week) his blood was tested again, but only the BUN, not the creatinine. This time, his BUN had dropped from 24 to 21.

After that, he was put on fluids again for 48 hours (and this takes us up to today). Halfway through his fluids he had his blood tested again and his BUN levels had risen to 30 - even whilst on fluids. He had also received some steroids and was eating and looking quite lively and energetic.

I'm not sure why the BUN would rise from 21 on Monday to 30 on Tuesday whilst receiving fluids. Does this mean his kidneys are failing badly or is there something else going on? I did notice, last week, that he was struggling to urinate. On the back of this information, I convinced the vets to run a urinalysis today - if they could get a sample before I come to pick him up.

The BUN is affected by extrarenal (outside the kidneys) factors far more than is the creatinine. A meal can double the BUN and so it must always be checked after a minimum of a 4 hour fast. Serial creatinine readings are more indicative of response to therapy. Steroids should be avoided in renal patients unless a steroid-responsive disease exists outside the kidneys and needs to be addressed. Steroids will increase the BUN because they're catabolic - cause muscle breakdown.

You can't know why the BUN rose from 21 to 30 without more complete diagnostics. It could simply be due to a meal or a host of extrarenal disorders.
Customer: replied 3 years ago.

ok, I have one or two final questions. As his creatinine is about 3.1 (it was 3.1 in early December and remained the same when tested about 6 weeks later). That suggests, as you mentioned, that he is into stage 3 and has about 25% of function left.

With appropriate treatment (and I will try to find out his proteinuria level to see if I should continue with Semintra - as well as see if I can find out if he needs phosphate binder), can the cat be expected to live a normal life for a reasonable period of time with 25% function? I know plenty of cats can cope very well with 10% and even less function in the kidneys.

His BUN level may have risen from 21 to 30 due to the food he was eating. I did manage to get that to drop a couple of weeks ago, so I think if I stick with what I was doing a couple of weeks ago then he could do well for a bit of time yet.

That issue he was having with chewing has not really been addressed. He was given the steroids to help with that, but I feel that is simply masking the problem and I don't like the idea of him having steroids, especially after what you said about how they effect renal patients. Ultimately, he may need another dental operation and I know that can be risky in renal patients. But if he is struggling to chew (turning his head one way, then the other and often with food dropping out of his mouth), then that surely looks like he has some issue in his mouth doesn't it?

Thank you in advance of your last reply for your help. It is much appreciated.

Yes, he can have a relatively normal life span if the creatinine remained at that level. It's prudent to attempt to clarify the etiology of that elevated creatinine as I've discussed and then schedule rechecks of it every month and tapering or increasing the frequency of the rechecks predicated upon prior test results.

Yes, I would perform full dental X-rays on such a patient. It sounds as if dental disease persists in his mouth. He can be anesthetized but attention to his blood pressure and diuresis prior to, during, and after anesthesia is essential. You're quite welcome.

Please continue our conversation if you wish.
Customer: replied 3 years ago.

He did have a dental about 5 weeks ago and he was anesthetized for 2 hours without problem. If his creatinine level is the same now as it was then, then he should be ok with being anesthetized as long as that due care and attention is paid as it was before.

Would antibiotics be an option for him? I know he didn't have any antibiotics after his dental and perhaps he should have? I am going to pick him up from the vets in about an hour's time. They don't seem keen to do much more for his mouth problem because he has been eating. But surely the steroids he is on are helping with that. I have seen him at home with a normal appetite but really struggling to chew, so I am sure he has issues with his mouth that do require attention.

Unless there's obvious infection or X-rays identify root abscessation, antibiotics needn't be administered. A painful stomatitis (inflammation of the oral cavity) might respond to steroids but you haven't mentioned that stomatitis exists. If it doesn't, steroids should be avoided considering his renal values.
Customer: replied 3 years ago.

He hasn't had a thorough examination of his mouth since his dental back in December. The vet who performed that dental suggested that further dental work may be required, which suggests that she felt that not all the work she would have wanted to do during the dental could not be done. He was anesthetized for 2 hours, so perhaps she didn't want to extend that any longer in a renal patient.

Either way, it seems that I should push for a more thorough examination of his mouth if this chewing problem continues when I bring him home? Ultimately, getting him anesthetized so that they can have a look in his mouth, maybe get an X-ray done and go from there.

Yes, I agree.
Dr. Michael Salkin and other Cat Specialists are ready to help you
Thank you for your kind accept. I appreciate it.

I'm going to check back with you in a few weeks for an update. Feel free to return to our conversation - even after rating - prior to my contacting you if you wish.

Please disregard the info request.
Customer: replied 3 years ago.

Just a quick update about my cat.

He was put on IV fluids for two days. Before the fluids his BUN was 21 (UK) and after 24 hours it had risen to 30. Someone I spoke to previously said that they would probably not go for the fluids as it may dilute something in the blood (not sure of what they meant, but this may have been what happened).

After he came home he was eating solid food. Maybe the steroids he was given helped, I don't know. But he has continued to eat/chew relatively normally for the last 2 weeks - which is the longest I've seen him eat normally.

He's still doing a bit of lip smacking (possibly nausea, but maybe just acid reflux). The stomach acid is something he can have a real problem with. He had no ranitidine (75mg zantac cut into quarter and given twice daily), although I had some. On Sunday he started to struggle and it seemed to be acid reflux. For the next two days he was withdrawn, not eating, not drinking and just looking quite unwell. I didn't know if this was a crash or problems with the reflux. On Monday morning he vomited and it was pinkish in color. I took this to mean his problem was indeed acid and the acid was disturbing the tissue in his stomach or maybe his esophagus. Either way, I gave him his zantac and gave him 24 hours to see how he recovered. Yesterday, he improved quite a lot. Started eating good and was up and about. Still not 100%, but a big improvement.

It all suggests to me, as someone with a CKD cat said to me, that he will need zantac everyday - whether he is showing signs of reflux or not. I can't afford for him to have a bout of bad reflux that has him suffer and go off his food for a couple of days. He is a slim siamese cat, so can't afford to lose too much weight.

He is difficult to pill and so I have ordered a pill shooter/pill gun, which I am sure will help.

Some people have mentioned famotidine but have also said that this drug can be tough for the kidneys to excrete if the kidney levels are high. He hasn't had his creatinine tested for a month, but I think he looks well. All the same, it sounds to me like zantac is the better option unless he starts having bigger problems with the acid reflux.

One thing I would be interested to know is your thoughts on dry food. Pretty much the only solids he eats are dry foods (specialist renal dry food). He has always been a dry food cat and so has always been a cat that drinks plenty. That is still the case but I see lots of people suggesting that dry food is something you need to get the cats off?

I've seen other people mention slippery elm bark as good for the stomach lining and good for reducing nausea.

Thank you for the update. I prefer famotidine over ranitidine because ranitidine doesn't increase the stomach pH to the extent that famotidine does. Both antacids should be prescribed at the lower range of dosing in renal-compromised patients; adverse reactions to either are rare, however. Dosing of ranitidine in cats is recommended at 3.5 mg/kg twice daily. Dosing of famotidine is recommended at 0.5 mg/kg once daily of the famotidine in PepcidTwo.

Yes, current thinking is to feed cats wet food only because as desert animals, they're not programmed to drink enough water - particularly to keep themselves properly hydrated when ill.

(The argument that giving supplemental fluids would detrimentally dilute the blood - is specious. Yes, the hematocrit (red blood cell concentration) will decrease because the volume of the blood is expanded but the same number of red blood cells is present after fluid therapy as was present prior to it.)

Yes, slippery elm has its proponents. I don't have any experience with it, however. I'm a died-in-the-wool allopath. Please continue our conversation if you wish.
Customer: replied 3 years ago.

I read some very interesting information from a veterinary nephrologist who prefered omeprazole to either ranitidine and famotidine. My cat was still doing a lot of lip licking about 3-4 hours after some ranitidine. It seemed to me that his stomach acid problem was not really being dealt with fully by the ranitidine. After some consideration, I decided to try the omeprazole. I started off with about 2mg once a day and this was gradually increased to 4mg once a day (which is his current dose).

Within a week, I noticed a huge improvement in his behaviour. He was very much back to his old self and the lip licking pretty much stopped.

Right now, he has 4mg of omeprazole a day, phosphate binder (given over the course of a day) and Semintra. All of this is given to him in food. Fingers crossed, at the moment he is in the best shape he has been for months. Pretty much back to normal.

The dry food issue is interesting. My thinking is, as he has always been a dry food cat, he has always had that instinct to drink. I've had a few cats through the years and none of them have been dry food cats. As a result, none of them have ever drunk the amount of water he always has. Therefore, I am hopeful that he should be ok with eating dry food. Certainly, at the moment, he is nicely hydrated.

The big plus is that he is eating. I don't know why he struggled chewing his food earlier in the year. But, since he came back from the vets (where he had fluids and steroids), he has been chewing normally and he is now eating wet food as well as dry food. Previously, he ate probably 90% dry food. Now, I would estimate that he is probably about 50/50 with dry/wet food. I use these malt/gravy products that are about 15g in weight and about 85% fluid. He loves them and they are ideal for secreting his meds in.

I was wondering about kidney capacity. I'd read that cats have much more kidney capacity than they need. Is it possible that, if my cat has about 25% of kidney function left, that he could operate within that function and minimise further damage to his kidneys quite significantly? I know the kidneys should remove some of the excess stomach acid and their lack of function is the reason why renal patients have acid problems. Would the use of a proton pump inhibitor like omeprazole further reduce the work the kidneys have to do and, subsequently, make life a little easier on them? Along with phosphate binders, Semintra and a renal diet, the kidneys are getting as much as help as possible?

All in all, a terrific update.

Yes, I use a lot of omeprazole.

We're all born with plenty of kidney reserve. The BUN and creatinine won't persistently elevate until 20-25% of kidney tissue is non-functional. Yes, Syi can remain at his level for quite some time. You would need to check serial creatinines to know the rate of failure.

Management of acid-base balance is the body is done by more than just the kidneys. Please see here: Omeprazole protects the GI tract from the hyperacidity resulting from many metabolic disorders causing a metabolic acidosis such as chronic renal failure. It doesn't protect the kidneys from that metabolic acidosis which the kidneys are causing.
Customer: replied 2 years ago.

Hi, just a quick little update. I wasn't able to get a blood test done for Syi until this week. Not ideal, but circumstances meant I had no choice. Anyway, it just so happened that he was unwell in the 4 or 5 days before I took him to the vets. He wasn't eating for those 4 or 5 days and not drinking either. He did try to use his litter tray yesterday and produced a reddish diarrhoea (that was after I'd given him some water with a syringe a few times throughout the day).

Anyway, he was quite dehydrated when I took him in to the vets today. They did a blood test rather than put him on intravenous drip first and rehydrate him. The numbers were not good at all. The creatinine was very high (just over 700) and, naturally, the vet told me that this means his kidneys pretty much on the point of failure.

Considering that he is quite dehydrated and has been unwell for a number of days, I know that that creatinine level is not a true representation of his actual remaining kidney function. However, the vet said that whilst this is true, those levels still show that there is very little function left. Is this true or is it possible that after a couple of days on IV (which he is on now) his actual kidney function could be a bit better than that?

For me, I felt that a blood test should not really have been done until he had been rehydrated. Is it possible that that creatinine level is a fair bit higher than what it actually would be if he was not dehydrated or is it correct that even with dehydration those levels still indicate very, very little remaining kidney function?

There's little question that his kidney function will improve after hydration but to what extent I can't know. The creatinine is relatively unaltered by dehydration - unlike the BUN. A creatinine of just over 700, however, gives a very poor prognosis for meaningful recovery. Can you give me the BUN too, please?
Blood tests should be taken both prior to and after 3 days of diuresis. That's the only way for us to know if therapy is of value. Please continue our conversation if you wish.
Customer: replied 2 years ago.

His BUN level is 40 mmol/L (UK).

The vet did mention that even with dehydration, those levels were very high. Considering that creatinine is not affected very much by hydration levels, this explains that assessment.

Is it not possible that an infection (particulary a kidney infection) would cause the creatinine levels to rise like this or is a rise in creatinine really only caused by general loss of function caused by kidney disease? I know it is most likely, by the sounds of things, that a rise in creatinine like this is down to failing kidneys. But would it not be possible that a renal patient contracts an infection that gives the impression that the kidneys are failing? I know it is clutching at straws, but it does seem a little bit of a surprise that his kidney function has dropped from about 25% in January to about 5% in 5 months - even whilst he has had a change in diet and been receiving treatments like phosphate binders and Semintra. I know that this can still happen. Some cats will carry on for 2 years or even longer and others will last less than 6 months. It's just still a bit of a surprise that his kidneys could have lost almost all of that 25% function in the space of a few months.

Oh my. Not good news. Yes, infection can cause "acute on chronic" symptoms - acute worsening of a pre-existing chronic disease. Such infection would be visible in the urinalysis as bacteria and increased numbers of white and red blood cells. 25% of function is the limit at which my patient can still function well; in fact, kidney values might still be normal at that level. Once more function is lost, however, my patient becomes symptomatic although the rate of decline is impossible to predict but is determined by serial testing every couple of months.
Customer: replied 2 years ago.

Right, ok, one more question. If he responds to this IV he is currently receiving and his numbers come down to a point where he is behaving normally and seemingly not in discomfort, would it be worth adminstering sub-q's at home to try and keep him healthy for maybe 2, 3 or 4 months rather not bother and allow him to have the 2, 3 or 4 weeks before his kidneys start to fail again and I have to opt for euthanasia?

It would be essential to do so.
Customer: replied 2 years ago.

Sorry to bother you again, but I feel I really need another opinion on the current state of Syi's situation.

Essentially, the vet is convinced his kidneys are failing and euthanasia is the kindest and best option.

His first blood tests had creatinine at 724 and BUN at 40. His second test (after 40 hours on IV) showed that the BUN had risen to 46 and the creatinine had dropped to 690. The vet said this changes are not good at all and are consistent with kidney failure. He also has anemia (16%) with his blood quite runny. Again, consistent with kidney failure. She says there is no sign of infection in the white blood cells, but someone said to me that there doesn't always mean there is no infection and that anti-biotics should still be tried.

My main concern is that we are now into day 8 since he last ate. His digestive system will have shut down, his muscles wasting away and of course he will be quite depressed.

I asked if they had given him an appetite stimulant and she said they hadn't. Surely, going 8 days without food will cause him to be very poorly, whatever state his kidneys are in? I know that this loss of appetite and shutting down of the digestive system is part and parcel of kidney failure. But perhaps the 4 or 5 days without food and water precipitated the problems he is now having and getting him eating again could make a different? I asked the vet to start with appetite stimulants and get him eating again. Would that help lower the levels in his blood and maybe help with the anemia?

I suggested that I would like him to have 72 hours on IV (currently, he is about 42 hours into IV treatment) and then look to take him home to start sub-q's at home. She said if he does not improve, he is far too poorly to return home and euthanasia would be the only option. If his crea came down to 600, she says that's still too high and if his demeanour is unchanged, then it is time to say goodbye rather take him home for sub-q's.

I just wondered about the 8 days without food and how that would effect him and his bloods. If it is purely a symptom of failing kidneys or whether it could make it look like his kidneys are worse than they are actually are and cause him to be very poorly?

It's unlikely that such a uremic cat could be appetent again. There's simply too many toxins in his blood stream which an appetite stimulant couldn't overcome. If intensive diuresis were effective in reducing that toxic load (uremia), he would have a chance but that hasn't been the case. He's at the point that he would require machine dialysis or a kidney transplant - neither of which are appropriate.
Force feeding isn't appropriate if only because his gastrointestinal tract would reject the food - vomiting and diarrhea (often bloody) would be expected due to the toxic effect of the uremia on his GI tract. I'm afraid it is time to say goodbye.
Customer: replied 2 years ago.

This is just a message to say that I did indeed say goodbye, just a couple of hours ago. He had the best part of 72 hours on IV fluids and still showed no sign of improvement and no appetite for food at all. He was given appetite stimulants and they had no effect. He also had treatment for acid and nausea, but still he simply did not respond. His digestive system had shut down and could not be roused. I had syringed some water into him the day before he went into hospital and, as you said would happen, he ended up producing a small amount of diarrhoea that was full of blood.

Ultimately, I had to accept that his kidneys were failing and nothing could be done. He was suffering and in pain, so there was no option but to end that suffering and pain.

The lesson I learn from this is that I should have taken him for a blood test some time ago. His last test was late in January and he should have had another by, at least, early April. That would have told us that we need to start sub-q's at home to give his kidneys maximum support. That way, I may have been able to extend his life, with quality, for a good few months. I was fooled by the fact that he was so happy and seemingly healthy and didn't realise that his kidneys were rapidly losing function.

Thanks for all your help and advice at a very difficult time for me. I appreciate greatly.

Oh my. My condolences for your loss of Syi. I appreciate your taking the time to let me know.
You may receive an inappropriate follow up sent by the site ostensibly sent by me. It wasn't and I apologize in advance should you receive it.
Please disregard the info request.
Customer: replied 2 years ago.

Thank you for your condolences. I haven't received any follow up (not yet anyway).

Thinking about Syi, I do have one lingering question about the potential of infection. Somebody I spoke to suggested that a rise from 300 crea to 724 crea in just over 4 months is a bit unusual and quite often the sign of an infection rather than a large loss of functioning kidney tissue. They also suggested that he should have been given anti-biotecs just in case.

I asked the vet and she told me that there was no sign of infection in the white blood cells. In response to that, the person who first mentioned infection to me said that there could easily still be an infection even if there is no sign of infection in the white blood cells.

That left me feeling like he could have been in that state mainly because of infection rather than failing kidneys and that anti-biotics could have made a difference. Would you still expect his numbers to drop on IV fluids even if he has an infection and is not receiving anti-biotics or would an untreated infection prevent the kidneys from responding to the fluids?

IV fluids should prompt a diuresis whether or not infection were present and so his BUN would be expected to drop in either event if his kidneys were healthy enough to respond to fluid administration. If there were no indication of infection in his urinalysis - elevated white or red blood cell numbers or bacteria and a urine culture were negative, there would be no indication for antibiotics.
Customer: replied 2 years ago.

As far as I am aware, there was no urinalysis. They based their belief that there was no infection on the white and red blood cell numbers only. Is it possible to have an infection that does not show up in the white and red blood cell numbers?

Either way, it seems academic if the expectation is that there should be an improvement in the cat and in the numbers with the adminstering of IV fluids even without anti-biotics being used. He didn't have a blood test today and it seemed pointless given that his demeanour had not improved at all fromthe time of his previous blood test (which was taken after about 40 hours of IV fluids and showed a raised BUN level and only a very slightly reduced crea level, from 724 to 690).

I just want to be clear in my mind that Syi's kidneys were failing and this wasn't a case of an infection that was missed and not treated.

Most assuredly.
Without a urinalysis and culture if the urine were dilute (it was) we can't know if infection were present or not. While contributory, the presence of infection becomes moot at those levels of creatinine and BUN, however.
Dr. Michael Salkin and other Cat Specialists are ready to help you