Kidney Function Tests Abnormal...what does this mean?

[Julia]

I learned today that my BUN is 44 (normal for this lab is 7-22), and that my creatinine is 2.2, (normal for this lab is .6-1.3).

I can't see my doctor until Monday, and wondered if someone might be able to help me to understand these values and what they might indicate.

Thanks very much.

Julia

[DoriSchatell]

Hi Julia,

It's good that you have an appointment coming up with your doctor so soon. Both of these numbers can indicate a problem with your kidneys. (A creatinine of 2.2 can mean that you have lost a significant amount of kidney function). The question is what kind of problem, why, and how can it be treated to prevent any further damage.

Before your doctor appointment, I'd suggest doing two things:

1). Go through the "Understanding Kidney Lab Tests" module of Kidney School, our free, on-line, interactive kidney learning center. You can find it at http://www.kidneyschool.org

2). Calculate your glomerular filtration rate (GFR), which is a measure of how much filtering your kidneys are doing. You can do this on-line at http://www.nephron.com/mdrd/default.html using your serum creatinine level (2.2), age, race (black-B or white-W only), and sex (M or F).

Please feel free to write back if you have more questions after you go through the Kidney School module--I do check this board over the weekend, and I want to help.

[Julia]

Thank you very much. I appreciate your response.

I saw my doctor and had a host of lab tests run, including blood work and several urine studies, including a 24-hour urine study. All were perfectly normal, including the BUN and creatinine.

My doctor consulted a nephrologist who has no idea what might have caused this to occur within a week's time (from so high way down to low normal), but they are recommending a CT scan to rule out a kidney stone moving around in there.

Any thoughts?

Thank you again.

[DoriSchatell]

Hi Julia,

Well, that's good news! My suspicion, since the repeat labs & all the other tests were normal, is that there was some sort of a lab error the first time around. Sometimes if a blood sample isn't handled correctly (it gets too warm, for example), the results can be affected.

Do you have any symptoms at all of kidney problems? These might include:
-- Changes in urination (more or less urine than usual, dark colored urine, bubbly or foamy urine, getting up at night to urinate)
-- Swelling in the feet, ankles, hands, under the eyes
-- Fatigue, weakness, dizziness
-- Metallic or ammonia taste in the mouth
-- Itching
-- Pain in the lower back
-- Feeling cold all the time
-- Mental confusion

If you don't have any symptoms, and your new lab tests are normal, those results may have just been a fluke.

Consider asking the doctor if an ultrasound would work for you rather than a CT scan, because it can show the kidney size & blood flow without using contrast dye. See whichever one you get turns up anything. If not, ask your doctor when you should get another BUN and creatinine test--and if that one is normal, too, you're probably off the hook.

[Julia]

Thank you for your kindness in responding. You are pretty wonderful to do this, you know. I certainly appreciate it very much.

I am having a CT scan without contrast tomorrow morning. My doctor consulted a nephrologist who can't think of any reason (other than error, as you've mentioned here) why a person would have such a dramatic rise and fall of BUN and creatinine within one week's time, unless there is a stone or something which moved during that period...an unlikely scenario, although I have had them in the past and my mother had a terrible history of them. In fact, she ultimately died of kidney cancer (transitional cell carcinoma), likely an off-shoot of the necrotic kidney tissue caused by all of those stones over her lifetime.

So...they're being cautious. And yes, I am having a repeat BUN and creatinine in another month.

I have right sided lower back pain, but no reason has ever been discovered for it. It is not at all debilitating...just irritating at times. And of course carrying around my 31-inch, 26-pound 10-month-old son doesn't help.

I'm cold a lot, but it's cold where I live. My TSH was normal, too.

I've long suspected I might have (and my mother may have had) hyperparathyroidism, but my doctor says no bloodwork has ever convinced her of that. (Blood calcium the high end of normal, but not excessive.)

So...who knows. Hopefully the CT scan will relieve concerns. By the way, I did request a renal ultrasound instead of a CT, because I don't care to have the radiation exposure of CT, even without contrast. But she and the nephrologist both feel the CT is in order for a variety of reasons, so...that's where I'll be at 7:00 tomorrow morning!

Thank you yet again.

Julia

[DoriSchatell]

Hi Julia,

By now you've had your CT scan, so I hope all is well for you. (I'm glad they could do it without contrast, and it seems wise to be cautious, with your own and your mom's past history). You may want to ask your doctor for a PTH level to check your suspicions of hyperparathyroidism. Since calcium binds to phosphorus so quickly, your blood levels might not be that elevated... It's an expensive assay, but might be worth it for peace of mind.

If you have any more questions, please feel free to ask--that's what we're here for.

[Beth Witten MSW ACSW]

I hope it turns out that you don't have a kidney stone and that the lab made an error, but if your CT scan shows that you do have a kidney stone, the National Kidney Foundation has a brochure on kidney stones that includes some suggestions of what you can do to reduce your risk of having stones:
www.kidney.org/atoz/atozItem.cfm?id=41. There are links at the bottom of the brochure to other materials that may be of interest as well.

I don't know if it helps to know this, but lots of people have had kidney stones, including some people I know. After they pass or after they have lithotripsy to break them up, they've done well...and never had another one.