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What is Creatinine Clearance?

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  • Written By: Madeleine A.
  • Edited By: Jenn Walker
  • Last Modified Date: 29 September 2016
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The creatinine clearance test refers to blood and urine tests that are used to assess kidney function. If the physician determines that a patient may have a kidney function abnormality, such as kidney failure or kidney obstruction, he may recommend a creatinine clearance test. This diagnostic medical test requires both a blood sample and a urine sample. The lab compares the creatinine level in both samples to calculate the clearance rate. Commonly, the patient's height and weight also are taken into account when calculating test results.

Creatinine is produced in the muscles and is a waste product. Typically, creatinine is removed by the kidneys, therefore, elevated levels of this waste product in the bloodstream is an indicator of less than optimal kidney filtration. Generally, the creatinine clearance test measures creatinine levels in the urine and blood that has been manufactured in the last 24 hour time period. These results are used to determine the levels of creatinine that have been cleared out of the blood and filtered into the urine.

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Symptoms that may alert the physician to order a creatinine clearance test include facial, abdominal or extremity swelling. In addition, decreased levels of urinary output and bloody, dark or foamy urine are important indicators that a creatinine clearance test may be warranted. Sometimes, flank or mid back pain and the presence of high blood pressure or protein in the urine may alert the physician to order a creatinine clearance test. Typically, there is no special preparation for the test on the part of the patient.

Generally, diseases or conditions that impair the ability of the kidneys to clear waste products from the blood will yield elevated creatinine levels in the blood. In addition, the creatinine clearance value can decrease because decreased amounts of creatinine are excreted through the urine. Sometimes, decreased values of creatinine clearance may indicate congestive heart failure, acute kidney failure, or kidney tumor. Occasionally, elevated values may indicate pregnancy or may be the result of vigorous exercise.

Sometimes, if the patient consumes a diet high in protein or meat, the test will be elevated and warrant a repeat. In addition, certain medications may alter the test. Medications called diuretics may give a false positive reading. Diuretic medications are also known as water pills. These medications promote frequent urination and are indicated in the treatment of hypertension, or high blood pressure. Other medications that may skew test results are stomach acid reducers and certain antibiotics.

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anon339717
Post 4

I have been having problem for several years now and am currently on medication in order to even get my kidneys to function. I also spent three weeks in the hospital with gross hematuria and almost died because my hemoglobin dropped to 2.7 as a result to my kidneys bleeding out. They thought I had stones and surgically implanted stents and a screen but there were none.

Eventually, everything cleared up but I keep taking the Creatinine Clearance test and it always comes up very high and my doctor told me that just means that my kidneys are fine and they are very healthy and efficiently doing their job cleaning everything out of the bloodstream. Then I read this and I am very upset, wondering who to believe.

Mor
Post 3

The problem with testing with a high creatinine clearance, is it means you've already got serious problems with your kidneys.

My sister has problem-prone kidneys and always has. It took her a while to recognize what can set them off with an infection (generally sugar, dehydration, too much exercise, too few veges, etc) but she's learned how to try and keep them healthy.

She's also made sure she can recognize what it feels like when something is going wrong, so that she can go straight on the medication she needs. If she waited until a creatinine clearance test came up positive, she'd already be quite sick as I understand it.

bythewell
Post 2

@browncoat - I have kidneys which are prone to infections, so I have to give the doctors a urine sample so they can assess my creatinine clearance levels all the time.

I had a problem with it at first as well, but eventually even peeing in a jar can become old hat I suppose.

What I found would really help was drinking a lot of water or tea before going in to the doctor. This was especially helpful if I managed to time it just right.

Unfortunately, if you time it wrong and have to wait in the waiting room for a while it can be torture!

Although I guess you can bring a sipper bottle and top up as needed depending on what the wait is going to be when you get there.

browncoat
Post 1

I hate having to go into the doctor for a urine test. No matter how many times I tell myself that it's just something they see every single day, I still feel uncomfortable. And when I feel that uncomfortable I find it impossible to pee!

So I end up sitting there, getting more and more anxious, which, of course, impedes my "performance" more and more.

I had to have a urine creatinine clearance about a year ago and I finally had to just ask the doctor if I could go at home and bring it in for him. Luckily he didn't mind as long as I brought it right in after going.

If you have the same problem, you might want to ask if this is possible.

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