BUN-To -Creatinine Ratio: An Overview to Renal Function Tests

BUN to Creatinine Ratio: An Overview to Renal Function Tests

July 18, 2019

The kidneys are one of the most vital organs in the body. And their functions can’t be overemphasized. They are located retroperitoneally. Normally there are 2 kidneys in each person. But due to one reason or the other, some people just have 1 kidney. Because of their great role in filtering and formation of urine so many tests are performed on kidney function. And one of these tests is bun creatinine ratio. All kidney function tests give your doctor a better perspective as to how well your kidney functions. And this could also help indicate if there’s a problem with your kidney.

A bun creatinine ratio tests help check for the function of your kidney. It particularly checks for conditions such as dehydration. And also a problem with the heart that decreases blood flow to kidneys. In this test, two different serum tests are combined and compared. Kidney problems are very common these days. And finding out early there’s a problem with the kidney would help out a lot. That’s because the person would start treatment as soon as possible. Let’s just have a quick overview of the different kidney function tests.


Types of Kidney Function Tests

So your doctor would request for some tests. These tests would help your doctor estimate your GFR. GFR is the glomerular filtration rate of your kidneys. And it indicates how well the kidney would help clear waste away from the body.

  • Urinalysis: This is a very common test that doctors request. This is particularly important in checking for kidney function. That’s because urinalysis helps check for the presence of protein and blood in the urine. If any of this is present it could be as a result of a problem with filtration of the kidney or other conditions.

Many other conditions can increase the protein in a person’s urine. Infections cause a rise in urine protein. Also doing heavy physical workouts has the same effect. In most cases, your doctor would request for urinalysis at intervals of weeks. That way he would be able to monitor any changes.

  • Serum creatinine test: This test checks your blood for high creatinine levels. The function of the kidney is to completely filter all the creatinine. So high levels are indicative of a problem with the kidney. For women, values higher than 1.2mg/dl is considered high. And for men values higher than 1.4mg/dl is considered high. Both values are indicative of kidney problems.
  • Blood Urea Nitrogen(BUN): This test checks for the amount of waste product in the blood. BUN tests would check for the amount of nitrogen in the blood. When protein is broken down one of the products is urea nitrogen. The thing though is that not all elevated BUN levels are indicative of kidney problem. High doses of some medications would also cause an elevated BUN level. The normal BUN level is between 7-20 mg/dl.
  • Estimated GFR: This test checks for how well your kidney filters waste. This test looks at factors such as age, race, gender, weight, height and even creatinine levels. If the test result is lower than 60 ml/minute/1.73m2 the that could be a sign of cancer.


Bun Creatinine Ratio

This is just the ratio of BUN test to serum creatinine test. Whatever the ratio is could indicate a lot of things. This test is commonly used to check for kidney problems but it can also be indicative of other conditions. Conditions such as congestive heart failure, bleeding in the GI tract, trauma and obstruction of the urinary tract.

An abnormal ratio could be as a result of dehydration. Dehydration would normally increase the creatinine levels. That would lead to a lower ratio. Kidney disease or a blockage in urine flow could also lead to abnormal values. High ratios mean that the blood supply to the kidney is less.

Normally, bun to creatinine ratio is either 10-1 or 20-1. This would actually differ from person to person due to some factors. Some of these factors are age and gender. Sometimes a higher ratio could just be as a result of aging. Low muscle mass is also known to cause a higher ratio.

When the ratio is higher because of higher BUN levels then it’s more problematic. If on the other hand, it’s because of creatinine then it’s not as problematic. But the fact remains the same that abnormal bun creatinine ratio could be indicative of a serious kidney problem.


How These Tests are Performed

For kidney function tests, usually, a 24-hour sample of urine is requested for. And also blood samples are also gotten.

24-hour urine sample

This sample is for a creatinine clearance test. This helps your doctor know how much creatinine your body expels in a day. And this would help your doctor in diagnosing.
Here’s how it’s done. On that day, you would have to void your first urine early in the morning. So you can urinate in the toilet normally first thing in the morning. Then after that, you would have to urinate into a special container for 24 hours.

During the collection process, you have to cover the container. And also keep the urine sample refrigerated. Make sure that you label it correctly. And if you’re not staying alone make others in your house know that there’s a urine sample in the refrigerator.

After the 24 hours of collection, you can go submit it at the hospital. Either at your doctor’s office or at the lab. This is solely based on the directives of your doctor.

Blood Sample

For Bun and creatinine tests blood samples are needed. So you have to go to the lab to get your blood extracted.

This could be a bit painful but just a little amount of blood is needed. Once your blood is gotten the bun and creatinine levels would be measured. Then the results would be passed to your doctor. With that, your doctor would be able to tell if there’s really a kidney problem or not. One thing your doctor would always check after getting the results is your bun creatinine ratio.