When it comes to evaluating the health and function of the kidneys and liver, there are numerous diagnostic tests that are done. Two of these tests include blood urea nitrogen or BUN and creatinine test. The respective values from both tests dictate the possible state of the kidneys and liver. So, what could it mean if the BUN/creatinine ratio is low? Also, what happens if the rate is high? Learn this and more below.
Before that, it is essential to go through both tests. First off is the BUN test that evaluates the amount of nitrogen in the blood. Nitrogen comes from urea, a waste product produced from the breakdown of protein. Urea is manufactured in the liver before it is excreted through the urine.
The values from a BUN test indicate how well the kidneys are working. A protein-rich diet, dehydration, and heart failure result in a high BUN value. On the other hand, liver damage and pregnancy can cause low values in a BUN test.
A waste product that comes from muscle breakdown is called creatinine which is excreted from the body via the kidneys. This test measures the levels of creatinine in the urine and the blood. Take note, however, that the standard values vary per age and gender. For example, children and women have a lower creatinine level than men.
Kidney Dysfunction Symptoms
A BUN test is ordered alongside a renal panel and creatinine test, especially if the doctor suspects kidney problems. An individual with kidney dysfunction is likely to manifest the following symptoms.
- Poor Appetite
- High Blood Pressure
- Difficulty Sleeping
- Difficulty Concentrating
- Swelling in Abdomen, Ankles, Thighs, Face, or Wrists
- Coffee-Colored, Bloody, or Foamy Urine
- Decreased Production of Urine
- Change in Frequency of Urination
- Abnormal Discharge During Urination
- Burning Feeling When Urinating
- Pain Felt in Mid-Back, Particularly in the Area Close to the Kidneys
BUN to Creatinine Ratio
As mentioned above, a BUN test is done alongside a creatinine test to find the BUN-to-creatinine ratio. This ratio helps a health practitioner check for the presence of disorders that result in abnormal creatinine and BUN levels. The rate falls between 10:1 and 20:1.
An increase in the ratio could be suggestive of a condition causing restricted blood flow to the kidneys like dehydration or congestive heart failure. This can also be noticed in an individual with increased protein due to his diet or from gastrointestinal bleeding. On the other hand, a drop in the ratio is associated with malnutrition and liver disease.
Normal Values of BUN and Creatinine
Again, the average ratio of BUN-to-creatinine should fall between 10:1 and 20:1. Take note, however, that the values are a reference range and vary from one lab to the next. Moreover, the values from the tests are evaluated based on other factors and on an individual’s health.
A. Average BUN Values
Adults: 10 to 20 mg per dL
Children: 5 to 18 mg per dL
B. BUN-to-Creatinine Ratio
Adults: 6 to 25 (15.5 as the Best Value)
Based on the results from a creatinine test, values that go below and above the normal are indicative of health problems. If there is an increase in the creatinine, then it may likely indicate kidney disease or another condition affecting the function of the kidneys. Such issues include the following.
- Glomerulonephritis: swelling or damage to the blood vessels in the kidneys.
- Pyelonephritis: bacterial infection of the kidneys.
- Acute Tubular Necrosis: the death of the cells in the small tubes of the kidneys usually caused by toxins or drugs.
- Urinary Tract Obstruction: which may likely be caused by kidney stones or prostate disease or the enlargement of the prostate.
- Reduced Blood Circulation to the Kidneys: This could be due to dehydration, shock, complications of diabetes, atherosclerosis, or congestive heart failure.
On the other hand, low values in a creatinine test are indicative of low muscle mass. Decreased values in a creatinine test are not a cause for concern since this is not common. Furthermore, all results of a 24-hour urine creatinine test are checked alongside the blood levels which is part of a creatinine clearance test.
Random and single urine creatinine tests usually do not have an average reference range. The results from such tests are used alongside other tests as a reference level for substances checked in the urine. These tests include urine protein test, urine albumin/creatinine ratio, and urine albumin test. Your doctor is likely to recommend any of the tests mentioned in addition to the BUN and creatinine tests.
As for BUN values, high and low levels are also associated with health problems. These include the following.
A. High Values
BUN levels that are beyond the normal range are indicative of an infection or fever. It is also associated with a diet that is high in protein, low consumption of water, dehydration, interval training or inflammation, bleeding in the gastrointestinal tract, poor blood circulation, and thyroid abnormalities. Other conditions that cause heightened values in a BUN test are listed below.
- Stress: which is often noticed in heart failure.
- Kidney Failure or Disease
- Blockage of the Urinary Tract: This is a result of the presence of kidney stones.
- Low IGF-1 or Growth Hormone: which inhibits the synthesis of urea.
B. Low Values
Decreased levels of a BUN test is associated with numerous health disorders as well. These include malnutrition, impaired liver activity, and overhydration or overconsumption of water. Other conditions that cause low BUN levels include the following.
- Diet Low in Protein
- Genetic Deficiency of Urea Cycle Enzymes
- Pregnancy (Usually in the Third Trimester)
- Anabolic Steroids
- High Levels of Growth Hormone and IGF-1
The results from a BUN and creatinine test are further evaluated against the results of other diagnostic tests. These help your doctor to adequately diagnose and detect any problems with the liver and kidneys. Imaging tests that include a CT scan, and MRI, and an x-ray also help doctors evaluate the health as well as the function of the said organs.