What are kidney values?
Kidney values are laboratory parameters that allow conclusions to be drawn about kidney function. The doctor very often determines the following kidney values:
Other blood values that provide information about kidney function are electrolytes, phosphate and blood gases. Urine values are also determined:
- pH value
- Protein
- blood
- ketones
- Sugar (glucose)
- Leukocytes
- nitrite
Creatinine and inulin clearance
Urea and uric acid
Uric acid is a degradation product of building blocks of the genetic information DNA (deoxyribonucleic acid), more specifically the purine bases adenine and guanine.
When are kidney values determined?
The doctor determines the kidney values in the blood and urine in order to diagnose kidney diseases or to monitor their progression. The urea value is also used to monitor protein intake in patients with known kidney weakness (renal insufficiency).
When are kidney values too low?
The clearance of the substances inulin or creatinine provides information about the filtration capacity of the kidneys. It therefore decreases when kidney function is impaired (acute or chronic renal insufficiency). To a lesser extent, creatinine clearance also decreases naturally with increasing age.
A reduced creatinine value in the blood is of no significance. It is only found as an incidental finding in patients who are underweight or have low muscle mass.
The most common cause of low uric acid levels is an overdose of medication designed to lower uric acid levels. These are used to treat gout.
Kidney values: Table with lower limit values
|
men |
Women |
|
|
Creatinine (in serum) |
< 50 years: 0.84 - 1.25 mg/dl > 50 years: 0.81 – 1.44 mg/dl |
0.66 – 1.09 mg/dl |
|
Creatinine (in urine) |
1.5 – 2.5 g/24 hours |
1.0 g/24 hours |
|
Cystatin C |
0.5 – 0.96 mg/l |
0.57 – 0.96 mg/l |
|
Urea |
< 50 years: 19 - 44 mg/dl > 50 years: 18 – 55 mg/dl |
> 50 years: 21 – 43 mg/dl |
|
Uric acid (in serum) |
3.4 – 7.0 mg/dl |
2.4 – 5.7 mg/dl |
When are kidney values too high?
The measured values of the individual kidney values respond differently to different diseases. Reasons for an elevated creatinine level are, for example
- High blood pressure due to narrowing of the kidney vessels (renovascular hypertension)
- Acromegaly (hormonal disease with enlargement of hands, feet, ears, nose, etc.)
- Chronic kidney failure (e.g. due to diabetes mellitus or connective tissue diseases)
If the concentration of uric acid is increased, doctors call this hyperuricemia. It is either due to a congenital metabolic disorder or is a symptom of
- fasting
- poorly controlled diabetes mellitus
- a high-fat diet
- hypofunction of the thyroid or parathyroid gland
- Poisoning (e.g. with lead)
Elevated kidney values are also found in severe general infections such as measles.
Kidney values: Table with upper limit values
|
men |
Women |
|
|
Creatinine (in serum) |
< 50 years: 1.25mg/dl > 50 years: 1.44 mg/dl |
0.96 mg/dl |
|
Creatinine (in urine) |
2.5 g/24 hours |
1.3 g/24 hours |
|
Cystatin C |
0.96 mg/l |
|
|
Urea |
< 50 years: 44 mg/dl > 50 years: 55 mg/dl |
< 50 years: 40 mg/dl > 50 years: 43 mg/dl |
|
Uric acid (in serum) |
7.0 mg/dl |
5.7 mg/dl |
|
Uric acid (around urine) |
What to do if kidney values change?
If the kidney values are elevated, the doctor must first and foremost rule out kidney disease. Urine tests provide many important indications of this. Among other things, they show whether protein or blood is being lost via the kidneys. The kidney specialist (nephrologist) can also assess the urine under a microscope.
Apart from various types of kidney damage, other diseases can also alter the kidney values. The doctor must also consider these possibilities in conjunction with the patient’s symptoms and carry out further examinations accordingly.
