Functional examination of the kidneys
Examination of glomerular filtration[edit | edit source]
For more information see Glomerular filtration test.
Examination of serum creatinine concentration[edit | edit source]
- Norm: 50–100 μmol/l.
- When kidney function is impaired, the serum concentration of creatinine increases.
- In some patients, even with impaired kidney function, the serum creatinine concentration may be within the reference limits - it depends on the production of creatinine by the skeletal muscle.
- Clearance of creatinine Ckr:
- Ckr expresses how the plasma is purified from the monitored substance;
- U = concentration of substance in urine, V = volume of urine per time unit, P = concentration of substance in plasma;
- normal values: 1.5 to 2.2 ml/s;
- depends on age, gender and weight.
- Accurate collection of urine after 24 hours is necessary.
Examination of renal tubular function[edit | edit source]
Examination of the concentration ability of the kidneys[edit | edit source]
- We find out the ability of the kidneys to create concentrated urine.
- We monitor urine osmolality. (in a healthy person; osmolality = 600–800 mmol/kg H2O = 500–1200 mOs/kg; without fluid intake = 1200–1400 mOs/kg).
- This ability is often impaired already at the beginning of kidney disease.
Concentration test - by thirst[edit | edit source]
- For 36 hours, the patient must not drink or eat food with a large amount of water.
- After 12 hours, urine is collected at 4-hour intervals, we determine density and osmolality.
- Before the last sample, we will take blood - concentration index.
- We will stop when it reaches the limit given for a certain age.
Adiuretin test[edit | edit source]
- It is much gentler, does not burden the patient as much.
- After a dinner without liquids, when the examinee no longer drinks in the evening, we apply ADH into the nose in the morning (he must not have a cold).
- Concentration disorders - mainly in diseases of the tubules and interstitium, in case of a violation of the gradient.
Investigating dilution functions[edit | edit source]
- We monitor how the patient reacts to increased water intake:
- In a healthy person, there will be an increase in urine volume, a decrease in ADH production, and thus an increased diuresis and a decrease in osmolality.
- ADH secretion increases in patients with kidney failure.
- This method is important in the investigation of water metabolism disorders.
Links[edit | edit source]
Related Articles[edit | edit source]
References[edit | edit source]
- SCHNEIDERKA, Peter. Chapters in Clinical Biochemistry. 2. edition. Prague : Karolinum, 2004. ISBN 80-246-0678-X.