Functional examination of the kidneys

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Examination of glomerular filtration[edit | edit source]

Searchtool right.svg 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.
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.