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Creatinine in the urine
Last reviewed: 05.07.2025
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The daily excretion of creatinine in urine is relatively constant, equivalent to the daily formation and directly depends on muscle mass and the excretory capacity of the kidneys. With a diet rich in animal proteins, the excretion of creatinine in urine increases.
Reference values (norm) of creatinine content in urine
Creatinine content in urine |
||
Age |
Mg/(kg×day) |
µmol/(kg×day) |
Children under 1 year |
8-20 |
71-177 |
Children from 1 year to 12 years |
8-22 |
71-194 |
Teenagers |
8-30 |
71-265 |
Adults: |
||
Men |
14-26 |
124-230 |
Women |
11-20 |
97-177 |
Or |
Mg/day |
Mmol/day |
Men |
800-2000 |
7.1-17.7 |
Women |
600-1800 |
5.3-15.9 |
Parallel determination of creatinine concentration in blood and urine significantly expands the diagnostic capabilities for assessing the functional state of the kidneys.
In clinical practice, it is important to determine the ratio of creatinine in urine to plasma creatinine. It is practically important to distinguish prerenal acute renal failure from renal, especially it is essential to establish the moment of transition from one form of acute renal failure to another, since this determines a change in the patient's treatment tactics.
Prerenal (functional) acute renal failure develops as a result of a decrease in the volume of circulating blood, severe heart failure, arterial hypotension, and liver failure. Renal acute renal failure is caused by processes affecting the glomerular and tubular apparatus of the kidneys, and by diseases of the renal vessels.
In prerenal acute renal failure, the kidneys respond to decreased perfusion by increased conservation of sodium and water. Renal water reabsorption is assessed by the concentration of nonreabsorbable creatinine in the urine, as the ratio (urine creatinine)/(plasma creatinine). In prerenal acute renal failure, this ratio is greater than 40, whereas in renal acute renal failure, the ability to conserve water is impaired, so it is less than 20. A decrease in the (urine creatinine)/(plasma creatinine) ratio in prerenal acute renal failure indicates its transition to the renal form and serves as a rationale for changing therapy. Acute urinary tract obstruction leads to changes in the (urine creatinine)/(plasma creatinine) ratio, characteristic of prerenal acute renal failure.
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