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Evaluation of the results of the Zimnitsky test
Last reviewed: 06.07.2025
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In various diseases, the following deviations can be detected in the Zimnitsky test:
- When comparing daily diuresis with the amount of liquid drunk, it may turn out that during the day, not 3/4 (65-80%) of the liquid drunk is excreted with urine, but a significantly larger or, conversely, smaller amount. An increase in diuresis compared to the volume of liquid drunk is observed when edema subsides, a decrease - when edema increases (regardless of their cause) and due to increased sweating.
- Daytime and nighttime diuresis are the same, or even nighttime diuresis is greater than daytime diuresis (nocturia). An increase in nighttime diuresis not caused by fluid intake may occur as an adaptive reaction to the limitation of the concentration function of the kidneys, as well as in heart failure.
- The urine density in all portions may be low, and its fluctuations in individual portions during the day will be less than 0.012-0.016, that is, isosthenuria may be detected.
Isosthenuria is the most important sign of renal failure and can be observed in patients with chronic glomerulonephritis, chronic pyelonephritis, and sometimes in patients with hypertension. In amyloid (or amyloid-lipoid) nephrosis, the concentration function of the kidneys can remain intact for a long time, isosthenuria appears with the development of an amyloid-shrunken kidney. Isosthenuria can occur with hydronephrosis and severe polycystic disease. This is an earlier sign of renal failure than an increase in creatinine and urea in the blood; it is possible with their normal content in the blood. It is necessary to remember that low urine density and its small fluctuations during the day can depend on extrarenal factors. Thus, in the presence of edema, density fluctuations can be reduced. The urine density in these cases (in the absence of renal failure) is high; hyposthenuria is observed only during the period of edema reduction (in particular, when using diuretics). With prolonged adherence to a protein-free and salt-free diet, the urine density may also remain low for 24 hours.
Low urine density with small fluctuations (1.000-1.001) with rare increases to 1.003-1.004 is observed exclusively in diabetes insipidus, it does not occur in any other diseases, including kidney diseases that occur with insufficiency of their concentration function. Nocturia can sometimes be caused by prostate hypertrophy of various etiologies.
An increase in the density of urine in all portions is caused by hypovolemic conditions and uric acid diathesis.
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