Volumes of urine portions can be varied from 50 to 250 ml, but it not be able lesser than 100 ml between small and big portions.

Equal amount urine in all portions is called isuria and indicates renal failure.

Concentrative Function. Fluctuations in specific gravity of the urine during the course of the day and its maximum value are determined thus.

Normally specific gravity of urine is from 1.005 to 1.028 and the difference between small and maximum value can't be lesser then 10.

If renal insufficiency is pronounced, decreased specific gravity becomes permanent (hyposthenuria).

If the renal function is upset significantly, the specific gravity of the urine in all portion is 1.009-1.011, which corresponds to the specific gravity of the primary urine or blood plasma (isosthenuria).

In diabetes mellitus the specific gravity is more than 1.028 (hypersthenuria).

Combination of polyuria which low specific gravity of the urine and nocturia is a specific sign of renal dysfunction.

 

 

The Examples of Analyses:

ZIMNITSKY'S TEST

Portion N	Time (hours)	Amount of urine in ml	Specific gravity
1	6.00 - 9.00	70	1020
2	9.00 - 12.00	70	1025
3	12.00 - 15.00	90	1018
4	15.00 - 18.00	70	1020
5	18.00 - 21.00	120	1018
6	21.00 - 24.00	160	1020
7	24.00 - 3.00	90	1025
8	3.00 - 6.00	110	1025

Daily diuresis 300

Noctural diuresis 480

Round-the-clock diuresis 780

Taken liquid during day 1300

    Conclusion: decreased amount of excreted urine (comparing with taken liquid) is typical for edema nocturia(prevalence of noctural diuresis), isuria (diviation between urine portions smaller than 100 ml), indicate disordered excretory function;

    deviation between specific gravity in urine portions smaller than 10 indicates disordered concentrative function.

    Such analysis can be in renal failure.         

 

 

THE REHBERG'S TEST.

 To determine the functional renal condition it is possible to examine the glomerular filtration, the percentage of reabsorbed water.

Renal insufficiency arises in cases where the mass of the active parenchyma is 20% and lower of normal weight. If a substance that is filtered in the glomeruli but is not reabsorbed or liberated in the tubules is used for the assessment of renal function, the clearance of this substance is actually equal to glomerular filtration. Using this phenomenon, Reberg proposed a test for studying the amount of filtration by endogenic or exogenic creatinine. If one assumes that creatinine content of plasma and glomerular filtrate is the same, it is possible to determine the degree of concentration of the glomerular filtrate as it passes the tubules.

Blood is taken from the vein of the patient on a fasting stomach and creatinine concentration is determined. Urine is collected during 2 hours. Diuresis is measured thoroughly and creatinine content is determined. Next, using the formula of the amount of glomerular filtration and reabsorbtion percentage are calculated.

In healthy individuals the amount of glomerular filtration is 65-125 ml/min.

The percentage of reabsorbed water is 98-99%.

As renal failure develops, glomerular filtration decreases gradually to attain as 5 ml/min. Tubular reabsorbtion changes less markedly to decrease in cases of pronounced insufficiency to 80-60%.

The prognostic value of the method increases if it is used in follow-up studies. Persistent decrease in glomerular filtration to 40-50 ml/min during 18-24 months following acute glomerulonephritis suggests the conversion of the acute process into the chronic disease.

To determine the functional renal condition it is possible to examine concentration of urea, residual nitrogen, creatinine in blood.

In norm: concentration of urea is 3,33-8,32 mmol/L;

            residual nitrogen - 14,28-25 mmol/L;

            creatinine - 53-106,1 mkmol/L.

In renal failure their amounts increase.

 

REBERG'S TEST

Glomerular filtration 40 ml/min

The percentage of reabsorbed water 94%

Residual nitrogen 68 mkm/L

Urea 19 mkm/L

Creatinine 110 mkm/L

 

Conclusion: decreased glomerular filtration and percentage of reabsorbed water, increased residual nitrogen, urea and creatinine indicate renal failure.