Urinalysis/Physical

The physical examination consists of assessing the color of the urine, its odor, its foam and itsturbidity. An important part of the physical examination is the determination of pH, density and osmolality. For the purpose of functional examinations, it is necessary to measure the volume of urine for a precisely defined period of time.

Polyuria
By polyuria we mean an increase in daily diuresis above 2500 ml.

There are two types of polyuric states:
 * Polyuria caused by the so-called water diuresis.
 * Water diuresis is given by a reduction of tubular resorption of water' in the distal segment of the nephron. Tubular resorption and excretion of osmotically active substances is within normal limits. Urine osmolality is lower than serum osmolality. It is always less than 250 mmol/kg H2O. We encounter water diuresis physiologically when taking in a larger volume of water or, for example, when insufficient secretion of antidiuretinu (diabetes insipidus).

Polyuria due to the so-called "osmotic diuresis".
 * It is caused either by increased filtration of osmotically active substances due to their increased osmotic concentration in ECT (e.g. hyperglycemia) or by their decreased tubular resorption. Unabsorbed osmotically active substances "bind" water to each other and the result is a decrease in their tubular resorption. Urine osmolality is higher than 250 mmol/kg H2O. Osmotic diuresis is characteristic, for example, of diabetes mellitus or the polyuric phase of renal failure or is the result of diuretics.

Color
Fresh urine has an amber-yellow coloration attributed to certain bilirubinoids, particularly urobilinu. The intensity of the coloring depends on the concentration and amount of urine, which is determined by fluid intake and extrarenal output. First morning urine, which is more concentrated, tends to be darker. Some pathological conditions or ingestion of certain exogenous substances can cause a change in color (e.g. beetroot, rhubarb). Selected characteristic changes in the color of urine are shown in the table:

Odor
We assess it in fresh urine, because exposure to light breaks down some components of urine and changes the smell. Certain diseases, listed in the table, cause a characteristic odor:

Foam
Normal urine foams little, the foam is white and disappears quickly. More abundant, colorless, more persistent foam occurs in proteinuria. In the presence of bilirubin, the urine foam is colored yellow to yellow-brown.

Turbidity
Fresh urine is usually clear. The turbidity that occurs after a longer period of standing is caused by epithelia and has no pathological significance. In fresh urine, turbidity can be caused by the presence of bacteria, leukocytes, lipids, phosphates, carbonates, uric acid, leucine, tyrosine and oxalates. It can be distinguished chemically or microscopically.

Density
In the literature, also 'specific gravity.

Relative density' (also relative specific gravity) is given by the mass concentration of all dissolved substances excreted in the urine. Unlike osmolality, it depends not only on the number of dissolved particles but also on their molecular weight. High molecular weight substances affect density to a greater extent than electrolytes. In the case of more pronounced glucosuria or proteinuria, the relative specific gravity rises. A protein concentration of 10 g/l increases the relative specific gravity of urine by 0.003 and a glucose concentration of 10 g/l by 0.004. The relative specific gravity of urine depends significantly on temperature.

Under physiological conditions, the density of urine ranges from 1.015–1.025. Extreme values ​​of 1.003-1.040 can be achieved with dilution trial and concentration trial.

As a general rule, the larger the volume of urine, the lower its density (diluted urine) and vice versa, with a smaller volume of urine (concentrated urine) it is higher. Conditions in which osmotic diuresis occur deviate from this rule: for example, in diabetes mellitus, the volume of urine is larger with a higher specific gravity.

Determination of the density enables an approximate estimation of the concentration capacity of the kidneys. Values ​​above 1.020 and above are indicative of good renal function and the ability of the kidneys to excrete excessive amounts of solutes. Highly concentrated urine indicates a substantial reduction in circulating plasma volume.

When the kidneys are unable to concentrate urine, poorly concentrated urine with a low specific gravity is excreted; we are talking about hypostenuria. The patient excretes the same amount of solids while consuming more water. Extremely dilute urine may be a symptom of impaired concentrating ability of the kidneys, such as in diabetes insipidus, or as a result of side effects of certain medications. The combination of hyposthenuria with polyuria indicates damage to the renal tubular system.

A serious symptom of kidney damage is isostenuria. The kidneys lose the ability to concentrate (and dilute) urine and excrete urine with the same density as the glomerular filtrate. The relative density of urine remains consistently low, around 1.010. The simultaneous finding of isosthenuria with oliguria is an indicator of severe renal insufficiency.

dehydration, proteinuria or glycosuria contributes to the increase in relative relative density - hyperstenuria.