Urine examination / Physical

Physical examination consists of assessing the color of urine, its odor, foam and turbidity. 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.

Volume
Daily urine volume is significantly affected by fluid and dietary intake. Volumes less than 400 ml / 24 hours and greater than 2500 ml / 24 hours are considered pathological.

Oliguria and anuria
Oliguria is indicated for urine volume <400 ml / 24 hours and anuria for urine volume <100 ml / 24 hours.

Oliguria and anuria are the basic symptoms of kidney failure. The cause may be dehydration from insufficient fluid intake or increased fluid loss (diarrhea, sweating). Decreased urine volume may be due to primary damage to the renal parenchyma or due to fluid retention (edema, effusions in body cavities).

Oliguria and anuria can also be caused by mechanical obstruction in the urinary tract (prostatic hypertrophy, wedged stone, tumors in the small pelvis). If the obstruction is located below the bladder, we speak of urinary retention.

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

There are two types of polyurethane states:
 * Polyuria caused by so-called water diuresis.
 * Water diuresis is due to a reduction in tubular water resorption in the distal part 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. Water diuresis is encountered physiologically when a larger volume of water is ingested or, for example, when there is insufficient secretion of antidiuretin (diabetes insipidus).


 * Polyuria caused by so-called osmotic diuresis.
 * It is caused either by increased filtration of osmotically active substances due to their increased osmotic concentration in the ECT (eg hyperglycemia) or by their reduced tubular resorption. Unabsorbed osmotically active substances "bind" water to each other and the result is a reduction 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 is amber in color, which is attributed to some bilirubinoids, especially urobilin. The intensity of the coloration depends on the concentration and amount of urine, which is determined by fluid intake and extrarenal output. The first morning urine, which is more concentrated, tends to be darker. Some pathological conditions or ingestion of certain exogenous substances may cause discoloration (eg beetroot, rhubarb). Selected characteristic changes in urine color are listed in the table:

Odor
We judge it in fresh urine, because by standing in the light, some parts of the urine decompose and the odor changes. The characteristic odor is caused by some of the diseases listed in the table:

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

Turbidity
Fresh urine is usually clear. Turbidity, which occurs after prolonged standing, causes epithelium and has no pathological significance. Turbidity in fresh urine 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
Also specific weight in the literature.

Relative density (also relative specific gravity) is given by the mass concentration of all solutes excreted in the urine. In contrast to osmolality, in addition to the number of dissolved particles, it also depends 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 increases. 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.

Relative urine density

Under physiological conditions, urine density ranges from 1,015 to 1,025. Extreme values of 1,003-1,040 can be reached in the dilution and concentration experiment.

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

Density determination allows an approximate estimation of renal concentration. Values above 1,020 and higher are indicative of good renal function and the ability of the kidneys to excrete excess solutes. Highly concentrated urine indicates a significant reduction in circulating plasma volume.

Inability of the kidneys to concentrate urine, low-concentrated urine of low specific gravity is excreted; we are talking about hypostenuria. The patient excretes the same amount of solids with higher water consumption. Extremely diluted urine may be a symptom of impaired renal concentration, such as diabetes insipidus, or due to the side effects of some medications. The combination of hypostenuria with polyuria indicates damage to the renal tubular system.

Isostenuria is a serious symptom of kidney damage. 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, at about 1,010. The current finding of isostenuria with oliguria is an indicator of severe renal insufficiency.

Dehydration, proteinuria or glycosuria contribute to the increase in relative density - hyperstenuria.