Urinalysis checks the urine as part of the internal composition of the body, that must remain constant. Its purpose is to excrete excess water and electrolytes continuously.
Although other organs (skin and intestine) contribute to this end, the kidney is the organ that maintains the body’s constant composition. Kidney exploration methods are based on the assessment of the functions that help the organ play its role in maintaining the homeostasis of the internal environment.
The kidneys, under normal conditions, develop urine that reflects the physiological state of the body. Removing the kidney function translates into the kidney incapacity to preserve domestic homeostasis. Under these conditions, the physicochemical properties of the urine may be altered, with different substances of clinical significance. The amount of urine emitted in 24 hours depends on the ingestion of fluids, sweat water loss and urinary function.
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- The amount of urine over 2500 ml / 24h defines polyuria.
- The amount of urine dropped below 500 ml / 24h is oliguria.
Usually, the amount of urine eliminated during the day is higher than at night. Reversing this report defines the pathological state called nocturia.
Full urine analysis includes the determination of physical characters (color, appearance, density), chemical (pH, protein, glucose, ketone, red blood cells, bilirubin, urobilinogen, leukocytes, nitrite, density) and microscopic sediment
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- Color: normal (yellow-straw); red blood cells (hematuria); black (melanuria); blue (administration of methylene blue), orange (administration of antipyretics).
- Transparency: normal (transparency); cloudy (phosphate-white or pink, mucus filaments, bacteria, leucocytes or red blood cells).
- Odor: normal (weakly aromatic because of volatile acids); in the presence of bacteria (hydrogen sulfide); in ketoacidosis: (acetone).
Chemical urine test
- pH-normal is 5-7: the kidney eliminates excess acid in the body by acidifying the urine into the contoured tube.
- Low pH values (strong acid urine) occur in: fever, abdominal diarrhea, diabetic or metabolic acidosis, diabetes mellitus, chronic polyarticular rheumatism, decompensated renal failure. Elevated pH values (alkaline urine) are found in respiratory and metabolic alkalosis, abundant vomiting, urinary tract infections. See more.
- Urine density (specific weight): quantifies the kidney’s ability to concentrate urine and the patient’s hydration status.
- Glucose: glycosuria occurs when blood glucose exceeds the kidney absorption threshold in glucose transport disorders.
- Ketone bodies: in normal urine are absent; are present when fatty acids form the main energy source, occurs in ketoacidosis, sanitation, abundant vomiting, unbalanced diet, intense effort.
- Protein-proteinuria: is the presence of abnormal amounts of protein in urine due to kidney or extrarenal affections.
- Urobilinogen: normally only 1% of urobilinogen gets into the urine; occurs in liver function overload, hemolytic anemia, intoxication, transfusion accidents, chronic hepatitis, cirrhosis, tumors.
- Bilirubin: usually not present in urine, if present is conjugated bilirubin; elevated values occur in obstruction of the bile duct by calculus, tumors, extrahepatic canalicular pressure, hepatic fibrosis.
- Leukocytes: high values occur in inflammation of the urinary tract due to bacteria, yeasts, parasites, in contamination with genital secretions (leukorrhea), bacterial leukocyturia in chronic pyelonephritis.
- Nitrites: in the urine where there are bacteria.
- Identification of renal, urinary, hepatic, metabolic dysfunctions and drug use.
Factors that can influence the results
- Erythrocytes: menstruation, intense exercise, smokers, prostatic infections, rapid lysis at a density below 1010 and pH> 7, bacteriuria (HB-like cataract secretory secreting strains).
- False negative reactions, some foods: blackberries, rhubarb beetles, pigments: porphyrins, ascorbic acid and captopril.
- Bilirubin: exposure to light, ascorbic acid, nitrate – false negative reactions.
- Antibiotic therapy inhibits intestinal flora: false negative reactions – diurnal variations – false positive reactions, light exposure and acid intensive pH, formaldehyde, p-aminosalicylic acid and p-aminobenzoic acid.
- Ketone cortices: fatigue, fever – false positive reactions, strong colored urine: false positive reactions, acetoacetic acid and acetone, captopril 50mg%, mercaptoethanesulfonic acid 10mg% and phenylpyruvic acid 10.
- Proteins: physical exercise, seizures, severe emotional stress, very low exposure, premenstrual, pregnancy, immediate postpartum (decreases).
- Hemoglobin (haematuria, infections, vaginal discharge, menstrual, mucus, ejaculation, alkaline pH, highly concentrated urine, antiseptic contamination (chlorhexidine): false positives, absorption on the walls of collecting urine, false positive reactions (phenazopyridine, 0.25% chlorhexidine) or false adverse responses.
- Nitrites: antibiotics inhibit nitrite formation, increased density-decrease, intense color of urine, false positive reaction (bilirubin, metabolites of azo dyes), ascorbic acid negative reaction.
- Glucose: pregnancy, high blood meal test, age, fever, stress, myocardial infarction, iv glucose test, storage at room temperature for a long time: false negative reactions (glycolysis), bacteria, ascorbic acid, ketone bodies (in large quantities): peroxide, strong oxidizing agents: false positive responses, hypochlorite, false positives.
- pH: diet (meat: low, vegetarian, -crashed), increases in the case of ammonia formation, ammonium chloride, mandelic acid: low false reactions, sodium bicarbonate, potassium citrate, acetazolamide.
- Density: ingestion of fluids, diuretics, precipitation of salt changes density, pH> 7.
- Leukocytes: vaginal discharge, intense exercise – increased lysis at a density below 1010 and pH greater than 7, intense urine color (bilirubin, nitrofurantoin): increased fake reactions, elevated glucose levels> 2000mg% and urinary proteins > 500mg%: some antibiotics (imipenem, meropenem, clavulanic acid) and positive and negative values.
The first morning urine is collected. The urinalysis is the method by which urine samples are cultivated and analyzed to identify pathogens that produce urinary tract infections. The test is used in clinical microbiology laboratories and is recommended by the specialist to determine the existence of a urinary tract infection. Harvesting is done in a special disposable, sterile, watertight container with a watertight lid to prevent sample contamination. The volume of urine required for a typical test is 10-15 ml.
The analysis of the urine is a good indicator of certain affections, so regular tests are recommended for health surveillance. Doctors recommend that the urine summary to be made every year, even if there are no symptoms indicating the presence of infectious pathogens. In fact, urinary tract infections may be asymptomatic. By collecting and analyzing urine samples, urinary tract infections and the factors that trigger them can be detected.