Urine Analysis Flashcards
What does the kidney eliminate?
excess body water
waste products of metabolism (i.e.: urea and creatinine)
foreign substance (drugs, vitamins, antibiotics)
Other functions of kidney
- Retention of substances necessary for normal body function (e.g. proteins, amino acids, glucose)
- Regulation of electrolyte balance and osmotic pressures of the body fluids (e.g. sodium chloride, phosphates
Composition of urine
95% water (1000 ml to 1500 ml/24 hr) 5% solute (60 g/24 hr)
Urine solutes and equivalents
- Urea – most of nitrogen excreted (10g/day)
- Sodium Chloride (NaCl) – 5 to 20g/day
- Potassium – 70 mEq/day
- Sulfate – organic or inorganic, 2g/day
- Phosphates – 1 g/day
Urine also contains small amounts of these:
• Sugars – pentoses
• Intermediary metabolites – oxalic acid, citric acid, pyruvate
• Free fatty acids and trace amounts of cholesterol
• Hormones – ketosteroids, estrogens, aldosterone, pituitary
gonadotropins
• Biogenic amines – catecholamines and serotonin metabolites
• Vitamins – ascorbic acid
• Porphyrins (trace amounts)
• Crystals – in concentrated urines; uric acid and phosphate
crystals (causes kidney stones)
Formed elements seen in urine
− Red Blood Cell (erythrocytes)
− White Blood Cell (leukocytes)
− Renal tubular epithelial cells (of the kidney)
− Transitional epithelial cells (of the kidney)
− Squamous epithelial cells (of the urethra)
Other substances present in urine
uric acid, creatinine, amino acids, ammonia and traces of proteins, glycoproteins, enzymes and purines
ideal urine specimen for isolation of anaerobes because it bypasses normal flora of urethra
Suprapubic aspiration
also: clean-catch midstream specimens
This method of specimen collection is used for specimens from children, infants and toddlers
collection bags
This method of specimen collection may cause staphylococcal infections (i.e.: S.epidermidis, S. saprophyticus)
Indwelling catheters
Other methods of specimen collection
straight catheterization
method used in clean-catch midstream specimens
• Clean urethral area with a series of sponges, soap, and clean water
• Retract skin folds (labia or prepuce) before voiding
→ To avoid contamination of epithelial cells
• The first-void urine is passed into the toilet to clear the urethra
• Collect the midstream specimen
• Continue voiding
urine needed for chemical and microscopic examination
voided specimen
urine needed for protein and microscopic examination of sediments
concentrated specimen (preferable; i.e.: morning urine)
Where is urine after a meal needed?
glucose examination
24-hour urine is usually used for
quantitative analysis
also for protein
Urine needed for bacteriologic examination
Voided mid-stream or catheterized specimen
Why is first morning urine collected?
counts increase overnight in bladder and organisms are concentrated
Why is fluids not forced in patients during time of collection
may dilute urine = false negative results, decrease count to <10^5 CFU/ml
Method of specimen collection for asymptomatic patients
Collect three consecutive early morning specimens
Important considerations in urine collection
- Containers (should be washed with detergent and rinsed well with water and dried; for ordinary urinalysis; sterile containers = bacteriologic examination)
- Deterioration of specimen (Should be collected in a dry, clean container; Should be examined when freshly voided)
- Storage
Consequences of detrioration of specimen
- RBC and WBC destroyed by hypotonicity of urine
- Casts decompose
- Bacterial contamination
- Decreased pH
This preserves sediments but interferes with test for protein
one crystal of thymol/ 10-15 ml. of urine
*one drop formalin/ 10 ml. urine also preserves sediments
The preservation method of freezing is used for
bilirubin, urobilinogen, or ketones
Preservative tablets are used for
routine screening; preserves glucose and other constituents
Container used for speciment transport
sterile, wide-mouthed, screw-capped
- anaerobic transporter for suprapubic aspirate
- urine bag for pediatric patients
Temperature at which specimen is transported
immediately refrigerated 4C or preserved
needed for culturing urine
If urine is not cultured, tubes are transported with
boric acid
glycerol
Na formate (and sometimes formalin)
*preserves bacteria without refrigeration for 24 hrs. when >10^5 CFU/ml is present in the initial urine specimen
General considerations during specimen transport
→ Transport urine to the lab as soon as possible after collection
→ Culture urine specimens within 2 hours after collection, or refrigerate and culture them within 8 hours whenever possible
→ Refrigerated urine specimens may be held for < 24 hrs.
Considerations for repeat specimen collection
• Request repeat specimen when:
→ There is no evidence of refrigeration and the specimen is more than 2 hours old
→ The collection time and method of collection have not been provided
• If an improperly collected, transported, or handled specimen cannot be replaced, document in the final report that specimen
quality may have been compromised
Procedure for routine urinalysis
- Number the urine specimens and the corresponding request
- Number the 15mL centrifuge tube corresponding to urine sample
- Mix each specimen thoroughly and place 12 mL to corresponding
centrifuge test tube. (Note the color, turbidity and pH reactions) - Measure specific gravity
- Centrifuge for 5 minutes at 1500 to 25000 rpm
• Use supernatant for testing of proteins, glucose and
reducing substances
• Use sediments for microscopic exam
Physical tests involved in macroscopic examination in routine urinalysis
Color, character (clarity of appearance), odor, urine volume, osmolality and specific gravity
normal color of urine
yellow and straw to amber-colored urine
Why is urine yellow?
urochrome pigment and small amounts of urobilins
[Abnormal findings of urine] orange urine is due to
concentrated urine
[Abnormal findings of urine] DEEP YELLOW URINE is due to
Riboflavin
[Abnormal findings of urine] amidopuride drugs causes this color of urine
bright orange
[Abnormal findings of urine]urobilin causes this color of drugs
orange-brown
[Abnormal findings of urine]greenish-orange urine is due to
bilirubin
[Abnormal findings of urine] smokey urine is due to
RBCs
[Abnormal findings of urine] What causes wine red urine?
hemoglobin pigments
[Abnormal findings of urine] What causes brown to black urine?
melanina
[Abnormal findings of urine] an almost colorless urine is due to
dilute urine
[Abnormal findings of urine] A reddish orange in alkaline solution is caused by
rhubarb or serra