Laboratory Urine

Question 1

What is included in a urinalysis ?

Answer 1

Inspection of the gross appearance.
Dipstick analysis.
Urine sediment.

Question 2

What is a dipstick analysis and how do you perform one ?

Answer 2

Pour 5-10 mL of urine into a centrifuge and spin the capped sample. Immerse briefly (1s) but completely the test strip into the sample. Remove the excess urine but sliding it against the test tube or using a paper napkin, then wait for 30-60 s (excepté leucocytes) to avoid error before comparing it with the coloured scale.

Question 3

How do you perform a urine sediment ?

Answer 3

Decant the sample and discard the supernatant (the top liquid to nobly keep the solide bottom). Mix the sediment and put it on microscope slide. Examine at x10 then x40.

Question 4

What do you look for in a urine sediment ?

Answer 4

At x10 : epithelial cells, cast, crystal, mucus.

At x40 : epithelial cells, crystal, red blood cells, white blood cells, bacterias, parasites.

Question 5

What do you look at in the gross inspection of an urine sample ?

Answer 5

Color, turbidity/transparency, odor.

Question 6

What are the normal values of a dipstick test ?

Answer 6

pH : 4.6-8.0, average sample of 6.0
Trace of urobilinogen
RBC : 0-3/hpf for male and 0-5/hpf for women (hpf = high power field)
WBC : 0-4/hpf
Negative for : bilirubin, blood, acetone, glucose, protein, nitrite, leucocytes.

Question 7

What are normal findings in an urine sediment ?

Answer 7

Only occasionally epithelial cells but a large amount could be due to contamination of the specimen.
Sometimes hyaline casts. Some crystal based on the pH. No bacteria.

Question 8

What is the meaning and cause of different urine color ?

Answer 8

Pale yellow : normal
Colorless : Polyuria or diabetes
Pink to dark red : hematuria (bleeding), myoglobinuria, hemoglobinuria (acute haemolytic reaction).
Red to black : porphyrinuria and alkaptonuria.
Red/brown/black : UTI
White milky urine : cholurie (presence of bile element)
Dark yellow : dehydratation

Question 9

What indicate the presence of bilirubin in urine ?

Answer 9

It’s an early indication of a liver disease.

Question 10

What are the different meaning of positive dipstick for blood ?

Answer 10

If there’s no erythrocytes then it could be free hemoglobin or myoglobin present. Or a high dose of vitamin C.
If there are erythrocytes present then : glomerular hematuria, renal or urologic causes, drug, trauma, menses, vaginal bleeding.

Question 11

What is the clinical significance of glucose in the urine ?

Answer 11

Beware the dipstick only react to glucose not other sugar.
It could indicate : diabetes, steroids, SGLT2 inhibitors (medication to reduce the glycemia), RTA (renal tubular acidosis)

Question 12

What is the clinical significances of ketones bodies in urine ?

Answer 12

Trace = 5mg/dL
It can indicate : starvation, DKA (diabetic ketoacidosis), vomiting, alcohol, hyperthyroidism, carbohydrate free diet.

Question 13

What is the meaning of leucocytes in urine ?
How are they detected ?

Answer 13

Positive UTI signs.
Detected by leucocytes esterase activity.

Question 14

What is the clinical significance of nitrite in urine ?

Answer 14

Some bacteria can turn nitrate into nitrite. It can then be a sign of an infection.

Question 15

What is the clinical significance of pH in urine?

Answer 15

Acidic : high protein diet, ammonium chloride, mandolin acid, medication.
Alkaline : UTI, renal tubular acidosis, diet.

Question 16

What is the clinical significances of proteinuria ?

Answer 16

Can be a sign of glomerulonephritis or nephrotic syndrome.

Question 17

What does the odor of the urine can tell you ?

Answer 17

Almost no smell : normal
Strong ammonia smell : possibly UTI, presence of bacteria that can transform urea, high level of waste product
Acetone (sweet smell) : diabetes because of ketones body
Rotten egg : presence of sulfite because of cystinuria, diet, UTI, necrosis of tissue

Question 18

What is the clinical relevance of specific gravity ?

Answer 18

Normal values : osmolarity
Increased values (concentrated urine) : decreased volume, CHF (congestive heart failure), adrenal insufficiency
- possibility of false positive
Decreased values (diluted urine) : diabetes, pyelonephritis, glomerulonephritis.
- possibility of false negative

Question 19

For what particule is the collection of mid stream urine not necessary ?

Answer 19

For glucose

Question 20

What does the pH level influence ?

Answer 20

If the pH level is too high (alkaline solution) it is difficult to trust the values of test (false positive = make illusion of the presence of other components).

Question 21

What does the presence of ascorbic acid signify ?

Answer 21

It comes from vitamin C.
Its presence may interfere with the other parameter like glucose level (false neg = mask the presence of others)

Question 22

Which technique of collection is best for the presence of blood in urine ?

Answer 22

A test strip with the first morning urine.

Question 23

What are the best collection methods in general ?

Answer 23

First morning urine = more concentrated
Mid stream urine = less contamination of the external world
Test less than 2 hours after collection = waiting too long affect the protein level

Question 24

How long should you wait to read the result of a dipstick test ?

Answer 24

30-60s except for leucocytes for which you should wait 60-120s

Question 25

What does the presence of blood in urine tell you ?

Answer 25

Hematuria.
Can be due to infections, kidney stones, cancer or blood disorders.

Question 26

Benefit and requirement of urinalysis ?

Answer 26

Non invasive, fast, cheap.
Require fresh, concentrated and acidic urine.

Question 27

Type of urine collection ?

Answer 27

First morning urine : just after waking up
Second morning urine : around 10-11h
Postprandial : after eating (generally dinner)
Periodical : collect at least a 24h sample

Question 28

What should be in the postprandial sample ?

Answer 28

Presence of urobilinogen. If there’s none there’s probably a bile duct obstruction.

Question 29

Foamy urine ?

Answer 29

Presence of protein.

Question 30

Glycosuria ?

Answer 30

Presence of reducing sugar in the urine.

Question 31

Porphyrinuria ?

Answer 31

Abnormally increased excretion of porphyrins in urine. Caused by iron toxicity, alcohol abuse, hepatitis C, HIV and medication.

Question 32

Myoglobinuria ?

Answer 32

Is the presence of myoglobin in the urine. Caused by trauma, alcohol and drug abuse related to muscle necrosis from prolonged immobilisation and pressure by body weight.

Question 33

Alkaptonuria ?

Answer 33

Rare disease inherited, producing black urine. It prevents the body from breaking down tyrosine and phenylalanine.

Question 34

Indication of UTI in appearance ?

Answer 34

Cloudiness, black, brown, red, ammoniac smell.

Question 35

What is a normal specific gravity for urine ?

Answer 35

Between 1.015 and 1.030 compared to the density of water.

Question 36

How do you recognise a contaminated urine sample ?

Answer 36

Presence of numerous epithelial cells on microscopy.

Question 37

How does the pH in urine changes with infection ?

Answer 37

Generally become more alkaline especially with infection of E.Coli. But can also become more acidic.

Question 38

Do you use a pipette when transferring urine ?

Answer 38

No its quicker and you will not lose sediment.

Question 39

What do you do if the dipstick is only slightly positive for leukocytes and the patient has symptoms ?

Answer 39

First choice : microscopy because it is quicker
If no microscopy result but still suspicious of UTI because of unclear sample for example then do a culture.