Lecture 2

Question 1

Characteristics of Urine

Answer 1

Colour somewhat yellow due to the pigment urochrome or urobilin (from the destruction of hemoglobin) and solutes
The more solutes in the urine, the deeper yellow its colour – Concentrated
Diluted urine is pale, straw colour
Sterile
Slightly aromatic – If allowed to stand for too long, gives an ammonia odour
Normal pH of around 6.0 (slightly acidic)
Urine pH varies from 5.0 to 8.0
pH is dependent on the foods one eats
Meat eater – pH is more acidic
Vegetarians – pH is more alkaline
Specific gravity of urine 1.010 to 1.025
SG = Density of Urine Density of Water

Question 2

Composition of Urine

Answer 2

Composed of 95% water 5% organic and inorganic waste products (solutes)
Organic products – urea (end product of protein metabolism – highest concentration), uric acid, creatinine
Inorganic products – sodium, chloride, potassium, calcium, phosphate, sulfate
Always contain water, urea, uric acid, creatinine and sodium

Question 3

If there is disease what does the urine show?

Answer 3

In the presence of disease, may contain protein, glucose, blood, ketones, increased creatinine level
For e.g Diabetes mellitus – positive glucose urine test

Urine must always be sent ASAP and if not tested in the hour refrigerate

Question 4

Urine pregnancy testing

Answer 4

require a first-voided morning specimen

Test for human chorionic gonadotropin (hCG)

Question 5

Presence of urinary tract infection (UTI),

Answer 5

require a clean-catch midstream specimen

Question 6

Random Specimen

Answer 6

Freshly voided, collected anytime during the day for routine testing
Should be midstream
Commonly used for R&M (Routine and Microscopic Urinalysis )
For qualitative or semi-quantitative tests

Question 7

First-Voided Morning Specimen (fasting)

Answer 7

Usually the specimen of choice for urinalysis
Contain the greatest concentration of dissolved substances (quantitative analysis)
Collect the first voided specimen of the morning
Should be midstream
Example of tests – R&M, urine pregnancy, C&S
Can be preserved by refrigeration (2C – 6C)

Question 8

Clean-Catch Midstream Urine (CCMSU)

Answer 8

Required for culture and bacterial examination – C&S
Assist in diagnosing UTI
Specimen collected from the middle portion of the urine stream (MSU –Midstream Urine)
Require special skin cleansing by the patient
The urinary bladder and most of the urethra are normally free of bacteria
The distal urethra and urinary meatus normally harbor microorganisms
Collect specimen in a sterile container

Question 9

24-Hour Urine Specimen

Answer 9

Collection of urine over a 24-hour period
Used for quantitative measurement of specific urinary components to assess kidney function
Measured substances include – Protein, creatinine/clearance, urea nitrogen, hormones, minerals, 17-hydroxy steroid, 17-ketosteroids

Creatinine is a waste product of creatine phosphate in muscle (related to muscle mass)
A constant amount of creatinine is excreted daily

Preservatives added to urine containers are concentrated acids, bases such as
6N HCl, Boric Acid, NaOH, Sodium Carbonate, Formaldehyde, Refrigeration (2 – 60C)

Volume is measured in the lab, using a 1L or 2L graduated cylinder

Question 10

increase in plasma creatinine indicates

Answer 10

An increase in plasma creatinine indicates impaired glomerular filtration – impaired renal function
Creatinine clearance – Formula used to measure creatinine excreted in the urine compared to blood creatinine
Creatinine clearance test assist in determining kidney function

Question 11

Samples required for Creatinine Clearance

Answer 11

Blood sample (serum) and a 24 hour urine sample
On the morning of the first day, the patient must discard the first morning sample and note the time
Collect all urine samples over the next 24 hours in a proper container – including the first void urine on the next morning
24 hour urine specimen should be kept refrigerated during collection
Note the time when the collection is completed
Patient must bring the completed 24 urine container to the lab ASAP
Note: The blood sample can be collected on the day the patient collects or returns the urine container

Question 12

Routine and Microscopic Urinalysis TEST TIME

Answer 12

Test within one hour or refrigerate (up to 4 hrs)
If refrigerated, warm to room temperature and mix well before testing

 consist of:
Physical Examination  - Gross Inspection
Chemical Analysis - Dipstick 
Microscopic examination of sediment
Volume, colour, clarity, odour and specific gravity are part of the physical analysis/properties

Question 13

Turbidity/Clarity

Answer 13

Fresh urine is usually clear or transparent, but becomes cloudy on standing (usually > 1 hour)
Cloudiness from a fresh void specimen may be caused by a UTI

Urine kept at Room Temperature for over 1 hour

a) Nitrite test would increase/positive if urine left standing for extended period at room temperature
b) pH level will increase as well as bacteria and urobilinogen levels
c) Casts would disappear

Question 14

Odour

Answer 14

Fresh voided urine – slightly aromatic odour
If left standing for a long time – ammonia odour from the breakdown of urea by bacteria
Foul odour – indicates UTI
Fruity odour – uncontrolled diabetes

Question 15

Foam

Answer 15

Normal urine - white foam when shaken
Very foamy urine – may represent large amount of protein in the urine
Yellow foam may be due to blirubin

Question 16

Reagent strips

Answer 16

are sensitive to light, heat and moisture
Bottles must be tightly capped after removing the reagent strip
Store in a cool, dry area with the cap tightly closed and in a dark container
Results are qualitative
Reagent strips should be tested daily with controls

Question 17

Strip Chemical Tests

Answer 17

Specific Gravity (concentration)
pH (acidity of the urine)
Protein (Albumin)
Glucose
Ketones
Blood
Leukocyte esterase (suggestive of white blood cells in urine)
Nitrite (suggestive of bacteria in urine)
Bilirubin (possible liver disease or breakdown of red blood cell)
Urobilinogen (possible liver disease)

Question 18

Specific Gravity (S.G.)

Answer 18

Indicate the amount of dissolved substances present in the urine
Dilute urine – lower specific gravity due to lower dissolved substances
Concentrated urine – higher specific gravity, due to increased dissolved substances
Derived from the ratio of the weight of urine to the weight of the same volume of distilled H2O
S.G of distilled H2O is 1.000
S.G of urine range from1.010 to 1.025

Question 19

Urine Analyzer

Answer 19

Perform automatic chemical examination of urine with reagent strips
Strip reading is standardized – timing errors and reader bias are eliminated
Increase precision
Increase in number of tests performed

Question 20

Dipstick Reagents - Glucose:

Answer 20

If the blood glucose level exceeds 10 mmol/L which is the normal renal threshold the tubules cannot reabsorb the filtered glucose. This is called glucosuria. The strip cannot detect sucrose, lactose, maltose or galactose

Question 21

Dipstick Reagents - Protein:

Answer 21

: in the urine (Proteinuria) is a serious problem and indicates glomerular disease, multiple myeloma. The strip can only detect albumin and not proteins such as immunoglobulins or Bence Jones

Question 22

Dipstick Reagents - Blood

Answer 22

The dipstick detect intact RBCs, hemoglobin from lysed RBCs and myoglobulin, a heme protein that facilitates the movement of oxygen in the muscle. False +ve: urine contaminated by menstrual blood

Question 23

Dipstick Reagents -Nitrites

Answer 23

is indicative of UTI or (bacteriuria) and the Enterbacteriacae family are the only bacteria that breakdown nitrates to nitrites

Question 24

Dipstick Reagents -Leukocyte Esterase:

Answer 24

an enzyme that is produced by the WHCs and indicates UTI

Question 25

Dipstick Reagents -Bilirubin:

Answer 25

is formed by the breakdown of hemoglobin and is not mormally found in the urine. The detection of bilirubin is diagnostic of obstruction of the biliary duct, liver diseaseFalse +ve: drugs. False –ve: large amounts of VitaminC

Question 26

Dipstick Reagents - Urobilinogen

Answer 26

Abnormal urobilinogen is indicative of liver function disorders

Question 27

Dipstick Reagents - Ketones

Answer 27

breakdown of fatty acids when carbohydrates are not available. Detected in patients with alcoholism, starvation, diabetes.