RENAL FUNCTION TEST

Clearance test

Standard tests used to measure the filtering capacity of the glomeruli;

Measures the rate in milliliters per minute at which the kidneys are able to remove a filterable substance from the blood;

Used to evaluate glomerular filtration

Urea clearance

Earliest glomerular filtration test;

No longer used

Affected by diet

Reabsorption of urea (40%)

Why is urea clearance not used anymore?

Inulin clearance

Original reference method for clearance test;

Clinical “gold standard” for measuring the glomerular filtration rate

Inulin

Polymer of fructose;

Extremely stable substance that is neither reabsorbed nor secreted by the tubules

Creatinine

Waste product of muscle metabolism that is produced enzymatically by creatine phosphokinase from creatine, which links with adenosine triphosphate (ATP) to produce adenosine diphosphate (ADP) and energy.

Improperly collected/timed urine specimen

Greatest source of error in any clearance procedure utilizing is the use of what?

Creatinine clearance

Most commonly used glomerular filtration;

Measure of the completeness of a 24-hour urine collection

Cystatin c

Small protein produced at a constant rate by all nucleated cells;

Filtered readily by the glomerulus and reabsorved and broken down by the renal tubular cells

No

Is cystatin c secreted by the tubules?

5,200 delton

Molecular weight of inulin

13,000 delton

Molecular weight of cystatin c

Beta2 microglobulin

Dissociates from human leukocyte antigens at a constant rate and is removed rapidly from the plasma by glomerular filtration

11,800 delton

Molecular weight of beta2-microglobulin

Cockcroft and gault

Most frequently used formula;

Age, sex and body weight

Modification of diet in renal disease (MDRD) system

Ethnicity, blood urea nitrogen and serum albumin

Exogenous procedure

Test that requires an infused substance

Radioisotopes

Inulin

Example of exogenous procedure

Endogenous proceduce

Test that requires substances already present in the body

Cystatin c

Beta2-microglobulin

Example of endogenous procedure

Tubular reabsorption

First function affected in renal disease

Concentration test

Test to determine the ability of the tubules to reabsorb the essential salts and water that have been nonselectively filtered by the glomerulus

Fishberg test

Patient is deprive of fluid for 24 hours. Urine SG is then measured (SG should be >1.026)

Mosenthal test

Compare day and night urine in terms of volume and SG;

Patient must maintain normal diet and fluid intake

Specific gravity

Influenced by numbers and density of particles in a solution

Lower

The lower the concentration; the __ the specific gravity

Osmolarity

Influenced by number of particles in a solution;

Determined by measuring the colligative property

PAH (p-aminohippuric acid)

Test most commonly associated with tubular secretion and renal blood flow;

Diagnostic agent used in medicine to measure effective renal plasma flow and kidney excretory capacity

PSP (phenolsulfonphthalein) test

Obsolete test used for measuring overall blood flow and tubular secretory function in the kidneys

95-97%

Water percentage in urine

3-5%

Total solids percentage in urine

60 grams

How much total solids are produced in 24 hours

35 grams

Total grams of organic substances in urine

25 grams

Total grams of inorganic substances in urine

Urea

Major organic substance in urine

Chloride

Major inorganic substance in urine

Creatinine

2nd major organic substance in urine

Sodium

2nd major inorganic substance in urine

Potassium

3rd major inorganic substance in urine

Sodium chloride

Principal salt in urine

Random/occassional/single

First morning urine

Second morning/fasting

2 hour post prandial

Glucose tolerance

Midstream clean catch

Catheterized

Suprapubic aspiration

Three-glass technique

Types of urine specimen (9)

Random/occasional/single

For routine and quantitative urine analysis and is the most commonly received specimen

First morning urine

Ideal specimen for routine UA and pregnancy test;

Most concentrated and most acidic;

8 hour urine

First morning urine is also known as what?

Orthostatic proteinuria

First morning urine is used for evaluation of what?

Second morning/fasting

Second voided urine after a period of fasting

Glucose determination

Second morning/fastng is used for what?

2 hour post prandial

Patient is instructed to void shortly before consuming a routine meal and to collect a specimen 2 hours after eating

2 hour post prandial

What is the preferred urine specimen for testing glucose?

Diabetic screening/monitoring

2 hour post prandial is used for what?

Glucose tolerance

Optional with blood samples in glucose tolerance test

Midstream clean catch

Safer, less traumatic method for obtaining urine for bacterial culture and routine urinalysis

Catheterized

Collected under sterile conditions by passing a hollow tube through urethra

Bacterial culture

Catheterized is used for what?

Suprapubic aspiration

What urine specimen is the most sterile?

Suprapubic aspiration

Bladder urine for anaerobic bacterial culture and urine cytology

Prostastic infection

Three-glass technique is used for what?

First portion of voided urine

Middle portion of voided urine

Urine after protastic massage

Three-glass technique (3)

1st and 3rd specimen

What specimen is examined microscopically in three-glass tehcnique?

Number of wbc and bacteria

What is being compared in three-glass technique?

10x greater

Prostatic infection if the no. Of wbc and bacteria in the 3rd specimen is how much than the 1st specimen?

Control

What is the purpose of the 2nd specimen in three-glass specimen?

Invalid

If the 2nd specimen is positive for WBCs and bacteria, the results from the 3rd specimen is considered what?

24 hour

Begin and end the collection period with an empty bladder

Ex. 8 am - 8 am

12 hour

8 am-8 pm

Addis count

12 hour urine is used for what?

4 hour

Urine remains in bladder for atleast 4 hours before voiding

Nitrate determination

4 hour is used for what?

Afternoon

Ex. 2 pm-4 pm

Urobilinogen determination

Afternoon urine is used for what?

Change of custody

Process that provides documentation of proper sample identification from the time of collection to the receipt of lab results

4 min

Change of custody must be done within how many min?

Adulteration

Change of custody prevents what?

30-45 ml

Required urine volume for change of custody

32.5-37.7 degc (body temp)

Urine temperature for change of custody

Bluing agent

Added to the toilet water reservoir to prevent specimen adulteration

2 hours

Following collection, urine specimens should be delivered to the lab promptly and tested within how many hours?

pH

Bacteria

Odor

Nitrate

Increases in unpreserved urine (PaBaON)

pH

Breakdown of urea into ammonia by urease-producing bacteria/loss of CO2

Urea

pH increased due to breakdown of what?

Ammonia

Breakdown of urea into what? (pH)

NH3

Odor is because of breakdown of urea into what?

Clarity

Glucose

Ketones

Bilirubin

Urobilinogen

RBC/WBC/casts

Trichomonas

Decreased changes in unpreserved urine

Clarity

Bacterial multiplication;

Precipitation of amorphous material

Glycolysis

Why does glucose decrease in unpreserved urine?

Volatilization

Why does ketones decrease in unpreserved urine?

Light exposure

Why does bilirubin decrease in unpreserved urine?

Oxidation to urobilin

Why does urobilinogen decrease in unpreserved urine?

Disintegrate in alkaline urine

Why does RBC/WBC/casts decrease in unpreserved urine?

Trichomonas

Become immobile or die;

Possible misindentification as WBCs

Room temperature

If urine is refrigerated, the urine must be what?

Refrigeration

Does not interfere with chemical tests;

Prevents bacterial growth up to 24 hrs;

Raises SG by hydrometer;

Precipitates amorphous urates and phosphates

Refrigeration

Thymol

Boric acid

Formalin

Toluene

Sodium fluoride

Phenol

Saccamano fixative

Specimen preservation

Thymol

Preserves glucose and sedimetns well; interferes with acid precipitation tests for protein

Boric acid

Preserves protein and sediment well; keeps pH at about 6.0;

Is bacteriostatic at 18 g/L, can be used for culture transport;

May precipitate crystals when used in large amounts;

Interferes with drug and hormone analyses

6.0

Boric acid keeps pH at what level?

18 g/L

Boric acid is bacteriostatic at what?

Formalin

Excellent sediment preservative;

Acts as a reducing agent, interferes with chemical test for glucose, blood, leukocyte esterase and copper reduction

Toluene

Does not interfere with routing analysis;

floats on urine surface; clings to pipettes and testing materials