Renal function tests and intro to urinalysis

RENAL FUNCTION TESTS
GLOMERULAR
FILTRATION TESTS
TUBULAR
REABSORPTION TESTS:
A. ENDOGENOUS:
1. CREATININE
CLEARANCE
2. UREA
CLEARANCE
3. BETA2-
MICROGLOBULIN
4. CYSTATIN-C
B. EXOGENOUS:
1. INULIN
CLEARANCE
2. RADIOISOTOPES
A. FISHBERG
B. MOSENTHAL
C. OSMOLARIITY
D. FREE WATER
CLEARANCE
1. FREEZING
POINT
2. VAPOR
PRESSURE
TUBULAR SECRETION
TESTS:
A. PHENOLSULFON
APHTHALEIN
(PSP)
B. P-
AMINOHIPPURIC
ACID (PAH)
C. TITRATABLE
ACIDITY
D. URINARY
AMMONIA

I. GLOMERULAR FILTRATION RATE TESTS
1. Some creatinine is secreted by the tubules, and secretion increases as blood level
rise
2. Chromogens present in human plasma react in the chemical analysis.
3. Medications, including gentamicin, cephalosporins, and cimetidine (Tagamet),
inhibit tubular secretion of creatinine
4. Bacteria will break down urinary creatinine if specimens are kept at room
temperature for extended periods.
5. An increased intake of meat can raise the urine and plasma levels of creatinine
during the 24-hour collection period.
6. Measurement of creatinine clearance is not a reliable indicator in patients
suffering from muscle-wasting diseases or persons involved in heavy exercise
or athletes supplementing with creatine.
7. Accurate results depend on the accurate completeness of a 24-hour collection.
8. It must be corrected for body surface area, unless normal is assumed, and must
always be corrected for children.
A. CREATININE CLEARANCE (ROUTINELY USED)
 SEVERAL DISADVANTAGES:

CREATININE CLEARANCE
CCR = UV x 1.74
P A
WHERE:
CCR = Creatinine
clearance
U= urine clearance
(mg/dL)
P= (Plasma creatinine)
V=urine volme (mL/min)
A= Body surface area
* x 0.17 for
pediatric patient instead
Sample:
Using urine creatinine of 120
mg/dL, plasma creatinine of 1.0
mg/dL , and urine volume of 1.4 L
obtained from a 24-hour
specimen of an average person,
calculate the GFR.
NV:
M: 107-139ml/min
F: 87-107ml/min
plasma creatinine : 0.5 to 1.5
mg/dL

Calculated Glomerular
Filtration Estimate using
Formula Developed by:
Cockcroft & Gault!
CCR= (140-age)(body weight in kg)
72 x serum creatinine (mg/dL)
• Result multiply by 0.85 (female)
• Variables: AGE, WEIGHT, SEX
The calculation for ideal body
weight (IBW) is:
Males: 50 kg 2.3 kg for each inch
of height over 60 inches
Females: 45.5 kg 2.3 kg for each
inch of height over 60
inches
The calculation for adjusted body
weight (AjBW) is:
IBW 0.3 (ABW-IBW)

At the present time the formula recommended by
the National Kidney Disease Education Program
(NKDEP) is called the MDRD-IDMS-traceable
formula when the serum creatinine method is
not standardized to IDMS.
GFR = 173 × serum creatinine–1.154 × age–0.203
× 0.742 (if patient is female) × 1.212 (if patient is
black)

B. B2-MICROGLOBULIN
 Molecular weight 11,800kD
 Dissociates from human leukocytes antigens at a
constant rate and is rapidly removed from the
plasma by glomerular filtration.
 Sensitive method: enzyme immunoassay
 Increase plasma level has > sensitivity as
indicator of a decrease in GFR than CCT.
 However test is not reliable in patients who has
immunologic history

C. CYSTATIN-C
 Is a small protein (13,359kD) produed at a
constant rate y all nucleated cells.
 It is readily filtered by the glomerulus and
reabsorbed and breakdown by the renal tubular
cells.
 Thus, serum concentration level is directly
related to GFR.
 Monitoring levels is recommended for pediatric
patients, persons with DM, the elderly and
critically ill patients.

 Earliest glomerular filtration tests
 Because approximately 40% of the filtered urea is
reabsorbed, normal values were adjusted to
reflect the reabsorption, and patients were
hydrated to produce a urine flow of 2 mL/min to
ensure that no more than 40% of the urea was
reabsorbed.
D. UREA CLEARANCE (OLD METHOD)

E. INULIN CLEARANCE (GOLD STANDARD)
 A polymer of fructose, is an extremely stable
substance that is not reabsorbed or secreted by
the tubules.
 It is not a normal body constituent, however, and
must be infused by IV at a constant rate
throughout the testing period.

F. RADIONUCLEOTIDES
 Injecting radionucleotides such as
125Iiothalamate
 provides a method for determining glomerular
filtration through the plasma disappearance of
the radioactive material and enables
visualization of the filtration in one or both
kidneys.
 This procedure can be valuable to
measure the viability of a transplanted
kidney.

II. TUBULAR REABSORPTION TEST
Concentration tests  used to evaluate tubular reabsorpion
A. OLD TESTS:
1. FISHBERG TEST
 The patient is deprived of fluid for 24 hours then
measure urine SG
 SG should be > 1.026
 Compare day and night urine in terms of volume
and SG
II. MOSENTHAL TEST

Concentration tests  used to evaluate tubular reabsorpion
B. NEW TESTS:
1. SPECIFIC GRAVITY
 Influence by the number and density of
particles in a solution
 Influenced by the number of particles in a
solution
II. OSMOLARITY

OSMOLARITY PROCEDURE AND
INTERPRETAION
1. Controlled intake procedures can include after
dinner overnight deprivation of fluid for 12 hours
followed by collection of a urine sample.
2. A urine osmolality reading of 800 mOsm or
higher is normal and the test can be
discontinued.
3. If the urine test is abnormal, the fluid is
restricted for another two hours and both urine
and serum species are collected for osmolality
testing. A urine to serum ratio (U:S ratio) of
3:1 or greater or a urine osmolality of 800
mOsm or greater indicates normal tubular

OSMOLARITY
A. FREEZING POINT
OSMOMETERS
B. VAPOR PRESSURE
OSMOMETERS
 Determine the freezing point of
a solution by supercooling a
measured amount of sample to
approximately 27O C.
 1 Osm or 1000mOsm/kg of
H2O will lower the freezing
point of H2O by 1.86oC
 Clinical osmometers use
solutions of known NaCl
concentration as their reference
standards because a solution
of partially ionized substances
is more representative of urine
and plasma composition.
 The depression of dew point
temperature by solute parallels
the decrease in vapor pressure,
thereby providing a measure of
this colligative property.
 The vapor pressure osmometer
uses microsamples of less than
0.01 mL; therefore, care must be
taken to prevent any evaporation
of the sample prior to testing.
 used primarily to analyze
serum and sweat
microsamples for disorders
not related to renal function,
such as cystic fibrosis.

III. FREE WATER CLEARANCE
 calculating the osmolar clearance using
the standard clearance formula:
COsm= UOsm X V
posm
 and then subtracting the osmolar
clearance value from the urine volume in
mL/min.
Fwc = COsm- Urine volume

FWC sample:
 Using a urine osmolarity of 600 mOsm , a urine volume
of 2 mL/min , and a plasma osmolarity of 300 mOsm ,
calculate the free water clearance:
 NV:
 (-) NEGATIVE result indicates that less than the
necessary amount of water is being excreted, a possible
state of dehydration.
 If the value had been 0, no renal concentration or dilution
would be taking place;
 lf the value had been POSITIVE, excess water would
have been excreted.

II. TUBULAR SECRETION TEST
& RENAL BLOOD FLOW
A. PHENOLSULFONAPHTHANLEIN
(PSP)
B. P-aminohippuric (PAH) acid Test
 normal values for the effective renal plasma
ﬂow range from 600 to 700 mL/min, making
the average renal blood ﬂow about 1200
mL/min
 The PSP test is not currently performed because:
 Standardization and interpretation of PSP results are difficult
 interference by medications, elevated waste products in
patients’ serum, the necessity to obtain several very
accurately timed urine specimens
 possibility of producing anaphylactic shock.

II. TUBULAR SECRETION TEST
& RENAL BLOOD FLOW
C. TITRATABLE ACIDITY & URINARY
AMMONIA The ability of the kidney to produce an acid urine depends on
the tubular secretion of hydrogen ions and production and
secretion of ammonia by the cells of the distal convoluted
tubule.
 A normal person excretes approximately 70 mEq/day of acid in
the form of titratable acid (H+), hydrogen phosphate ions
(H2PO4–), or ammonium ions (NH4+).
 In normal persons, a diurnal variation in urine acidity consisting of
alkaline tides appears shortly after arising and postprandially at
approximately 2 p.m. and 8 p.m.
 The lowest pH is found at night.
 By titrating the amount of free H+ (titratable acidity) and then the
total acidity of the specimen the ammonium concentration can be
calculated as the difference between the titratable acidity and the
total acidity.

 Urinalysis – marked the beginning of laboratory
medicine; included observations of color, turbidity,
odor, volume, viscosity, and even sweetness
 1140 AD – color charts were developed that described
the significance of 20 different colors
 1627 – Thomas Bryant wrote a book about charlatans
(pisse prophets) which inspired the passing of the first
medical licensure law in England
 1694 – Frederik Dekkers’ discovered albuminuria by
boiling urine
 17th century – microscope was invented which led to
the examination of urinary sediment and to the
development by

Hippocrate
s
• Credited as being
the Western
father of
modern
medicine
• 5th century BC-
wrote a book
on uroscopy

Richard
Bright
1827 –
introduced
the concept
of urinalysis
as part of
routine
patient
examination

Henry
Bence-Jones
• Associated a
urine protein
with patients
suffering from
multiple
myeloma
• Published
work 1848

Thomas Addis
 of methods for quantitating the
microscopic sediment
 Accurate count / assessment of
urine sediment
 Urine sediment is analyzed in a
hemacytometer an individual
elements reported as number per
24 hours.

 To aid in the diagnosis of diseases
 To screen asymptomatic populations
for undetected disorders
 To monitor the progress of disease
and the effectiveness of therapy

A. First morning – ideal specimen for routine screening,
pregnancy test, detection of orthostatic proteinuria ,
most concentrated and acidic; for well preservaion of
cell and cast
B. Random – routine and qualitative UA; done within 2
hours
C. 24-hour – quantitative chemical tests, hormone studies ,CCT,
begin and end the collection with an empty bladder
D. 12-hour (ex. 8am  8pm) – Addis count
E. Afternoon specimen (2-4 pm) – urobilinogen
determination(alkaline tide); protect from light
F. 4 hour- for nitrite determination; for bacteria to convert
nitrate to nitrite; urine remains in the bladder for atleast
4 hours before being collected

H. 5 hour urine- for determining D-xylose
I. Fasting/Second morning – second
voided urine, diabetic screening/monitoring
J. Midstream clean-catch – routine
screening, bacterial culture, (OPD)
K. 2-h Postprandial – diabetic monitoring

L. Suprapubic aspiration (cystocentesis)
 urine is obtained from a needle through the
abdominal wall.
 bladder urine for anaerobic bacterial culture
and urine cytology

M. Pediatric Specimen-
 use of soft, clear plastic bag with adhesive (wee
bag)
N. Catheterization – bacterial culture

L. Three-glass collection – diagnosis of prostatic
infection
1. First portion of vioded urine (less WBC/bacteria)
2. Middle portion of voided urine (control, must be no
bacteria/WBC, for bladder nad kidney infection) : if positive,
indicative of UTI, invalid 3rd tube
3. Urine after prostatic massage (prostatitis>WBC/bacteria);10x
greater than tube #1
M. Drug testing specimen
 COC: process that provides documentation of proper sample
identification from the time of collection to the receipt of
laboratory results
 Required urine volume: 30-40mL
 temperature (within 4 mins) should be within 32.5- 37.7ºC;
 blueing agent added to the toilet water reservoir in unwitnessed
collection to prevent adulteration

 Composition of Urine:
 95% water, 5% analytes
 a. Organic components – urea, creatinine,
uric acid, ammonia, undetermined nitrogen,
others
 b. Inorganic components – Cl-, >Na+, >K+,
Ca2+, phosphates, sulfates

 Containers: for routine urinalysis should have a
wide mouth to facilitate collections from female
patients and a wide, flat bottom to prevent
overturning.
 Specimens must be collected in clean, dry, leak-
proof containers and clear material to allow for
determination of color and clarity.
 The recommended capacity of the container is 50
mL, which allows 12 mL of specimen needed for
microscopic analysis, additional specimen for repeat
analysis, and enough room for the specimen to be
mixed by swirling the container.

 Labels must be attached to the container, not
to the lid, and should not become detached if the
container is refrigerated or frozen.
 A requisition form (manual or computerized)
must accompany specimens delivered to the
laboratory. The information on the form must
match the information on the specimen label.

1. Improperly labeled and collected
specimens
2. Nonmatching labels and requisition forms
3. Specimens contaminated with feces or
toilet paper
4. Containers with contaminated exteriors
5. Specimens of insufficient quantity
6. Specimens that have been improperly
transported

Sodium
benzoate
Does not interfere with reagent strip for glucose
HCl Preservation for cathecolamines and 5-HIAA determination

Renal function tests and intro to urinalysis

List of reference
 Lillian Mundt & Kristy Shanahan, Graff’s Textbook of Urinalysis and
Body Fluids, 2nd Ed.
 Susan Strassinger & Marjorie Di Lorenzo, Urinalysis and Body
Fluids, 5th & 6th Ed.
 Roderick Balce, RMT-CEU Professor AUBF Notes
 Erol Coderres,RMT-AUBF notes
 Meryl Haber, MD, A Primer of Microscopic Urinalysis, 2nd Ed.
 Zenggang Pan, MD, PhD., Dept of Pathology, U of Alabama at
Birmingham
 http://www.enjoypath.com/cp/Chem/Urine-Morphology/Urine-morphology.htm
 Department of the Army, Landstuhl Regional Medical Center
 http://www.dcss.cs.amedd.army.mil/field/FLIP%20Disk%204.2/FLIP42.html
 Nobuko IMAI, Central Laboratory for Clinical Investigation, Osaka
University Hospital
 http://square.umin.ac.jp/uri_sedi/Eindex.html

Renal function tests and intro to urinalysis

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