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Urinary System Physiology - 1
Background: Urinary System Physiology
PREPARATION Read Chapters 18 19. Watch lecture videos on D2L:
Week11A G Read the background provided here. OBJECTIVES The
objectives for this weeks laboratory are to:
Evaluate how different drinks affect the characteristics (i.e.
concentration and volume produced) of urine.
Collect and analyze the results of a urinalysis test. Conclude
and defend your results of 5 urinalysis case studies.
Background Reading The production of urine is a complex process
that is highly regulated and performs many functions in the body
(including the filtration and excretion of wastes, osmoregulation,
and maintenance of plasma volume). Many factors can affect this
process including the amount and type of beverages that you
consume. In todays lab we will be exploring: 1) How common
beverages affect the volume and concentration of the urine that is
excreted. 2) How to perform a basic urinalysis with microscopic
examination.
A urinalysis is a simple, yet, powerful laboratory tool that is
often used to gather information on a patients carbohydrate
metabolism, kidney and liver function, and/or acid-base balance to
diagnose and monitor the progression of many diseases, such as
diabetes, liver disease, and urinary tract infections. The
simplicity of this test allows it to be used in a variety of
medical settings, such as doctors offices, urgent care facilities,
and hospitals. Physical examination of the urine Color-The color of
urine is usually described after visual inspection with common
color terms like clear, pale straw, light yellow, light amber, dark
amber, red, or other. Since these terms are subjective and take
some training to recognize, we will be using the adjacent color
chart for uniform data collection. Turbidity Normally, freshly
voided urine is clear. When urine is allowed to stand, amorphous
crystals, usually urates, may precipitate and cause urine to be
cloudy. The turbidity of urine should always be recorded and
microscopically explained. If a fresh sample is cloudy (turbid) it
may be an indicator of infection. Turbidity is recorded as clear or
cloudy.
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Urinary System Physiology - 2
Volume Urinary volume is dependent upon fluid intake; amount of
solutes to be excreted; loss of body fluids by normal processes,
such as perspiration and respiration, and abnormal processes, such
as diarrhea, and cardiovascular and renal function. Although the
volume of a random specimen is clinically insignificant, the volume
of the specimen received should be recorded for purposes of
documentation and standardization. Urine volumes can be measured
two ways: volumetrically or by mass. We will be using mass. The
volume is estimated by weighing the urine sample in a tared
container and assuming that 1g = 1mL of urine. Specific Gravity As
light moves from air (low density) to water (high density), the
speed of the light wave slows down and causes the light wave to
bend. The more concentrated the solute, the more the light bends.
By comparing the amount light bends through a known solution of
water to an unknown solution, we can measure the density of the
solution. Refractometers can relate the density of a solution to
specific gravity in a ratio of: Density of solution = Specific
Gravity Density of water So if the solution has the same density as
water, the specific gravity would be 1.000 g/ml. However, as the
amount of solute increases in the solution, so does the specific
gravity. Therefore, higher specific gravity of the urine indicates
more concentrated urine which could be due to water conservation by
the kidney. The refractive index scale can be calibrated to measure
the specific gravity of most urine samples up to 1.036 g/ml.
Chemical Testing of the Urine Reagent-strip Testing A plastic strip
is used, which contains pads that contain the reagents that react
with various urine components and change color. The strip is dipped
into the urine and the colors on the pads can be read manually by
comparison with color charts or with the use of automated machines
that examine the color change. The observation of color change must
be performed at the specific times indicated on the test strip
instructions. The test strips we will be using measure the
following values:
1. pH 2. Proteins 3. Glucose
4. Ketones 5. Blood and
myoglobin
6. Bilirubin 7. Urobilinogen 8. Nitrites
The specific gravity is determined by where the start of the
blue field intersects the specific gravity scale. The specific
gravity of this sample is approximately 1.026. Note: The
refractometers we use in lab have the specific gravity scale on the
right side!
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Urinary System Physiology - 3
Microscopic Examination of Urine Sediment Clinical Significance
of Microscopic Examination As part of a urinalysis, the urine
sediment is centrifuged and examined microscopically for crystals,
casts, red blood cells, white blood cells, and bacteria or yeast.
In healthy people, the urine contains small numbers of cells and
other formed elements from the entire urinary tract, and epithelial
cells from the kidney, ureter, bladder, and urethra. In renal
disease, the urine often contains increased numbers of substances
discharged from an organ that is otherwise accessible only by
biopsy or surgery. A microscopic examination of urine sediment
detects the presence and amounts of the following clinically
significant components:
Red and white blood cells Bacteria and yeast Casts Epithelial
cells Crystals
Examination of urinary sediment provides a direct sampling of
the cells and debris from the urinary tract and it provides
important information useful for both diagnosis and prognosis.
Leukocytes - Normally, 0 to 3 leukocytes per high-power field (40x
objective) will be seen on microscopic examination. More than 3
cells per high-power field probably indicates disease somewhere in
the urinary tract. Erythrocytes - Normally there should be only an
occasional red blood cell in the urine (2-3 per high-power field).
If erythrocytes are found, it is important to estimate the count
and rule out an underlying cause. In women, it is important to make
sure that the urine specimen was not contaminated by the menstrual
flow. Inserting a tampon and collecting urine midstream are ways to
prevent contamination. Erythrocytes may be differentiated from
white blood cells in several ways:
1. White blood cells are larger than red blood cells. 2. When
focusing with the high-power lens, the red blood cells appear as a
bi-concave
without a nucleus; the white blood cells tend to appear granular
with a visible nucleus.
General rules to be followed when performing urine reagent strip
testing.
1. Do NOT touch the test strip to the side of the container!
2. Make sure you have a timer and read the boxes at the
appropriate times
3. Beware of interfering substances. Certain drugs and dietary
factors can alter results.
4. Understand the advantages and limitations of the test.
Positive results from reagent-strip testing may require
confirmation with chemical and microscopic methods.
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Urinary System Physiology - 4
Epithelial cells- Some epithelial cells from the skin surface,
renal tubules, or outer urethra can appear in the urine. These
cells are large, flat, and quite common. Bacteria and Yeast - Urine
stored in the bladder is normally free of bacteria or yeast.
However, bacteria are commonly found in urine specimens because of
the abundant normal microbial flora of the vagina or external
urinary meatus and due to the ability of bacteria to multiply
rapidly in urine standing at room temperature. As a result,
bacteria noted on a microscopic examination should be interpreted
in view of clinical signs and symptoms of urinary tract infection.
Diagnosis of bacteria in a patient with a suspected urinary tract
infection requires a urine culture and sensitivity. Mucus- This is
a common finding in urine sediment. It looks like long, ribbon
threads and is secreted by glands in the lower urinary tract.
Crystals- Sediment and crystals are solids found in urine. Some
forms of crystals appear in the urine of healthy individuals.
Abnormal crystals can indicate liver disease or some forms of
genetic abnormalities. CastsThese urinary sediments are formed by
coagulation of protein or cells in the kidney tubules. Casts are
cylindrical and vary in diameter. The sides are parallel, and the
ends are usually rounded. Casts in the urine always indicate some
form of kidney disorder and should always be reported. If casts are
present in large numbers, the urine is almost sure to be positive
for albumin. There are seven types of casts. They are as
follows:
Hyaline casts Red cell casts White cell casts
Granular casts Epithelial casts Waxy casts
Fatty casts
Urine Handling Precautions: As with all human bodily fluids,
there is a chance of transmission of infectious diseases. As a
result, you should always wear latex gloves when handling urine
samples and DO NOT touch table surfaces, lab manuals, or writing
utensils while you have gloves on.
Testing Procedures Supplies needed:
Refractometer Disposable pipette ChemWipes Absorbent paper for
desktop
Latex gloves Ethanol
Biohazard waste receptacle
1. Pick up the refractometer and lift the cover of the
refractometer. 2. If there is any liquid in the refractometer, wipe
it away gently with a soft
absorbent paper. 3. Draw up 1 or 2 drops of urine into a
pipette. 4. Place one drop of urine into the refractometer and
close the cover gently.
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Urinary System Physiology - 5
5. Dispose of the pipette into the Biohazard bag. 6. Hold the
end of the refractometer with the eyepiece up to your eye and point
the other end
towards the light. 7. Looking through the eyepiece, you will see
several grids. The refractometer bends the light
through the urine and produces a line on a scale where the white
areas and blue areas intersect.
8. The Specific Gravity will be displayed in the scale on the
far right. Report this value as the refractometer specific gravity
to your data recorder, who should write it in the data table.
9. Open the cover and carefully wipe away the urine from the
refractometer surface. 10. After the final sample is measured, wipe
the sample surface with ethanol to clean any urine
residue. Chemical Test Strip Testing Procedures Supplies
needed:
Urinalysis testing strips Disposable pipette Absorbent paper for
desktop
Latex gloves Biohazard waste receptacle Timer
Be familiar with these instructions before you begin!
Timing is critical for this exercise.
Assign different jobs in the group. You will need a timer, a
tester and a data recorder.
1. Check that you have all of your necessary supplies before you
open your urine sample. 2. Tester: Put on latex gloves. 3. Gently
mix the urine sample before testing with the test strip. 4. Remove
a test strip from the bottle and replace the cap. 5. Observe the
important time intervals that you need to measure the samples as
listed on
the color chart. Check with your timer before you proceed. 6.
Dip all of the test strips into the urine to wet each pad and
immediately remove the strip.
Timer: start the time. 7. Gently tap the strip on the absorbent
paper to remove the excess urine. 8. Hold the test strip near the
color blocks on the bottle. Keep the bottle and the test strip
level (horizontal) or the color will bleed between the color
blocks. 9. Do NOT let the test strip touch the bottle! 10. Hold the
test strip near the laminated color block and compare each test pad
to the
corresponding row of color blocks. Be sure and read each pad at
the time shown! 11. Hold the test strips close to the color and
match them as precisely as possible. 12. Report the lab results to
your data recorder.
a. Do not record them yourself until after your gloves are
removed and your hands are washed.
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Urinary System Physiology - 6
Preparing a slide for Microscopic Examination We will be
preparing 2 different samples for microscopic examination. Supplies
at the slide station: Disposable pipette Sedistain
Cenislide tube and cap Cenislide Microscope stage holder
Glass microscope slide a cover slip
Sharpie
Cenislide centrifuge Preparing a slide using the CeniSlide
system 1. Obtain a clean centrifuge tube and cap. 2. Pipette the
urine from the bottom of the sample into a centrifuge tube to the
fill line. 3. Add one drop SediStain to the centrifuge tube. 4.
Secure the cap on the tube, label the tube with your table number,
and place it in the
centrifuge at the front desk. Always place tubes in opposite
pairs so the rotor is balanced. 5. The instructor will check that
the centrifuge is balanced and then spin the tubes for the
required time. 6. When you retrieve your centrifuge tube, place
the tube into the microscope slide holder for
examination. 7. After viewing your sample in the microscope,
dispose of your slide and all urine-
contaminated items in the large red biohazard container in the
lab.
Preparing a Microscope slide 1. Place a SMALL drop of Sedistain
on a clean microscope slide. 2. Very carefully draw up 1 or 2 drops
of the urine sample from the bottom of the container
into a pipette. 3. Place a drop over the drop of Sedistain from
#1. If there is any sample left in the pipette,
return it to the sample tube. 4. Gently lower a cover slip onto
the droplet. 5. Dispose of the pipette into the Biohazard
container. 6. Set up your microscope with high contrast by closing
the iris diaphragm and lowering the
condenser of the microscope.
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Urinary System Physiology - 7
Laboratory Procedures Urine Handling Precautions: As with all
human bodily fluids, there is a chance of transmission of
infectious diseases. As a result, you should always wear latex
gloves when handling urine samples and DO NOT touch table surfaces,
lab manuals, or writing utensils while you have gloves on. EXERCISE
1: The Effects of Beverage Intake on Urine
At the very beginning of lab, all of the subjects will be asked
to go to the bathroom and empty their bladder. This sample will not
be saved.
1. Your TA will post the first name, weight (kg), height (cm),
age, and sex for each subject volunteering for this experiment. Be
sure to record these data in the spaces provided on your data
sheet.
2. After 30 minutes, each subject will collect his or her
baseline (time 0) sample in a clean, dry beaker that has been
previously weighed.
a. The subject will go to the bathroom and urinate into the
beaker, catching all of the urine while trying to completely empty
the bladder.
b. The subject will bring the entire sample back to the lab
where it will be measured. 3. At this time, the subjects will be
given their drinks, which must be consumed in 5 minutes.
Note the time the beverages are completed as time 0. 4. Be sure
and keep track of time and take your urine samples at 30-minute
intervals for a total
of 4 samples (including the initial sample). 5. For each sample
you will need to record the following:
Total Urine Sample mass (g): Before you begin, you need to zero
(tare) the scale. Place the beaker in the scale and record the mass
in Table 2. (1 g =1ml) Urine color: Compare the color to the color
chart and record your observations. Specific Gravity: Test the
specific gravity using the refractometer.
6. Make sure all of the data were recorded correctly for that
sample and dispose of the urine by pouring it into the large
collection container on the front desk.
7. Rinse and dry the beaker and place it on the absorbent paper.
8. Repeat the previous steps for the other samples. 9. After
collecting a sample at all time intervals, make two graphs showing
urine volume over
time and specific gravity over time. Insert these graphs into
your electronic data sheet in the location specified.
EXERCISE 2: Urinalysis with Microscopic Examination 1. Get one
volunteer from each table to obtain a free-catch, midstream urine
sample in the
bathroom using the Urine sample collection instructions on the
next page. 2. Your TA will divide up the samples and bring one to
your table. 3. For your sample you will need to do the
following:
Subject Reminder: Subjects should limit fluid and salt intake on
the day of the experiment and do not drink anything 2 hour prior to
lab.
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Urinary System Physiology - 8
Urine sample collection Collect a sample of urine in a clean or
sterile
container. About 1 - 2 ounces of urine is needed for a test.
Remove the container from the urine stream without stopping the
flow. You may finish urinating into the toilet bowl.
Replace the cap and bring the sample to the lab and place the
sample in the ice chest outside the lab next to the door.
a. Record urine color and turbidity: Compare the color to the
color chart and record your observations.
b. Specific Gravity: Test the specific gravity using the
refractometer.
c. Follow the Chemical Test Strip Testing Procedures.
4. Record your results in Table 3 of your data sheet.
How to scan your glass slide under the microscope: 1. Place the
glass slide under the scope
and begin the examination under low power.
a. Be sure to use low light (adjust the iris and condenser). Too
much light makes the cellular and crystalline elements harder to
see.
b. Scan the slide under low power to locate areas of interest.
Look for casts just inside the perimeter of the cover slip.
2. Then switch to 40X magnification and examine ten random
fields in the central part of the coverslip.
a. Count the numbers of red blood cells and white cells in each
and report the range of findings. If the field is covered with
cells, report as "TNTC" (too numerous to count) or "packed."
b. Record these results in Table 4 of your data sheet. 3. Make a
sketch on the data table of any sediment particles you find.
a. Label your sketched items as cells, crystals, droplets, or
artifacts. b. The Explanation of Urinalysis Results section of the
lab manual contains pictures of
the most common things you may see on the urine. 4. Repeat Steps
1-3 for the CeniSlide tube and record your results in Table 5 of
your data sheet. EXERCISE 3: Case Studies Use the patient profiles
in your data sheet to complete the Case Studies in your data sheet.
CLEAN UP
Make sure you are finished with your sample. Pour the urine
sample into a waste container at the front desk. This waste
container will be flushed down the toilet at the end of the
lab.
Dispose of your glass slides and cover slips in the sharps
container. Disposable items such as urine sample containers,
absorbent paper, gloves, and pipettes will
need to be disposed of in the biohazard bags. Place all
glassware that is reused (like beakers) in the 10% bleach solution
in the 5-gallon
bucket at the front of the room. Make sure the refractometer is
clean and dry. Wipe down microscopes with alcohol pads. Spray and
wipe all surfaces with disinfectant. Replace absorbent paper on all
surfaces.
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Urinary System Physiology - 9
Section no. __ Group Member Names (last, first): Place an *
after the name of the typist
LABORATORY DATA SHEET FOR TAKING NOTES AND DRAFTING YOUR
RESPONSES
EXERCISE 1: The Effects of Beverage Intake on Urine Table 1:
Subject Data
Subject #1: Consumes small volume of water First Name: Sex: Wt.
(kg): Ht. (cm): Age:
Subject #2: Consumes large volume of water First Name: Sex: Wt.
(kg): Ht. (cm): Age:
Subject #3: Consumes Gatorade
First Name: Sex: Wt. (kg): Ht. (cm): Age:
Subject #4: Consumes Gatorade with salt First Name: Sex: Wt.
(kg): Ht. (cm): Age:
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Urinary System Physiology - 10
Table 2: The effects of beverage intake on the urine volume,
color, and specific gravity
Elapsed time (min)
Subject
Total Urine
sample mass (g)
Beaker weight
(g)
Urine volume (ml)
(Total urine sample beaker
weight)
Urine color
Specific gravity
0
Subject #1 Subject #2 Subject #3 Subject #4
30
Subject #1 Subject #2 Subject #3 Subject #4
60
Subject #1 Subject #2 Subject #3 Subject #4
90
Subject #1 Subject #2 Subject #3 Subject #4
Using the data in Table 2, create two graphs USING EXCEL
depicting the four subjects urine volume over time and the four
subjects specific gravity over time. Be sure to include a legend
and proper figure title. Insert these graphs here: Insert Graphs
here 1. Describe the trends in the graphs of urine volume and
specific gravity between the 4 subjects
in Exercise 1.
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Urinary System Physiology - 11
2. Compare the urine results from 2 water subjects. Which had
the highest urine volume?______ Which had the lowest specific
gravity? ___________ Is this what you expected? Why or why not?
Explain.
3. Compare the urine results from the Gatorade subjects. Which
had the highest urine
volume?______ Which had the lowest specific gravity? ___________
Is this what you expected? Why or why not? Explain.
EXERCISE 2: Urinalysis with Microscopic Examination
Table 3: Chemical Test Strip Testing
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Urinary System Physiology - 12
Table 4: Microscopic Examination of Sediment on glass slide with
stain
Field RBC's WBC's Other
1
2
3
4
5
Slide 1
Sketch area:
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Table 5: Microscopic Examination of Sediment on CeniSlide
Field RBC's WBC's Other
1
2
3
4
5
Slide 1
Sketch area:
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EXERCISE 3: Case Studies Use the following patient histories and
urinalysis results obtained for the following individuals to answer
the corresponding questions in terms of how the kidney works. There
is a table outlining the clinical significance of each test on the
last page which will be very helpful for this exercise. Patient A-
This patient is a 25-year-old male who is complaining that he needs
to go all of the time, but only produces a small amount of urine
each time (
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Urinary System Physiology - 15
Patient B- This patient is a 28-year-old male with a height of
57 and weight of 357 lbs. He complains of insatiable thirst,
frequent urination and lethargy. Test parameter Patient values
Normal Sample volume 3.8 L in 24 hours Color Yellow Specific
gravity 1.025 1.001-1.035 pH 6.0 4.6 to 8
Glucose (mg/dl) 500 negative (less than
30mg/dl) Protein (mg/dl) 8 less than 15mg/dl
Ketones (mg/dl) 15 negative (less than2mg/dl
acetacetoacetic acid) Bilirubin (mg/dl) negative Negative
Nitrites Negative Negative Leukocytes Negative negative Blood
Negative negative Sediment analysis Few cells and casts
6. List the abnormal findings. 7. What is your diagnosis?
____________________ What other tests could you perform to
confirm your diagnosis? 8. Why do you think this patients urine
volume is so high?
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Urinary System Physiology - 16
Patient C- This patient is an 18-year-old female who has come in
for a routine physical exam. She is asked for a urine sample and
has great difficulty producing a small amount of urine despite not
having urinated for several hours. She reported having 2 cups of
coffee and a donut for breakfast about 6 hours ago, but nothing
else to eat all day. Test parameter Patient values Normal Sample
volume 0.05 L Color Very dark Specific gravity 1.030 1.001-1.035 pH
6.5 4.6 to 8 Glucose (mg/dl) Negative negative (less than 30mg/dl)
Protein (mg/dl) Negative less than 15mg/dl Ketones (mg/dl) Negative
negative (less than2mg/dl
acetacetoacetic acid) Bilirubin (mg/dl) Negative negative
Nitrites Negative Negative Leukocytes Negative Negative Blood
Normal Negative Sediment analysis Contained few nucleated cells
9. List the abnormal findings. 10. What do you think is wrong
with this patient? Explain.
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Patient D- This patient is a healthy 19-year-old male that
wrestles competitively and has provided a urine test following his
wrestling competition. His normal body weight is 185 lbs., but for
this competition, he competed in the 172-lb. weight class. Test
parameter Patient values Normal Sample volume Normal Color Pale and
hazy Specific gravity 1.01 1.001-1.035 pH 6.8 4.6 to 8 Glucose
(mg/dl) Negative negative (less than 30mg/dl) Protein (mg/dl) Trace
less than 15mg/dl Ketones (mg/dl) 30 negative (less than2mg/dl
acetacetoacetic acid) Bilirubin (mg/dl) Negative Negative
Nitrites Negative Negative Leukocytes Negative Negative Blood
Negative Negative Sediment analysis Few casts
11. List the abnormal findings. 12. How are ketones generated?
13. Can you explain the abnormal findings in this patients
urine?
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Urinary System Physiology - 18
Patient E- This patient is a 38-year-old vegetarian. He is
complaining of mild irritation during urination.
14. What type of crystals are described in the sediment
analysis? 15. List the abnormal findings. 16. How does this
patients diet affect his urinalysis?
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Urinary System Physiology - 19
Conclusions 1. Hormonal control of water and ion reabsorption in
the kidney helps us regulate the specific gravity and volume of
urine excretion. How does the body control urine output and
concentration? 2. How do the different beverages alter the blood
plasma osmolarity and ultimately the urine output and specific
gravity? Be sure to include how changes are sensed by the body and
how it responds to maintain homeostasis. 3. The following table
represents the osmotic solution values in mOsm-units: SOLUTION
OSMOLARITY [mOsm] Water 10-20 Sweat 170-220 Gastric Fluids 280-303
Blood Serum 300 Gatorade** 290-303 Pepsi-Cola 568 Coca-Cola 650
Fruit Juice 690 Explain why fruit juice, Coca-Cola, or Pepsi-Cola
would not be effective in rehydrating a dehydrated person.
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Urinary System Physiology - 20
Physical Examination Results
Test Normal ranges Clinical significance
Urine Color
Clear, Hazy or
Straw (for our lab it is a number)
The color of urine is related to its concentration. The color of
non-pathological urine varies widely from colorless to deep yellow;
the more concentrated the urine, the deeper the color. By-products
from the breakdown of hemoglobin are present in the urine and can
greatly affect the color. Furthermore, some dietary factors can
alter the color of the urine (ie. Multi-vitamins, vegetables and
some food dyes). For instance, students who take B-vitamin
supplements will have their urine quickly turn bright yellow
following ingestion of Vitamin B.
Turbidity
Clear, (should NOT be cloudy!)
Normally, freshly voided urine is clear. When urine is allowed
to stand, amorphous crystals, usually urates, may precipitate and
cause urine to be cloudy, so the time the sample was taken and the
time it was analyzed should be considered. If a fresh sample is
cloudy (turbid) it may be an indicator of infection and should
always be followed up by a microscopic exam to explain the
turbidity!
Volume varies Although the volume of a random specimen is
clinically insignificant, the volume of specimen received should be
recorded for purposes of documentation and standardization.
Test Normal ranges Clinical significance of Chemical test strip
results
pH 5.0 to 9.0 Measurement of urinary pH is a useful for managing
renal stones or crystals. Uric acid stones form in acidic urine and
are more soluble in alkaline urines. Alkaline urine will
precipitate calcium or calcium phosphate crystals, while acidic
urine
will tend to dissolve them.
Protein up to 100 mg /day
Protein is not normally present in urine because it is too large
to pass through the filtration barrier. Most of the urine protein
is albumin from the plasma. Smaller-molecular-weight proteins such
as globulins may also be present in urine. Proteinuria (excess
urinary protein) can be the result of either increased filtration
at the glomerulus or decreased tubular reabsorption. Protein in
urine can be seen with vigorous exercise, muscle wasting, and
pregnancy. It can also result from bacterial infection and
glomerular damage. Renal disease can cause the filtration barrier
to become leaky to protein, which increases glomerular filtration
and can also lead to increased urine volume.
glucose not
normally present
Glucose is not normally present in the urine because it is
completely reabsorbed in the proximal tubule. Temporary elevation
of glucose excretion measurable by test strips can occur after
treatment with some drugs, cases of shock and
during pregnancy. Repeated positive testing is almost always
diagnostic for diabetes. Glucose in urine attracts water by
osmosis, increasing the urine volume. Diabetics urinate frequently
and are excessively thirsty as a result.
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Urinary System Physiology - 21
Ketones not
normally present
Ketones are by-products of the metabolism of fat. Ketosis and
ketonuria (excess ketones in the urine) are characteristic of
starvation, various metabolic disorders, and diabetes. For
diabetics the production of ketones results from the inability to
properly regulate insulin, which plays a key role in the metabolism
of fats. This catabolism is incomplete, resulting in the
formation of large amounts of ketones.
Blood and Myoglobin
not normally present
Blood, often referred to as occult blood (meaning mysterious
origin), indicates bleeding somewhere in the urinary system and is
an abnormal finding. A positive test indicates the presence of red
blood cells in the urine (hematuria), free
hemoglobin in the urine (hemoglobinuria), or rapid breakdown of
muscle (myoglobinuria). The peroxidase assay cannot distinguish
between the presence of hemoglobin or myoglobin in urine, so a
positive test should be followed with other
testing including a sediment analysis.
Bilirubin not
normally present
Red blood cells in the body live for about 120 days, after which
time they are broken down and the hemoglobin they contain recycled
in a complex process that results in formation of bilirubin.
Bilirubin is formed in the liver and excreted with the bile into
the intestine. The presence of bilirubin in the urine indicates
blood levels that are too high, either because excessive numbers of
red blood cells are being broken down (hemolytic anemia, infection
or exposure to lysing agent) or because the liver is failing to
properly metabolize the hemoglobin (hepatitis, cirrhosis, or bile
blockage due to gall stones).
Uro-bilinogen
2 to 10 mg/L
This is another by-product of the breakdown of hemoglobin. A
fresh specimen is essential because it is a light-sensitive
compound. Due to the variable excretion pattern and the rapid
breakdown in light, the clinical value of this test is
controversial and all significant results should be confirmed by
other methods.
Nitrite not
normally present
Normally there is no nitrite in urine, which is a product of the
bacterial reduction of nitrate. Therefore, a positive result is
indicative of a bacterial infection. If this is associated with
painful urination, the infection is located in the lower urinary
tract (urethra or bladder). Infections in the kidney do not
normally produce pain during urination. The amount of nitrite
formed depends on many things, including the type of bacteria,
how long the urine is stored in the bladder, and the presence of
nitrate in the diet.
Leukocyte not
normally present
The intensity of the color reactions is proportional to the
number of leukocytes in the specimen. The assay will detect both
lysed and intact leukocytes. Urine specimens that are test positive
by the reagent strip test need to be examined microscopically.
Specific Gravity
1.000-1.035
This is an estimate of specific gravity that is measured using
special indicators whose colors vary from blue-green to
yellow-green. However, this is an estimate and abnormal results
should be confirmed using specialized equipment.
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Urinary System Physiology - 22
Microscopic Examination
image Clinical significance of Microscopic Examination
Leukocytes
Associated with the inflammatory process in or adjacent to the
urinary tract. Presence of many WBCs in urine, especially in
clumps, is strongly suggestive of acute infection such as
pyelonephritis, cystitis, or urethritis.
Erythrocytes
RBCs normally dont appear in urine, but presence of 1-2 RBCs per
high powered field is not abnormal. High amounts of RBCs needs to
be evaluated as it could be benign as an unclean catch from a
female during menstruations or something more serious such as
hematuria.
Mucus
Mucus is a normal finding and is not clinically significant.
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Test Image Clinical significance of Microscopic Examination
Hyaline casts
Hyaline casts are the most frequently occurring casts in urine.
They are colorless, homogeneous, transparent, and usually have
rounded ends. These may be increased after strenuous exercise and
are formed when protein solidifies in the nephron.
Red cell casts
Red cell casts indicate renal hematuria. Red blood cells may
stick together and form red blood cell casts that can appear brown
to almost colorless. The presence of oddly shaped red blood cells
in the urine suggests a glomerular disease such as
glomerulonephritis, as the odd shape is caused by the passage of
the cells through a distorted and abnormal glomerular
structure.
White cell casts
White cell casts are present in renal infection and in
noninfectious inflammation. The majority of white blood cells that
appear in casts are hypersegmented neutrophils.
Granular casts
Granular casts almost always indicate significant renal disease.
Granular casts that contain fine granules may appear grey or pale
yellow in color. Granular casts that contain larger coarse granules
are darker. These casts often appear black because of the density
of the granules.
Waxy casts
Waxy casts result from the degeneration of granular casts. Waxy
casts have been found in patients with severe chronic renal
failure, malignant hypertension, and diabetic disease of the
kidney. Waxy casts appear yellow, grey, or colorless. They
frequently occur as short, broad casts, with blunt or broken ends,
and often have cracked or serrated edges.
Epithelial cast
Epithelial casts are rarely seen in urine because renal disease
that primarily affects the tubules is infrequent. Few epithelial
cells may often be observed as a result from sloughing of old
cells. A significant increase may be indicative of inflammation of
the urinary tract in the area from which the cells are derived..
Epithelial casts may
be arranged in parallel rows or haphazardly.
Fatty casts
Fatty casts are seen when there is fatty degeneration of the
tubular epithelium, as in degenerative tubular disease. Fatty casts
also result from lupus and toxic renal poisoning. A typical fatty
cast contains both large and small fat
droplets. The small fat droplets are yellowish-brown in
color.
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Urinary System Physiology - 24
Test Image Common Crystals found in Microscopic examination of
Urine
Amorphous urates
Amorphous urates are normal in urine. Appearance: often appear
in noncrystalline amorphous form. Have yellowish-brown (pinkish)
granular
appearance. In urine with uric acid in it, amorphous urates will
precipitate out of solution upon refrigeration. They appear
as a heavy pink sediment and impart acloudy to turbid appearance
of the mixed urine. Amorphous urates will re-solubilize when heated
at 60oC
Triple Phosphate Crystals
Common, colorless, coffin-lid prism Can be present in neutral
and alkaline urines. Frequently found in normal urine but can also
form urinary calculi.
.
Calcium oxalate
Colorless octahedrons found in acidic urine. Calcium oxalate
crystals in the urine are the most common constituent of human
kidney stones that can obstruct tubules, causing significant damage
and pain. Twelve
percent of males form stones, with those between the ages of 30
and 50 at greatest risk for stone disease. Oxalate is common in
nuts and dark green leafy vegetables. It is the reason rhubarb
leaves are considered toxic. When pets or children drink
antifreeze, oxalate is formed from the ethylene glycol in
antifreeze by metabolism in the
liver. In both cases, kidney failure due to massive tubular
damage is the cause of death. To avoid kidney stones, at risk
individuals are urged to keep urine volumes high, and oxalate
levels and urine pH low. This reduces the
concentration and increases solubility of calcium oxalate in
tubular fluid.
Uric Acid
Uric acid is the final oxidation product of purines, a natural
substance found in food. Food items like meat, dried beans,
anchovies, sea fish, oatmeal, etc. are purine rich and
over-consumption of purine rich foods increases uric
acid levels in the body. If it reaches above the specified
limit, the condition is known as hyperuricemia. Small crystals pass
through urine and the severity of symptoms vary with increase in
uric acid content of urine.
Most common disorders associated with high levels of uric acid
are gout, Lesch-Nyhan syndrome,
cardiovascular disease, diabetes, uric acid stone, urolithiasis,
and metabolic syndrome.
Hippuric
Hippuric not often diagnosed in urine analysis, but they are
often associated with a neutral pH. Associated with diets high in
fruits and vegetables that contain large quantities of benzoic
acid
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Urinary System Physiology - 25
Ca Phosphate
These crystals may be present in normal urine, but they may also
form calculi.
Ca Carbonat
e
Calcium carbonate crystals are normal in urine Appearance:
small, colorless granules or dumbbells.
Not clinically significant but can be confused with other
elements. A unique feature of calcium carbonate is that the
crystals effervesce with hydrochloric acid or acetic acid. This can
help to confirm the presence of calcium
carbonate in the urine.
Ammonium Biurate
Ammonium biurate crystals are normal in urine. Appearance:
yellowish-brown, can be seen in a "thorn apple" shape (round with
thorny projections) or in
spherical form. Ammonium biruate crystals can be seen in normal
urine. However, the presence of ammonium biurate crystals
especially in combination with a urine pH 9.0 or higher usually
indicates an old or poorly preserved specimen. Best practice is to
NOT report any urinalysis results on the sample as it has been
compromised. A recollect
should be requested.
Bilirubin
Bilirubin crystals are abnormal crystals in urine. Appearance:
Yellow-brown needles or granules. They are frequently attached to
the surface of cells.
Bilirubin crystals are seen in several hepatic disorders. The
appearance of bilirubin crystals should be accompanied by a
positive biochemical test for bilirubin (reagent
test pad and Ictotest).
Cystine
Cystine Crystals are abnormal in urine. Appearance: colorless,
thin, hexagonal plates
Cystine crystals are found in the inherited condition,
cystinuria. Cystine crystals are the most frequent cause of kidney
stones in children.
The presence of cystine crystals should be confirmed by
cyanide-nitroprusside test (turns red-purple)
Leucine crystals are abnormal in urine Appearance: yellow-brown
spheroids with concentric rings around the outer edge and radial
striations in the
center. Leucine crystals may be seen in liver disorders in which
amino acid metabolism is impaired.
The presence of leucine crystals is often accompanied by a
positive biochemical test for bilirubin and is often accompanied by
tyrosine crystals in the same sediment.
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Urinary System Physiology - 26
Tyrosine crystals are abnormal in urine Appearance: colorless to
yellow-brown single needles. Also seen as sheaves or rosettes.
Tyrosine crystals may be seen in tyrosinemia and in certain
liver disorders in which amino acid metabolism is impaired.
The presence of tyrosine crystals is usually accompanied by a
positive biochemical test for bilirubin and are often accompanied
by the presence of leucine crystals in the sediment.
Sulfanomide crystals are considered abnormal in urine.
Appearance: flat needles, sheaves of small needles or as spheroids.
Often brown in color.
The presence of sulfanomide crystals usually indicates
administration of the drug and not necessarily a pathological
condition. However, their presence is also associated with kidney
stone formation.
Cholesterol crystals are abnormal in urine Appearance: clear,
flat plates with notched corners.
The appearance of cholesterol is associated with the Nephrotic
Syndrome. Cholesterol crystals are accompanied by a positive
biochemical test forprotein. They usually appear after the
urine sample has been refrigerated and may be accompanied by
oval fat bodies, fatty casts, and free fat droplets in the
sediment.
Background: Urinary System PhysiologyTable 1: Subject Data