Lab Activity 32
Urinalysis
Portland Community College
BI 233
Filtration
• Occurs in the renal
corpuscles: blood
pressure forces water
and small dissolved
molecules to move
from the glomerular
capillaries to the
capsular space and is
called the filtrate
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Filtrate
• Contains mostly water
along with excess ions
(mostly sodium and
potassium), glucose,
amino acids and
nitrogenous waste
products.
• Lacks RBCs and large
plasma proteins.
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Reabsorption
• Almost all the water
(99%)
• As well as glucose,
amino acids and
various ions.
• These are returned to
the blood by passing
from the renal tubules
to the peritubular
capillaries or vasa
recta
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Secretion
• Unwanted substances
such as metabolic
wastes, drugs and
excess ions (hydrogen
and potassium) are
removed from the
blood and enter the
renal tubules.
• Most occurs in DCT
and collecting ducts
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Urine
• Normally contains
about 95% water
• Various ions (sodium,
potassium, sulfate,
calcium, magnesium,
bicarbonate)
• Amino acids, lipids
and carbohydrates
• Urea, uric acid and
creatinine
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Universal precautions
• You will be examining the physical and
chemical characteristics of your own urine
sample
• Work with your urine only
• Wear gloves, safety eyewear, and a mask
• Clean spills with 10% bleach solution
• Anything that comes into contact with urine
goes into an autoclave bag.
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Physical Characteristics of Urine
• Color and transparency
• Clear, pale to deep yellow (due to urochrome)
• Concentrated urine has a deeper yellow/amber color
• A red or red-brown (abnormal) color could be from a
food dye, eating fresh beets, a drug, or the presence
of either hemoglobin or myoglobin.
• If the sample contained many red blood cells, it
would be cloudy as well as red.
• Turbidity or cloudiness may be caused by excessive
cellular material or protein in the urine
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Physical Characteristics of Urine
• Odor
• Fresh urine is slightly aromatic
• Standing urine develops an ammonia odor
• Some drugs and vegetables (asparagus) alter the
usual odor
• Elevated ketones smells fruity or acetone-like
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Physical Characteristics of Urine
• Specific gravity measures density of
urine compared to water
• Ranges from 1.001 to 1.035
• 1.001 is dilute
• 1.035 is concentrated
• Is dependent on solute concentration
• > 1.035 is either contaminated or
contains very high levels of glucose
• Patients who have received
radiopaque dyes or dextran can also
have high specific gravity
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Chemical Composition of Urine
• Urine is 95% water and 5% solutes
• Nitrogenous wastes include urea, uric acid,
and creatinine
• Other normal solutes include:
• Sodium, potassium, phosphate, and sulfate ions
• Calcium, magnesium, and bicarbonate ions
• Abnormally high concentrations of any
urinary constituents may indicate pathology
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Urinalysis
• “Dipstick" method:
chemical reactions
cause color changes on
ten different pads on
the test strip.
1. Leukocytes 6. Blood
2. Nitrite
7. Ketones
3. Urobilinogen 8. Bilirubin
4. Protein
9. Glucose
5. pH
6. Blood
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Dipstick Urinalysis Interpretation
pH: large range 4.5 to 8.0 (average is 6.0)
• The urine pH should be recorded, although it is seldom
of diagnostic value.
• Diet can alter pH
• Acidic: high protein diet, ketoacidosis
• Alkaline: vegetarian diet, UTI
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Dipstick Urinalysis Interpretation
Nitrite: Might indicate bacterial infection
with gram-negative rods (like E. coli)
If bacteria are present, they convert
nitrates to nitrites
Normal=negative
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Dipstick Urinalysis Interpretation
Bilirubin: indicates the presence of liver
disease or biliary obstruction
A small amount of bilirubin in urine is
normal excessive amounts is called
• Bilirubinuria: appearance of bilirubin in urine
• Yellow foam when sample is shake
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Dipstick Urinalysis Interpretation
Urobilinogen: Produced in the intestine from bilirubin. Gives
feces brown color
Normal=small amount
•
•
Absence: renal disease or biliary obstruction
Increased in any condition that causes an increase in
production or retention of bilirubin
• Hepatitis, cirrhosis or biliary disease
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Dipstick Urinalysis Interpretation
Leukocytes: Indicates infection or
inflammation
Normal=negative
•
•
•
Pyuria: Leukocytes in urine
Cystitis: Bladder infection
Pyelonephritis: Kidney infection
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Dipstick Urinalysis Interpretation
Blood: Almost always
indicates pathology
because RBC are
too large to pass
through glomerulus
Normal=negative
• Hematuria: Blood in urine
• Possible causes: Kidney stone, infection,
tumor
• Caution: Very common finding in women
because of menstruation.
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Dipstick Urinalysis Interpretation
Protein: Usually proteins are too large to pass through
glomerulus (Proteinuria usually represents an
abnormality in the glomerular filtration barrier.)
Normal=negative
•
•
Trace amounts normal in pregnancy or after eating
a lot of protein
Albuminuria: Albumin in urine
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Dipstick Urinalysis Interpretation
Glucose: In general the presence of glucose
indicates that the filtered load of glucose
exceeds the maximal tubular reabsorptive
capacity for glucose.
Normal=negative
(can occur
temporarily after eating a high carb meal or
during stress)
• Glycosuria: Glucose in urine
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Dipstick Urinalysis Interpretation
Ketones: Intermediate products of fat metabolism
• Urine testing only detects acetoacetic acid, not the
other ketones, acetone or beta-hydroxybuteric acid.
• Normal=negative or trace amounts
• Ketonuria: ketones in urine
• (Ketonuria + glucose in urine may indicate diabetes
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mellitus)
Urine sediments
• If a urine sample is
centrifuged, the
sediment can be
viewed
microscopically to
examine the solid
components.
• Some solids are
normally found in
urine
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Chemical Analysis
• Sulfates: Normal constituent of urine
• The urinary sulfate is mainly derived from sulfurcontaining amino acids and is therefore determined by
protein intake.
• Phosphates: Normal constituent of urine
• Important for buffering H+ in the collecting duct
• Chlorides: Normal constituent of urine.
• Major extracellular anion.
• Its main purpose is to maintain electrical neutrality,
mostly as a counter-ion to sodium.
• It often accompanies sodium losses and excesses.
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sediments
• Cells- small numbers
of epithelial cells that
are shed from various
regions of the urinary
tract.
• Large numbers of
WBSs and any
amount of RBCs are
abnormal usually
indicate disease
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Microscopic Examination
Pyuria: WBC in Urine
• Normal:
• Men: <2 WBCs per hi
power field
• Women: <5
• WBC generally indicate
the presence of an
inflammatory process
somewhere along the
course of the urinary
tract
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Microscopic Examination
Hematuria: RBC in Urine
• RBC's may appear normally
shaped, swollen by dilute
urine or crenated by
concentrated urine.
• The presence of
dysmorphic (odd shaped)
RBC's in urine suggests a
glomerular disease such as a
glomerulonephritis.
Crenated RBC
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Dysmorphic RBC
Microscopic Examination
Epithelial Cells
• Transitional epithelial
cells originate from the
renal pelvis, ureters,
bladder and/or urethra.
• Large sheets of
transitional epithelial
cells can be seen in
bladder cancer.
Squamous epithelial cell
Transitional epithelial cell
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Microscopic Examination
Casts
• Casts: hardened cell fragments formed in
the distal convoluted tubules and collecting
ducts
• Form when cells clump together
• Usually form when urine is acidic or
contains high level of proteins or salts
• Usually pathological.
• Can only be seen with microscopic
examination
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Microscopic Examination
Epithelial Cells
• Too many
squamous
cells: suggest
contamination,
poor specimen
collection
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White Cell Casts
• Usually indicates pyelonephritis (kidney infection)
• Other causes: Interstitial Nephritis (inflammation of the
tubules and the spaces between the tubules and the
glomeruli. )
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Red Cell Casts
• Red blood cells may stick together and form red
blood cell casts.
• Indicative of glomerulonephritis, with leakage of
RBC's from glomeruli, or severe tubular damage.
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Hyaline Casts
• Hyaline casts are
composed primarily
of a mucoprotein
(Tamm-Horsfall
protein) secreted
by tubule cells.
Hyaline Casts appear Transparent
• Causes: Low flow rate, high salt concentration, and
low pH, all of which favor protein denaturation and
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precipitation of the Tamm-Horsfall protein.
Calcium Oxalate Crystals
• They can occur in
urine of any pH.
• Causes: Dietary
asparagus and
ethylene glycol
(antifreeze)
intoxication
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Uric Acid Crystals
• High uric acid in blood (by-product of
purine digestion/high protein diet)
• Associated with gout (arthritis)
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Struvite Crystals
• Formation is favored
in alkaline urine.
• Urinary tract infection
with urease producing
bacteria (eg. Proteus vulgaris) can promote struvite
crystals by raising urine pH and increasing free
ammonia.
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Chemical Analysis
• Urea: The end product of protein breakdown
• Uric acid: A metabolite of purine breakdown
• Creatinine: Associated with muscle
metabolism of creatine phosphate.
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Microscopic Examination
Bacteria
• Bacteria are common in urine specimens (from
contamination)
• Therefore, microbial organisms found in all but
the most scrupulously collected urines should be
interpreted in view of clinical symptoms.
A = crenated RBC, B = RBC, C = bacteria
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The End
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