lab activity 32
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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. Filtrate. - PowerPoint PPT PresentationTRANSCRIPT
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Lab Activity 32
Urinalysis
Portland Community CollegeBI 233
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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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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. Leukocytes2. Nitrite3. Urobilinogen4. Protein5. pH6. Blood
6. Blood
7. Ketones
8. Bilirubin
9. Glucose
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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
Bilirubin: indicates the presence of liver disease or biliary obstruction or erythrocyte destruction (hemolytic anemia)
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
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 mellitus)
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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• Or low water intake
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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
pH: large range 4.5 to 8.2 (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
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
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
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
Leukocytes: Indicates infection or inflammation
Normal=negative• Pyuria: Leukocytes in urine• Cystitis: Bladder infection• Pyelonephritis: Kidney infection
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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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Organisms in urine
• Some organisms commonly found in urine:• Yeasts
• Trichomonas vaginalis- common protozoan infection
• Candida albicans- causes vaginal yeast infections
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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.
Dysmorphic RBC
Crenated RBC
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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 Epithelial Cells
• Too many squamous cells: suggest contamination, poor specimen collection
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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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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.
• Causes: Low flow rate, high salt concentration, and low pH, all of which favor protein denaturation and precipitation of the Tamm-Horsfall protein.
Hyaline Casts appear Transparent
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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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Renal Calculi
• Kidney Stones• Caused by mineral
buildup in the kidneys or by amino acid or amino acid oxidative product deposition.
• The stones are masses of crystals that fuse; where they can block the ureter.
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The End