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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.

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Lab Activity 32

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Lab Activity 32


Portland Community College

BI 233


  • 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


  • Contains mostly water along with excess ions (mostly sodium and potassium), glucose, amino acids and nitrogenous waste products.

  • Lacks RBCs and large plasma proteins.


  • 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


  • 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


  • Normally contains about 95% water

  • Various ions (sodium, potassium, sulfate, calcium, magnesium, bicarbonate)

  • Amino acids, lipids and carbohydrates

  • Urea, uric acid and creatinine

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.

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

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

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

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

“Dipstick" method: chemical reactions cause color changes on ten different pads on the test strip.












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

Dipstick Urinalysis Interpretation

Nitrite: Might indicate bacterial infection with gram-negative rods (like E. coli)

If bacteria are present, they convert nitrates to nitrites


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

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

Dipstick Urinalysis Interpretation

Leukocytes: Indicates infection or inflammation


  • Pyuria: Leukocytes in urine

  • Cystitis: Bladder infection

  • Pyelonephritis: Kidney infection

Dipstick Urinalysis Interpretation

Blood: Almost always indicates pathology because RBC are too large to pass through glomerulus


  • Hematuria: Blood in urine

  • Possible causes: Kidney stone, infection, tumor

  • Caution: Very common finding in women because of menstruation.

Dipstick Urinalysis Interpretation

Protein: Usually proteins are too large to pass through glomerulus (Proteinuria usually represents an abnormality in the glomerular filtration barrier.)


  • Trace amounts normal in pregnancy or after eating a lot of protein

  • Albuminuria: Albumin in urine

  • 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

    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)

  • 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

    Chemical Analysis

    • Sulfates: Normal constituent of urine

      • The urinary sulfate is mainly derived from sulfur-containing 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.


    • 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

    Microscopic ExaminationPyuria: 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

    Microscopic ExaminationHematuria: 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

    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

    Microscopic ExaminationCasts

    • 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

    Microscopic ExaminationEpithelial Cells

    • Too many squamous cells: suggest contamination, poor specimen collection

    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. )

    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.

    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

    Calcium Oxalate Crystals

    • They can occur in urine of any pH.

    • Causes: Dietary asparagus and ethylene glycol (antifreeze) intoxication

    Uric Acid Crystals

    • High uric acid in blood (by-product of purine digestion/high protein diet)

    • Associated with gout (arthritis)

    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.

    Chemical Analysis

    • Urea: The end product of protein breakdown

    • Uric acid: A metabolite of purine breakdown

    • Creatinine: Associated with muscle metabolism of creatine phosphate.

    Microscopic ExaminationBacteria

    • 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

    The End

    The End

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