Week 7: Intro to UA

• Urinalysis

• Renal anatomy and physiology

• Nephron anatomy

• Urine collection and preservation

• Physical properties of urine• Color

• Appearance

• Specific gravity

• Volume

• Odor

• Foam

Urinalysis

• One of the oldest “lab” procedure• Diabetes mellitus vs

diabetes insipidus

• Examination of urine samples• Physical properties

• Chemical components

• Microscopic sediments

Renal Anatomy

• Kidneys• Renal artery and vein• Medulla• Cortex• Calyx

• Ureter• Bladder• Urethra• Adrenal glands

Nephron

• Functional unit of kidneys

• About one million per kidney

• Concentrate urine

• Filter blood

• Excrete waste products

Nephron Anatomy

• Afferent and efferent arterioles

• Glomerulus• Bowman’s capsule• Proximal convoluted

tubules• Loop of Henle• Distal convoluted

tubules• Collecting duct

Nephron Function

• Ultrafiltration of blood• 180 L/day of blood filtered• >80% reabsorbed• Antidiuretic hormone cause another 20%

absorption• 1-2 L/day urinary output

• Reabsorption of minerals and nutrients• Active secretion of waste

Antidiuretic Hormone ADH

• Also called vasopressin• Made in hypothalamus and secreted from posterior

pituitary• Increases porosity in distal tubule and collecting

duct• Lack of ADH result in d. insipidus• Unable to concentrate urine (isosthenuria):

constant specific gravity at 1.010

Normal Urine Contains…

• Urea from ammonia and CO2

• Uric acid from DNA metabolism

• Creatinine from muscle

• Electrolytes

Urine Collection

• Random• 12 hour or 24 hour timed• First morning void• Clean catch• Mid-stream• Fasting• Postprandial• Urethral catheter• Suprapubic aspiration

Decomposition of Urine

• Bacterial growth

• Ammonia or acid formation

• Change in pH

• Ketone evaporate

• Urobilinogen oxidized

• Bilirubin degradation with light

• Crystals

• Cells and casts lyse

• Change in color• Alkaptonuria

• Change in specific gravity

Urine Preservation

• Refrigeration up to 8 hours

• Thymol to prevent bacterial growth

• Formalin to preserve cells

• Acid or base to preserve compounds

More Terms to Study

• Polyuria

• Oliguria

• Anuria

• Dysuria

• Hematuria

• Glycosuria

• Proteinuria

• Bacteriuria

• Cylindruia

• Hemoglobinuria

Color

• Normal: shade of yellow (straw to amber)

• Urochrome, uroerythrin

• Yellow due to bile in jaundice

• Red due to Hb or myoglobin

• Black in alkaptonuria after light exposure

• Other color due to medication

Appearance

• Normal: clear to slightly hazy

• Cloudy to turbid due to microscopic sediments• White and red cells

• Bacteria and yeast

• Crystals

Specific Gravity

• Normal: 1.015 - 1.025 (wider range with random collection)

• Urinometer: true reading of specific gravity• Refractometer: use light refraction by

dissolved substances• Reagent strip: ionic concentration• Osmometer: most accurate measurement of

total dissolved substance

Refractometer vs Dipstix SG

• Refractometer measures dissolved substances• Each gram of glucose raises SG by 0.004• Each gram of protein raises SG by 0.003• Correction gives more accurate measure of

kidneys’ concentration ability

• Reagent strip measures ionic concentration• Urinary waste will ionize so good measure of

kidneys’ ability to concentrate• Non-ionizing substances: glucose, protein, IVP

Other Information…

• Volume: 600 - 1,600 mL per day• For timed collection only

• Foam: white• Yellow due to bile in

hepatitis

• Excessive due to proteinuria

Other Information…

• Odor: faintly aromatic• Foul due to bacterial growth• Fruity due to ketones• Maple Syrup Urine Disease• Other due to food or medication