Renal function []

Urinalysis
Urinalysis
• an array of tests performed on urine
• one of the most common methods of medical
diagnosis
• easy to perform, non-invasive
• fresh urine (midstream urine collection, 30-60 ml)
or 24 h urine
Reasons to perform
• Routine medical evaluation:
–
–
–
–
general yearly screening,
assessment before surgery (pre-operative assessment), admission to hospital,
screening for kidney disease,
chronic diseases: diabetes mellitus, hypertension (high blood pressure), liver disease
• Assessing particular symptoms:
–
–
–
–
–
–
–
–
abdominal pain,
jaundice,
thirst,
weight loss
painful urination,
flank pain,
fever,
blood in the urine
• Diagnosing medical conditions:
–
–
–
–
–
urinary tract infection,
kidney infection,
kidney stones,
kidney impairment,
kidney inflammation (glomerulonephritis)
• Monitoring disease progression and response to therapy:
–
–
diabetes related kidney disease,
blood pressure related kidney disease
Urinalysis
• macroscopic analysis
–
–
–
–
quantity
color
odour
clarity
• biochemical examination
–
–
–
–
specific gravity / density
pH
blood, protein
glucose, ketones, bilirubin, urobilinogen
• microscopic assessment
Macroscopic analysis
• Quantity
– 1500-2000 ml daily – normal water intake
– under 500 ml daily: oliguria
– under 100 ml daily: anuria
– above 2500 ml daily: polyuria
Macroscopic analysis
• Color
– transparent solution
– can range from colorless to amber, a pale yellow
– physiological: the color comes primarily from the
presence of urobilin (← heme ← hemoglobin ←
aging red blood cells)
Macroscopic analysis
• Abnormal color:
–
–
–
–
–
–
–
–
–
dark yellow ← dehydration
light orange ← B vitamins
orange ← drugs (rifampicin, phenazopyridine)
dark orange to brown ← jaundice,liver diseases
black or dark-colored (melanuria) ← melanoma
reddish or brown ← porphyria, hematuria
pink or reddish ← consumption of beets
greenish ← consumption of asparagus
fluorescent yellow / greenish ← dietary supplemental
vitamins (B vitamins)
Macroscopic analysis
• Odor
– described as urinoid
– can be strong in concentrated specimens, does not
imply infection
– fruity or sweet odor ← diabetic ketoacidosis
– ammoniacal odor ← alkaline fermentation
– pungent odor ← UTIs
– other abnormal odors : medications and diet,
gastrointestinal diseases
Macroscopic analysis
• Turbidity / Clarity
← bacterial infection
← proteinuria
← crystallization of salts:
• phosphates – clears if 10% acetic acid is added
• urates – clears by heating
• oxalates – clears if HCl is added
Biochemical properties
• aqueous solution:
–
–
–
–
–
–
–
> 95% water
urea 9.3 g/l
chloride 1.87 g/l
sodium 1.17 g/l
potassium 0.750 g/l
creatinine 0.670 g/l
other dissolved ions, inorganic and organic compounds
• some diseases alter the quantity and consistency
of the urine
– e.g. glucose ← diabetes
Biochemical properties
• Density / specific gravity
• normal urine specific gravity: 1.015-1.025
• high values:
← the kidney is actively reabsorbing water ← fluid
depletion or renal failure due to reduced renal
perfusion
← abnormal urinary compounds – e.g. glucose in
diabetes
• low values:
← failure of the renal tubules to concentrate urine
usually associated with high urine volumes
Biochemical properties
• Acidity (pH)
– normally acid (pH = 5-6)
– pH can vary between 4.4-8.4
– pH can be modified by drugs, diseases (diabetes,
renal tubular acidosis), urinary infections
– pH ↑: drugs (acetazolamide, potassium citrate, and
sodium bicarbonate), diet high in citrus, vegetables
– pH ↓: drugs (ammonium chloride, chlorothiazide
diuretics, methenamine mandelate), diet high in meat
or cranberries
– modified pH can lead to stone formation
Biochemical properties
• Demonstration of proteins
• macromolecules → they are not normally present in
measurable amounts in the glomerular filtrate or in the
urine
• proteinuria
← the permeability of the glomerulus is abnormally
increased
← the function of the proximal convolute tube is altered
• pathological if > 30mg/24 h
Biochemical properties
• Esbach's test
– put 5 ml of urine in a test tube
– add 1 ml of Esbach's reagent (10g picric acid and 20
g citric acid dissolved in 1 l of water)
– appearance of a white-yellow precipitate indicates the
presence of proteins
Biochemical properties
• reaction with trichloroacetic acid
– put 5 ml of urine in a test tube
– add 1 ml of trichloroacetic acid (10% or 20%)
– appearance of a flocculent precipitate indicates the
presence of proteins
Biochemical properties
• Qualitative determination of urobilinogen
• Ehrlich's test
– put 5 ml of fresh urine in a test tube
– add 3-4 drops of Ehrlich reagent (pdimethylaminobenzaldehyde in HCl)
– after 1-2 min pink or faint red color that intensifies on
heating indicates increased urobilinogen levels
Biochemical properties
• Qualitative determination of reducing sugars
• Nylander's test
– a test for glucose in the urine using a solution containing
bismuth subnitrate which forms a black precipitate in a
positive reaction
– put 5 ml of urine in a test tube
– add 1 ml of Nylander's reagent (potassium sodium
tartrate, sodium hydroxide, and bismuth subnitrate in
water) and heat for 4 min
– in the presense of a reducing sugar the bismuth is
reduced and forms a black precipitate
Microscopic assessment
• the urine sediment is centrifuged and examined using
low power microscope (at least 10 microscope fields)
– cells:
• epithelial cells
• red blood cells
• white bloods cells
– crystals
– casts
– bacteria or yeast
• in counting chambers using urine produced over a
determined time (ex. 180 minutes)
Microscopic assessment
• red blood cells
–
–
–
–
1-5 RBC/HPF (400x) or 1000 RBC/min
renal origin: deformed, faded color
from the urinary tract: normal shape and color
inflammation, injury, or disease in the kidneys or
elsewhere in the urinary tract
Microscopic assessment
• white blood cells:
–
–
–
–
3-5 WBC/HPF or 2000 WBC/min
usually in groups of 10-15 cells
if they form casts: renal origin
increase ← infection or inflammation in the urinary
tract
Microscopic assessment
• epithelial cells
– from the bladder: transitional epithelial cells
– from the external urethra: squamous epithelial cells
– increase ← urinary tract infections, inflammation,
malignancies
Microscopic assessment
• Urinary casts:
– cylindrical structures produced by the kidney
– formed in the distal convoluted tubule and collecting
ducts of nephrons
– types:
•
•
•
•
•
•
hyalin
red cell
granular
epithelial
waxy
fatty
Microscopic assessment
• hyaline casts:
– the most frequently occurring
– colorless, homogeneous, transparent, usually
rounded ends
Microscopic assessment
• red cell casts:
– ← renal hematuria
– brown to almost colorless
– usually diagnostic of glomerular disease
Microscopic assessment
• white cell casts:
– indicative of inflammation or infection of the kidneys
Microscopic assessment
• granular casts:
– indicate significant renal disease
– color: black to pale yellow
Microscopic assessment
• epithelial casts:
– rare; in renal diseases that primarily affects the
tubules
Microscopic assessment
• waxy casts:
– result from the degeneration of granular casts
– ← severe chronic renal failure, malignant
hypertension, and diabetic disease of the kidney
– short, broad casts, with blunt or broken ends
Microscopic assessment
• Crystals
– solutes can form crystals if:
• the urine pH is increasingly acidic or basic;
• the concentration of dissolved substances is
increased; and
• the urine temperature promotes their formation
– they may group together to form kidney
"stones" or calculi