Download URINE ANALYSIS

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What is a urine analysis
Significance of physical, chemical, microscopical
& cultural characteristics of a urine.
Sample required.
Search for the following article:
◦ Urinalysis: a Comprehensive Review in the American
Family Physician Journal, 2005 March 15; 71 (6): 1153 1162.
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Complete urine analysis include:
◦ Physical
◦ Chemical
◦ Microscopic examinations and
◦ Culture &
◦ sensitivity testing
 Midstream
clean-catch technique.
 Refrigerate urine if not examined
promptly.
◦ Delay of > 2 hrs between collection and
examination often cause unreliable results.
 Abnormal
urine colour caused by:
◦ Foods
◦ Medications
◦ Metabolic products &
◦ Infections
◦ (See table 1 in urinalysis article)
 Cloudy urine often = precipitated phosphate
crystals in alkaline urine OR pyuria
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Normal odour for urine described as urinoid.
◦ Odour could be strong in concentrated specimens.
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Diabetic ketoacidosis :
◦ Urine = fruity or sweet smell.
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Alkaline fermentation:
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◦ Ammoniac odour after prolonged bladder retention.
UTI infection often:
◦ Pungent odour.
 Other
causes of abnormal odour:
◦ Gastointestinal-bladder fistulas (associated
with faecal smell)
◦ Cystine decomposition (sulfuric smell)
◦ Medication and diet (eg. Asparagus)
 Conveniet
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false positive/negative results could
be seen. (see table 2 in urinalysis article)
 Lets look at table 3 in article.
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Important insight into patient’s hydration status.
Reflects the concentrating ability of kidneys.
Normal = 1.003 – 1.030
Value < 1.010 indicates relative hydration
Value > 1.020 indicates relative dehydration.
Increased USG = glycosuria & syndrome of
inappropriate antidiuretic hormone.
Decreased USG = diuretic use, diabetes insipidus,
adrenal insufficiency, aldosteronism, impaired renal
function.
Intrinsic renal insufficiency, USG fixed at 1.010 ( SG of
glomerular filtrate)
Range 4.5 – 8.
 Normally slightly acidic (5.5 – 6.5) due to
metabolic activity.
 Ingestion of proteins & acidic fruits = cause
acidic urine.
 Diets high in citrate can cause alkaline
acidosis.
 Urinary pH generally reflects serum pH,
EXCEPT in patients with renal tubular
acidosis (RTA).
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Inability to acidify urine to pH, 5.5, despite
overnight fast & administration of acid load –
indicated RTA.
Type 1 (distal) RTA – serum is acidic but urine
alkaline – 2° to an inability to secrete protons into
the urine.
Type II (proximal) RTA – characterized by an
inability to reabsorb bicarbonate – initially results
in alkaline urine, but as filtered load of
bicarbonate decreases, urine become more acidic.
Determination of urinary pH – useful in the
diagnosis & management of UTI’s and calculi.
 Alkaline urine in patients with UTI suggests
presence of urea-splitting organisms, which
may be associated with magnesiumammonium phosphate crystals & can form
staghorn calculi.
 Uric acid calculi – associated with acidic
urine.
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American Urological Association
states – presence of 3/> RBC’s per HPF in 2 of
3 urine samples = definition of haematuria.
 Dipstick test for blood detects peroxidase
activity of erythrocytes.
 BUT myglobin & haemaglobin also catalyse
this reaction.
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◦ Positive test may therefore indicate haematuria,
myoglobin or haemoglobinuria.
Visualisation of intact RBC’s on microscopic
examination of urine – distinguish
haematuria from other conditions.
 Microscopic exam – detect RBC casts or
dysmorphic RBC’s.
 Haematuria divided into glomerular, renal
(nonglomerular) and urologic etiologies.
 See table 4
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Glomerular Haematuria
◦ Associated with significant proteinuria,
erythrocyte casts & dysmophic RBC’s.
◦ BUT 20% of patients with biopsy-proven
glomerulenephritis present with haematuria
alone.
◦ IgA nephropathy (Berger’s disease) – most
common cause of glomerular haematuria.
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Renal (nonglomerular) Haematuria:
◦ 2° to tubulointerstitial, renovascular, or
metabolic disorders.
◦ Often associated with significant proteinuria
BUT with no dysmorphic RBC’s or erythrocyte
casts.
◦ Further evaluation of patients with glomerular
& nonglomerular haematuria should include
determination of renal function and 24hr urine
protein or spot urinary protein-creatinine ratio.
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Urologic Haematuria
◦ Causes include tumors, calculi & infections.
◦ Urologic haematuria is distinguished from other
etiologies by the absence of proteinuria,
dysmorphic RBC’s and erythrocyte casts.
◦ Significant haematuria will not elevate the
protein concentation to 2+ - 3+ range on dipstick.
◦ 20% of patients with gross haematuria – urinary
tract malignancies
 Full work-up with cystocscopy & upper-tract imaging is
indicated in this condition.
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Urologic Haematuria
◦ Asymptomatic microscopic haematuria (without
proteinuria/pyuria):
 5 – 22% have serious urologic disease.
 0.5 – 5% have a genitourinary malignancy.
◦ Exercise-induced haematuria – relatively
common.
 Benign condition , associated with long running.
 Results of repeat urinalysis after 48 – 72 hrs should be
negative.
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Normal urinary proteins include:
◦ Albumin
◦ Serum globulins and
◦ Proteins, all secrected by the nephron.
Proteinuria = urinary protein excretion of >
150mg per day (10-20mg/dL)
 Proteinuria = renal disease.
 Microalbuminuria defines as excretion of 30150 mg of protein per day = early sign of
renal disease (especially in diabetic patients)
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Dipstick sensitive to albumin but not to low
[ ] of y-globulins and Bence Jones proteins.
 Trace = 5-10mg/dL (lower than significant
proteinuria)
 1+ = 30mg/dL…considered positive
 2+ = 100mg/dL
 3+ = 300mg/dL
 4+ = 1000mg/dL
 Dipstick reliable predict albuminuria with
sensitivities & specificities > 99%.
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Proteinuria = transiet OR persistent (see table
5)
 Transient = temporary change in glomerular
hemodynamics causes the protein excess –
condition follow a benign, self-limited course.
 Orthostatic (postural) proteinuria – benign
condition result from prolonged standing.
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◦ Confirmed by obtaining a negative result after 8 hrs
of recumbency.
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Persistent proteinuria – 3 general categories:
◦ Glomerular
◦ Tubular
◦ Overflow
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1) Glomerular:
◦ Most common type
◦ Albumin 1° urinary protein
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2) Tubular:
◦ Due to malfunctioning tubule cells no longer
metabolise or reabsorb normally filtered protein.
◦ Low-molecular weight proteins predominate over
albumin (rarely exceed 2g/day)
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3) Overflow:
◦ Low-molecular-weight proteins overwhelms the
ability of tubules to reabsorb filtered proteins.
Further evaluation of persistent proteinuria
usually includes:
◦ determination of 24-hr urinary protein excretion
or spot urinary protein-creatinine ratio.
◦ Microscopic examination of urine
◦ Urinary protein electrophoresis &
◦ Assessment of renal function.
Glycosuria occurs = the filtered load of glucose
exceeds the ability of the tubule to reabsorb.
(180 – 200mg/day).
 Etiologies include:
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diabetes mellitus,
◦ Cushing’s syndrome
◦ Liver disease
◦ Pancreatic disease
◦ Fanconi’s syndrome
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Ketonuria – dipstick reagents detect acetic
acid through a reaction with sodium
nitroprusside or nitro-ferricyanide & glycine.
 Ketonuria – commonly associated with:
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uncontrolled diabetes
◦ During pregnancy
◦ Carbohydrate-free diets
◦ Starvation
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Nitrites in urine result when bacteria reduce urinary
nitrates to nitrites.
Many GP & GN organisms are capable of this conversion
= resulting in positive dipstick nitrite
Positive dipstick nitrite = org. present in significant
numbers (> 10 000/ml)
Test is specific BUT not highly sensitive.
Positive result = helpful
Negative result = does NOT rule out UTI.
The nitrite dipstick reagent is sensitive to air
exposure.
 THEREFORE containers should be closed
immediately after removing a strip.
 After 1 week of exposure, 1/3 = false positive
 After 2 weeks exposure, ¾ = false positive
 Non-nitrate-reducing organisms also may cause
false-negative results.
 Patients consuming low-nitrate diet – false
negative results
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Leukocyte esterase produced by neutrophils – it may signal
pyuria associated with UTI.
Detecting significant pyuria accurately, 30 sec. – 2 min.
should be allowed for the dipstick reagent strip to change
colour. (brand related)
Leukocyte casts in urine can help localise area of
inflammation to the kidney.
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Pyuria with negative culture – consider Chlamydia &
Ureaplasma urealyticum.
Other causes of sterile pyuria include:
◦ Balanitis,
◦ Urethritis,
◦ Tuberculosis,
◦ Bladder tumours,
◦ Viral infections,
◦ Nephrolithiases,
◦ Foreing bodies,
◦ Exercise,
◦ Glomerulonephritis,
◦ Corticosteroid &
◦ Cyclophosphamide use.
Urine normally does not contain detectable
amounts of bilirubin.
 Unconjugated bilirubin is water insoluble and
can’t pass through the glomerulus.
 Conjugated bilirubin is water soluble and if
present in urine indicates further evaluation
for:
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◦ liver dysfunction &
◦ Biliary obstruction
Normal urine = small amount of urobilinogen.
 Urobilinogen = end product of conjugated bilirubin.
 Urobilinogen is reabsorbed into the portal
circulation.
 Small amount filtered by glomerulus.
 Elevated levels:Haemolysis & hepatocellular
disease
 Decreased levels: antibiotic use & bile duct
obstruction
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Important part of urine analysis.
Identification of:
◦ Casts
◦ Cells
◦ Crystals
◦ Bacteria
Aids in diagnosis of a variety of conditions.
10 – 15 ml of urine centrifuged @ 1500 – 3000 rpm for 5
min.
Supernatant decanted - sendiment resuspended - single
drop transferred to clean glass slide – cover slip – exam OR
counting chamber (uncentrifuged urine used)
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Leucocytes can be seen under low & high power
magnification (see picture).
Men normally < 2 WBCs/HPF
Women normally < 5 WBCs/HPF
Picture: Squamous epithelial cells & leucocytes
(200x).
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Epi’s often seen in urine wet preps.
Squamous epithelial cells = large & irregularly shaped,
with small nucleus & fine granular cytoplasm = seen in
urine = contamination.
Presence of transitional epi’s = normal.
Transitional epi’s = smaller & rounder, large nuclei.
Presence of renal tubule cells = significant renal
pathology.
Picture: Convoluted renal tubule
cells (200x)
Erythrocytes are best visualised under high
power magnification.
 Dysmorphic erythrocytes = odd shapes
because of passage through an abnormal
glomerulus – suggest glomerular disease.
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Casts in urine – used to localise disease to specific location in
genitourinary tract.
See table 6 in article.
Casts = coagulum of Tamm-Horsfall mucoprotein & trapped
contents of tubule lumen.
It originate from the distal convoluted tubule or collecting
duct during peroids of urinary concentration/stasis/when
urinary pH is very low.
It’s cylindrical shape reflects the tubule in which they are
formed & is retained when casts are washed away.
Type of cast = predominant cellular element – hyaline, RBC,
WBC, epi, granular, waxy, fatty, broad.
Figure 3.
Urinary casts. (A) Hyaline cast (200 X); (B) erythrocyte cast (100 X);
(C) leukocyte cast (100 X); (D) granular cast (100 X).
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Crystals may be present in healthy patient urine.
Calcium oxylate crystals – have a refractile sqaure
“envelope” shape that can vary in size.
Uric acid crystals – are yellow – orange-brown and may
be diamond- or barrel-shaped.
Triple phosphate crystals may be normal but often
associated with alkaline urine & UTI (typically associated
with Proteus species) – colourless & have a characteristic
“coffin lid” appearance.
Cystine crystals – colourless, have a hexagonal shape &
are present in acidic urine – diagnostic of cystinuria.
Figure 4.
Urinary crystals. (A) Calcium oxalate crystals (arrows; 100
X); (B) uric acid crystals (100 X); (C) triple phosphate
crystals with amorphous phosphates (400 X); (D) cystine
crystals (100 X).
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High-powered magnification can distinguish between,
GNB, Streptococci and Staphylococci by their
characteristic appearance.
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Gram staining can guide in therapy, BUT are not
done routinely.
Clean-catch specimens from female patients
frequently are contaminated by vaginal flora.
5 bacteria/HPF represent roughly 100 000 colonyforming units (CFU) per ml.
Classic diagnostic criteria for asymptomatic
bacteriuria – compatible with a UTI.
Symptomatic patients – a colony count as low as
100 CFU per ml suggests UTI & antibiotics should
be considered.
Presence of bacteria in properly collected male
urine suggests an infection, and a culture should be
done.
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Define importance of a urine analysis
Explain the significance of physical, chemical,
microscopical & cultural characteristics of a urine.
Describe the required sample for a urine analysis.