3- Chemical Analysis of Urine Flashcards
Def: a basic diagnostic tool used to determine pathological changes in a patient’s urine in standard urinalysis
urine test strip
urine test strip aka
dipstick
whats the time frame to read the dipstick
60 to 120 seconds
Urine pH normally fluctuates between
acidic and alkaline
what is the Acid indicator
methyl red
what is the Alkaline indicator
bromthymol blue
Urine pH range
5.0 to 8.5
more phosphates, sulfates results in more
acidic urine
Vegetable diet results in urine pH higher than
6
Factors resulting in persistent Acidity
– Dehydration
– Diarrhea
– Fever
– Diabetes ketoacidosis
– Gout
– Pulmonary emphysema
– High protein diets or cranberries
– Renal tubular acidosis (proximal tubular, distal tubular) metabolic acidosis
– Acidifying drugs ( for ammonium magnesium stone prevention)
Factors resulting in persistent Alkalinity
– Acute and chronic renal failure
– Urinary tract infections
– Bacterial contamination of urine
– Alkaline drugs
– Diuretics
the source of low–molecular weight protein could be found in the urine
genito-urinary tract
Mucoprotein Tamm-Horsfall (T-H) is secreted by
renal tubules (renal epithepial cells)
Mucoprotein Tamm-Horsfall (T-H) is not derived from
blood plasma
the amount of T-H protein is
excreted in urine?
Less than 150 mg/24 h (or 20 mg/dL)
T-H protein is a ____ for formation of calculi or casts
matrix
Testing for protein is based on
Protein Error of pH Indicators
define “Protein Error of pH Indicators”
ability of protein to alter the color of some acid-base indicators without altering the pH
Protein Error of pH Indicators is more sensitive
to _____ than ______
more sensitive to albumin than to globulin
Urine protein:
false positive May result from
- highly buffered alkaline urine (medications or old urine)
- prolonged exposure to the sample (too long)
- container cleaning compounds (quaternary ammonia)
- some skin cleaners
- blood in urine
Urine protein:
false negative may result from:
- diluted urines
- elevated amounts of proteins other than albumin
Urine protein: significance
Which factors which could result in temporary proteinuria (transient proteinuria, “trace”):
- strenuous exercise
- postural proteinuria
- dehydration
- exposure to heat or cold
- fever
- emotional stress
- pregnancy
what Diseases tha resutl in persistent proteinuria
- glomerulonephritis
- pyelonephritis
- malignant hypertension
____ % of glucose is reabsorbed in the proximal tubules
100%
*** Usually, urine doesn’t present unless threshold levels exceeded ______
160-180 mg/dl
*** Dipstick test is sensitive for what kind of sugars?
Glucose only
Urine glucose:
false positive may result from
- after using oxidizing cleaniers (peroxide, hypochlorite)
- in patients taking Levodopa (Parkinson’s disease)
- high levels of ketones in urine
Urine glucose:
false negative may result from
- cool urine
- high specific gravity urine (due to uricosuria)
- alkaline urine due to bacterial contamination of old urine
- ascorbic acid (Vitamin C) in high doses can inhibit the enzymatic reaction
Glucose can be present in urine after how many hours from eating sweets?
2 hours
urine glucose that presnt after eating sweets is known as:
transient glucosuria
Glucosuria depends on
– blood glucose levels
– glomerular filtration rate
– tubular reabsorption
Glucosuria is seen in patient with
(what conditions)
diabetes mellitus
congenital forms of glucosuria
Persistent glucosuria develops in:
- diabetes mellitus
- CNS problems (stroke, neoplasms)
- kidney problems (e.g. uremia)
- endocrine problems (e.g. acromegaly, pheochromocytoma)
- liver disorders (e.g. glycogen storage disease)
- pharmaceutical agents (e.g. diuretics, birth control pills)
a second method for the measurement of sugar in urine
Clinitest
what kind of sugars does clinitest measures?
Glucose, and other reducing sugars
Clinitest: false positive may result from
• Ascorbic acid
• Cephalosporins
• Probenecid (treating gout and hyperuricemia)
• Urinary preservatives:
– formalin<br></br> – formaldehyde
Clinitest: false negative may result from
Technique errors
what test is used to determine the presence of
reducing sugars?
Benedict’s test
reducing sugars in urine includes
fructose
glucose
maltose
galactose
lactose
Urine reducing sugar test Is used for early screening detection of
galactosemia or diabetes
_____ are produced normally by the liver as part of
fatty acid metabolism
Ketones
Normally, the urine (should/should not) contain a noticeable concentration of ketones
Should not
Dipstick test determines wich acid? (acetoacetic acid/beta-hydroxybutyric acid)
acetoacetic acid
Urine ketones: false positive or atypical color
results from:
• Highly pigmented urine
• Combination of high specific gravity and a low pH
• Dehydration
• Phenylketones
• Some medications
• Ascorbic acid
• Positive and questionable results may be confirmed with a
tablet test
Urine ketones: false negative
resutls from
- Delay in testing (old urine)
- Loss of reagent reactivity
Urine ketones confirmatory test is called
Acetest
does Acetest react with beta-hydroxybutyric acid?
No
(no body likes beta-hydroxybutyric)
• Ketone bodies can be determined in the following diseases:
- diabetes mellitus
- malabsorption syndrome (diarrhea)
- exposure to cold
- fasting
- fever
- insufficient carbohydrate intake
- malnutrition
- strenuous exercise
- vomiting
Hematuria: blood in urine may be released from any organ of ________
genito-urinary tract
Hemoglobinuria is due to
intravascular distraction of RBC - Glomerular filtrate
Myoglobinuria is due to
muscle damage - Glomerular filtrate
Blood color chart
Urine blood/hemoglobin: false positive
- Cleanser - Oxidizing contaminant (Hypochlorites)
- Bacterial peroxidases
- Menstrual blood
Urine blood/hemoglobin: false negative
- Technique errors inadequate mixing of urine sample
- Formalin preservative
- High concentrations of ascorbic acid (Vitamin C)
- High specific gravity
- Nitrites
- Proteins
Define Hematuria
the presence of blood or intact RBCs in the urine
highly alkaline urine or has a very lowspecific gravity (1.007) can cause the red cells to
Lyse and release hemoglobin to urine
empty red cell membranes aka
“ghost” cells
Transient hematuria may result from:
- strenuous exercises
- menstrual contamination
- *Persistent** hematuria:
- can develop in renal diseases in:
glomerular
tubular
interstitial
vascular
trauma of kidneys
- *Persistent** hematuria:
- also present in patients with
urolithiasis (kidney stones)
urinary tract infections
urinary tract tumors
bleeding disorders related to anticoagulant therapy prostatic cancer gynecological disorders virus infection (e.g. Ebola)
Define myoglobinuria
Damage to cardiac or skeletal muscles
Both hemoglobin & myoglobin will be + on strip blood results becasue both contain:
heme
Normal Bilirubin Pathway
because only conjugated bilirubin appears in
urine, bilirubinuria implies what diseases?
Liver or cholestatic diseases
Why unconjugated bilirubin is not filtered by the glomerulus?
bilirubin is tightly bound to albumin
A positive test for urine bilirubin confirms that any raised plasma levels are from:
conjugated hyperbilirubinemia
Normally, _____ amounts of bilirubin are present in urine
no detectable
Urine bilirubin: false positive
• Technique errors:
– reading after the prescribed time
• Atypical color reactions produced by some medicines
• Confirm results with Ictotest
Urine bilirubin: false negative
• Large amounts of ascorbic acid decrease the sensitivity of the dipstick
• High levels of nitrite
• Exposure to light and room temperature
– bilrubin oxidizes to biliverdin
Urine bilirubin confirmatory test is called
Ictotest
The presence of bilirubin in urine indicate to:
– gallbladder, bile duct obstruction
– liver pathology (e.g. hepatitis)
About ____% of urobilinogen reabsorbed into the bloodstream, returns to the liver, and reexcreted into the intestines
10–15
Normal level of urobilinogen excretion
1–4 mg/24 h
or
less than 1.0 Ehrlich unit/2h
Urobilinogen color chart
Urine urobilinogen: false positive
- aspirin
- sulfonamides
- nitrites (e.g. in UTI)
- porphyria
– which test is used to differentiate
between porphobilinogen and urobilinogen
Watson-Schwartz test
Urine urobilinogen: false negative
- Use of stale urine that has been exposed to light
- Formalin
- Antibiotics (broadspectrum) which alter the normal<br></br>bacteria flora in the intestines, because urobilinogen<br></br>cannot be formed in the intestines.
urobilinogen Peak levels between
2-4 p.m
urobilinogen Elevated in
(diseases)
– Liver disease
– Intestinal obstruction
– Hemolytic anemia
a rapid, indirect method for the early
detectionof significant and asymptomaticbacteriuria
nitrite
To convert nitrate to nitrite, urine must have incubated in the bladder for a minimum of
4 hours
If UTI is caused by __________, the reaction will be negative
non-nitrate reducers (e.g. Mycobacteria),
Nitrite color chart
Urine nitrite: false positive
The dipstick is highly sensitive to air exposure
The urine should be tested shortly after voided, because at room temperature for several hours specimen could be contaminated by bacteria
Urine nitrite: false negative
- Specimen containing non-nitrate reducing pathogens
- Insufficient time in the bladder (less than 4 hours)
- Low or no nitrate diet
- Elevated specific gravity of urine
- High level of urobilinogen in urine
- Ascorbic acid
If there are clinical symptoms, then ______________ should be performed, even if the nitrite test is negative
regular bacteriology tests
Leukocyte Esterase color chart
Urine leukocyte esterase: false positive
- Trichomonas infection
- Contamination by vaginal discharge
- Formalin used as preservative
Urine leukocyte esterase: false negative
- High level of Ascorbic acid
- High level of protein, glucose ( high specific gravity)
- Some antibiotics (Cephalexin, Keflex,Tetracycline)
