CLS Review - Urinalysis

• A: Glomerulus

• B: Proximal tubule

• C: Loop of Henle

• D: Distal tubule

• E: Collecting Tubule

• A: Nephron

• B: Cortex

• C: Medulla

• D: Ureter

• Major functional unit of kidney

• 1 million per kidney

• Composed of glomerulus and renal tubules

Nephron characteristics (purpose, quantity, components)

• Nonselective

• <70,000 MW

The glomerulus does (——) filtration of plasma substances tht re less than (——) MW

• Water

• Glucose

• Electrolytes

• Amino acids

• Urea

• Uric acid

• Creatinine

• Ammonia

Glomerular filtrates (8)

120 mL/min (1/5 renal plasma)

Glomerular filtration rate

• Water

• Sodium chloride

• Bicarbonate

• Potassium

• Calcium

• Amino acid

• Phosphates

• Protein

• Glucose

What does the PCT reabsorb (9)

• Glucose

• 160-180 mg/dL

(——) is the threshold substance of the PCT with reabsorption being (——) or less

• Sulfates

• Glucuronides

• Hydrogen ions

• Drugs

What is secreted in the PCT (4)

Reabsorbs water (no solutes)

What is reabsobed in the descending LoH

Reabsorbs solutes (sodium, chloride, calcium, magnesium)

What is reabsorbed in the ascending LoH

• Reabsorbs sodium

• Secretes potassium, ammonia, and hydrogen

• (Potassium exchanged for sodium)

What is reabsorbed (1) and secreted (3) in the distal and collecting tubules

1200-1500 mL/day

Volume for normal urine output

• >2500 mL/day

• Diabetes insipidus, diabetes mellitus, diuretics, caffeine, alcohol, excessive water intake

Urine output volume for polyuria and associated diseases/causes (6)

• <400 mL/day

• Dehydration, vomiting, diarrhea, burns, perspiration

Urine output volume for oliguria and its associated diseases/causes (5)

• Complete cessation

• Kidney damage, decreased blood flow to kidneys

Urine output volume for anuria and its associated deases/causes (2)

Nocturia

Increasd volume of urine output at night

• Urea

• Other organic solids (Uric acid and creatinine)

• Inorganic solids (Chloride*, sodium, potassium)

• Water

Composition of urine (4)

Urea

Metabolic waste product produced in liver from breakdown of protein; ½ total urinary dissolved organic solids

• Aldosterone

• Adrenal gland

What hormone increases the rate of sodium reabsorption, and where is its source

• Arginine Vasopressin (AVP/ADH)

• Posterior pituitary gland

Which hormone regulates the reabsorption of water from the distal tubules, and where is its source

Diabetes insipidus

What disease has a deficiency in vasopressin (ADH)

Random

(Collection method) most common specimen type; easiest to collect; useful for routine screening tests

First morning

(Collection method) First voided specimen upon waking; ideal screening specimen (most concentrated)

Midstream clean catch

(Collection method) external genital area is cleaned; first an dlast stream of urine voided while midstream is collected; specimen of choice for routine bacterial culture

Catheterization

(Collection method) Insertion of catheter directly into bladder via urethra; avoids external contamination, but may introduce infection

Pediatric

(Collection method) Sterile, plastic collection bag placed over genital area with adhesive; bag checked every 15 minutes; many sources of contamination

Suprapubic aspiration

(Collection method) Insertion of needle through suprapubic abdominal area directly into bladder; avoids external contamination but may introduce infection; optimum specimen for bacterial culture, but invasive

First specimen discarded while all others collected

How is 24 hour urine collected

Creatinine levels (>1.0 mg/dL)

Completeness of 24 hour urine collection is monitored by…

1 hour of voiding (NOT 1 hour after received in lab)

Urine samples should be analyzed within…

• Nitrite (bacterial growth)

• pH (urea → ammonia)

• Turbidity (bact growth, RBC/WBC, amorphous material)

What increases in urine samples that are left in room temperature for too long (3)

• Glucose (glycolysis from bact/yeast)

• Ketones (volitilization)

• Bilirubin (light)

• Urobilinogen (oxidize → urobilin)

• Cells and casts (lysis)

What decreases in urine samples that are left in room temperature for too long (5)

Refrigeration

Preservation method of choice up to 24 hours

• Amorphous crystals

• Return to room temperature (15 min)

Refrigeration may result in the formation of (——) in urine samples; fefore testing, the samples must (——)

• Fruity → ketones

• Ammonia → old urine

• Mousy → phenylketonuria (PKU)

• Maple syrup → Maple syrup disease (branched chain aminoaciduria)

What may different odors of urine specimens indicate (4)

Urinary elements (cells, casts, crystals) or bacteria

What may make urine cloudy

Urochromes

What gives urine their normal color

Usually slightly acidic (6.0) but can range 4.5-8.0

What is the pH of urine

• Eating

• Standing at room temp or warmer

• Vegetarian diet

What can make urine more alkaline (3)

• Metabolic/respiratory acidosis

• High protein diet

• Cranberry juice

What can make urine more acidic? (3)

• Hemoglobin

• RBCs

• Myoglobin

• Porphoryin

• Uroerythrin

What makes urine red (5)

• Hemoglobin

• RBCs

• Myoglobin

What makes urine red-brown (3)

• Bilirubin

• Biliverdin

What makes urine yellow-brown/amber-yellow-green (2)

• Bilirubin

• Urobilin

• Pyridium (drug)

What makes urine yellow-orange (3)

Vitamin C

What makes urine bright yellow

• Concentrated specimen

• Bilirubin

• Urobilin

What makes urine dark yellow (3)

• Methemoglobin (oxidized RBCs)

• Homogentisic acid (Alkaptonuria)

• Melanin

What makes urine brown-black (3)

Indican (Tryptophane metabolic disorder)

What makes urine blue

• Old urine

• Pseudomonas

What makes urine green/green-blue (2)

Porphyrin

What makes urine a wine color

1.002-1.035 (≤1.040 is physically possible)

Normal urine specific gravity

Glucose or radiographic dyes from renal x-ray

High specific gravity of urine is due to… (2)

• Defect: low insulin

• SG: ↑

• Glucose: ↑

• Ketones: ↑

Diabetes mellitus characteristics (defect, specific gravity, glucose, ketones)

• Defect: low ADH/AVP

• SG: ↓

• Glucose: N

• Ketones: N

Diabetes insipidus characteristics (defect, specific gravity, glucose, ketones)

Polyuria and polydipsia

Symptoms shared between diabetes mellitus and diabetes insipidus (2)

“Protein error of indicators” (more sensitive to albumin than globulin)

• Test pad kept at pH 3.0

• Albumin binds to dye

• Dye shifts yellow → green

Principle of protein reagent strip

Highly alkaline urine → false positives

Interfering substances of protein reagent strip

Proteinuria

Best single indicator of renal abnormality, specifically glomerular involvement

• Multiple myeloma

• Orthostatic proteinuria (benign condition: proteinuria after standing)

• Strenuous exercise

Besides glomerular abormalities, what is proteinuria associated with (3)

• Diabetes

• Hypertension

• Peripheral vascular disease

Microalbuminuria can be periodically monitored for patients with (——), so that treatment can begin before kidney disease occurs

Glucose oxidase (double sequential enzyme reaction)

Principle for glucose reagent strip

Sugar or other reducing substances other than glucose

Positive copper reduction test and negative glucose strip test is indicative of…

Low amounts of glucose present

Positive glucose strip test but negative copper reduction test is indicative of…

Oxidizing agents (bleach, peroxide) → false positive

Interfering substances for glucose reagent strip

• Glucose

• Other reducing sugars

  • Galactose, lactose, fructose, maltose, pentose

What does clinitest detect in urine (6)

Galactosemia

Clinitest is a screening test for (——), a rare congenital carbohydrate metabolic condition in pediatric patients

Ascorbic acid (vitamin C) high dose → false negative

Interfering substance for clinitest

2 drops (5 drops → pass through rxn negative-positive-negative)

How many drops should be administered in Clinitest

• Benedict’s copper reduction

• CuSO4 + NaOH + reducing substance = Cu2O

• blue-green → orange-red

Principle of clinitest, the chemical reaction, and color change

• Acetone

• Diacetic acid (acetoacetate)

• Beta-hydroxy-butyric acid (fat metabolism end product)

Ketones that can be found in urine (3)

Sodium nitroprusside + ketone = purple color

Principle of ketone reagent strip and tablets

Diacetic acid

Ketone reagent strip is specific for…

• Diacetic acid

• Acetone

Ketone confirmation tablets (Acetet) are specific for… (2)

Highly pigmented urine and levadopa metabolites → false positive

Interfering substances for ketone reagent strip and tablets (2)

• Uncontrolled diabetes mellitus

• High protein diets

• GI disturbances

Which conditions give positive results for ketones (3)

• Peroxide on strip + blood = O2

• O2 + color producer = color change

Describe the 2-step enzymatic procedure for the detection of blood on a reagent strip

• Bleach and other oxidizing agents → false positive

• Ascorbic acid (vitamin C) → false negative

Interfering substances for blood reagent strip

Hemoglobin and myoglobin

What other substances have peroxidase activity that may affect the detection of blood in reagent strip

• Systemic bleeding disprders

• Renal diseases

• Cystitis

• Calculi

• Strenuous exercise

Positive blood in urine may be due to hematuria associated with… (5)

• Hemolytic anemias

• Incompatible transfusions

• Malaria

• Strenuous exercise

Positive blood in urine may be due to hemoglobinuria associated with… (4)

Muscle destruction

Positive blood in urine may be due to myoglobinuria associated with…

• Diazo

• Diazonium salt + bilirubin = bluish-purple color

Principle of bilirubin strip reagent or tablet and its associated chemical reaction

Ictotest (tablet)

(——) is more sensitive in the detection of bilirubin in urine than the reagent strip test

• Ascorbic acid

• Exposure to light

What can cause false negatives in bilirubin strip reagent

• Bile duct obstruction

• Liver damage (cirrhosis and hepatitis)

Bilirubinuria is associated with… (2)

• Erlich’s reaction

• Para-dimethylaminobenzaldehide in acid buffer + urobilinogen → pink color

Principle or urobilinogen reagent strip and its associated chemical reaction

• Formalin (preservative) → false negative

• Highly pigmented urine and some medicatins → false positive

Interfering substances for urobilinogen reagent strip

≤ 1 mg/dL (1 EU)

Normal amount of urobilinogen in urine

• Liver damage (hepatitis, cirrhosis)

• Hemolytic disease

High urobilinogen is associated with… (2)

Bile duct obstruction

Negative urobilinogen is associated with…

None

Normal level of urine bilirubin

• Bilirubin: 0

• Urobilinogen: ↑

Expected bilirubin and urobilinogen values for hemolytic conditions

• Bilirubin: 0 or ↑

• Urobilinogen: ↑

Expected bilirubin and urobilinogen values for liver disease

• Bilirubin: ↑

• Urobilinogen: ↓ (N on strip)

Expected bilirubin and urobilinogen values for obstructive conditions

• Priniciple: Diazo reaction

• Nitrite + amine reagent at acidic pH → diazonium compound

• Diazonium compound + 2-hydroxy-1,2,3,4 tetrahydrobenz (h) - quinolin → pink color

Principle of nitrite reagent strip and its associated chemical reactions

False negatives

• Lack of dietary nitrate

• Urine not in bladder long enough (4hr) for bacteria to reduce

• Non-nitrate reducing bacteria

• Ascorbic acid

Interfering substances/conditions for nitrite detection with reagent strip

Any shade of pink

What result is considered a clinically significant amount of bacteria with nitrite reagent strips

• Leukocyte esterase + ester → pyrrole compound

• pyrrole compound + diazo reagent → purple color

Principle chemical reaction for leukocyte reagent strip

Pyuria

Positive result for leukocyte reagent strip indicates the presence of leukocytes in urine, also known as…