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Renal > urinalysis > Flashcards

urinalysis Flashcards

1
Q

What is a clean catch urine ssample

A

collected midstream

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2
Q

Methods of urine collection

A

random collection is taken at any time of day with no precautions (urine may be dilute, isotonic or hypertonic), eraly morning sample before ingestion of fluids (hypertonic), catheterization of bladder or suprapubic needle aspiration of bladder

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3
Q

What causes foul, sweet, fruity or maple-syrup like smelling urine

A

Foul, offensive: Old specimen, pus or inflammation. Sweet: Glucose. Fruity: Ketones. Maple syrup-like: (Maple Syrup Urine Disease)

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4
Q

What causes deep yeelo, yello-green, red, brownish-red and brownish-black colored urine?

A

Deep Yellow: Concentrated Urine, Riboflavin. Yellow-Green: Bilirubin / Biliverdin. Red: Blood / Hemoglobin. Brownish-red : Acidified Blood (Acute GN). Brownish-black: Homogentisic acid (Melanin)

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5
Q

How is glucose detected by urine dipstick?

A

Glucose oxidase converts glucose + water and O2 to gluconic acid and peroxide. Then, Horseradish peroxidase converts peroxide + KI (also on the strip) to KIO3 and water, then the oxygen liberated binds with dye forming a colored substrate

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6
Q

False negative glucose urine dipstick

A

As ascorbic acid is an oxygen acceptor and most likely to be present in large amounts in the urine of pregnant women, this will cause a false-negative result. Also, this can not detect sugars other than glucose, so not beneficial in newborn screens

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7
Q

Another method used to detect sugars

A

CuSO4 can detect reducing sugars: Galactose (galactosemias), fructose (fructose intolerance), lactose (lactase deficiency), pentoses (essential pentosuria), maltose (non-pathogenic). NOT sucrose b/c it is not reducing

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8
Q

How is bilirubin detected by urine dipstick?

A

Bilirubin combines with a diazo salt in an acidic medium to form azobilirubin which forms a light-dark tan color.

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9
Q

False negative and positive bilirubin are caused by…

A

Indican (indoxyl sulfate) will cause a false-positive result, while ascorbate will cause a false-negative result

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10
Q

Limitations of urine bilirubin dipstick

A

Only measure direct bilirubin (which correlates with urobilinogen and serum bilirubin), not indirect. Interference can occur with prolonged exposure of sample to light.

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11
Q

Other methods for measuring bilirubin

A

Ictotest (more sensitive tablet version of same assay) and serum test for total and direct bilirubin

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12
Q

How are ketones detected by urine dipstick?

A

The ketones (acetoacetate) reacts with nitroprusside to form a purple color Also detects acetone but not beta-hydroxybutyrate

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13
Q

What causes ketones in urine

A

Diabetic ketosis or other form of calorie deprivation

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14
Q

Limitations of urine ketone detection

A

Interference can occur with expired reagents(due to degradation with exposure to moisture in air) and it only measures acetoacetate, not other ketone bodies.

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15
Q

Other methods for urine keytone detection

A

Ketostix (more sensitive tablet version of same assay) and serum glucose measurement to confirm Diabetic ketoacidosis.

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16
Q

How is specific gravity measured by urine dipstick?

A

by measuring the change in pKa of polyelectrolytes in relation to ionic concentration

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17
Q

What is the normal range for urine specific gravity

A

1.003-1.035

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18
Q

Uses and limitations of urine specific gravity

A

Useful for diabetes insipidus. Limitations: alkaline urine interferes with test and does not measure non-ionized solutes such as glucose.

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19
Q

Other methods for urine specific gravity detection

A

refractometry, hydrometer, osmolality measurement

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20
Q

What will show up as a positive in the urine blood dipstick

A

RBCs, free hemoglobin or free myoglobin. While hemoglobin and RBCs are normally too large to pass through glomerulus, myoglobin passes freely through glomerulus.

21
Q

How is blood detected by urine dipstick

A

pseudoperoxidase reaction, which is more sensitive to hemoglobin and myoglobin than intact RBCs.

22
Q

Describe urine in hematuria vs hemoglobinuria

A

In cases of hematuria, the urine is red and cloudy, but will clear if centrifuged.Hemoglobinuria will have reddish brown urine that does not become clear after centrifugation

23
Q

Normal range of urine pH, and causes of high/low pH

A

Normal is 4.5-8.0. Acidic urine 8.0 occurs in renal tubular acidosis.

24
Q

Interference of urine pH test

A

bacterial overgrowth (alkaline or acidic), or “run over effect” effect of protein pad on pH indicator pad where buffers from protein area of strip spill over to pH area and make pH appear more acidic than it really is.

25
Q

Other methods for urine pH

A

Acidity titer and blood gases

26
Q

define proteinuria

A

> 150mg/ day protein in urine.

27
Q

How are proteins measured by urine dipstick and its limitations

A

Bromophenol blue is used as an indicator dye. It is most sensitive to albumin and interference occurs with highly alkaline urine.

28
Q

Other tests for urine protein detection

A

sulfosalicylic acid can detect albumins, globulins, and Bence Jones protein. Urine protein electrophoresis

29
Q

Which proteins can be found in normal urine

A

albumin, Tamm-Horsfall, immunoglobulins, secretory IgA all at small amounts

30
Q

What is urobilinogen

A

Urobilinogen is formed by intestinal bacteria from the breakdown of conjugated bilirubin, and it is usually excreted in feces. However a small amount may be reabsorbed and excreted in urine

31
Q

How is urobilinogen detected on urine dipstick

A

based on a modified Ehrlich reaction, in which p-dimethyl amino benzaldehyde in conjunction with a color enhancer reacts with urobilinogen in a strongly acid medium to produce a pink-red color. A positive test response indicates normal enterohepatic circulation of biliary pigments. High concentrations of biliary pigments may occur in hemolytic crisis, or cases of hepatic or intestinal dysfunction. Low indicaties bile obstruction

32
Q

Causes of a false positive and false negative urobilinogen urine test

A

A false positive test result may occur if the temperature of the reagent strip is elevated. A false negative test result may occur if there is formalin residue in the collection container, or if the sample is old, because urobilinogen is very unstable when exposed to light and air.

33
Q

What causes nitrites in the urine

A

A positive nitrite test indicates that bacteria may be present in significant numbers in urine. Gram negative rods such as E. coli are more likely to give a positive test.

34
Q

What causes positive leukocyte esteraste in urine

A

A positive leukocyte esterase test results from the presence of white blood cells either as whole cells or as lysed cells. If negative, there is no need t loo for further signs of infection

35
Q

Causes of false positive and false negative leukocyte esterase in urine

A

False positive test results also may occur in the event of vaginal contamination. False negative test results may develop if the patient has been treated with high doses of antibiotics. Glucosuria or increased urine specific gravity may cause false negative test results

36
Q

Preservation of cells/casts for microscopic analysis

A

Cells and casts begin to disintegrate in 1 - 3 hrs. at room temp. Refrigeration for up to 48 hours (little loss of cells).

37
Q

For a high power field, what is the definition of abnormal: erythrocytes, leukocytes, renal tubular cells , bacteria, neutrophils

A

Per high power field (400x): > 3 erythrocytes, >5 leukocytes, >2 renal tubular cells, >10 bacteria, >1 neutrophil per 3 HPF

38
Q

For low power field, what is the definition of abnormal: hyaline/granular casts, squamous cells, RBC/WBC casts

A

per low power field (200x): >3 hyaline casts or >1 granular cast, >10 squamous cells (contamination), any number of RBC/WBC casts

39
Q

Causes of hematuria and dysmorphic RBCs

A

glomerular damage, tumors which erode the urinary tract anywhere along its length, kidney trauma, urinary tract stones, renal infarcts, acute tubular necrosis, upper and lower urinary tract infections, nephrotoxins, and physical stress and contamination. dysmorphic RBCs are found in glomerular disease where passage through abnormal glomerulus distorts the RBC shape

40
Q

Oval fat bodies

A

renal tubular epithelial cells that contain numerous fat droplets and exhibit a Maltese cross configuration by polarized light microscopy

41
Q

Where are casts formed

A

distal convoluted tubule or the collecting duct

42
Q

What are hyaline casts

A

composed primarily of a mucoprotein (Tamm-Horsfall protein) secreted by tubule cells. The Tamm-Horsfall protein secretion, forms hyaline casts in the distal collecting duct. Most casts are made of Tamm-Horsfall mucoprotein

43
Q

Factors favoring protein cast formation

A

low flow rate, high salt concentration, and low pH, all of which favor protein denaturation and precipitation, particularly that of the Tamm-Horsfall protein.

44
Q

Cylindroids

A

Protein casts with long, thin tails formed at the junction of Henle’s loop and the distal convoluted tubule

45
Q

What are granular and waxy casts? Broad casts?

A

When cellular casts remain in the nephron for some time before they are flushed into the bladder urine, the cells may degenerate to become a coarsely granular cast, later a finely granular cast, and ultimately, a waxy cast They are derived from renal tubular cells and are seen in end stage chronic renal disease

46
Q

Telescoped urinary sediment and what cuases is

A

red cells, white cells, oval fat bodies, and all types of casts are found in more or less equal profusion. 1) lupus nephritis 2) malignant hypertension 3) diabetic glomerulosclerosis, and 4) rapidly progressive glomerulonephritis

47
Q

Causes of fatty casts

A

nephrotic syndrome

48
Q

Normal crystals and abnormal crystals

A

Normal: calcium oxalate, triple phosphate crystals and amorphous phosphates. Uncommon/abnormal: cystine crystals in urine of neonates with congenital cystinuria or severe liver disease, tyrosine crystals with congenital tyrosinosis or marked liver impairment, or leucine crystals in patients with severe liver disease or with maple syrup urine disease.

Renal (26 decks)

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