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Clin Lab Med Unit 2 > 2 Urinalysis And K Disorders > Flashcards

2 Urinalysis And K Disorders Flashcards

1
Q

What are the three components of the UA?

A

Gross Examination

Urine Dipstick

Microscopic Analysis

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2
Q

Proper collection technique for UA

A

Local disinfection of urethral meats with a nonfoaming disinfectant (allow to dry to avoid mixing the disinfectant with the urine specimen)

Spread the labia or retract the foreskin

Discard the first voided portion which may contain urethral contaminants

Collect midstream specimen

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3
Q

What are you assessing on gross examination of the UA?

A

Color

Turbidity

Odor

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4
Q

Normal color for urine

A

Pale straw-colored to dark amber in very concentrated urine

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5
Q

What does red or red-brown urine indicate?

A

Blood (hematuria) or hemoglobin (hemoglobinuria)

R/o menstrual contamination

Consider myoglobin, food dyes, or ingestion of beets or rhubarb

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6
Q

What does dark brown or black urine indicate?

A

Bile or bilirubin due to liver or biliary disease

Alkaptonuria

Malignant melanoma

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7
Q

What is Alkaptonuria?

A

Rare disorder with lack of enzyme homogentisic acid oxidase (urine turns black on standing)

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8
Q

Why does malignant melanoma change the color of urine?

A

Melanogen turns it black

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9
Q

Turbity can also be described as…

A

Cloudy

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10
Q

Turbity is due to a bunch of stuff in the urine, such as…

A 
Crystal precipitation (called “amorphous material”)
Bacteria, yeast 
WBCs, RBCs
Mucus, squamous epithelial cells 
Sperm, prostatic fluids, lipids
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11
Q

Normal odor for urine

A

Faint, aromatic odor due to volatile acids from food products

Sometimes distinctive food odors: asparagus, onions, garlic

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12
Q

A putrid, foul odor suggests …

A

UTI (from bacteria)

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13
Q

Fruit odor suggests…

A

Ketone bodies

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14
Q

“Ash tray” urine smell suggests

A

Cigarette smoker

Duh

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15
Q

What all does a urine dipstick test?

A 
PH
Specific gravity
Glucose
Ketones
Proteins
Blood 
Nitrite
Leukocyte Esterase
Bilirubin
Urobilinogen
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16
Q

How are urine dipstick results reported?

A

As a value, as a positive/negative, or on a scale (+1, +2, +3, +4 or Small, Medium, Large)

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17
Q

Normal range for urine pH

A

4.5 - 8.0

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18
Q

What is considered to be “acidic” urine

A

4.5 - 5.5 pH

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19
Q

What is considered to be “alkaline” urine?

A

6.5 - 8.0 pH

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20
Q

A pH of < ____ or > _____ is not physiologically possible.

A

< 4.5 or > 8.0

PH > 8 indicates delay in processing with overgrowth of urease-producing bacteria

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21
Q

Urine pH parallels…

A

Serum pH

Most often used clinically in patients with metabolic acidosis

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22
Q

A measure of the weight of a substance (urine) compared with an equal volume of pure, solute-free water at the same temperature

A

Specific Gravity

The specific gravity of water is 1.000

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23
Q

Because urine is water containing dissolved substances (primarily urea, sodium, and chloride), the normal range of urine specific gravity is …

A

1.003-1.035

The more concentrated the urine, the higher the SG

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24
Q

SG reflects the ability of the kidney to…

A

Concentrate and dilute urine

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25
Q

What is Isosthenuria?

A

With kidney disease, the ability to concentrate urine may be lost, and the SG may become fixed at ~1.010 (similar to the initial plasma filtrate at the glomerulus)

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26
Q

Normal range of Urine volume

A

500cc - 2000cc/24 hours

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27
Q

What is Oliguria?

A

< 500cc in 24 hours

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28
Q

What is Anuria?

A

< 100cc in 24 hours

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29
Q

What is polyuria?

A

Excessive amounts of urine, usually quite dilute with SG 1.000-1.002

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30
Q

When do you get glucose in the urine?

A

Not normally detectable

When plasma glucose is about 150-180mg/dL, the renal “threshold” is exceeded and the patient will “spill” glucose in the urine

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31
Q

What can cause a false negative for urinary glucose?

A

Ascorbic acid

Aspirin

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32
Q

Products of incomplete fat metabolism, occurring when carbohydrate stores are diminished

A

Ketones

Their presence in urine may indicate acidosis (seen in DKA, rapid weight loss, fasting, starvation, pregnancy)

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33
Q

The urine dipstick test for protein is most sensitive to …

A

Albumin

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34
Q

Urine proteins are an indication of …

A

Renal endothelial dysfunction - an early sign of kidney disease

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35
Q

What are some limitations to the protein test on urine dipstick?

A

A dilute urine will underestimate the degree of albuminuria and vice versa

Moderately increased albuminuria in the range of 30 to 300 mg/day typically cannot be detected with dipstick testing

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36
Q

What might cause a false positive for urine protein?

A

Pyridium

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37
Q

Moderately Increased Albumin (formerly known as microalbuminuria) is a marker for …

A

Staging and prognosis for kidney disease

Albumin-to-Creatinine ratio on a random (spot) urine
24-hour urine collection

Especially useful in screening for kidney damage in high risk patients (BM, HTN, CVD)

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38
Q

Persistently positive dipstick test for protein should also have…

A

Albuminuria quantified

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39
Q

Dipstick can detect presence of RBCs, Hb from lysed RBCs, and myoglobin, but…

A

Must centrifuge and do micro to determine which

Sensitivity is 5-10 RBCs or 0.05-0.3mg/dL of Hb

Result SHOULD be negative

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40
Q

False negatives for blood on dipstick can be due to …

A

Ascorbic acid

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41
Q

Nitrites are produced by what type of bacteria?

A

Those that are capable of reducing nitrates to nitrite (ENTEROBACTERIACEAE)

Test should normally be negative

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42
Q

Nitrite test is ~50% sensitive in the diagnosis of …

A

UTI

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43
Q

What can cause a false negative for urine nitrites?

A

Urine in bladder for <4 hours (no time to reduce)

Bacteria which do not have necessary enzymes

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44
Q

________ is released by lysed neutrophils and macrophages and is a marker for _______________.

A

Leukocyte Esterase

Marker for the presence of WBCs, indicating infection

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45
Q

What can give you a false positive for Leukocyte esterase?

A

Vaginal contamination

Trichomonads

46
Q

Sensitivity for UTI increases if both…

A

+LE and +Nitrite

47
Q

_______ & _________ are used in conjunction to determine underlying pathology

A

Bilirubin & Urobilinogen

Dipstick is normally negative for both

48
Q

Urine turns _____ in the presence of bilirubin

A

BROWN

49
Q

Urine pH can be used to determine…

A

Metabolic acidosis or alkalosis

50
Q

What do we look at on the dipstick if concerned about acute kidney failure?

A

Specific Gravity

51
Q

Urinary ______ on dipstick = diabetes

A

Glucose

52
Q

Ketones in urine?

A

DKA

53
Q

Protein in the urine?

A

Kidney disease

54
Q

Moderately increased albumin in the urine?

A

Early kidney disease

55
Q

WBCs and RBCs on microscopy are reported as ….

A

The number per high power field (HPF)

56
Q

Casts are reported on microscopy as …

A

Number per low power field (LPF)

57
Q

On microscopy, RBCs in urine appear as…

A

Refractive disks

With hypertonicity of the urine, the RBCs begin to have a crenated appearance (shrunken)

58
Q

> _____ RBC/HPF is abnormal

A

> 3

59
Q

Conditions in which you will see increased RBCs

A 
Renal or lower urinary tract trauma
Kidney stones
Glomerular damage
Tumors
UTIs
Acute tubular necrosis
Nephrotoxicity
Contamination from vaginal bleeding
60
Q

Causes of hematuria more common in young patients?

A 
Transient/unexplained
UTI
Stones
Exercise
Trauma
61
Q

Causes of hematuria more common in the elderly

A

Cancer (bladder, kidney, prostate)***
BPH

Can also be transient, UTI, stone, or trauma related

62
Q

If positive blood on dipstick, what do you do first?

A

Centrifuge result

If sediment red —> hematuria

If supernatant red —> Dipstick heme
• If negative —> Beeturia, porphyria, other cause
• If positive —> could be myoglobin or hemoglobin
—> centrifuge blood sample —> clear plasma is myoglobinuria, red is hemoglobinuria

63
Q

How do you recognize WBCs on microscopy?

A

WBCs have lobed nuclei and refractive cytoplasmic granules

0-5 WBC/HPF is normal (>5 abnormal)
10-20 WBC/HPF is suspicious for UTI
≥ 20 WBC/HPF usually indicates UTI

64
Q

How are bacteria reported in urine microscopy?

A

As 0-4+/HPF

65
Q

Are bacteria in urine microscopy significant?

A

Maybe, maybe not

Depends on method of collection - clean catch midstream vs catheterized

Depends on how soon after collection the specimen is examined
• The longer it stands, the more bacteria grow
• Refrigeration will delay bacterial growth

66
Q

What are renal tubular and transitional epithelial cells?

A

Normally occur in small numbers; slough from tubule lining

Occur in larger numbers if there is tubular degeneration

67
Q

Degenerated tubular cells containing abundant lipoproteins, which appear refractile

A

Oval fat bodies

Exhibit “Maltese cross” configuration by polarized light microscopy

Indicative of NEPHROTIC syndromes

68
Q

Large polygonal squamous epithelial cells with small nuclei in increased numbers usually indicate…

A

A contaminated specimen of skin or external urethral origin (NOT A CLEAN CATCH)

69
Q

Urine casts are formed only in the _________ or __________.

A

Distal convoluted tubule (DCT) or collecting duct (CD)

They are not formed in the proximal convoluted tubule or loop of Henle

70
Q

_______ casts appear very pale and slightly refractile

A

Hyaline casts

Composed primarily of a mucoprotein (Tamm-Horsfall Protein) secreted by tubule cells

Common finding in normal urine

71
Q

Red cell casts suggest…

A

A glomerular or renal tubular injury

GLOMERULONEPHRITIS

72
Q

White blood cell casts suggest…

A

Acute pyelonephritis

May also be present in glomerulonephritis

73
Q

Renal tubular cell casts suggest…

A

Injury to the tubular epithelium

ACUTE TUBULAR NECROSIS

74
Q

What are granular casts?

A

Cellular casts which remain in tubules may break down, so that the cells forming them degenerate into granular debris

Initially coarse, then finely granular, then waxy cast

A non-specific finding

75
Q

Uric acid crystals in acidic urine

A

Secondary to hyperuricemia

76
Q

Cystine crystals?

A

Cystinuria

Rare genetic cause of kidney stones

77
Q

Struvite crystals in alkaline urine?

A

Secondary to infection by urease-producing bacteria

78
Q

Calcium oxylate crystals independent of pH

A

Cause of kidney stones

Can be monohydrate or dihydrate

79
Q

What do you use to confirm the presence of bacteriuria and to provide abx susceptibility info on the causative organism

A

Urine culture

> 100,000 colonies/ml most consistent with infection

80
Q

Why might you say that a UTI could still be present even with fewer than 100,000 colonies on urine culture?

A

If dysuria, frequency, and microscopic evidence of pyuria are present

81
Q

_____ is the major intracellular cation

A

Potassium

82
Q

What is the major route of elimination of K+?

A

Renal excretion

Regulation of renal K+ excretion and total body K+ balance occurs in distal nephron

83
Q

What are the main actions of aldosterone?

A

Increase renal sodium reabsorption

Increase renal potassium excretion

84
Q

Hyperkalemia is a serum [K+] of …

A

> 5.0 mEq/L

K+ > 6.0-6.5 may cause serious problems

85
Q

Elevated potassium may be caused by …

A

False elevation (pseudohyperkalemia)

Inadequate excretion by kidneys

Redistribution from ICF to ECF space

Excess administration

86
Q

Pseudohyperkalemia is artificially high K+ occurring from …

A

Hemolysis due to poor venipuncture technique

If you get a high K+, promptly repeat K+ to check for artificial elevation

87
Q

Typical etiologies for the inadequate excretion of K+

A

Renal failure: Check BUN/Cr

Meds that inhibit K+ excretion:
• Aldosterone antagonists
• K+ sparing diuretics
• ACEI/ARBs

Hypoaldosteronism
• Adrenal insufficiency (Addison’s)
• Congenital adrenal hyperplasia
• NSAIDS (uncommon)
• Renal tubular dysfunction
88
Q

Hyperkalemia due to redistribution of K+ occur when?

A

With conditions which move K+ from intracellular to extracellular space

Examples:
• Tissue damage (ie Rhabdomyolysis)
• Acidosis
• Decreased insulin

89
Q

In acidosis, a 0.1 decrease in pH raises serum K+ approximately ________.

A

0.5-1.0 mEq/L due to ECF shift

90
Q

What should you watch out for in patients with some renal impairment to avoid excess administration hyperkalemia?

A

Potassium-containing salt substitutes

Beware K+ administration in pt with impaired kidney function

91
Q

Clinical features of hyperkalemia

A

Generally occur when serum potassium ≥ 7

Muscle weakness
• Begins with legs and ascends to trunk and arms
• Can lead to flaccid paralysis

Conduction abnormalities and arrhythmias if K+ rises high enough

92
Q

Classic ECG finding in hyperkalemia

A

Peaked T waves

Prolonged SR segment

93
Q

Hyperkalemia! It’s A FACT!

A

A = arrhythmias

F = flaccid paralysis
A = ascending muscle weakness
C = conduction abnormalities
T = T waves
94
Q

Urgency of treatment for hyperkalemia depends on …

A

Degree of K+ elevation and clinical SSx

95
Q

Send the patient to the ER or ICU for monitoring if K+ > _____

A

> 6.5

96
Q

How do we rapidly correct hyperkalemia?

A

Calcium Chloride IV

Maneuvers to shift K+ from ECF to ICF:
• Sodium bicarbonate IV to increase pH
• D50W plus insulin IV

97
Q

Slow correction of hyperkalemia is usually through…

A

Loop or thiazides diuretics (beware decreased renal function)

Hemodialysis if kidney failure, esp severe, refractory

98
Q

The real key to correcting hyperkalemia?

A

Correct the underlying cause

Stop potassium-sparing diuretics
Stop ACEIs, ARBs, K+ supplements etc
Mineralocorticoid replacement (Addison’s)

99
Q

What is considered Hypokalemia?

A

Serum K+ < 3.5 mEq/L

Potassium <3.0 is potentially dangerous

100
Q

Low potassium may be caused by…

A

Inadequate intake
GI tract loss
Renal loss
Redistribution from ECF to ICF

101
Q

___________ is most likely to be a problem if patient is taking a medication that promotes K+ loss (ie Thiazides/loops)

A

Inadequate K+ intake

Potassium-containing foods or potassium supplements are often advised in order to prevent the development of hypokalemia

102
Q

_______ is a very common cause for low potassium

A

GI Loss

Upper GI Loss:
• Vomiting, NG suction
• Causes metabolic ALKALosis which promotes renal potassium loss

NOTE: lower GI loss (diarrhea) usually causes metabolic ACIDosis

103
Q

Causes of renal loss of potassium

A

Diuretics (very common)

Bicarbonate excretion

Mineralocorticoid excess (hyperaldosteronism or Cushings)

104
Q

Causes of redistribution of K+ from ECF to ICF

A

Metabolic ALKALOSIS (each 0.1 increase in pH lowers serum K+ by 0.5-1.0 mEq/L)

Insulin administration

Beta-adrenergic agonists (not ß-blockers!) induce cellular uptake of K+ and promote insulin secretion by pancreas

Hypokalemia periodic paralysis

105
Q

Clinical features of hypokalemia

A

Muscle weakness/paralysis - ascending pattern

Respiratory failure

Muscle cramping/rhabdomyolysis (vs flaccid paralysis in hyper)

GI distress (anorexia, N/V)

Cardiac arrhythmias (ECG - U Waves, flattened T waves, ST depression)

106
Q

Classic ECG findings in Hypokalemia

A

U WAVES, flattened T waves, ST depression

107
Q

Ed’s silly mnemonic for HYPOKALEMIA

A

“YOU CRAMP”

hYpOkalemia U waves

Cramping
Respiratory failure/Rhabdomyolysis
Anorexia, N/V
Muscle weakness
Paralysis
108
Q

Urgency of treatment for hypokalemia depends upon…

A

Severity of symptoms and K+ level

Correct the underlying cause if possible

Check for hypomagnesemia (causes potassium wasting), low K+ is harder to correct if Mg not corrected also

109
Q

If Dx of hypokalemia is unclear…

A

Get 24˚ urine potassium

If < 20 mEq/d suggests extrarenal/redistribution

If > 20 mEq/d suggests renal losses

110
Q

How do you rapidly correct hypokalemia?

A

Cardiac monitor

IV potassium chloride

Check stat K+ every 2-4 hours

Slow correction? Orally

Clin Lab Med Unit 2 (4 decks)

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