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Renal Week 1 > Urinalysis > Flashcards

Urinalysis Flashcards

1
Q

How should you obtain a sample for urinalysis?

A

obtain a fresh sample clean catch midstream and analyze within 60 minutes

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2
Q

Then how should the urine be processed?

A

centrifugation to produce supernatant for urinary dipstick analysis and urinary pellet for light microscopy

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3
Q

What are the two ways to determine urinary concentration?

A

-specific gravity (determined by the number AND the weight of solutes in solution)

or

-osmolality (determined only by the number of solutes in solution)

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4
Q

When is specific gravity not a good marker of urine concentration?

A

when there are abnormal numbers of heavy solutes in the urine (glycosuria or contrast media

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5
Q

Isotonic urine (isosthenuria) has a SG of what?

A

1.010 (~300mOsm/kg)

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6
Q

What is the SG of a maximally dilute urine? maximally concentrated?

A
  1. 002 (50-100mOsm)

1. 030 (1200 mOsm)

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7
Q

What is a normal urinary pH?

A

5-6.5

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8
Q

Metabolic acidosis is associated with a pH of what?

A

less than 5.3

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9
Q

Urinary pH greater than 7.5 suggests what?

A

UTI with urea splitting bacteria (e.g. proteus, E coli)-gram negative usually

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10
Q

Glucose should normally be negative in urine. How can you differentiate between the causes of glycosuria?

A

hyperglycemia due to diabetes will oversaturated reabsorption transporters in the PT

but if serum glucose levels are normal and you have glycosuria, it implies PT dysfunction (aka Falcon syndrome)- commonly associated with MM or heavy metals

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11
Q

T or F. Ketones are normally found in urine

A

F.

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12
Q

When would ketones be seen in the urine?

A
  • fasting
  • diabetic ketoacidosis
  • alcoholic ketoacidosis

where plasma ketoanions leads to filtered load exceeding the PT reabsorptive capacity

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13
Q

Dipstick for ketones is specific for what?

A
  • acetone

- acetoacetate

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14
Q

Is Bilirubin normally found in the urine?

A

No, only in pathologic states of liver disease or failure (in these states, it is conjugated bilirubin that’s found in the urine). Unconjugated bilirubin is insoluble and not present in any state in the urine

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15
Q

What is uronilinogen?

A

metabolic byproduct of bilirubin metabolism that is excreted in urine

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16
Q

Is nitrite normally found in the urine?

A

No, nitrate is though and when you have a positive nitrite test, it is because the nitrate in urine has been reduced by a gram neg. organism and this is indicative of a UTI

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17
Q

What would a positive urine leukocyte esterase suggest?

A

this is an enzyme common in neutrophils so its presence in urine would suggest infection (UTI) but can also be seen in inflammatory renal diseases such as lupus

18
Q

What is normal protein urine levels?

A

less than 150 mg/day and is mainly represented by Tamm-Horsfall proteins, which are low molecular weight proteins (with small amounts of albumin) secreted by the tubular cells

19
Q

How does a urinary dipstick estimate protein excretion?

A

It is semi-quantitative and is expressed on a scale of: trace to 3+

20
Q

How can a truly quantitative proteinuria be measured?

A

have to do a 24 hr urine collection (gives g/hr) or

look at the ratio of urine protein over creatinine (both measured as mg/dl) in a ‘spot’ urine sample

(ex. ratio of 5= 5gm/24hr)

21
Q

A dipstick protein test is specific for what?

A

albumin- the most common protein by far (3+ would be nephrotic almost)

22
Q

What would you do if you wanted to measure all protein in urine?

A

sulfosalicyclic acid test (precipitates all protein in urine and is graded the same way)

3+ also suggests nephrotic range depending on how cloudy it gets

23
Q

What is tubular proteinuria?

A

failure of the PT to reabsorb the low molecular weight proteins via pinocytosis that are normally filtered reflecting PT dysfunction

24
Q

What is overflow proteinuria?

A

when you have excess production of low molecular weight proteins that exceed the reabsorptive capacity of the PT such as in light chain proteinuria in MM

25
Q

T or F. Overflow proteinuria is negative for dipstick, but strong positive for the sulfosalicyclic acid test

A

T. Because light chains and immunoglobulins are being precipitated

26
Q

What else can be measured with urinalysis?

A
  • Na, K, Cl, Ca, uric acid, Pi
  • urinary osmolality in supernatant
  • urinary anion gap
  • urinary creatinine and urine urea nitrogen
27
Q

What is a urinary anion gap used to assess?

A

hyperchloremic metabolic acidosis- is it due to loss of HCO3 in diarrhea/vomit or is it due to inability to excrete acid in urine?

Eqn. Na+K-Cl

A negative UAG suggests a GI cause because the kidneys are excreting as much acid into urine as possible

28
Q

Does normal urine have rbcs?

A

0-2 per high powered field and urine dipstick will be negative for blood. Dipstick also sensitive to hemoglobin and myoglobin

29
Q

How can you tell if rbcs in a urine sample are of renal origin or extra-renal?

A

RBC’s in sediment are of renal origin are often dysmorphic (extra renal are normal shaped), have casts, lack clots in urine and are often associated with proteinuria

both dipsticks will be positive

30
Q

Does normal urine have wbcs?

A

0-4 per high powered field (aka glitter cells)

31
Q

What are some causes of urinary wbcs?

A
  • UTI
  • pyelonephritis
  • allergic interstitial nephritis
  • intense glomerulonephritis such as in lupus
32
Q

When would renal tubular epithelial cells be seen in urine?

A

when there is acute tubular injury, such as acute tubular necrosis

hard boiled egg look

33
Q

When are hyaline casts found in urine?

A

normally after a lot of exercise with volume depletion

aka ghost cells

34
Q

What are urinary casts?

A

Represent precipitates of protein forming in the lumen of tubules (collecting tubules) held together by Tamm-Horsfall protein as the matrix of the casts

cylindrical in shape and may contain cellular debris

hyaline casts are the only normal casts found in urine

35
Q

What makes Tamm-Horsfall protein?

A

thick ascending limb

36
Q

What are waxy casts?

A

acellular, pathologic casts that are more dense in appearance and bordered by a whiteish border (aka renal failure casts)

CHRONIC indication

37
Q

When are waxy casts found?

A

CKD

38
Q

T or F. Lipiduria is absent in normal urine

A

T.

NOTE: Maltese cross, oval fat bodies, and fatty casts may be seen using polarized light

39
Q

Lipiduria is associated with what commonly?

A

nephrotic syndrome

40
Q

what are granular casts? What do they suggest?

A

They are not normal but not really suggestive of any particular disease. Caused by breakdown of debris as they pass through the tubules

Cant tell what cell type they originated from

41
Q

RBC cast are pathonmeomic for what?

A

glomerulonephritis

Renal Week 1 (20 decks)

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