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UA Spring > Microscopic exam of urine pt 2 > Flashcards

Microscopic exam of urine pt 2 Flashcards

1
Q

Where are casts formed?

A

Only in the nephron (PCT, Loop of Henle, DCT, collecting duct)

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2
Q

Structure of cast

A
  • Parallel sides
  • Rounded ends
  • Some fragmented
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3
Q

Cast composition

A

Tamm-Horsfall protein
- glycoprotein constantly excreted by RTE cells for lubrication
- Forms gel matrix of protein

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4
Q

Is Tamm-Horsfall protein detected by reagent strip

A

Nope! Even though it’s a protein, NOT detected

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5
Q

List steps of cast formation

A
  1. Tamm-Horsfall aggregates to RTE cells to form protein fibrils
  2. Fibrils form loose network such that components in urine can get trapped
  3. Further interweaving of fibrils to form solid matrix
  4. Urine components attach to matrix
  5. Cast detaches from RTE and exits nephron
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6
Q

Cylinduria

A

Casts in urine

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7
Q

Cast formation occurs more readily if:

A
  • Decreased urine flow (stasis)
  • Acidic pH bc casts dissolve in alkaline pH
  • Increased electrolytes
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8
Q

T/F
Cast formation can block urine flow within nephron

A

True

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9
Q

Non-pathological causes of casts

A

Exercise and dehydration

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10
Q

Pathological causes of casts

A

Renal conditions

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11
Q

List the types of casts

A
  • Hyaline
  • Cellular (RBC, WBC, RTE)
  • Fatty
  • Granular (fine or coarse)
  • Broad
  • Waxy
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12
Q

Hyaline cast normal value

A

0-2/hpf

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13
Q

Which cast is most frequently seen?

A

Hyaline cast

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14
Q

Non-pathological causes of hyaline casts (hint: there’s 3)

A
  • Strenuous exercise
  • Dehydration
  • Heat exposure
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15
Q

Pathological causes of hyaline casts (hint: there’s 4)

A
  • Acute glomerulonephritis
  • Pyelonephritis
  • Chronic renal disease
  • Congestive heart failure
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16
Q

How to visualize hyaline casts?

A
  • Decreased light bc refractive index similar to urine
  • Sternheimer-Malbin stain or phase microscopy
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17
Q

RBC casts

A
  • RBCs imbedded inside the matrix, NOT stuck outside
  • Must distinguish from clump of RBCs
  • Typically see free-floating RBCs
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18
Q

Chemical strip test result if RBC casts are present

A

Blood = positive

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19
Q

Non-pathological cause of RBC casts

A

Strenuous exercise (rare)

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20
Q

Pathological cause of RBC casts

A
  • Indicates nephron bleeding
  • May see proteinuria
  • Associated with glomerulonephritis
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21
Q

ID element and medical state

A
  • RBC cast
  • Hemoglobinuria (orange-red or red-brown)
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22
Q

ID element and medical state

A
  • RBC cast
  • Methemoglobinuria (brownish)
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23
Q

ID the element

A
  • WBC cast with WBCs imbedded in the matrix (don’t confuse with WBC clumps)
  • PMNs, granular appearance
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24
Q

Pathological causes of WBC casts

A
  • Pyelonephritis (upper UTI), presence of bacteria may be significant
  • Acute interstitial nephritis (absence of bacteria, may see eosinophils)
  • Glomerulonephritis
25
Q

WBC casts associated with __

A

Infection or nephron inflammation

26
Q

T/F
Cystitis of lower UTI produces WBC casts

A

False, it does not

27
Q

Bacterial casts

A
  • Bacteria inside the cast, not attached outside of a hyaline cast
  • WBC and free-floating bacteria present
  • Hard to ID, confused with granular casts
  • Rare
  • Confirm with Gram stain
28
Q

Bacterial casts associated with

A

Pyelonephritis

29
Q

ID the element

A

Bacterial cast

30
Q

RTE cast

A
  • Seriously pathological but rare
  • Caused by tubular destruction
  • Must distinguish from WBC cast (use staining and mononuclear structure)
31
Q

ID the elements

A
32
Q

Fatty/oval fat body cast

A
  • Composed of fat droplets or oval fat bodies
  • Fat appears refractile
  • Confirm with polarized light and fat stain (will not stain with Sternheimer-Malbin)
33
Q

Pathological causes of fatty/oval fat body casts

A
  • Nephrotic syndrome
  • Tubular necrosis
  • Crush injuries
34
Q

ID the element

A

FATTY CAST

35
Q

ID the element

A

Mixed cellular cast (RBCs and WBCs)

36
Q

How to ID mixed cell casts

A

Use staining

37
Q

Common mixed cellular cast mixtures and their disease associations

A
  • RBC + WBC = glomerulonephritis
  • WBC + RTE = pyelonephritis
38
Q

Granular casts

A

These casts pick up materials from urine, which start to degrade and form granularity (crystals, RBC, WBC, cellular material from RTE is most common)

39
Q

What are the two ways that granular casts can form?

A
  1. Free cells in tubular lumen are destroyed and incorporated as cast forms
  2. Cellular cast forms first and the cells get destroyed inside the already-formed cast
40
Q

T/F
Granular cast starts as coarse and becomes fine over time as granules disintegrate

A

True

41
Q

What is required for a granular cast to form?

A

Urinary stasis (can’t pee)

42
Q

ID the element

A

Fine granular cast

43
Q

ID the element

A

Coarse granular cast

44
Q

ID the element

A

Coarse granular cast

45
Q

Waxy cast

A
  • Occur from long-term urinary stasis
  • Occur from the further breakdown of granules contained within granular casts, also associated with destruction of hyaline matrix
46
Q

Waxy casts associated with

A

Chronic renal failure

47
Q

Waxy casts usually seen ___

A

Along with other casts

48
Q

ID the element

A

Waxy cast

49
Q

ID the element

A

Waxy cast

50
Q

ID the element

A

Waxy cast

51
Q

How to distinguish between hyaline and waxy casts?

A
  • Waxy cast = broken/brittle ends
  • Hyaline casts = intact, rounded ends
52
Q

Distinguish the elements

A
53
Q

Broad casts

A
  • Frequently referred to as renal failure casts bc cell death leads to wider casts
  • 2-6x wider than the typical casts and usually occur from very long-term urinary stasis
  • Can form from any type of cast
54
Q

Broad casts formed from ___

A
  • Any type of cast
  • Most common are granular or waxy type
55
Q

Two ways to form broad casts

A
  1. From DCT due to dilation or tubular wall destruction (get wider)
  2. Collecting ducts (wider than DCT) due to severe decrease in renal flow
56
Q

ID the element

A

Broad granular cast

57
Q

ID the element

A

Broad waxy cast

58
Q

ID the element

A

Broad casts

UA Spring (8 decks)

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