Casts

Question 1

Cast structure

Answer 1

Parallel sides
Rounded ends
sometimes fragmented

Question 2

Cast composition

Answer 2

Uromodulin
excreted by RTE cells
gels to form a matrix
not detected on a reagent test strip

Question 3

Cast formation process

Answer 3

Tamm-horsfall protein aggregates
fibrils for loose network
further interweaveing forms a Matrix
cast detaches from the RTEs and is excreted

Question 4

Cast formation conditions

Answer 4

Urinary stasis
acidic pH
increased electrolytes

Question 5

Hyaline casts

Answer 5

Most frequent.
Formed in: LoH, distal tube, collecting duct
normal: 0-2/lpf
Non-patho: strenuous excersize, dehydration, heat exposure
patho: acute glomerulonephritis, pyelonephritis, chronic renal disease, congestive heart failure

Question 6

Hyaline cast appearence

Answer 6

Parallel sides with rounded ends
few components in matrix if any

Question 7

RBC cast

Answer 7

RBCs imbedded in the matrix
non-patho: rarely strenuous exercise
Path: bleeding in the nephron, glomerulornephritis

Question 8

RBC cast appearance

Answer 8

Methemoglobin breakdown - Brownish color
Hemoglobinuria - orange red to red brown

Question 9

WBC cast

Answer 9

WBCs (PMNs) trapped in the matrix
Pathologic: infection or inflam in the nephron
Pyelonephritis: upper UTI. Bacteria may be significant
Acute interstitial nephritis. Bacteria absent, may see Eosinophils
Glomerular nephritis

Cystitis does NOT produce WBC casts

Question 10

bacterial casts

Answer 10

Associated with pyelonephritis
WBC and free bacteria present
Very rare - confirm with gram stain

Question 11

RTE casts

Answer 11

Very serious, very rare
Tubular destruction
differentiate from WBC cast with stains

Question 12

Fatty/Oval fat body cast

Answer 12

refractile
stain with sudan III or oil red O
cholesterol -> maltese cross
Will not stain with sternheimer-malbin

Question 13

Fatty/oval fat body cast pathogenicity

Answer 13

Lipiduria
Nephrotic syndrom
tubular necrosis
crush injuries

Question 14

Mixed cell casts

Answer 14

ID difficult without staining
Common types:
RBC and WBC: glomerularnephritis
WBC and RTE: pyelonephritis

Question 15

granular cast

Answer 15

Cellular materials degrade to form granules
Most common: from RTEs
Coarse to fine
REQUIRES urinary stasis

Question 16

Waxy cast

Answer 16

It’s a waxy cast
long term urinary stasis
Chronic renal failure
Seen along with other casts - long term breakdown of other materials

Question 17

Waxy cast appearance

Answer 17

Brittle & high refractive index
fragmented or squared ends
stain dark pink
Notches on sides

Question 18

Broad cast

Answer 18

“Renal failure cast”
2-6x wider than other casts
very long urinary stasis, can form of any other cast

Question 19

Ways Broad casts form

Answer 19

Dilation or destruction of distal tube walls (causes expansion)

collecting ducts - severe decrease in renal flow