Microscopic examination CASTS

Cylindroids

structures w/ tapered ends that are formed at the junction ascending loop of Henle and the distal convoluted tubule

Cylindruria

presence of urinary casts

uromodulin

glycoprotein, made by kidneys, forms the matrix of casts (Tamm-Horsfall)

Where are casts formed?

in the lumen of the distal and collecting tubules of the kidney

In what pH will casts disolve?

alkaline

Other than in casts, where else is uromodulin found?

mucus

When is uromodulin increased?

stress and exercise

Hyaline casts

In which pathologic conditions would you expect to see hyaline casts?

acute glomerulonephritis, pyelonephritis, CHF, renal disease

non-pathologic causes of hyaline casts:

stress, exercise, dehydration

RBC casts

What is the significance of RBC casts?

- bleeding in the nephron
- damage to the glomerulus
- hemo/myoglobinuria

Will the presence of RBC casts be identified on the reagent strip?

yes

WBC casts

When would you expect to see WBC casts?

inflammation, infection, pyelonephritis

What would be present in acute interstitial nephritis?

WBC casts, NO bacteria

What would be present in pyelonephritis?

WBC casts and bacteria

Epithelial cell casts

Where are epithelial cell casts formed?

distal convoluted tubule (DCT)

What is the clinical significance of epithelial cell casts?

- advanced tubular destruction
- urinary stasis w/ disruption of tube linings
- heavy metal/chemical/drugs
- viral infections
- allograft rejection

How can you differentiate epithelial and WBC casts?

single nucleus

What is the defining characteristic of fatty casts under polarized light?

maltese cross formations

Fatty casts

Disorders where fatty casts are seen:

- NEPHROTIC SYNDROME
- tubular necrosis
- diabetes mellitus
- crush injuries

What mixed casts are associated with pyelonephritis?

WBC (predominant) and RTE (renal tubule epithelium)

Mixed casts associated with glomerulonephritis:

RBC and WBC (mostly RBC)

Granular casts

Causes of granular casts:

from lysosomes excreted by RTE cells, strenuous exercise

What do granular casts become after degradation?

waxy casts

Waxy casts

What does the presence of waxy casts indicate?

chronic renal failure

Broad casts

What is another name for Broad casts?

Renal failure casts

Broad casts are associated with?

viral hepatitis, extreme urine stasis