Microscopic Findings

Question 1

Uromodulin

Answer 1

Another name for Tamm-Horsfall protein that creates casts, major constituent of mucus, it is a glycoprotein excreted by the RTE cells of the distal convoluted tubules and upper collecting ducts

Question 2

Cast Formation

Answer 2

Protein gels more readily under conditions of urine flow stasis, acidity, in the presence of sodium and calcium.

Question 3

Stepwise Cast Formation

Answer 3

1. Uromodulin aggregates into individual protein fibrils attached to the RTE cells
2. The fibrils interweave to form a loose fibrillar network
3. The fibrils further interweave to form a solid structure
4. Urinary constituents attach to the solid matrix
5. Approaching fibrils detach from the epithelial cells
6. The cast is excreted

Question 4

Bacterial Casts

Answer 4

Bacterial casts (both within and bound to the protein matrix) are seen in pyelonephritis.

Question 5

Epithelial Casts

Answer 5

Similar to RTE cells, they are associated with:

• heavy metal and chemical toxicity
• drug-induced toxicity
• viral infections
• allograft rejection

When tubular damage is present, the majority of cells will be attached to the cast surface.

Question 6

Fatty Casts

Answer 6

Seen with oval fat bodies and free fat droplets in disorders causing lipiduria. Associated with nephrotic syndrome, toxic tubular necrosis, diabetes mellitus, and crush injuries. Confirmation of fatty casts is performed using polarized microscopy and Sudan III or Oil Red O fat stains.

• Cholesterol demonstrates characteristic Maltese cross formation under polarized light
• Triglycerides and neutral fats stain orange with fat stains.

Question 7

Granular Casts

Answer 7

The origin of the granules in nonpathologic conditions is from the lysosomes excreted by RTE cells during normal metabolism

Question 8

RBC Casts

Answer 8

Show bleeding in the nephron, primarily associated with damage to the glomerulus - allows passage of cells through the membrane, however any damage to the nephron capillary structure can cause their formation

Granular, dirty, brown casts representing hemoglobin degradation products such as methemoglobin may also be present, associated with the acute tubular necrosis often caused by the toxic effects of massive hemoglobinuria that can lead to renal failure

Question 9

Waxy Casts

Answer 9

Show extreme urine stasis, indicating chronic renal failure. Brittle, highly refractive cast, caused by degeneration of the hyaline cast matrix and any cellular elements or granules contained in the matrix.

Last stage of degradation of granular casts.

Question 10

Broad Casts

Answer 10

“Renal failure casts”, extreme urine stasis. As a mold of the distal convoluted tubules, the presence of broad casts indicates destruction (widening) of the tubular walls.

Question 11

Sternheimer-Malbin Stain and 2% Acetic Acid

Answer 11

Consists of crystal violet and safranin O (WBCs)

2% acetic acid enhances nuclear detail in the sediment

Question 12

Neutrophils in Urine

Answer 12

Neutrophils lyse rapidly in dilute alkaline urine and begin to lose nuclear detail

If they’re exposed to hypertonic urine they absorb water and swell, Brownian movement of the granules within these larger cells produces a sparkling appearance and they referred to as “glitter cells”

Question 13

Lipid Stain

Answer 13

Oil red O and Sudan III and polarizing microscopy can be used to confirm the presence of free fat droplets and lipid containing cells

Question 14

Hansel Stain

Answer 14

Preferred stain for urinary eosinophils consisting of methylene blue and eosin Y

Question 15

What to do with a doubtful RBC ID

Answer 15

Adding acetic acid will lyse RBCs, leaving the yeast, oil droplets, and WBCs intact

Question 16

Urinary Eosinophil Association

Answer 16

Primarily associated with drug induced interstitial nephritis

Question 17

RTE cells

Answer 17

Are usually larger than WBCs with an eccentrically located nucleus

Question 18

Pyuria

Answer 18

Increasing urinary WBCs indicating the presence of an infection or inflammation

Question 19

Transitional Epithelial Cells, Types, Size, Numbers

Answer 19

• Smaller than squamous cells and appear in several forms, including spherical, polyhedral, and caudate, All forms have distinct centrally located nuclei
• Cells in direct contact with the urine absorb water, becoming spherical and forming cells much larger than the polyhedral and caudate cells.
• Increased numbers of transitional cell seen singly, in pairs, or in clumps are present following invasive urologic procedures such as catheterization

Question 20

Renal Tubular Epithelial Cells

Answer 20

Cells from the proximal convoluted tubule are larger than other RTE cells and have coarsely granular cytoplasm

Cells from the distal convoluted tubule are smaller than those of the PCT and are round or oval
Collecting duct RTE cells are cuboidal and are never round along with the ecentrically placed nucleus the presence of at least one straight edge differentiates them
The presence of RTE cells are clinically significant in that increased amounts indicate necrosis of renal tubules, caused by exposure to heavy metals, drug-induced toxicity, hemoglobin and myoglobin toxicity, viral infections, pyelonephritis, allergic reactions, malignant infiltrations, salicylate poisoning, and acute allogenic transplant rejection

Question 21

Lipiduria

Answer 21

Most frequently associated with damage to the glomerulus caused by the nephrotic syndrome, also seen with severe tubular necrosis, diabetes mellitus, and in trauma cases that cause release a bone marrow fat being released from the long bones

Question 22

Yeast, Patients Found In

Answer 22

Most commonly seen in diabetic patients, immunocompromised patients, and women with vaginal moniliasis