¾ Hyaline casts imply possible damage to the glomerular capillary membrane, which is permitting leakage of proteins through the glomerular filter Urine Analysis 99 ¾ Hyaline casts may be temporarily seen in:

 

Casts (Fig. 5.21)

These are cylindrical; diameter varies according to the

size of the renal tubule or duct of their origin. The ends are

usually rounded but may be flat, irregular or tapered.

Urine Analysis 95

A B

Transitional cell (white) and a

leukocyte (black), 400 x

Transitional cell and bilirubin crystals

FIGS 5.19A AND B: Transitional epithelial cells in urine

A B

FIG. 5.20A AND B: (A) Squamous cells in urine; (B) Urinary

squamous cells

FIG. 5.21: Casts seen in the renal tubule

A

B

FIGS 5.18A AND B: Renal tubular epithelial cells

Hyaline (Fig. 5.22)

These are colorless, homogeneous, transparent.

Coarse Granular Casts

These contain fat, degenerated cell or protein aggregates

which appear as dark granules (Figs 5.18 to 5.20).

Finely Granular Casts

These contain fine granules in all or in part of the cast (Figs

5.21 to 5.23).

Fatty Casts (Fig. 5.24)

These contain highly refractile globules of varying size. Fat

droplets will stain bright orange with Sudan III.

Red Cell Casts (Fig. 5.25)

Yellow under LP objective. If many cells are present in

each cast, the matrix will not be visible.

96 Concise Book of Medical Laboratory Technology: Methods and Interpretations FIGS 5.23A TO I: Array of casts observed in urine (A) Hyaline cast;

(B) Fatty cast; (C) Hyaline to finely granular cyst; (D) Cellular cast;

(E) Cellular to coarsely granular cast; (F) Coarsely granular cast;

(G) Finely granular cast; (H) Granular to waxy cast; (I) Waxy cast

A A

D

G

E

H

F

C

I

FIG. 5.24: Fatty cast

FIG. 5.25: RBC cast

FIG. 5.26: RBC casts in urine

FIG. 5.22: Hyaline cast in urine

Blood Casts (Fig. 5.26)

These contain hemogobin from degenerated RBCs. Are

yellow to orange in color, best seen with LP objective.

Leukocyte Casts (Fig. 5.27)

These contain small granular cells in a clear matrix. The

leukocytes may be admixed with red cells or epithelial

cells. Clumps of leukocytes may sometimes look like casts.

Urine Analysis 97

Tubular Epithelial Casts (Fig. 5.28)

These resemble leukocyte or mixed cell casts. They often

appear as two rows of cells in a narrow cast.

Waxy Casts (Figs 5.21 to 5.23)

These are yellow and homogeneous, have sharper outlines

than hyaline casts with irregular ends and cracks.

Structures commonly confused with casts are mucous

threads and rolled, cigar-shaped squamous epithelial cells.

Mucous threads are long, ribbon-like strands with poorly

defined edges and have pointed or split ends. Often, they

appear to have longitudinal striations.

Fat: Free globules are seen in grape-like clusters. They vary

in size more than the yeast cells or red cells (Fig. 5.29).

Detailed Study of Important Urinary

Microscopy Constituents

Red Cells and Red Cell Casts

Normal Values of RBCs

1-2/LPF (low powered field)

0-1/HPF (high powered field)

Red cell casts Nil (zero)/LPF.

In a healthy subject, red cells are only occasionally

found in the urine, but persistent finding needs to be

investigated. Examine sediment under low and high

power. RBCs are studied under high power.

Clinical Relevance

Red cell casts :

¾ Casts composed largely of RBCs are rarely found

normally and indicate hemorrhage or desquamative

conditions of the nephron

¾ RBC casts imply acute inflammatory or vascular

disorder in the glomerulus

FIG. 5.28: Renal tubular epithelial cell casts in urine

FIG. 5.27: Leukocyte casts

FIG. 5.29: Casts as seen in urine—diagrammatic presentation

98 Concise Book of Medical Laboratory Technology: Methods and Interpretations ¾ They may be the only manifestation of:

• Acute glemerulonephritis

• Renal infarction

• Collagen disease

• Kidney involvement in subacute bacterial endocarditis.

¾ The usual finding in SLE is RBC casts and epithelial cell

casts.

Red Blood Cells

The finding of more than one to two RBCs per HPF is an

abnormal condition that can indicate:

¾ Renal or systemic disease

¾ Trauma to kidney.

Increased Red Cells are found in

¾ Pyelonephritis

¾ SLE

¾ Renal stones

¾ Cystitis

¾ Hemophilia

¾ Prostatitis

¾ Tuberculosis of urinary tract

¾ Malignancies of urinary tract.

Red cells in excess of WBCs: Imply bleeding into the urinary

tract as may occur in:

¾ Trauma

¾ Tumors

¾ Aspirin consumption

¾ Anticoagulant therapy

¾ Thrombocytopenia.

Interfering Factors

¾ Increased numbers of RBCs can be found following

violent exercise, a traumatic catheterization, passage of

stones, or contamination by menstrual fluid

¾ Alkaline urine hemolysis RBCs and dissolves casts

¾ Many drugs can cause RBC appearance in urine

¾ Red cell casts may occur after strenuous physical

activity and contact sports.

White Cells and White Cell Casts

Normal Values

WBCs : 0–5/high powered field (HPF)

WBC casts : none (zero)/LPF.

WBCs may come from anywhere in the genitourinary

field. While white cell casts always come from renal tubules.

Clinical Relevance

Leukocytes:

¾ Large numbers of WBCs indicate bacterial infection of

urinary tract

¾ If infection is in the kidney, WBCs may be associated

with cellular and granular casts, bacteria, epithelial

cells and relatively few red cells

¾ Usually, presence of abnormal numbers of WBCs in

urine necessitates urine culture

¾ WBC casts

¾ White cell casts indicate renal parenchymal infection

¾ May be found in:

• Pyelonephritis most common cause

• Acute glomerulonephritis

• Interstitial inflammation of the kidney

¾ It is difficult to differentiate between WBC and epithelial

cell casts

¾ As pyelonephritis may remain completely asymptomatic even though renal tissue is being progressively

destroyed, careful examination (using low power) of

urinary sediment for leukocyte casts is mandatory.

Interfering Factors

Vaginal discharge can contaminate the sample. Either

a “clean catch” (midstream sample) or a catheterized

specimen should be taken to rule out contamination.

Epithelial Cells and Epithelial Cell Casts

Normal Values

Occasional renal epithelial cell may be found.

Renal epithelial cell casts are formed by cast-off tubular

cells. Since tubular cells are being replaced, it is of little

importance, therefore, to find an occasional epithelial cells

or clumps.

Clinical Relevance

Large numbers of epithelial cells are abnormal.

May be seen in:

¾ Nephrosis

¾ Amyloidosis

¾ Poisoning from heavy metals and toxins.

Squamous epithelial cells (squames) are usually seen

when urine is contaminated with vaginal discharge.

Hyaline Casts

Normal Value

Occasional hyaline cast/LPF may be found.

These are clear, colorless casts and are formed when

protein (Tamm-Horsfall) within the tubules precipitates

and gels. Their appearance in the urine depends on the

rate of urine flow, urine pH, and the degree of proteinuria.

Examine under low power.

Clinical Relevance

¾ Hyaline casts imply possible damage to the glomerular

capillary membrane, which is permitting leakage of

proteins through the glomerular filter

Urine Analysis 99

¾ Hyaline casts may be temporarily seen in:

• Fever

• Postural strain

• Emotional fatigue

• Strenuous exercise

• Palpation of kidney.

¾ When large numbers of hyaline casts appear in the

urine along with heavy proteinuria, fine granular casts,

fatty casts, or oval fat bodies or fat droplets, nephrotic

syndrome should be considered