Lecture 4 - Sediment Analysis Pt1

What should be done before centrifuging a urine sample?

Mix urine sample thoroughly.

What temperature should a urine sample be for centrifugation?

Room temperature.

Why should urine specimens be capped before centrifugation?

To prevent the formation of aerosols and the spread of zoonoses (e.g., leptospirosis).

What is the recommended RPM and time for urine centrifugation?

1000-3000 RPM for 5-6 minutes

How are crystals and casts quantified in a wet mount?

As an average number per LPF (10x).

How are cells quantified in a wet mount?

As an average number per HPF (40x).

How are sperm and bacteria reported in a wet mount?

As none, few, moderate, or many per HPF.

What stains can be used for staining a wet urine sediment?

Sedi-Stain® (Sternheimer-Malbin stain) or New Methylene Blue (NMB).

How is a wet stained slide prepared for urine sediment analysis?

Add 1-2 drops of stain to sediment, then prepare a wet mount as for unstained specimens.

How is a dry mount prepared from urine sediment?

Make a line smear, air-dry quickly, and stain with Diff-Quik.

Which objective should be used to examine bacteria in a dry mount?

100x oil immersion.

What is a dry mount best used for?

Bacteria and cell types, including neoplastic cells.

What is a dry mount NOT good for?

Viewing crystals or casts.

Which urine collection methods can cause iatrogenic hemorrhage?

Cystocentesis

Which urine collection methods contribute to squamous epithelial cells and bacteria?

Free flow (voided) and catheterization.

What are the major components of urine sediment?

Epithelial cells, erythrocytes, leukocytes, casts, mucus, fat, bacteria, sperm, parasites, fungi, and crystals.

Which parasites or parasite eggs may be found in urine sediment?

Bladder worm (pearsonema spp), giant kidney worm (Dioctophyma renale), microfilaria (if parasite load is high) pig kidney worm (Stephanurus dentatus)

What are the three main types of epithelial cells in urine?

Squamous, transitional, and renal epithelial cells.

Where do squamous epithelial cells originate?

Distal urethra, vagina, and prepuce.

Where do transitional epithelial cells originate?

Proximal urethra, bladder, ureter, and renal pelvis.

How many transitional epithelial cells per HPF are normal?

Fewer than 5/HPF.

What does an increased number of transitional epithelial cells indicate?

Cystitis (usually seen with RBCs and WBCs).

Where do renal epithelial cells originate?

Renal tubules.

Are renal epithelial cells commonly seen in urine?

No, they are rare. Large numbers indicate renal tubule disease.

Which neoplasia is most common in the urinary tract?

Transitional cell carcinoma (TCC).

What are the clinical signs of transitional cell carcinoma (TCC)?

Hematuria, stranguria, and pollakiuria.

How is transitional cell carcinoma diagnosed?

Tissue biopsy or tumor cells in sediment with clinical signs.

Which type of neoplasia may be seen in urine sediment after appearing in blood first?

Lymphoma.

What happens to RBCs in concentrated urine?

They undergo crenation (spiky edges).

What happens to RBCs in dilute urine?

They swell and may appear as ghost cells.

What condition is indicated by more than 4-5 RBCs per HPF?

Hematuria.

What are common causes of hematuria?

Iatrogenic trauma, inflammation, estrus, neoplasia.

What type of WBCs are most commonly found in urine?

Neutrophils.

How do WBCs appear in urine?

Round, granular, larger than RBCs, smaller than epithelial cells.

What condition is indicated by more than 5 WBCs per HPF?

Pyuria.

What should be checked for if bacteria are present in urine sediment?

WBCs (and vice versa).

What is needed to confirm intracellular bacteria in WBCs?

A stained smear.

What are casts primarily composed of?

Mucoprotein (Tamm-Horsfall protein).

Where are casts formed?

In the renal tubules.

How does the appearance of casts change over time?

Cellular casts degrade into granular, then waxy casts.

Does the number of casts correlate with severity of disease?

No, but the type of cast does.

Which urine conditions promote cast formation?

Acidic pH, high salt concentration, reduced tubular flow rate, presence of mucoprotein matrix.

What happens to casts in alkaline urine?

They dissolve.

What are the seven main types of casts?

Hyaline, epithelial, leukocyte, erythrocyte, granular, waxy, fatty.

What do hyaline casts look like?

Colorless, homogenous, semi-transparent with rounded ends.

What are hyaline casts composed of?

Mucoprotein.

Are hyaline casts normal?

A few may be seen in healthy animals.

What are epithelial casts composed of?

Renal epithelial cells embedded in a hyaline cast.

What do epithelial casts indicate?

Damage to tubular epithelium.

What do leukocyte casts indicate?

Inflammation, such as pyelonephritis.

Which type of WBCs are usually present in WBC casts?

Neutrophils.

What do RBC casts indicate?

Hemorrhage or inflammation in the tubules.

Are RBC casts common in cats and dogs?

No, they are rare.