Urinalysis Continued
The Microscopic Exam

Microscopic Exam Background
Introduction
A microscopic examination is a procedure to determine if cells, crystals, casts, and microorganisms are present in the urine. If performed manually, the examination begins by placing about 10 milliliters of urine in a glass tube, then centrifuging the contents for about 5 minutes. A small portion of the sediment is placed on a glass slide and flattened with a coverslip. The glass slide is then moved to a microscope stage and surveyed for suspended components.
Cells Found in Urine
Squamous epithelial cells – line the distal end of the urethra and cover the inner surface of the vagina. A high number (> 20 per High-Power Field; 400X) indicates the sample may be contaminated.
Renal tubular epithelial cells (RTEs) originate from the walls of the nephron tubules in the kidney, including the distal and proximal convoluted tubules and collecting ducts. Two or more cells per HPF indicate damage to the renal tubules.
Transitional epithelial cells line the interior of the ureters, bladder, and a portion of the urethra. More than a few cells per HPF indicates a possible urinary tract infection (UTI).
Squamous Cells
(400 X)

Renal Tubulars Cells
(400 X)

Transitional Cells
(400 X)

Red blood cells in high numbers (> 5 five per HPF) indicate bleeding along the urinary tract or prostate. Possible causes for urinary tract bleeding are kidney infection or disease, urinary tract infections (UTIs), kidney or bladder stones, and kidney injury.
White blood cells (most commonly neutrophils) above 5 cells per HPF indicate a possible bacterial urinary tract infection (UTI) or inflammation of the urinary tract or kidneys.
Red Blood Cells (RBCs)
(400 X)

White Blood Cells (WBCs)
(400 X)

Crystals Found in Urine
Crystals appear in the urine when particular substances become too concentrated, and they aggregate to form larger solids, often due to dehydration. Dehydration, the overconsumption of certain foods, changes in urine pH, or certain medicines can cause crystals to form.
The accumulation of crystals can cause stones that block the urinary tract passageways (kidney stones), urinary tract infections (UTIs), and kidney infections.
Substances that often combine to form crystals include calcium oxalate, uric acid, struvite (triple phosphate crystals), cystine, bilirubin, and calcium carbonate.
Urine Crystals that are Often Present in Small Numbers
Calcium Oxalate Dihydrate Crystals
(400 X)

Calcium Oxalate Monohydrate Crystals
(400 X)

Uric Acid Crystals
(400 X)

Struvite Crystals
(400 X)

Urine Crystals that Indicate Pathology and Should Not be Present
Cystine Crystals
(400 X)

Bilirubin Crystals
(400 X)

Calcium Carbonate Crystals
(400 X)

Cholesterol Crystals
(400 X)

Casts Found in Urine
Casts are relatively large cylindrical structures, each having a matrix made of glycoproteins (Tamm-Horsfall proteins). The epithelial cells of the nephron tubules secrete the matrix glycoproteins, especially if the urine pH is low, urine concentration is high, or the urine flow rate is low. Because of their large size, casts are typically viewed at 100X.
The most common type of cast, the hyaline cast, consists primarily of matrix glycoproteins. They often appear in the urine in low numbers due to stress, dehydration, or strenuous exercise and are usually not concerning.
In comparison, casts containing erythrocytes, leukocytes, epithelial cells, or fat indicate kidney disease or infection and should not be present in the urine. Granular and waxy casts probably result from the degeneration of cellular casts, and are also associated with kidney disease or infection.
Hyaline Cast
(400 X)

Red Blood Cell Cast
(400 X)

White Blood Cell Cast
(400 X)

Fatty Cast
(400 X)

Granular Cast
(400 X)

Waxy Cast
(400 X)

Microorganisms Found in Urine
Microorganisms are usually not in the urine. Their presence, even in lows numbers, indicates a bacterial, fungal, or parasitic infection of the urinary tract (kidney, ureters, bladder, and urethra).
Bacteria (Cocci) and WBCs
(400 X)

Bacteria (Rods) and WBCs
(400 X)

Fungi (Yeast Cells) and WBCs
(400 X)

Parasites (Trichomonas vaginalis)
(400 X)

Microscopic Exam Procedures
Transfer Urine to Centrifuge Tube
First, mix the freshly collected urine sample to re-suspend the solid components.
Transfer about 10 ml of urine to a 15 ml conical tip centrifuge tube.
Seal the centrifuge tube with a screw cap.
Place Tube in Centrifuge
Place the urine-filled tube in an empty slot in a centrifuge rotor bucket.
Arrange other fluid-filled centrifuge tubes to balance the rotor assembly.
Adjust Centrifuge Settings and Start Rotor
Turn on the centrifuge using the push toggle switch.
Adjust the rotor speed to 1,500 rpm and the time to 5 minutes.
Start the centrifuge rotor. The outward force generated by the spinning rotor will move any suspended particles to the bottom of the tube.
Remove Centrifuge Tube
Remove the urine-filled tube from the centrifuge.
Place the centrifuge tube in one of the open slots in a holder rack.
Remove the screw cap from the top of the centrifuge tube.
Remove Urine Supernatant
Use a transfer pipette to withdraw the urine supernatant (top portion) from the centrifuge tube, leaving the urine sediments at the bottom of the tube.
Place the supernatant in a small beaker so that it can be discarded appropriately.
Transfer Sediment to a Glass Slide
Draw a small volume of the urine sediment into a transfer pipette from the centrifuge tube.
Squeeze a drop from the transfer pipette onto the surface of a glass slide.
Prepare Slide for the Microscope
Spread the sediment into a thin, transparent layer by placing a coverslip on top of the sample droplet.
Move the glass slide to the microscope stage so the sediment can be examined.
Microscopic Exam Results
Examine Urine Sediment
Position the microscope’s 40X objective over the coverslip and examine three fields of urine sediment for cells, casts, crystals, and microorganisms.
Use the images below to identify and record the structures seen in the urine sediment.
For each type of structure, record your findings as the average number seen per HPF (High Power Field; 400x).
Urine Sediment Identification Images
Squamous Cells
(400 X)

Renal Tubulars Cells
(400 X)

Transitional Cells
(400 X)

Red Blood Cells (RBCs)
(400 X)

White Blood Cells (WBCs)
(400 X)

Urine Crystals that are Often Present in Small Numbers
Calcium Oxalate Dihydrate Crystals
(400 X)

Calcium Oxalate Monohydrate Crystals
(400 X)

Uric Acid Crystals
(400 X)

Struvite Crystals
(400 X)

Urine Crystals that Indicate Pathology and Should Not be Present
Cystine Crystals
(400 X)

Bilirubin Crystals
(400 X)

Calcium Carbonate Crystals
(400 X)

Cholesterol Crystals
(400 X)

Hyaline Cast
(400 X)

Red Blood Cell Cast
(400 X)

White Blood Cell Cast
(400 X)

Granular Cast
(400 X)

Waxy Cast
(400 X)

Fatty Cast
(400 X)

Bacteria (Cocci) and WBCs
(400 X)

Bacteria (Rods) and WBCs
(400 X)

Fungi (Yeast Cells) and WBCs
(400 X)

Parasites (Trichomonas vaginalis)
(400 X)

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References /Attributions
General
The University of Utah – Urinalysis
Cells
Labpedia – Urine Analysis:- Microscopic Examination, and Interpretations
Oxford University Press – Cells in the Urine Sediment
National Library of Medicine (NIH) – Urinalysis
The University of Wisconsin School of Pharmacy – Urinalysis Interpretation
Crystals
Illinois State Veterinary Medical Association – Urinalysis Made Easy
Kidney Support and Protection – Can You Prevent Kidney Stones
Medical News Today – Urine Crystals
National Kidney Foundation – Kidney Stones
NIH National Library of Medicine – Urinary pH and Stone Formation
Casts
Cornell University College of Veterinary Medicine – Casts
Lincoln Memorial University – Urinalysis
Oxford University Press – Casts in the Urine Sediment
Renal Fellow – Granular and “Muddy Brown” Casts
Renak Fellow – Waxy Casts
University of California (San Francisco) – Urinary Casts
Microorganisms
Clevand Clinic – Urinary Tract Infections