Urine sediment evaluation Flashcards
Why look for urine sediment
A microscopic examination is performed on a centrifuged sample
The sediment exam is used to look for cells, casts, bacteria crystals, etc
Microscopic examination complements the urine test strip
Sediment exam is the best method for performing a preliminary screen for the presence of bacteria
It is used to confirm the presence of RBCs and WBCs
It is hugely limited by the users technical abilities
What type of collection would you use for urine sedimentation
A freecatch sample is the best option for assessing the lower urogenital tract
First morning sample preferred
Cystocentesis is the best option to asses for the presence of bacteria in the bladder or kidneys
What should you do with urine after collected and why
The sample should be assessed right away
The sample should be stored in the fridge if it will not be evaluated within one hour of collection
Storage at room temp may result in bacterial overgrowth
Storage in the fridge may cause crystal artifacts
Casts may dissolve in alkaline urine
How much urine should you collect
Collect 3-10mL of urine and place it in a labelled centrifuge tube
The text recommends using 10mL of urine→ we often only acquire 3-5mL from SA patients; either volume is acceptable, but be consistent
Remember: always set aside small “sterile” sample (0.5cc at least) in the event that a urine culture is required
What to do to look at urine sedimentation
Centrifuge the sample
Make sure sample is balanced in the centrifuge
Centrifuge at 100-2000 RPM for 3-6 minutes
Use “urine setting” if available
Allow centrifuge to stop on its own
You may see a small pellet at the bottom of the tube
Decant supernatant leaving 0.5-1mL of urine in the tube
Pur the decant into a separate container if the chemical analysis has not yet been performed
Re-suspended sediment by flicking the tube or by gently drawing the sample up and down with a pipette
Place on drop of urine on a slide and add the cover slip
Optional- stain can also be added to the slide at thai time
Let slide sit for 30-60 sec
Scan with the entire slide on 10x objective to look for large formed elements like casts and clusters of cells
Move to high dry (40x objective)
What should you look for on high dry for urine
Identify the following with unstained urine (presence may be confirmed in stained urine)
RBC
WBC
Fat droplets
Bacteria
Crystals
Epithelial cells
Transitional cells
Debris/other
Look at a minimum of 10 fields of view under high power and record your results
What should you record on a urine sediment evaluation
Record the average number of casts and crystals per low power field (lpf)
Record the average number of all other cellular elements per high power field (hpf)
Bacteria
Sperm and mucus are only reported as being present
How to record cellular elements in urine
The number of RBCs, WBCs and epithelial cells present can be reported as an average number per 10 hpfs OR as a range of the number present in the fields examined
How to quantify bacteria in urine
Few: <5% of the filed os occupied
Moderate: 5-25% of the field is occupied
Many: 25-75% of the field is occupied
TNTC: >75% of the field os occupied
How to describe bacteria and crystals in urine
Bacteria may be reported as few, moderate, or many OR by the number range that is present/hpf (can also be reported as TNTC)
Bacteria and crystals may also be reported on the 1+ to 4+ scale
Give morphological description of any bacteria that are noted (cocci, rods, single, diploid, chains, clumps)
What stain is comonly used on urine
Sedi-stain
Advantages of sedi-stain
Highlights cells so that it is easier to identify the cell type
Fat droplets do not stain
Disadvantages of sedi-stain
Often contaminated so may result in falsely elevated bacterial counts
Stain sediment can be easily confused with crystals
Can remove stain sediment by filtering stain weekly
Quantification of elements MUST be done on the unstained slide as the stain will dilute the sample
Never add the stain directly to the collection tube
How to use sedi-stain on urine
Never add the stain directly to the collection tube
To stain
Add 1 drop urine+1 drop stian to slide, then coverslip
OR
Add one drop stain to edge of coverslip after viewing the unstained urine
Normal sediment in cat and dog urine is
Normal cat/dog urine has very little to no sediment
May have small numbers of sperm, epithelial cells, RBCs and WBCs depending on the method of collection and neuter status
May have fat droplets, mucus threads, hyaline casts and struvite/amorphous crystals
Normal sediment in equine and rabbit urine
Normal equine and rabbit urine can have a significant amount of sediment
This is due to large numbers of calcium carbonate crystals in healthy animals
Types of cells found inurine
Squamous epithelial cells
Transitional epithelial cells
Renal epithelial cells
RBCs
WBCs
Influenced by the collection method used
Common cells in free catch urine
squamous epithelial
sometimes WBC
common cells in catheter samples
squamous and transitional epithelial
RBC
Common cells found in cysto urine
sometimes Squamous and transitional epithelial
sometimes RBCs
Hematuria is
present of blood in urine
RBC in urine can indicate
Usually indicates haemorrhage of the urogenital tract
Causes of hematuria
Inflammation, infection, trauma, calculi, strenuous exercise, neoplasia, estrus, clotting/breeding disorder, severe renal disease
What can cause contamination hematuria
Can be contaminated due to cystocentesis, manual expression, or rough catheterization
What are common signs of hematuria
Usually corresponds with increase protein level on the dipstick
Cells appear as pale reddish brown to yellow colour with paler centre
Is fresh sample they will be uniform in size and shape (round and smooth)
Often crenated in concentrated urine or a sample that has sat for a period of time
Can be confused with fat globules or yeast
Fat globules have significant variation in size, sit on a different plane, refract light, and do not take up stain
Whit blood cells in urine is caused by
Indicates inflammation, infection, trauma, or peripheral blood contamination
May be present in small numbers in free catch samples due to contamination from the lower urogenital tract
When is WBCs in urine abnormal
> 2-3/hpf is abnormal- blood contaminations needs to be taken into consideration
What do WBCs in urine look like
WBC are uniformly round cells, slightly larger than RBCs but smaller than renal epithelial cells
Can have a slight grey to greenish-yellow colour
They often have granules in the cytoplasm and will have a lobulated nucleus
Most WBC present in urine are neutrophils
Cellular features are heightened with stain
May be found alone or in clumps
Pyuria is and can indicate
Increased numbers of WBCs in the urine are called pyuria
Pyuria can indicate a bacterial UTI even if bacteria are not visible on the sediment exam
Indication to culture
Are epithelial cells in urine normal and what will their presence increase
A few are normal in a urine sample
The acceptable number depends on the method of collection used
A marked increase in number usually indicates inflammation
Their presence will increase the protein level reading on the urine test strip
What are the 2 types of epithelial cells that can be present in urine
Squamous epithelial cells
Transitional epithelial cells
Renal epithelial cells