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Completed my research fellowship with @OchsnerNephro @OchsnerEdu last week. I couldn’t have been happier with my experience and I wanted to share some of what I learned.
I tried my best to cover the basic steps of spinning urine and some tips that were helpful for me below
I tried my best to cover the basic steps of spinning urine and some tips that were helpful for me below
To start, you’ll need:
1) Microscope slide
2) Cover slip
3) 15 mL conical tube
4) Sternheimer Malbin Urine Sediment Stain (Sedi stain)*
5) Plastic transfer pipet
6) Tabletop centrifuge
7) Microscope
8) Liquid gold (urine)
*Consider other stains ie Sudan III for lipid droplets
1) Microscope slide
2) Cover slip
3) 15 mL conical tube
4) Sternheimer Malbin Urine Sediment Stain (Sedi stain)*
5) Plastic transfer pipet
6) Tabletop centrifuge
7) Microscope
8) Liquid gold (urine)
*Consider other stains ie Sudan III for lipid droplets
Obtain fresh urine. We’ve found within 1 hour is best whether it’s provided by the patient or from foley tubing. Avoid using urine from the foley bag, if possible.
Once collected, give the sample a quick swirl and pour 10 mL (or whatever you have into the conical tube).
Once collected, give the sample a quick swirl and pour 10 mL (or whatever you have into the conical tube).
Balance your centrifuge with an equivalent amount of water in a tube across from your urine. Spin for 5-10 mins.
Retrieve your sample and check out your pellet.
Some samples may not produce a significant pellet (notice haziness toward bottom) but don’t underestimate what you may find even in the smallest pellets.
Some samples may not produce a significant pellet (notice haziness toward bottom) but don’t underestimate what you may find even in the smallest pellets.
Now...pour everything out. Dump the contents of tube right into the sink. You’ll inevitably have a few microliters of supernatant that remain with the pellet due to surface tension.
* Large pellets may require more supernatant or resuspending less pellet
* Large pellets may require more supernatant or resuspending less pellet
Give the tube a series of vigorous flicks. Continue until your pellet is resuspended.
Grab your pipette and plate your slide. Remember, you don’t need to flood the slide with urine. A single drop will do.
Add a drop of Sedi stain to your tube and plate a stained sample.
Add a drop of Sedi stain to your tube and plate a stained sample.
Begin with low power objectives and use high power field as needed. Scan the entirety of the slide because you never know where a stray acanthocyte or cast might be lurking.
When it comes to acanthocytes, phase contrast is king.
Don’t be fooled by fungi that can mimic this finding. They have a more oval elongated shape.
A crenated cell is not an acanthocyte, it’s the result of tonicity.
“We do not miss acanthocytes here.” - @VelezNephHepato
Don’t be fooled by fungi that can mimic this finding. They have a more oval elongated shape.
A crenated cell is not an acanthocyte, it’s the result of tonicity.
“We do not miss acanthocytes here.” - @VelezNephHepato
Amorphous crystals in low power field can mimic muddy brown casts sometimes. Make use of high power.
A slide may look less “muddy brown” if sitting around for a bit. However, we’ve found a pellet can sit for hours (maybe days
) without reducing sample quality. Just replate.
A slide may look less “muddy brown” if sitting around for a bit. However, we’ve found a pellet can sit for hours (maybe days
) without reducing sample quality. Just replate.
Granular casts have a lot of diagnostic and prognostic value. (See Chawla an Perazella scores)
Don’t stop looking just because you’ve confirmed ATN. Multiple etiologies of AKI can exist at once!
Don’t stop looking just because you’ve confirmed ATN. Multiple etiologies of AKI can exist at once!
The composition of cellular casts (tubular epithelial, RBC, WBC) is often difficult to determine, but finding cells around the cast may be a critical clue and sedi stain is invaluable.
Utilize everything your microscope has to offer:
Phase contrast objectives - acanthocytes
Polarized light - fat droplets, crystals
Dark field - great definition of casts, cool factor
Everything has its niche uses
Phase contrast objectives - acanthocytes
Polarized light - fat droplets, crystals
Dark field - great definition of casts, cool factor
Everything has its niche uses
There is an abundance of world class urine microscopists on twitter and they are always happy to help.
@VelezNephHepato @JoseTesser @jrseltzer @zxnboy and many more #pisseprophets
@VelezNephHepato @JoseTesser @jrseltzer @zxnboy and many more #pisseprophets
There is not a ton of literature on urine microscopy, the composition of casts, and the natural history of casts. To top it all off, you may not get paid to spin urine. However, few things in medicine are as diagnostic as an acanthocyte or the abundance of muddy brown casts.
Grateful for the productive research and learning over the last 5 months! Nowhere near the Jedi level urine microscopy skills of @VelezNephHepato but I’m sure I’ll find my way into the urine lab a few times as a PGY1!
