[Histonet] Re: uric acid crystals in tissue for gout

Robert Richmond rsrichmond <@t> gmail.com
Mon May 16 12:13:35 CDT 2011

To see uric acid (actually monosodium urate) crystals in tissue, the
best thing to do is pick them out of the wet tissue with a needle, put
them on a slide in a drop of water with a coverslip, and examine them
promptly with polarization.

If they can't be seen on gross examination, then the special
processing techniques mentioned certainly help, though often MSU will
come through in routine processing.

The real problem is for the pathologist. Most of the small-hospital
pathologists I work with aren't allowed to have a polarizer on their
microscopes, so they have to take the trouble to go to the urine scope
(no, the broken-sunglasses shtick doesn't work), if they're allowed in
the urine lab which they sometimes aren't. And if they're willing to
take the time.

To identify MSU, you need to demonstrate negative birefringence. That
requires a full wave plate system (sometimes called a first order
plate), and somebody has to have preserved the documentation so that
the microscopist knows which way is up. In the absence of a procedure
manual, the pee scope can be quite frustrating. (Also I have to spend
five minutes cleaning and aligning it.)

I'm not telling you anything I don't have to put up with at least once a month.

Bob Richmond
Samurai Pathologist
Knoxville TN

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