[Histonet] Re: gout crystals

Robert Richmond rsrichmond <@t> gmail.com
Wed Jul 7 18:31:16 CDT 2010

Gout crystals are monosodium urate. In clinical material they're found
in large masses, called tophi (TOE-fie, singular tophus). The
individual crystals are long and needle-like, with negative
birefringence if your pathologist is so fortunate as to have a full
wave plate (a.k.a. first order plate, gout slider) on their

The alcohol fixation and processing routine is ideal, but rarely
achievable. The specimen will normally come to you in formalin. The
crystal masses in the tophi can be picked out with the point of a
scalpel blade (if you're still allowed scalpel blades with points on
them) into water or alcohol, and looked at as a wet preparation in a
polarizing microscope, where you can see the crystals with the aid of
a polarizer. Calcium pyrophosphate ("pseudogout") crystals, blocky
with positive birefringence, can also be identified with this

The CPT code for crystal examination cannot, I think, be assigned in
addition to the 88305.

Bob Richmond
Samurai Pathologist
Knoxville TN

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