Мікроскопічне дослідження кристалів у суглобах
Crystal Type | Birefringence | Elongation* | Shape | Length (micrometer) |
|---|---|---|---|---|
Monosodium urate | Strong | Negative | Needle- or rod- shaped | 2–15 |
Weak or often not birefringent | Positive | Rhomboid- or rod- shaped | 2–15 | |
Calcium oxalate (rare)† | Weak or strong | Positive or indeterminate | Bipyramidal | 5–30 |
Not birefringent with polarized light | — | Shiny, coinlike, or slightly irregular (often too small to delineate) | 3–65 (aggregates) | |
* Elongation is determined by inserting an additional red plate or compensator between the two polarizing plates in the microscope and aligning a crystal with an orienting arrow denoting the axis of slow vibration. Crystals that have negative elongation are yellow parallel to the axis of slow vibration marked on the compensator; positive elongation appears blue in the same direction. In clinical practice, these have also been termed negative or positive birefringence. | ||||
† These crystals occur primarily in patients with renal failure. | ||||