What is negative birefringence gout?

Negatively birefringent urate crystals are seen on polarizing examination in 85\% of specimens. Microscopic analysis in pseudogout shows calcium pyrophosphate (CPP) crystals, which appear shorter than MSU crystals and are often rhomboidal.

What does it mean to be negatively birefringent?

Negative birefringence means that Δn = ne − no is less than zero. In other words, the polarization of the fast (or slow) wave is perpendicular to the optic axis when the birefringence of the crystal is positive (or negative, respectively).

What are negatively birefringent crystals?

Uric acid crystals are often intra-cellular and appear needle-shaped and yellow (negatively birefringent) while CPPD crystals appear rhomboid shaped and blue (weakly positively birefringent).

What does positively birefringent mean?

Definition of positive birefringence : birefringence of a medium (as quartz) that transmits the ordinary rays with greater speed than the extraordinary.

What color is negative birefringence?

Under polarizing light microscopy, urate crystals are yellow when aligned parallel to the axis of the red compensator and blue when aligned across the direction of polarization (ie, they exhibit negative birefringence).

What are the crystals in gout?

Gout and pseudogout are the two most common crystal-induced arthropathies. Gout is caused by monosodium urate monohydrate crystals; pseudogout is caused by calcium pyrophosphate (CPP) crystals and is more accurately termed calcium pyrophosphate disease (CPPD).

What is the difference between gout and pseudogout?

What is the difference between pseudogout and gout? Pseudogout and gout are both types of arthritis, and they’re both caused by the accumulation of crystals in the joints. While pseudogout is caused by calcium pyrophosphate crystals, gout is caused by urate (uric acid) crystals.

What birefringent means?

Birefringence is formally defined as the double refraction of light in a transparent, molecularly ordered material, which is manifested by the existence of orientation-dependent differences in refractive index.

Is pseudo gout positively birefringent?

Pseudogout crystals (CPP) are rod-shaped with blunt ends and are positively birefringent. Thus, pseudogout crystals are blue when aligned parallel to the slow ray of the compensator and yellow when they are perpendicular. Crystals must be distinguished from birefringent cartilaginous or other debris.

What is difference between positive and negative crystal?

(optics) a doubly refracting crystal in which the index of refraction for the extraordinary ray is greater than for the ordinary ray, and the former is refracted nearer to the axis than the latter, such as as quartz and ice; as opposed to negative crystal: one in which this characteristic is reversed, such as Iceland …

What do you mean by negative crystal?

Definition of negative crystal 1 : a cavity that has the form of a crystal and occurs in a mineral mass. 2 : a crystal showing negative double refraction.

What color are gout crystals?

Characteristic	Monosodium urate crystals	Calcium pyrophosphate dehydrate crystals
Birefringence	Strong	Weak
Shape	Needle-like, sharp edges	Rhomboid, rod-like
Color parallel to polarizer	Yellow	Blue
Color perpendicular to polarizer	Blue	Yellow