What is the characteristic feature of the crystals found in gout?

The characteristic feature of the crystals found in gout is that they are negatively birefringent. In gout, the crystals consist of monosodium urate, which can be identified under polarized light microscopy. When these crystals are oriented in one plane, they appear yellow, and when rotated 90 degrees, they appear blue, demonstrating their negative birefringence.

This property is vital for diagnosing gout and differentiating it from other conditions that might involve similar symptoms, such as pseudogout, where the crystals are positively birefringent due to the presence of calcium pyrophosphate dihydrate. Understanding the birefringence pattern aids clinicians in making accurate diagnoses and providing appropriate treatment for patients with gout.

The other options, such as spherically shaped or thin and needle-like, do not accurately describe the crystal morphology, which is predominantly needle-shaped and can be variable in thickness but is characterized primarily by its birefringent properties.