What feature is indicative of acute gouty arthritis in joint fluid analysis?

The characteristic feature indicative of acute gouty arthritis in joint fluid analysis is the presence of cloudy fluid containing negatively birefringent needle-shaped crystals.

In gout, the condition is caused by the deposition of monosodium urate crystals due to elevated levels of uric acid in the blood. When joint fluid is examined under polarized light microscopy, these crystals display a specific appearance: they are needle-shaped and show negative birefringence. This means that the crystals appear differently when viewed under polarized light compared to regular light, thus aiding in distinguishing gout from other forms of arthritis.

The identifying features in the joint fluid, such as cloudiness and the specific type of crystals, help confirm the diagnosis of acute gouty arthritis and guide appropriate treatment. Additionally, the presence of these crystals correlates with acute inflammation, as the body's immune response to the crystals leads to joint swelling, redness, and pain.

In summary, the identification of cloudy fluid with negatively birefringent needle-shaped crystals is a definitive hallmark of acute gouty arthritis, making it the correct answer in this context.