The fundamental difference between these two instruments lies in their physical construction and how they navigate the urinary anatomy.

• Semi-Rigid Ureteroscopes: These feature a long, slender, and straight shaft made of stainless steel. While called "semi-rigid," they are mostly inflexible, offering only a slight "give" to accommodate minor anatomical curves. They typically use fiberoptic or fused-quartz image bundles.

• Flexible Ureteroscopes: These are highly sophisticated devices with a shaft that can bend. They feature an actively deflectable tip (often up to 270°) controlled by a lever on the handle. Modern versions utilize "chip-on-tip" digital technology, providing high-definition video directly from the end of the scope.