Scope specifications: a glossary
- French gauge (Fr)
- A measure of outer circumference, not diameter: 1 Fr is one third of a millimetre of diameter, so a 7.5 Fr shaft is 2.5 mm across.
- Working channel
- The internal lumen an instrument, laser fibre or basket passes through, and the route for irrigation. The single most consequential number on a ureteroscope.
- Deflection
- How far the tip articulates from straight, quoted per direction. Not always symmetrical.
- Field of view
- The angular width of the image, usually 90° to 120°. Wider is not automatically better.
- Depth of view
- The range over which the image stays in focus — "2–50 mm", "5–80 mm".
- Working length
- Usable shaft length: around 650–700 mm for ureteroscopes, 380–390 mm for cystoscopes.
- Dual lumen
- Two separate channels, so irrigation or suction can continue with an instrument in place.
- Intrarenal pressure (IRP)
- Pressure inside the collecting system during ureteroscopy, associated with pain, fluid absorption and infective complications when elevated.
- "Not stated"
- The manufacturer does not publish this figure. It is not zero, and not an invitation to substitute a competitor's number.