Guidewires in Endourology
Placement of a guidewire is the most critical step of an endoscopic procedure. The majority of injuries that occur during an endourologic surgery are ureteral injuries – and these typically occur with passage of a guidewire past an impacted stone or site of ureteral edema. While it has been proposed that the routine use of a safety wire is not required [1,2], I believe that it is a prudent safety measure that should be taken to provide emergency access to the upper urinary tract throughout the procedure.
Guidewires differ in size, tip design, surface coating and shaft rigidity. An ideal guidewire requires little force to flex in response to resistance and requires a large force to perforate tissue. A slippery hydrophilic guidewire is used to bypass an impacted calculus, whereas a stiffer guidewire is used to straighten a tortuous ureter or to pass instruments and access sheaths into the upper collecting system. 
Clayman et al.  compared nine available guidewires in an in vitro study, and concluded that the Boston Scientific Glidewire required the greatest force to puncture in an in vitro model whereas the Boston Scientific Amplatz super stiff was the most resistant to bending. This indicated that in this in vitro model, the Boston Scientific Glidewire would be the safest wire for initial access and the Boston Scientific Amplatz super stiff would be the best wire for passing instruments.
Hybrid wires incorporating features of different glidewires (a hydrophilic distal tip for bypassing an obstructing stone, a kink-resistant body, and a flexible proximal tip for backloading of instruments) have been developed.  We have evaluated the two commercially available hybrid wires (Bard NiCore and Boston Scientific Sensor). Neither hybrid wire is as stiff as a Boston Scientific Amplatz superstiff, suggesting the importance of continued reliance on this wire for passage of ureteral access sheaths and large stents.
- Eandi JA, Hu B, Low RK. Evaluation of the Impact and Need for Use of a Safety Guidewire during Ureteroscopy. Journal of Endourology. 22(8): 1653-58 (2008).
- Dickstein RJ, Kreshover JE, Babayan RK, Wang DS. Is a Safety Wire Necessary During Routine Flexible Ureteroscopy? Journal of Endourology. 24(10): 1589-92 (2010).
- Holden T, Pedro RN, Hendlin K, Durfee W, Monga M: Evidence-based instrumentation for flexible ureteroscopy: a review. Journal of Endourology J Endourol. 22(7):1423-6,2008
- Clayman M, Uribe CA, Eichel L, etal. Comparison of Guide Wires in Urology. Which, When and Why? Journal of Urology. 171:2146-50 (2004).
- Sarkissian C, Korman E, Hendlin K, Monga M: Systematic evaluation of guidewires: stiffness, lubricity and tip configuration. Urology 79(3):513-7,2012.
Practical Information About Guidewire
Commonly used guidewires in endourology—– proper selection for specific task at hand saves time and ensures success of procedure without complications.
- Roadrunner (Hydrophilic) ——————————————— Cook Urological,USA
- PTFE Guidewire ———————————————– Cook Urological,USA
- Glidewire ———————- ► Zebra urological ———– Boston Scientific Microvasiv, USA
- Benston-type 15cm.flexible tip PTFE coated wire ———– Boston Scientific Microvasiv, USA
- Amplatz Superstiff Urowire XF ———– Boston Scientific Microvasiv, USA
- Benston Guidewire ——————————————————- Applied Medical, USA
- Amplatz Guide wire ——————————————————- Applied Medical, USA
- PTFE coated Bard Guidewire —————- ► Bard urological Division,US A
- Terumo hydrophilic coatednitinolGuidewire———— ►Terumo co. Ltd.
Guidewire differ in size, tip design, surface coating (PTFE, hydrophilic polymer) and shaft rigidity.
They are usually 150cm (80-260cm) long and come in different diameters – 0.018 inch (1.4F), 0.025 inch (1.9F), 0.032 inch (2.5F), 0.035 inch (2.7F) and 0.038 inch (2.9F)
May be straight or angled (J tip) with flexibility of varying length (usually 3 cm)to minimize trauma during passage. Guidewire with floppy tip at both ends helps in backloading of instruments without injury to instrument or guidewire.
STRUCTURE OF GUIDEWIRE:
The basic design is round central core or mandrel over which is bound tightly coiled stainless steel springwire. Core provides rigidity to guidewire. In glidewire and many others at present, in place of stainless steel,nitinol core (alloy of nickel and titanium )is used which is surrounded by polyurethane shell and covered with hydrophilic polymer. Nitinol is memory metal and so regains their shape after twisting (kink resistant). For frictionless performance glidewires must be kept wet during passage. They are radio opaque but laser fibres can damage them during lithotripsy. Guidewires are supplied in coiled sheathsto allow ease of handling and storage.
Dr. Nikhil Choudhary & Dr. Atul Khandelwal
Dept, of Urology, IGIMS, Patna 14.