604 CHAPTER 16 Urological surgery and equipment

Sterilization of urological equipment

Techniques for sterilization

Autoclaving

Modern cystoscopes and resectoscopes, including components such as light leads, are autoclavable. Standard autoclave regimens heat the instruments to 121°C for 15 minutes or 134°C for 3 minutes.

Chemical sterilization

This involves soaking instruments in an aqueous solution of chlorine dioxide (Cidex), an aldehyde-free chemical (there has been a move away from formaldehyde because of health and environmental concerns). Chlorine dioxide solutions kill bacteria, viruses (including HIV and hepatitis B and C), spores, and mycobacteria.

Cameras cannot be autoclaved. Use a camera sleeve or sterilize the camera between cases.

Sterilization and prion diseases

Variant Creutzfeldt Jacob disease (vCJD) is a neurodegenerative disease caused by a prion protein (PrP). Other examples of neurodegenerative prion diseases include classic CJD, kuru, sheep scrapie, and bovine spongiform encephalopathy (BSE). Variant CJD and BSE are caused by the same prion strain and represent a classic example of cross-species transmission of a prion disease.

There has been much recent concern about the potential for transmission of vCJD between patients via contaminated surgical instruments. Classic CJD may be transmitted by neurosurgical and other types of surgical instruments because normal hospital sterilization procedures do not completely inactivate prions.1 It is not possible at present to quantify the risks of transmission of prion diseases by surgical instruments. To date, iatrogenic CJD remains rare, with 267 cases having been reported worldwide, up to the year 2000.2

The risk of transmission of CJD may be higher with procedures performed on organs containing lymphoreticular tissue, such as tonsillectomy and adenoidectomy, because vCJD targets these tissues and is found in high concentrations there. For this reason there was a move toward the use of disposable, once-only-use instruments for procedures such as tonsillectomy. However, these instruments have been associated with a higher postoperative hemorrhage rate.3

Prions are particularly resistant to conventional chemical (ethylene oxide, formaldehyde, and chlorine dioxide) and standard autoclave regimens, and dried blood or tissue remaining on an instrument could harbor prions that will not then be killed by the sterilization process. Once

1 Collinge J (1999). Variant Creutzfeldt-Jakob disease. Lancet 354:317–323.

2 Collins SJ, Lawson VA, Masters CL (2004). Transmissible spongiform encephalopathies. Lancet 363:51–61.

3 Nix P (2003). Prions and disposable surgical instruments. Int J Clin Pract 57:678–680.

606 CHAPTER 16 Urological surgery and equipment

Telescopes and light sources in urological endoscopy

There are three types of modern urological telescopes—rigid, semi-rigid, and flexible. These endoscopes may be used for inspection of the urethra and bladder (cystoscourethroscopes, usually simply called cystoscopes), the ureter and collecting system of the kidney (ureteroscopes and ureterorenoscopes), and, via a percutaneous access track, the kidney (nephroscopes).

The light sources and image transmission systems are based on the innovative work of Professor Harold Hopkins, University of Reading.

The Hopkins rod-lens system

The great advance in telescope design was the development of the rodlens telescope, which replaced the conventional system of glass lens with rods of glass, separated by thin air spaces that essentially were air lenses (Fig. 16.13). By changing the majority of the light transmission medium from air to glass, the quantity of light that could be transmitted was doubled. The rods of glass were also easier to handle during manufacture, and therefore their optical quality was greater.

The angle of view of the telescope can be varied by placing a prism behind the objective lens. 0°, 12°, 30° and 70° scopes are available.

Lighting

Modern endoscopes (urological and those used to image the gastrointestinal tract) use fiber-optic light bundles to transmit light to the organ being inspected. Each glass fiber is coated with glass of a different refractive index so that light entering at one end is totally internally reflected and emerges at the other end (Fig. 16.14).

These fiber-optic bundles can also be used for image (as well as light) transmission, as long as the arrangement of the fibers at either end of the instrument is the same (coordinated fiber bundles are not required for simple light transmission). The fiber bundles are tightly bound together only at their end (for coordinated image transmission). In the middle, the bundles are not bound—this makes the instrument flexible (e.g., flexible cystoscope and flexible ureteroscope).

TELESCOPES AND LIGHT SOURCES IN UROLOGICAL ENDOSCOPY 607

(a)

Glass Air

(b)

Glass Air

Figure 16.13 (a) Diagram of conventional cystoscope. The glass lenses are held in place by metal spacers and separated by air spaces. (b) Rod-lens telescope with “lenses” of air, separated by “spaces” of glass, with no need for metal spacers.

Reprinted with permission from Blandy J, Fowler C (1996) Urology. Wiley-Blackwell, pp. 3–5.

Figure 16.14 Total internal reflection permits light to travel along a flexible glass fiber. Reprinted with permission from Blandy J, Fowler C (1996) Urology. Wiley-Blackwell, pp. 3–5.