Flexible endoscopy has been used in human and veterinary medicine for many years. Over time instrumentation has become more sophisticated and prices have reduced, encouraging more widespread use. With a vast array of new and secondhand endoscopes on the market, it is easy to make a wrong decision and be left with an expensive white elephant. No single endoscope will be suitable for all procedures in small animal practice. It is therefore important to understand your clinical requirements first of all and then to understand enough about endoscope design and function to find an instrument to meet them.
Types of Flexible Endoscope
There are two main types of flexible endoscope in common clinical use. Gastroscopes and bronchoscopes. Gastroscopes should have four-way tip deflection (at least 180 degrees in one direction), automatic air/water insufflation, a biopsy/suction channel and a working length of at least 100 cm. For large breeds a working length of 130-150 cm is essential to examine the small intestine and caecum. The diameter of the insertion tube should be no larger than 10 mm or it will not be possible to pass through the pylorus of smaller patients. A diameter of less than 8 mm makes passage through the pylorus easier in small dogs and cats but must be offset against the smaller biopsy channel--usually around 2 mm as against 2.8 mm in the larger endoscope. Smaller biopsy samples can be more difficult for pathologists to interpret.
Bronchoscopes should have two-way tip deflection of at least 100 degrees in each direction, and preferably 180 degrees in one direction to allow retroflexion over the soft palate. You will also require suction and air/water insufflation, a biopsy/working channel and a working length of at least 80 cm. An outer diameter of 3.5-5 mm is ideal for all adult dogs and cats, although a 7-8 mm gastroscope can double as a bronchoscope for medium to large dogs.
Flexible endoscopes can be further divided into fibreoptic and videoendoscopes. Fibreoptic endoscopes transmit the image to the eyepiece via a bundle of coherent fibres, resulting in a pixelated image that is viewed directly through the eyepiece or via an attached camera, on a monitor. A videoendoscope has no eyepiece, the image being transmitted electronically from a CCD video chip at the tip of the insertion tube directly to a video monitor. This gives a vastly superior image but at greater cost, since each endoscope essentially incorporates its own camera system.
Decide What Sort of Endoscope You Need
An endoscope must be fit for purpose--what is your caseload? Do you deal primarily with cats, small dogs, or large dogs? Do you see mainly gastrointestinal (GI) or respiratory cases? What quality, especially of optics, do you require? Do you feel that a warranty is important and what about servicing costs and loan of an instrument during repairs? Look at the individual characteristics of an instrument--does it feel good in your hands; is it comfortable to use?
One endoscope is rarely sufficient and you will eventually purchase another, or you may already have a range of rigid endoscopes. How can the new endoscope be integrated with current equipment and future expansion plans? Can you use the same light source and camera system on all your endoscopes to spread the cost? What is the total cost--both initial and ongoing maintenance? How are you going to recoup this?
New or Secondhand
An important decision to make is whether to buy new or secondhand. There are a lot of excellent 'veterinary specific' endoscopes appearing on the market. These are more suited to our patients than many human models, having a 130-150 cm insertion tube as standard. In addition, buying new provides you with a warranty for at least a year, and servicing and spares should not be a problem. Suppliers will usually be happy to provide training in use, care and maintenance free of charge for yourself and your staff. Proper care is vital if your investment is not to be damaged, incurring expensive repairs
Large numbers of secondhand endoscopes are available from the human market. However--'caveat emptor'--there are a number of things to look out for:
Insertion tube length. Most human paediatric endoscopes are 100 cm, too short for GI work in large dogs.
Insertion tube diameter >10 mm is not suitable for small animal work.
Size of instrument channel--aim for 2.8 mm with a minimum of 2 mm. Pass an instrument through the channel to ensure there is no blockage or damage to the channel.
Check the rubber at flexible tip for perishing or damage.
Fibreoptic or video? Videoendoscopes will require a specific light source/video processor which may not be usable with any other equipment. CCD technology cannot currently be miniaturised sufficiently to enable the manufacture of smaller endoscopes and bronchoscopes.
Electronic equipment imported from the US may require a transformer to work with UK power supplies.
Some older hospital endoscopes hitting the market are not fully immersible, making cleaning and adequate disinfection extremely difficult.
Fibre damage. Remember there are light guide fibres in a video endoscope as well. Look for adequate light transmission by viewing the image with the endoscope tip placed in a large dark box. (Your hand will reflect too much light and show a good image in any case.) Check fibreoptic endoscopes for black spots on the image in the eyepiece and on a monitor, depicting broken fibres.
Damage to guide wires. These are the wires that move the flexible tip of the endoscope. The tip should move through the whole range of movement expected--and at least 180 degrees in one direction. The tip should start moving as soon as the wheel or lever is moved, with no delay. On gastroscopes, the tip should be straight with the control wheels in the neutral position (usually with the U & L markers uppermost).
Is the instrument water tight? This is vital as the delicate fibres and guide wires are very easily damaged by the slightest leak, and repair can cost almost as much as a new endoscope. Always attach a leak tester to the pressure compensation port and inflate to the prescribed pressure. Look for a pressure drop. If you are unsure, immerse the pressurised endoscope in water and look for escaping bubbles.
Accessories, spares and servicing. Does the endoscope come with necessary accessories such as a leak tester, pressure compensation valve, cleaning brushes and all the necessary buttons and grommets for the working channel? Is there any documentation giving the cleaning instructions? Where will you get it serviced and are spare parts still available?
Where to Buy
New
Major manufacturers in both the human and veterinary market produce their own endoscopes. These are usually the most expensive, but are high quality instruments backed up by a large company that is unlikely to disappear, good supplies of spare parts and excellent service contracts that will often loan a replacement instrument if yours is not functional. Many veterinary resellers also offer excellent deals on instruments manufactured by smaller companies. Often the quality is not quite so high, but this is reflected in the price, and you will still get a warranty and excellent service deals.
Secondhand
Secondhand equipment can be bought direct from hospitals, via hospital auctions or even on eBay. However, purchasing flexible endoscopes this way is fraught with danger and you can easily end up with an expensive piece of junk that costs more to repair than it is worth. A number of resellers offer secondhand reconditioned equipment that will at least have been tested and will come with a short warranty. Try and persuade them to allow you to use it on trial for a month or so on real cases before purchase.
Care and Maintenance
With proper care and maintenance your endoscope should last years:
Always clean your endoscope thoroughly immediately after use with an enzymatic cleaner. Dried debris can block channels and be extremely difficult to remove.
Resterilise your endoscope after cleaning using gas sterilisation or a recommended cold steriliser.
Always use a manufacturer-recommended enzymatic cleaner and cold steriliser. Inappropriate chemicals can damage seals.
Never leave the pressure equalisation valve in place when the endoscope is immersed. This opens the inner working of the endoscope to the atmosphere and will damage it beyond repair. The valve is only ever used for air transport or N2O gas sterilisation.
Storage. Always store your endoscope hanging with the insertion tube vertical and the buttons removed to allow the channels to drain. Fibres retain a memory if coiled and will be more prone to breakage if constantly coiled and straightened. Never store your endoscope in its case. This not only coils the insertion tube, it provides an ideal environment for bacterial growth within the endoscope. Pseudomonas is commonly isolated from incorrectly stored endoscopes.
References
1. Chamness C. Instrumentation. In: Lhermette, P; Sobel, D. eds. BSAVA manual of endoscopy in the dog and cat. In production expected late 2007/2008.
2. Chamness C. Introduction to veterinary endoscopy and endoscopic instrumentation. In: McCarthy, T. ed. Veterinary endoscopy for the small animal practitioner. Elsevier Saunders, 2005; 1-20.
3. Chamness C. Endoscopic instrumentation. In: Tams, T. ed. Small animal endoscopy, second edition. St Louis: Mosby, 1999; 1-16.