Basic principles of endoscopy
1.5.3.1 Choice of endoscopes
Entering and biopsying the duodenum is often the most important but also most difficult part of gastroduodenoscopy. An endoscope with a smaller outer diameter makes it easier to enter the duodenum.
However, endoscopes with a smaller diameter also have a smaller biopsy channel (e. g., 2.0 to 2.2 mm). Larger diameter biopsy channels (i. e., 2.8 mm) facilitate obtaining good quality tissue samples as well as the removal of foreign bodies. For cats and most dogs, a one meter long insertion tube will allow visualization and biopsy of the duodenum and ileum, but some large dogs and those with long body conformations may require a 1.4 to 1.6 meter insertion tube. Unfortunately, the extra 0.4 to 0.6 meter in length can be very awkward when scoping cats and medium to small-sized dogs. Video endoscopes generally provide superior visualization compared to fiberoptic scopes, plus they allow two people to work together when removing some difficult to remove foreign bodies. However, fiberoptic scopes are less expensive and allow a competent endoscopist to accomplish almost everything that can be done with a video endoscope.Having a selection of endoscopes is optimal (e.g., a pediatric gastroduodenoscope with a 7.9-mm outer diameter and a 1- meter-long insertion tube and a 2.2-mm biopsy channel; a standard gastroduodenoscope with a ≤9.0-mm outer diameter and a 1-meter-long insertion tube and a 2.8-mm biopsy channel; and a pediatric colonoscope with an outer diameter of 11 mm, a 1.4-meter-long insertion tube and a 2.8- to 3.0mm biopsy channel). If only one scope is to be purchased, the dimensions should depend on the size of animals that most commonly undergo endoscopy (i.e., cats versus dogs) and the number of endoscopies anticipated to be performed on a weekly basis. If only 2-3 gastroduodenoscopies will be done per month, it is probably best to obtain a smaller diameter scope (e. g., 7.9-mm outer diameter) because it is doubtful that the endoscopist will achieve a high level of skill in passing the endoscope into the duodenum of cats and small dogs. If at least two endoscopies will be done weekly, then one is likely to become proficient enough to be able to maneuver slightly larger endoscopes (i. e., 8.6- to 9.0-mm outer diameter) with larger biopsy channels (i.e., 2.8 mm) into the duodenum of most adult cats.
1.5.4