Overview of small animal gastrointestinal endoscopy (Proceedings)
More veterinary hospitals are now incorporating endoscopy equipment in their clinics. It's important for the technician to know what's involved in these procedures and to anticipate what the veterinarian needs to efficiently complete and gather enough information to accurately diagnose and treat the patient.
GI endoscopy encompasses 5 areas of the GI tract—esophagus, stomach, duodenum, colon and ileum. These areas are divided into 2 separate procedures-gastroduodenoscopy, which examines the esophagus, stomach and duodenum, and colonoscopy, which examines the colon and ileum. Instrumentation- rigid and flexible endoscopes are used in GI endoscopy. Rigid endoscopes are hollow metal or plastic tubes with a fiberoptic light and manual air insufflation capabilities. They are mainly utilized in proctoscopies, which examine the rectum and descending colon. They can also be used in esophagoscopies and foreign body retrieval. Flexible endoscopes for GI procedures must be versatile enough for a majority of small animal patients. Required functions include 4 way deflection, air/water/suction capabilities, favorable optics, adequate insertion tube length and large biopsy channel. Video endoscopes have better image resolution than fiberscopes but require more equipment and are more expensive.
Biopsy forceps are designed to be used in the biopsy channel of the endoscope. The outer diameter of the forceps should be slightly smaller than the endoscope's biopsy channel. For example, if your biopsy channel measures 2.0 mm, the forceps ordered should be 1.8 mm and be about 50 cm longer than the channel.Retrieval forceps should include a single loop snare, 3 or 4 prong grasper, and basket retrieval forceps. Guarded cytology brushes and aspiration catheters are also available. Balloon dilators of 6-8 cm lengths and 15-20 mm inflatable diameter are recommended for GI tract strictures.
Gastroduodenoscopy procedures are performed under general anesthesia and in left lateral recumbency. A complete oral exam should be done before the procedure. A mouth gag should always be in place to protect the endoscope. The endoscope is passed through the oropharynx and upper esophageal sphincter. Insufflation is then needed to achieve a luminal view of the esophagus. Normal esophageal mucosa should be smooth, pale, and glistening. Submucosal vessels and a circular pattern surrounding the esophagus are normal in felines. The lower esophageal sphincter is usually closed and has a red appearance of the surrounding mucosa. Gentle advancement and minimal insufflation is needed to pass the LES.
Once in the stomach, a systematic approach is needed to complete a thorough and reproducible examination. A cursory view with minimal insufflation is all that is initially needed since the pyloric sphincter can be affected by excessive air introduced into the antrum. The stomach is comprised of the cardia, fundus, greater and lesser curvature, incisura, antrum, and pyloric sphincter. The mucosa should appear smooth, glistening and pink with longitudinal rugal folds leading to the antrum. The endoscope will slide along the greater curvature until the junction between the antrum and the body comes into view. The endoscope should then be advanced slowly towards the pyloric sphincter. Intubating the pylorus can be the most difficult part of the procedure. Slow advancement of the endoscope while keeping a luminal view is usually successful. Repositioning the patient can also be beneficial.
Advancing the endoscope through the duodenum should be smooth and effortless. Once a luminal view is achieved and the endoscope's working length is fully inserted, the duodenum can be examined and biopsied. Normal intestinal mucosa is paler, more granular, and more friable than gastric mucosa. Peyer's patches, areas of lymphoid follicles, are found in the normal duodenum and are often multiple.
Biopsies and/or other diagnostic procedures should be taken as the endoscope is withdrawn, taking into account possible red streaks caused by the endoscope. Sites where the biopsy forceps can be perpendicular to duodenal mucosa, such as the cranial duodenal flexure just past the pylorus or the incisura in the stomach, can yield diagnostic biopsy samples.
Once back in the stomach, all areas can be examined more closely. A J-maneuver, or retroflex, can be used to look at the cardia, lesser curvature and fundus for possible lesions. To perform this maneuver, retract the endoscope to the greater curvature and retroflex 180 degrees. When biopsying this area, be sure to insert the biopsy forceps into the biopsy channel before retroflexing. This will avoid excessive wear and tear on the channel. If a foreign body is found and can be removed, using the correct forcep is pivotal. Coins and other such objects with a lip can be removed with the pronged retrieval forceps. Sharp objects such as fish hooks that are lodged in the esophagus can be removed with regular biopsy forceps and drawn into the proctoscope to shield the esophagus. It is important for the forceps handler to keep firm traction on the forceps when withdrawing the object, especially through the cardia.
When the procedure is complete, and before the endoscope is withdrawn, be sure to suction all the air from the stomach and, if necessary, any residual fluid observed in the esophagus.