In general, it was readily possible to pass the lubricated (e.g. with K-Y Jelly; Johnson and Johnson, Inc., New Brunswick, NJ) endoscope through the left oropharyngeal region and into the distal oesophagus. Neither ingesta nor watery fluid were found in the oesophageal lumen of any giant panda, and typically there was minimal mucus. The oesophagus of this species is characterised by the presence of numerous strong aboral waves of peristalsis which periodically (every 30 to 120 seconds)
and markedly reduce the size of the oesophageal lumen. Despite the use of general anaesthesia, the oesophagus did not appear dilated in any individual (Figs. 18.2, 18.3; Plate XXVIII and XXIX), as is common in companion animals (Gualtieri, 2001). Air insufflation was mandatory for securing good visibility of the oesophageal luminal structures. The trachea made a curved impression on the ventral oesophageal wall, and pulsation was observed where the base of the heart and the aortic arch were adjacent to the oesophageal wall. Oesophageal mucosal coloration was pale pink/tan with smooth surfaces distally (near the oral cavity), transitioning to a markedly cobblestone or corrugated appearance proximally (adjacent to the gastroesophageal junction) (Fig. 18.4; Plate XXX). Submucosal vessels were not prominent, and the gastroesophageal junction was not typically difficult to negotiate, even when closed.
The oesophageal mucosa was evaluated for erythema, erosions, ulceration, gastric reflux and strictures. Minimal gross abnormalities were observed. In one giant panda (SB 387), the texture of the distal oesophageal mucosa was smooth, but lymphoid aggregates (appearing as small, focal cavitations) were evident adjacent to the gastroesophageal junction (Fig. 18.4; Plate XXXI). Interestingly, and in contrast to all other pandas, the gastroesophageal junction was difficult to negotiate in this individual. One of the study animals (SB 575, a nine-month-old individual) differed from its adult counterparts by having a smooth, 'uncorrugated' proximal oesophageal mucosa (Fig. 18.6; Plate XXXII). Thus the cobblestone appearance (see Fig. 18.5) may be distinctive to adults.
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