OBJECTIVE To assess the feasibility of esophageal insufflation CT (EICT) for evaluation of the esophagus in dogs. ANIMALS 7 clinically normal adult Beagles. PROCEDURES Each dog was anesthetized twice with 1 week between anesthesia sessions. Dogs were positioned in sternal recumbency during all CT scans. During the first anesthesia session, a CT scan was performed before the esophagus was insufflated (insufflation pressure, 0 mm Hg) and unenhanced and contrast-enhanced EICT scans were performed after CO(2) was insufflated into the esophageal lumen to achieve a pressure of 5 mm Hg. For the contrast-enhanced scan, each dog received iohexol (600 mg/kg, IV), and the scan was performed 30 seconds later. During the second anesthesia session, unenhanced and contrast-enhanced EICT scans were performed in the same manner except the insufflation pressure achieved was 10 mm Hg. The esophageal luminal cross-sectional area and wall thickness were measured at each of 5 segments, and mean values were compared among the 3 insufflation pressures and between unenhanced and contrast-enhanced images. RESULTS Mean esophageal luminal cross-sectional area increased and esophageal wall thickness decreased as insufflation pressure increased. Measurements did not differ significantly between unenhanced and contrast-enhanced images. The stomach became distended with CO(2) at an insufflation pressure of 10 mm Hg but not at 5 mm Hg. No adverse effects were observed. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested EICT was feasible for esophageal evaluation in dogs. Further research is necessary to determine the optimal insufflation pressure for the procedure and its diagnostic efficacy in diseased patients.

OBJECTIVE To evaluate the efficacy and safety of gastroscopy and biopsy of the proventriculus and ventriculus in pigeons (Columba livia). ANIMALS 15 adult pigeons. PROCEDURES Each pigeon was anesthetized, and the upper gastrointestinal tract (from the cervical portion of the esophagus to the ventriculus) was endoscopically evaluated by use of a rigid endoscope inserted orally. Saline (0.9% NaCl) solution was orally infused to achieve lumen dilation and visibility. Two mucosal biopsy specimens were collected from each of the proventriculus and ventriculus, histologically evaluated, and graded for crush artifacts and depth. Pigeons were monitored for adverse effects for 3 to 6 days after the procedure, after which they were euthanized for necropsy. RESULTS Gastroscopy via the oral approach provided excellent visibility of the lumen and mucosal surfaces of the proventriculus and cranial portion of the ventriculus and was safe provided that appropriate precautions were taken. Two intraoperative deaths occurred at the beginning of the study; following procedure refinement, no additional deaths occurred. No major adverse effects of the procedure were detected in the remaining 13 pigeons during the postoperative monitoring period or at necropsy. Diagnostic quality of proventriculus specimens was adequate for 10 of 13 pigeons. Eight of 13 ventriculus specimens were of inadequate quality, and only 3 were of adequate quality. CONCLUSIONS AND CLINICAL RELEVANCE Gastroscopy was useful for evaluating the lumen and mucosal surface of the proventriculus and ventriculus in pigeons, and biopsy of those organs was safely performed with the appropriate technique. Further evaluation of these techniques is needed in birds with clinical disease and birds of other species.

OBJECTIVE To determine effects of catheter shape, interelectrode spacing (IS), and electrode size (ES) on pacing threshold (PT), extraneous muscular stimulation (EMS), and zone of capture (ZOC) for dogs undergoing transesophageal atrial pacing (TAP). ANIMALS 10 purpose-bred dogs without cardiac conduction disturbances. PROCEDURES 7 configurations for TAP catheters were tested in each dog to evaluate effects of catheter shape (curved or straight), IS (5, 15, and 25 mm), and ES (2, 4, and 6 mm). Each catheter was passed into the esophagus to a location aboral to the heart and slowly withdrawn until atrial pacing was achieved. Then, catheters were withdrawn in 5-mm increments until pacing could not be achieved. Outcomes measured at each pacing site included PT, degree of EMS, and ZOC. RESULTS There was a significantly lower PT, wider ZOC, and less EMS for the curved catheter than for the straight catheter. An ES of 6 mm induced significantly more EMS than was induced by an ES of 2 or 4 mm. An IS of 5 mm induced significantly less EMS and a significantly narrower ZOC but required a significantly higher PT, compared with results for an ES of 15 or 25 mm. Additionally, there was a significant direct correlation between IS and ZOC. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that a curved catheter with multiple 4-mm electrodes that provides for variable IS would be ideal for TAP in dogs. IMPACT FOR HUMAN MEDICINE TAP catheters currently used in human medicine are straight. The PT in humans may potentially be reduced with curved catheters.

Objective-To characterize the ultrasonographic appearance of the canine esophagus. Animals-14 healthy Beagles. Procedures-Endoscopic ultrasonography (EUS) examinations were performed with a radial ultrasonographic gastrovideoscope in anesthetized dogs. Images were obtained at 3-cm intervals along the esophageal length to allow evaluation of the esophageal wall. Images were obtained with the probe in direct contact with the esophageal wall and with a water-filled balloon as a standoff. Results-Images were obtained with (12 dogs) and without (10) the water-filled balloon. Median thickness of the esophageal wall was 2.19 mm (range, 1.03 to 5.62 mm) in the proximal third of the esophagus, 2.15 mm (range, 1.10 to 4.45 mm) in the middle third, and 2.84 mm (range, 1.35 to 5.92 mm) in the distal third. Wall thickness differed significantly between proximal and distal thirds. Results were similar when the water-filled balloon was used. Esophageal wall layers appeared as 5 alternating hyperechoic and hypoechoic bands that could not be consistently identified in all dogs. All layers could be identified in 26 of 198 (13%) images, 3 layers could be identified in 67 of 198 (34%) images, and 105 of 198 (53%) images had no layers. Visual identification of layers in images obtained with and without the balloon did not differ significantly. Conclusions and Clinical Relevance-EUS appeared to be a useful technique for assessing esophageal wall integrity in dogs; however, complete evaluation of all layers could not be accomplished in all instances. Further studies with this technique in dogs are needed.

The effect of a passive heat and moisture exchanger on tracheal and large airway temperature, as reflected by esophageal temperature at the thoracic inlet, was determined for 12 anesthetized and ventilated tumor-bearing dogs undergoing whole-body hyperthermia at 42 C. Delivered thermal dose to the esophagus and rectum during 120 minutes of whole-body hyperthermia was quantified as the thermal dose summary measure EQ43. The heat and moisture exchanger significantly increased esophageal EQ43 from 7.3 minutes to 12.1 minutes. Esophageal EQ43, however, remained lower than rectal EQ43. Although use of a heat and moisture exchanger improved esophageal temperature during whole-body hyperthermia, presumably through improved airway temperature, additional methods will be necessary to increase esophageal and airway temperature to the target value of 42 C.

OBJECTIVE To assess feasibility of flexible endoscopic evaluation of swallowing (FEES) in awake dogs, determine whether specific variables associated with the oropharyngeal phase of swallowing can be recognized, and evaluate the safety and tolerability of FEES. ANIMALS 6 healthy client-owned large- and giant-breed adult dogs. PROCEDURES A topical anesthetic was applied to the nasal passage of each dog, and a fiberoptic endoscope was passed transnasally until the tip of the scope was positioned in the oropharynx. All dogs voluntarily drank colored water followed by consumption of a commercial canned diet and then a kibble diet mixed with food color. During each swallow, laryngeal and pharyngeal anatomic structures were evaluated and depth of bolus flow prior to the pharyngeal phase of swallowing was assessed. Evidence of bolus retention in the vallecula or pyriform sinuses and laryngeal penetration of the bolus were recorded. RESULTS FEES was completed without major adverse events and was tolerated well by all 6 dogs. Mild, self-limiting epistaxis was noted for 2 dogs. The nasopharynx, oropharynx, and hypopharynx were observed in all dogs; movement of food boluses through the esophagus was observed in 2 dogs, and food boluses in the stomach were visible in 1 dog. Pharyngeal and laryngeal function was considered physiologically normal in all dogs. CONCLUSIONS AND CLINICAL RELEVANCE FEES appeared to be a feasible diagnostic tool for use in large- and giant-breed dogs. Studies are warranted in dogs with oropharyngeal dysphagia to determine whether FEES can be tolerated and whether it can augment videofluoroscopy findings.

Objective: To develop a technique for radiographic evaluation of the gastrointestinal tract in ball pythons (Python regius). Samples: 10 ball python cadavers (5 males and 5 females) and 18 healthy adult ball pythons (10 males and 8 females). Procedures: Live snakes were allocated to 3 groups (A, B, and C). A dose (25 mL/kg) of barium sulfate suspension at 3 concentrations (25%, 35%, and 45% [wt/vol]) was administered through an esophageal probe to snakes in groups A, B, and C, respectively. Each evaluation ended when all the contrast medium had reached the large intestine. Transit times through the esophagus, stomach, and small intestine were recorded. Imaging quality was evaluated by 3 investigators who assigned a grading score on the basis of predetermined criteria. Statistical analysis was conducted to evaluate differences in quality among the study groups. Results: The esophagus and stomach had a consistent distribution pattern of contrast medium, whereas 3 distribution patterns of contrast medium were identified in the small intestine, regardless of barium concentration. Significant differences in imaging quality were detected among the 3 groups. Conclusions and Clinical Relevance: Radiographic procedures were tolerated well by all snakes. The 35% concentration of contrast medium yielded the best imaging quality. Use of contrast medium for evaluation of the cranial portion of the gastrointestinal tract could be a reliable technique for the diagnosis of gastrointestinal diseases in ball pythons. However, results of this study may not translate to other snake species because of variables identified in this group of snakes.

Objective-To compare effects of oxytocin, acepromazine maleate, xylazine hydrochloride-butorphanol tartrate, guaifenesin, and detomidine hydrochloride on esophageal manometric pressure in horses. Animals-8 healthy adult horses. Procedure-A nasogastric tube, modified with 3 polyethylene tubes that exited at the postpharyngeal area, thoracic inlet, and distal portion of the esophagus, was fitted for each horse. Amplitude, duration, and rate of propagation of pressure waveforms induced by swallows were measured at 5, 10, 20, 30, and 40 minutes after administration of oxytocin, detomidine, acepromazine, xylazine-butorphanol, guaifenesin, or saline (0.9% NaCl) solution. Number of spontaneous swallows, spontaneous events (contractions that occurred in the absence of a swallow stimulus), and high-pressure events (sustained increases in baseline pressure of > 10 mm Hg) were compared before and after drug administration. Results-At 5 minutes after administration, detomidine increased waveform amplitude and decreased waveform duration at the thoracic inlet. At 10 minutes after administration, detomidine increased waveform duration at the thoracic inlet. Acepromazine administration increased the number of spontaneous events at the thoracic inlet and distal portion of the esophagus. Acepromazine and detomidine administration increased the number of high-pressure events at the thoracic inlet. Guaifenesin administration increased the number of spontaneous events at the thoracic inlet. Xylazine-butorphanol, detomidine, acepromazine, and guaifenesin administration decreased the number of spontaneous swallows. Conclusions and Clinical Relevance-Detomidine, acepromazine, and a combination of xylazine butorphanol had the greatest effect on esophageal motility when evaluated manometrically. Reduction in spontaneous swallowing and changes in normal, coordinated peristaltic activity are the most clinically relevant effects.

The position, dimensions, and structure of the thyroid gland, the portion of the esophagus in the neck the cervical lymph nodes, and the major blood vessels of the neck were determined via ultrasonography in cattle. The left and right ventral neck regions of 30 healthy Swiss Braunvieh cows were examined ultrasonographically, using 3.5- and 5.0-MHz linear transducers and a 3.5-MHz convex transducer. The external jugular vein was situated directly beneath the skin in the upper and middle parts of the neck and 2.7 to 6.6 cm from the body surface in the lower part of the neck. In contrast, the common carotid artery was located further from the body surface along the entire ventral neck region; depending on the measuring point, this distance varied from 2.6 to 10.9 cm. The external jugular vein narrowed from caudad to craniad. The diameter of the common carotid artery remained fairly constant along its course in the ventral part of the neck and varied from 0.9 to 1.4 cm. The thyroid gland was identified via ultrasonography caudodorsal to the larynx It appeared as an echogenic spindle-shaped structure with finely granular echogenic pattern. The esophagus appeared as a band-shaped structure in longitudinal section, and it could be followed to the thoracic inlet. Its width increased from craniad to caudad, and mean +/- SD diameter was 2.9 +/- 0.23 cm. The medulla, hilus, cortex, and capsule of the cervical lymph nodes could be clearly differentiated via ultrasonography. Mean length and width of the left cervical lymph node were 3.0 +/- 0.45 and 1.8 +/- 0.23 cm, respectively. To determine reproducibility and reliability of the results, 10 cows were examined by ultrasonography 10 times within 2 weeks. The interassay coefficients of variation determined from these examinations varied from 3.0 to 12.3%; most of the coefficients of variation ranged from 5 to 10%. The smallest coefficients of variation were determined for diameter of the common carotid artery, and the largest were for diameter of the external jugular vein. Description of the ultrasonographic appearance of the structures of the ventral neck region in healthy cattle represents the basis for use of diagnostic ultrasonography in cattle with suspected diseases involving this area. The technique is noninvasive and can be performed on cattle in standing position.

In healthy adult goats, closure of the esophageal groove was induced by thirst, IV administered vasopressin, and intracarotid administration of hypertonic NaCl solutions. The efficiency of stimulation was tested directly by visual inspection of the course taken by orally administered solutions through a ruminal or abomasal fistula, palpation of the lips of the esophageal groove through a ruminal fistula, and indirectly by following the glucose dynamics in the blood after oral administration of glucose solution. Esophageal groove closure was observed during drinking after a 48-hour period of water deprivation. Intracarotid administration of 1.5 ml of a saturated solution or 10.5 ml of a 1.5% solution of NaCl also stimulated groove closure; however, groove closure stimulated by administration of vasopressin is the most satisfactory procedure for passing compounds of therapeutic importance directly from the cardiac orifice to the abomasum.