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EQUINE VETERINARY EDUCATION / AE / MAY 2015


clarify the severity of several strictures complicated by megaoesophagus. With this information, the owner declined further diagnostics and the foal was discharged with antibiotics. Not surprisingly, the colt’s status deteriorated and it was subjected to euthanasia. Necropsy confirmed the 3 independent narrowed areas consistent with fibromuscular oesophageal stenosis. If this colt had been a candidate for intervention and attempted therapy for the stenosis, the knowledge gained via contrast radiography of 3 separate affected areas complicated by cervical megaoesophagus would have helped with planning and expectations. The case described by Berlin et al. (201 ) was a 3-day-old


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Fig 2: Contrast radiograph of a foal with stricture of the thoracic oesophagus. An endoscope has been placed just orally of the stricture (A) and air pumped into the oesophagus followed by contrast (B) which flows and then pools just orally to the stricture (C).


base before travelling through the diaphragm to enter the stomach within the abdomen. Several structures can cause varying degrees of extramural pressure on the oesophagus but circumferential constriction of the oesophagus from extramural sources would likely be confined to vascular anomalies such as persistent right aortic arch. In the case presented by Berlin et al. (201 ) computed tomography (CT) was used as an additional diagnostic procedure once an oesophageal stricture was established. On first glance, the use of the CT may seem superfluous given that the underlying reason for the presenting complaint, milk regurgitation, had been established as an oesophageal stricture. However, oesophageal stricture in the thorax of a foal could be due to a vascular anomaly and the presence of a vascular anomaly such as a persistent aortic arch can be of clinical importance, particularly if the persistent aortic arch is patent (Bartels and Vaughan 1969; Petrick et al. 1978; Mackey et al. 1986; Butt et al. 1998; Smith 2004). Knowledge of such an anomaly may change the treatment plan and may affect the prognosis so the addition of a CT for evaluating thoracic oesophageal stricture is wise if the modality is available, the client can afford it and the patient is stable enough to undergo the procedure.


5 Two different outcomes


The 2 cases reported in this issue are good representations of the patient presentation seen with congenital oesophageal strictures as well as the modalities used in establishing this diagnosis. In the case described by Bezdekova et al. (201 ) an 11-day-old colt was presented with milk regurgitation and was diagnosed with triple oesophageal stricture, megaoesophagus and aspiration pneumonia. The clinicians were initially able to pass a stomach tube in this case, indicating the strictures were not tight enough to completely preclude passage to the stomach. The clinicians used double contrast radiography to further clarify the clinical picture by identifying a total of 3 independent areas of narrowing with the addition of cervical megaoesophagus. Although the cause of milk regurgitation was likely clear following the endoscopy, the additional diagnostics helped to


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filly also presenting with milk regurgitation and subsequently diagnosed with oesophageal stricture and aspiration pneumonia. The initial endoscopy included only the larynx and pharynx. The initial impression from this abbreviated endoscopic examination was that the filly was suffering from mild pharyngeal weakness and dysfunction based on mild collapse of the pharynx and oedema of the arytenoid cartilages. A feeding tube was passed and a large amount of milk aspirated from the oesophagus. This prompted a more complete endoscopy that included the oesophagus and revealed oesophageal dilation cranial to a severe oesophageal stricture. Radiographs clarified that the stricture was located at the caudal aspect of the base of the heart at the level of the 8th intercostal space. This location introduces the concern that the stricture was caused by a vascular anomaly. The clinicians were eventually able to place a feeding tube using endoscopic guidance and then over several days stabilised the foal with fluid and antibiotic therapy as well as using a feeding tube to provide mare’s milk. Once stabilised, the clinicians attempted their first balloon bougienage of the stricture under light sedation, which met with firm resistance and was unsuccessful. A CT scan under general anaesthesia with the addition of intravenous (i.v.) contrast was used to clarify that the stricture was not caused by vascular anomaly and this clarification was important given the location of the stricture as defined by the previous radiographs. The lack of vascular anomaly indicates that the use of the balloon dilation is a valid approach to this case as there is no external structure precluding stretching. A second dilation was attempted, this time with a more aggressive sedation and pain management protocol and was successful in that a small lumen opening was obtained. Client resources precluded additional bougienage sessions but by Day 17 both the stricture and cranial oesophageal dilation were significantly improved as seen on endoscopy. This filly was discharged from the hospital and remains healthy at long-term follow-up.


Further commentary oesophageal relaxation


In both cases, the clinicians worked to achieve some degree of oesophageal relaxation during the course of treatment. In the case presented by Berlin et al. (201 ) the clinician used oxytocin (0.11 u/kg bwt i.v. q.12 h) and N-butylscopolammonium (0.9 mg/kg bwt i.v. q. 12) over 48 h. Relevant commentary on these 2 drugs should reflect that both drugs have a relatively short time of action with oxytocin lasting less than 10 min at the reported dosing (King et al. 1990; Meyer et al. 2000) and N-butylscopolammonium lasting 30 min (Gomaa et al. 2011). Perhaps these short-acting drugs would have better effects if given directly prior to the passing of the feeding tube or prior to the balloon bougienage. In addition to


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