Macroscopic findings of idiopathic congenital megaoesophagus in a calf

MEGAOESOPHAGUS is a congenital or acquired dilation of the oesophagus (Vestweber and others 1985, Ndikuwera and others 1990, Jubb and others 1992). Functional or morphologic defects due to systemic diseases are the underlying cause of acquired megaoesophagus. Congenital megaoesophagus is considered to be a disorder of neuromuscular development in dogs; the pathogenesis of the condition is not clear in other domestic animals (Jubb and others 1992). This short communication describes the clinical and macroscopic postmortem findings in a calf with congenital megaoesophagus. A 15-day-old, male Simmental cross Holstein calf, weighing 23 kg, was referred to the large animal clinic at the Faculty of Veterinary Medicine, Adnan Menderes University, with a history of regurgitation and a swelling on the left side of the neck since birth. The calf was able to drink milk continuously for approximately one to three minutes but this was followed by extension of the head and neck ventrally and reflux of milk from the nose and mouth. The calf was alert. Physical examination revealed a normal rectal temperature (39·2°C), respiratory rate (76 breaths/minute) and heart rate (128 bpm). Increased bronchovesicular sounds could be heard on auscultation. A blood sample was taken from a jugular vein for haematological and biochemical tests. The packed-cell volume (PCV) was measured in whole blood using a microhaematocrit centrifuge (Hettich). The activities of gamma glutamyltransferase, alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase in the plasma, and the plasma concentrations of total bilirubin, glucose, urea and total protein, were measured on a spectrophotometer (Model 1601; Shimatzu) using a commercially available kit (Randox). The gamma glutamyltransferase, glucose, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and total bilirubin were all within normal ranges. The PCV was 35 per cent (reference range 19 to 34 per cent), total protein was 75·5 g/l (reference range 57 to 73 g/l) and urea was 11·35 mmol/l (reference range 1·6 to 6·0 mmol/l). The slight increase in these parameters might have been related to dehydration or protein catabolism. Lateral and ventrodorsal plain cervicothoracic radiographs revealed enlargement of the oesophagus, and contrast radiography with barium sulphate (R-X suspension 150 g/ 240 ml; Yenisehir) confirmed a megaoesophagus (Fig 1). Because of the poor prognosis, euthanasia was performed with the owner’s consent. Immediately after the calf had been euthanased, its abdominal cavity was opened and the abdominal aorta was cannulated, the vessels were washed with 0·9 per cent physiological saline and red-coloured latex was injected. Macroscopic examination confirmed the dilation of the oesophagus, which caused stretching of the vagus nerve. The broncho-oesophageal artery was enlarged and its caudal branch had a tortuous path, like a rete, at the level of the caudal mediastinal lymph node (Fig 2). The oesophagus was pale and thin walled. There were two constrictions present: the first was at the level of the aortic arch, between the aortic arch on the left, the mediastinal lymph node on the right, the broncho-oesophageal artery dorsally and the trachea ventrally. The colour of the oesophagus was darker at the constriction site from its colour in other parts. The second constriction was observed where the dorsal branches of the vagus nerve on the left and right sides united to form the dorsal vagus trunk (Fig 2). There was no vascular ring anomaly present. The oesophagus was marked at six different regions, removed and emptied, and its diameter was measured using micrometric callipers. Its diameter increased from the neck (22·47 mm) and thoracic inlet (23·79 mm) to the level of the third thoracic vertebra (27·34 mm). The narrowest diameter of the thoracic oesophagus was 23·64 mm, at the level of aortic arch, and it enlarged to 26·45 mm caudally. At the level of the dorsal vagus trunk it again decreased to 24·97 mm (Fig 2). A 10-day-old Holstein calf weighing 37 kg, which had been euthanased because of a pelvic fracture, was examined similarly: the diameter of its oesophagus was 14·48 mm, 14·60 mm, 13·57 mm, 14·07 mm, 14·08 mm and 16·49 mm at the respective regions. In this case, microscopic examination was not performed and the macroscopic examination did not reveal any gross morphological defect that would cause oesophageal dilation. While there are a few reports about acquired segmental megaoesophagus in cattle (Anderson and Vestweber 1984, Vestweber and others 1985, Ross and Rebhun 1986), there has Veterinary Record (2006) 158, 26-27