Esophageal Dilation (Megaesophagus) and Hiatal Hernia
Bradford P. Smith
Megaesophagus rarely occurs in ruminants. It has been reported in association with pharyngeal trauma and resultant inflammatory involvement of the vagus1 and with hiatal hernia (diaphragmatic hernia with herniation of the reticulum into the thorax) in which the megaesophagus was large (10 cm in diameter ? 20 cm in length).2 Vagotomy and hiatal hernia are recognized as causes of diminished esophageal pressure.
A 4-month-old calf with megaesophagus lacked esophageal muscle cells and ganglion cells, and many fat cells were present.3 The esophagus of a 12-month-old ram with megaesophagus was found to be heavily infected with Sarcocystis arieticanis, and eosinophilic inflammation and degeneration of muscle fibers were noted.4 However, Sarcocystis spp. have been found in the esophagus of many sheep without megaesophagus, which makes the diagnosis difficult. An 18-month-old heifer with megaesophagus also had eosinophilic submucosal infiltration, but no sarcocysts were seen.5 Megaesophagus due to unknown causes in a goat was also reported.6The principal clinical signs of megaesophagus are regurgitation and vomiting, usually shortly after eating. Mild, recurrent bloat and discomfort when a stomach tube is passed are also observed. In other cattle with a hiatal (diaphragmatic) hernia or an esophageal diverticulum, regurgitation or vomiting and bloat have also been reported. Contortion of the neck while eating, apparently caused by pain, was seen in one cow and is reported in human beings with hiatal hernia. In some cases of herniation of the reticulum into the thorax, bloat and regurgitation are not seen; in others, diaphragmatic hernia resulted in chronic bloat.7 Diaphragmatic hernias may be either congenital or acquired. It appears that acquired diaphragmatic hernias are most common.
A stomach tube should be passed to the rumen to rule out choke or an intraluminal mass obstructing the esophagus as a cause. If a tube can be passed freely to the rumen, plain and contrast radiographs of the esophagus should be taken. If this is not possible, the abdomen should be explored surgically for a diaphragmatic hernia, and the cardia and terminal esophagus should be palpated digitally by means of rumenotomy.
Megaesophagus associated with pharyngeal trauma has a good prognosis,1 whereas megaesophagus associated with hiatal hernia has a more guarded prognosis.2 Supportive treatments and stomach tubing with fluids may be required for 1 to 2 weeks until the animal is able to drink unaided. Longer-term support can be given to a valuable animal by surgical creation of a ruminal fistula fitted with a rubber cannula through which feed and water can be given until normal deglutition returns.