Certain signs are pathognomonic; others may be regarded as of secondary importance. By carefully watching an animal which is feeding the following symptoms may be noted: As a general rule hunger is very marked, and the animal chews its food and swallows the first few mouthfuls in a perfectly normal way. Three, five, eight, or even ten mouthfuls may be swallowed; then the animal suddenly stops, appears a little anxious, extends its head and neck, an antiperistaltic contraction occurs, and one or two masses of food are rejected and fall into the manger. The discomfort being thus momentarily relieved, the animal, which is dying of hunger, although faced with food which it is unable to swallow, returns to its meal, swallows one, two, or three boluses of food, regurgitation again occurs, and the whole process is repeated.
What is going on under these circumstances is easy to explain.
At the commencement of the meal the dilatation is usually empty, or nearly empty. A mouthful of food is swallowed. It descends the œsophagus until it arrives at the diverticulum, into which it partially or wholly passes, the peristaltic wave of contraction ceasing at this point. The second mouthful follows with the same result, then a third, a fourth, etc. The diverticulum soon becomes filled to repletion, and no more food can enter it. The food therefore accumulates in the upper portion of the œsophageal tube until the latter becomes nearly filled; but as this tube, provided its innervation is intact, is intolerant of the presence of any foreign body, and as efforts to swallow prove fruitless, a sudden antiperistaltic wave of contraction occurs, with the result that all the material contained in the tube above the dilatation is ejected into the mouth, whence it falls into the manger. The same result follows any further attempts to swallow during a particular feeding time. From this it will be seen that the animal can ingest at a given time only as much as the dilatation will contain.
In the intervals between meal times and under the action of the saliva and warmth, the food collected in the dilatation becomes softened, breaks down, and slowly moves onward towards the rumen. When the next feeding time arrives the dilatation is almost empty, and the same set of symptoms recurs.
If, instead of forage, the animal begins by taking gruel or very fluid material, deglutition appears normal, or at least fairly easy; but if drinking is deferred until after taking hard food, it becomes almost impossible, because the passage is obstructed. These symptoms are, so to speak, pathognomonic. Under any circumstances they are so significant that error in diagnosis is unlikely.
By careful examination œsophageal regurgitation can very easily be distinguished from true vomiting; the character of the rejected material shows that it has not come from the stomach, while the boluses of food preserve their cylindrical form, and are still saturated with saliva.
Some secondary signs also deserve to be mentioned, such as the animal’s anxiety and restlessness whilst its neighbours are feeding, the existence of trifling and intermittent tympanites due to suppressed eructation, suppression or irregularity of rumination, constipation, etc. At a later stage there is rapid wasting and disordered appetite, and finally the patients die slowly of hunger, whatever efforts are made to feed them.
When the seat of dilatation is in the cervical portion of the œsophagus, there are other symptoms which leave no doubt as to the condition. When empty the pouch cannot be detected; but during a meal the accumulation of food causes it to assume the appearance of a doughy, diffuse, indolent swelling, which alters the outline of the jugular furrow, yields to pressure, and sometimes produces respiratory disturbance by pressing on the trachea, the pneumo-gastric and inferior laryngeal nerves, etc.
When the dilatation is intra-thoracic and the above-described symptoms have been observed, the dilated spot can only be detected and localised by using the probang. The greatest possible prudence, however, is required in manipulating the instrument, in order to avoid rupturing the thin walls of the dilated portion.
The diagnosis is not always easy; when food is regurgitated, and one finds by auscultation that the sound usually produced by the passage of solids or liquids into the rumen is absent, there need be no hesitation in diagnosing either a dilatation or a stricture. The clinical consequences being the same, the possible error would be of little importance.