Page 835 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition
P. 835

810                                        CHAPTER 4



  VetBooks.ir    production, then gastric dilation occurs. When   an obstructive small-intestinal lesion is present. If
             If aboral movement of gas does not equal
                                                          primary gastric dilation is suspected, diet and man-
           the stomach is distended, the conformation of the
           gastro- oesophageal junction changes so that the   agement should be evaluated.
           cardiac sphincter is tightly closed, and fluid and gas  Prognosis
           cannot move from the stomach into the oesophagus.   The prognosis depends on the cause. The prog-
           As dilation increases, signs of colic may develop.  nosis for primary gastric dilation is excellent. The
                                                          prognosis  for  secondary  dilation  depends  on  the
           Clinical presentation                          severity of the inciting lesion. The presence of
           Non-specific signs of colic are most commonly   spontaneous gastric reflux is a very poor prognostic
           observed. Pain may be severe and heart rate may be   indicator because of the typical severity of disease
           markedly elevated (>100 bpm) if the stomach is very   and the potential for complications such as aspira-
           distended. Tachypnoea may be present because of   tion pneumonia.
           compression of the thoracic cavity by a large, dis-
           tended stomach. Other clinical abnormalities may  GASTRIC IMPACTION
           relate to the underlying disease process in horses
           with secondary gastric dilation.               Definition/overview
                                                          Gastric impaction is an uncommon cause of colic.
           Differential diagnosis
           Other causes of colic should be investigated.  Aetiology/pathophysiology
           Particular attention should be paid to small- intestinal   Accumulation  of  excessive  amounts  of  ingesta  in
           disorders that may result in gastric distension.  the stomach from a variety of causes may result in
                                                          gastric impaction (Fig. 4.139). Impacted ingesta
           Diagnosis                                      become dessicated, firm and resistant to rehydration.
           Gastric dilation is identified and relieved by passage   Gastric distension may result in signs of abdominal
           of a NG tube as part of a thorough colic evaluation.   pain. Many cases are idiopathic. Dental disorders,
           In uncomplicated cases, relief following passage of   EGUS, poor-quality diet, abnormal GI motility
           the NG tube should result in near complete reso-  (e.g. grass sickness) and gastric outflow obstruction
           lution of clinical signs and the presence of ongoing   may be associated with gastric impaction. Gastric
           pain or tachycardia should prompt further evaluation   impactions may occur concurrently with large-colon
           of other differentials. No abnormalities are typically   impactions.
           detectable p/r unless gastric dilation is secondary to
           a small-intestinal lesion;  however, marked  gastric
           dilation can displace the spleen caudally. Gastric
           distension may be evident   ultrasonographically.   4.139
           A thorough evaluation for small-intestinal lesions is
           warranted.

           Management
           Decompression of the stomach and resolution of the
           primary cause, if present, are the most important
           components of treatment. If a large volume of gas or
           fluid reflux is obtained, the NG tube should be left
           in place or intubation repeated as often as hourly.
           The NG tube can be removed once gas and fluid
           reflux are minimal. Surfactants such as DSS are not   Fig. 4.139  Gastric impaction. Note the large mass of
           effective. Surgical intervention may be required if   dry ingesta in the stomach.
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