Page 894 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.2 The lower gastrointestinal tr act 869

VetBooks.ir 4.185 4.186

Figs. 4.185, 4.186 Dorsoventral (4.185) and lateral (4.186) thoracic radiographs of a horse with a
diaphragmatic hernia. The large colon is within the thoracic cavity. Ingesta in the colon obscures the ventral
thoracic viscera. Colonic-wall sacculations are visible dorsally because of gaseous distension.

exercise, breeding or parturition. Clinical manifes- Perception of an empty caudal abdomen may occur
tations are frequently non-specific and may include during palpation p/r. Standing lateral thoracic radio-
colic, exercise intolerance and dyspnoea. graphs are used to diagnose diaphragmatic hernia.
Radiographic signs include gas-filled intestinal loops
Differential diagnosis in the thoracic cavity, increased ventral thoracic den-
All disorders resulting in acute abdominal pain in sity and absence of the cardiac shadow (Figs. 4.185,
the horse should be included in the differential diag- 4.186). Loss of the diaphragmatic shadow in the area
nosis. Horses with a diaphragmatic hernia may be of the hernia is the most consistently observed radio-
exercise intolerant. Any disorder of the respiratory, graphic sign. Thoracic ultrasonography may show
circulatory and musculoskeletal systems that results the presence of pleural fluid and abdominal viscera
in exercise intolerance must be included in the dif- in the thoracic cavity.
ferential diagnosis. Pneumonia and pleuritis should Hypercapnoea, as a result of hypoventilation, may
also be included in the differential diagnosis. Horses be present. Respiratory acidosis or uncompensated
with diaphragmatic hernias are not usually pyrexic, metabolic acidosis is usually observed in horses with
depressed or have an inflammatory leucogram. a diaphragmatic hernia, whereas the most com-
mon acid–base derangement in horses with colic
Diagnosis is metabolic acidosis with respiratory compensa-
Even with careful examination, diagnosis of dia- tion. Abdominocentesis is usually normal; however,
phragmatic hernia can be difficult and is sometimes haemorrhagic fluid may be obtained with an acute
only made at the time of surgery or necropsy. Careful acquired diaphragm defect and serosanguineous,
thoracic auscultation and percussion should be per- turbid fluid may be present if intestinal strangula-
formed in all horses with unexplained colic, particu- tion has occurred.
larly those with a history of trauma or parturition.
Areas of thoracic dullness or reduced cardiac sounds Management
may be identified during thoracic auscultation or Horses with intractable abdominal pain or respi-
percussion. Referred GI sounds are frequently ratory distress require an emergency exploratory
heard over the caudoventral thorax in normal horses coeliotomy with assisted positive-pressure ventila-
and thus cannot be used for definitive diagnosis. tion. Care should be taken in sedating horses with