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==Description==
==Description==
A hiatal hernia is an abnormality of the diaphragm that allows part of the stomach and the abdominal oesophagus to displace into the thoracic cavity. Two types of hiatal hernia have been recognised in the dog and cat:
A hiatal hernia is an abnormality of the diaphragm that allows part of the stomach and the abdominal oesophagus to displace into the thoracic cavity. Two types of hiatal hernia have been recognised in the dog and cat:
*'''Sliding hiatal hernia''' - Cranial displacement of the distal oesophagus and stomach into the mediastinum through the oesophageal hiatus of the diaphragm. This is the most common form and it can occur in the dog and cat as a congenital or acquired lesion. Congenital hernias result from the incomplete fusion of the septum transversum (which forms the diaphragm) during early embryonic development.
*'''Sliding hiatal hernia''' - Cranial displacement of the distal oesophagus and stomach into the mediastinum through the oesophageal hiatus of the diaphragm. This is the most common form and it can occur in the dog and cat as a congenital or acquired lesion. Congenital hernias result from the incomplete fusion of the ''septum transversum'' (which forms the diaphragm) during early embryonic development.
*'''Para-oesophageal or Rolling hiatal hernia''' - Cranial displacement of the gastric fundus into mediastinum through the oesophageal hiatus but adjacent to the oesophagus and gastric cardia which remain in their normal positions. This form of hernia is rare in animals.
*'''Para-oesophageal''' or '''Rolling hiatal hernia''' - Cranial displacement of the gastric fundus into mediastinum through the oesophageal hiatus but adjacent to the oesophagus and gastric cardia which remain in their normal positions. This form of hernia is rare in animals.
==Signalment==
'''Acquired''' hernias can occur in any breed of dog or cat and these often occur with disorders that cause increases in intra-abdominal pressure (such as chronic vomiting) or decreases in intrathoracic pressure (such as intermittent airway obstruction seen with laryngeal paralysis and brachycephalic obstructive airway syndrome (BOAS)).
Breeds of dog that develop '''congenital''' sliding hernias include Chinese Shar-peis and Chow-chows whereas brachycephalic dogs (such as English and French bulldogs) often develop acquired hernias.
==Diagnosis==
==Diagnosis==
===Clinical Signs===
===Clinical Signs===
Some animals may be asymptomatic but otherwise clinical signs include:
Some animals may be asymptomatic but otherwise clinical signs include:
*'''Regurgitation''' due to impaired function of the herniated lower oesophageal sphincter.
*'''Regurgitation''' due to impaired function of the herniated lower oesophageal sphincter
*'''Hypersalivation''' related to regurgitation
*'''Hypersalivation''' related to regurgitation
*'''Dyspnoea''' and '''coughing''' if the hernia is large and impinges on the lungs or if the animal develops aspiration pneumonia as a result of regurgitation.
*'''Dyspnoea''' and '''coughing''' if the hernia is large and impinges on the lungs or if the animal develops aspiration pneumonia as a result of regurgitation
*'''Dehydration''' and '''weight loss''' due to chronic regurgitation.
*'''Dehydration''' and '''weight loss''' due to chronic regurgitation
===Diagnostic Imaging===
===Diagnostic Imaging===
*'''Plain survey radiographs''' may show a gas-filled soft tissue opacity in the caudodorsal thorax, continuous with the diaphragmatic margin. Secondary megaoesophagus may develop in longstanding cases and an alveolar lung pattern may be apparent, especially cranio-ventrally, if the animal is developing aspiration pneumonia.
*'''Plain survey radiographs''' may show a gas-filled soft tissue opacity in the caudodorsal thorax, continuous with the diaphragmatic margin. Secondary [[Megaoesophagus|megaoesophagus]] may develop in longstanding cases and an alveolar lung pattern may be apparent, especially cranio-ventrally, if the animal is developing aspiration pneumonia.
*'''Barium contrast studies''' may be used to confirm a diagnosis.
*'''Barium contrast studies''' may be used to confirm a diagnosis.
Intermittent hiatal hernias can be difficult to detect and therefore it is sometimes necessary to put pressure on the abdomen during radiography to induce displacement of the stomach.
Intermittent hiatal hernias can be difficult to detect and therefore it is sometimes necessary to put pressure on the abdomen during radiography to induce displacement of the stomach.
If the hernia is acquired, the underlying cause should be treated.
If the hernia is acquired, the underlying cause should be treated.
===Medical Management===
Medical management should be initiated to reduce [[Oesophagitis|oesophagitis]] caused by regurgitation. Medical management can be continued for cases with acquired hernias and it may achieve success in some cases with congenital hernias. This approach involves the use of:
*'''[[Gastroprotective Drugs]]''' including oral sucralfate suspensions and gastric acid secretory inhibitors such as cimetidine, ranitidine or omeprazole.
*'''[[Gastroprotective Drugs]]''' including oral sucralfate suspensions and gastric acid secretory inhibitors such as cimetidine, ranitidine or omeprazole.
*A '''low fat diet''' fed from a height will increase the tone of the lower oesophageal sphincter and increase the speed of gastric emptying, reducing the likelihood of regurgitation.
*A '''low fat diet''' fed from a height will increase the tone of the lower oesophageal sphincter and increase the speed of gastric emptying, reducing the likelihood of regurgitation.
*'''Antibiotics, nebulisation and coupage''' may be used to manage aspiration pneumonia.
*'''Antibiotics, nebulisation and coupage''' may be used to manage aspiration pneumonia.
===Surgical Management===
Surgical management can be used with congenital cases (after medical management has been attempted) and to treat the underlying cause in acquired cases.
*'''Hernia repair''' is achieved via a cranial ventral coeliotomy. The oesophageal hiatus is exposed by transection of left triangular ligament (between the liver and diaphragm) and retraction of the liver. The phreno-oesophageal ligament is partially incised and the oesophagus is retracted into the abdomen until the lower oesopageal sphincter is identified. Sutures are then placed to reduce the size of the oesophageal hiatus.
*'''Hernia repair''' is achieved via a cranial ventral coeliotomy. The oesophageal hiatus is exposed by transection of left triangular ligament (between the liver and diaphragm) and retraction of the liver. The phreno-oesophageal ligament is partially incised and the oesophagus is retracted into the abdomen until the lower oesopageal sphincter is identified. Sutures are then placed to reduce the size of the oesophageal hiatus.
*An '''oesophagopexy''' may also be performed (tacking the oesophagus to the left body wall) or a '''fundic gastropexy'''. A tube gastropexy has the added advantage of allowing cases to be fed if they are suffering from severe [[Oesophagitis|oesophagitis]] or oesophageal ulceration.
*An '''oesophagopexy''' may also be performed (tacking the oesophagus to the left body wall) or a '''fundic gastropexy'''. A tube gastropexy has the added advantage of allowing cases to be fed if they are suffering from severe [[Oesophagitis|oesophagitis]] or oesophageal ulceration.
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