Congenital diaphragmatic hernias occur as a consequence of failure of the pleuroperitoneal folds to fuse with other parts of the developing diaphragm (particularly the septum transversum) or as a result of an incomplete closure of the pleuroperitoneal canals on the ventral part of the diaphragm. In human medicine, congenital diaphragmatic hernias have been linked to vitamin A deficiency, and intra-uterine exposure to NSAIDs and nitrofen herbicide.
The pleural cavity may contain the liver, intestines, spleen and stomach, depending on the extent of the diapragmatic hernia.
In most cases the herniated viscera are located within a hernial sac in the pleural space, surrounded by parietal diaphragmatic pleura and sometimes by peritoneum. This type of hernia, due to the presence of the hernial sac, is called a true hernia. In addition to hernias of the ventral diaphragm, a second group of congenital diaphragmatic hernias consists of esophageal hiatal hernias and sliding perivascular hernias (of the opening of the aorta and the jejunal vein on the side of the cauda).
Clinically affected dogs usually present with dyspnea, regurgitation, muffled heart sounds and borborygmi on auscultation and in severe cases, acute shock due to vascular compromise. In chronic cases, more nonspecific symptoms may also be evident such as anorexia, lethargy and weight loss.
Abdominal palpation of the dog may reveal an 'empty' feel to the abdomen, although this depends on the severity of herniation. With traumatic herniation, there may be also be a history of recent trauma, particularly motor vehicle accident.
Diagnosis is usually based on radiographic or CT imaging, which may show the diaphragmatic defect, the presence of visceral organs within the chest cavity, pulmonary edema, cardiomegaly or cardiac tamponade. At least two radiographs, at different angles, are usually required for a valid diagnosis since some radiographic signs are not visible in a single view. The location of the stomach axis and the displacement of tracheal and bronchial segments may assist in establishing a diagnosis.
Barium meal radiographs may show delayed emptying of intestinal loops within the thoracic cavity.
Treatment usually involves various methods of reconstructive surgery using rectus abdominis muscle or connective tissue pedicle flaps or appositional suture placements. A midline laparotomy approach is usually required although some dogs necessitate a median sternotomy, particularly in large herniations. With chronic herniations, adhesions of the lungs or diaphragm to the herniated organs may be necessary to permit reduction of the hernia. Some difficult cases require resection of portions of the lungs, liver, or intestine.
With hiatal hernias, closure of the diaphragmatic hernia is usually accompanied with esophagopexy and tube gastropexy to minimize recurrence.
Early surgical correction in cases of congenital hernias are usually curative. With traumatic diaphragmatic hernias, early surgical intervention is essential to prevent hepatic, gastric of intestinal torsion and is usually associated with good perioperative survival rates.
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