Hernia, Peritoneopericardial Diaphragmatic

Description

Pericardio-Peritoneo-Diaphragmatic Hernia (PPDH) is a congenital abnormality characterised by incomplete formation of the septum transversum during early embryonic development, meaning that the peritoneal cavity and pericardial sac remain continuous in later life. The defect may also result from a failure of the septum transversum to fuse with the pleuroperitoneal folds. Since the diaphragm (which is formed by the septum transversum) does not separate the two cavities, abdominal organs are able to move into the pericardial sac. Many animals are diagnosed as adults and show few clinical signs on presentation.

Signalment

The defect may be inherited in the Weimaraner breed and it occurs most commonly in Himalayan and Domestic Long Hair cats. It is often accompanied by other congenital defects, such as umbilical hernias, sternal malformations, cardiac septal defects and pulmonary vascular anomalies.

Diagnosis

Clinical Signs

The disease is frequently asymptomatic but clinical signs may include:

• Gastro-intentinal signs, including vomiting, diarrhoea, abdominal pain, anorexia and weight loss.
• Respiratory distress may occur if abdominal contents occupy a large amount of the thoracic cavity.
• Cardiac signs are unusual but cardiac tamponade (with right-sided heart failure) may develop if abdominal organs are incarcerated in the pericardial sac. The heart sounds will be muffled on auscultation and borborygmi may be apparent. A heart murmur may be present if the animal has concurrent septal defects.

Radiography

On plain radiographs of the chest, the cardiac silhouette is enlarged and continuous with that of the diaphragm. If loops of small intestine have passed into the pericardial sac, areas of lucency may be apparent overlying the cardiac silhouette and, if necessary, this can be confirmed by a barium contrast study. The trachea may also be displaced dorsally. In cats, an area of radio-opacity may be apparent in the area of the dorsal diaphragm on a lateral radiograph, referred to as the 'dorsal peritoneo-pericardial remnant.'

Ultrasonography

Definitive diagnosis generally relies on the identification of abdominal organs within the pericardial sac. Septal defects may also be diagnosed during the scan.

Treatment

If the animal is showing few clinical signs or if the hernia is discovered incidentally, conservative treatment may be all that is required. In animals showing overt clinical signs, the abdominal organs can be retracted via a midline coeliotomy and the defect in the diaphragm can then be closed surgically. This procedure may trap air within the pericardium so it is important not to close the pericardium and to perform pericardiocentesis before closure of the abdominal incision. Even though organs may have been present in the pericardial sac for prolonged periods, it is rare for adhesions to form as these structures are in constant motion.

Prognosis

A study assessing treatment regimes used in cats showed a post-operative mortality rate of 14%, whereas progressive disease was reported in 9% of those managed conservatively. This result may largely reflect the criteria used for determining whether a cat was a surgical candidate .

References

Reimer SB, Kyles AE, Filipowicz DE, Gregory CR Long-term outcome of cats treated conservatively or surgically for peritoneopericardial diaphragmatic hernia: 66 cases (1987-2002) J Am Vet Med Assoc. 2004 Mar 1;224(5):728-32

Gorman N 1997 Canine Medicine and Therapeutics Blackwell Science Fourth Edition