Peritoneopericardial diaphragmatic hernia

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Radiograph of a 12-month-old dog with a congenital vertebral anomaly and associated peritoneopericardial diaphragmatic hernia[1]

Peritoneopericardial diaphragmatic hernia are a congenital defect of dogs characterized by a persistent communication between the pericardial and peritoneal cavities, resulting in herniation of abdominal viscera into the pericardial sac.

True congenital diaphragmatic hernias are very rare in dogs[2].

This condition is usually caused by abnormal fusion of the septum transversum with the pleuroperitoneal folds during development[3]. Intrapericardial cysts can also occur as a consequence of entrapment of omentum or a portion of the falciform ligament into the pericardial sac[4].

These hernias can be of variable size and frequently contain the liver, but less frequently the small intestine, spleen and stomach. The Weimaraner appears predisposed.

Other congenital defects may be present, such as umbilical hernia, pectus excavatum or ventricular septal defect.

Clinical signs reflect either respiratory or gastrointestinal disturbances or development of acute cardiac tamponade or cardiac decompensation from liver entrapment[5].

Symptoms such as dyspnea or intermittent diarrhea or regurgitation are more frequently observed[6]. An 'empty' abdomen may be appreciable on abdominal palpation.

Auscultation of the chest usually reveals muffled heart sounds (on one side or bilaterally), borborygmi and murmurs. The point of maximal intensity of heart sounds may be displaced dorsally.

Diagnosis is usually made incidentally on radiographic, ultrasonographic[7] or CT imaging studies, which usually show varying degrees of altered radiographic density in the caudoventral portion of the pericardial space. Ventral to the caudal vena cava there may be a persistent mesothelial remnant indicating the dorsal border of the hernia. Often the carina is displaced cranial relative to the caudal border of the heart.

Pulmonary edema and pyothorax have been reported complications of this condition[8].

Contrast barium meal or ultrasonography may show intestinal loops anterior to the diaphragm. Cardiac tamponade is an infrequent complication and urgent care is more likely to become necessary should there be entrapment of a loop of bowel or strangulation of the liver.

The condition is treated surgically, but since the hernia is often an incidental finding in mature animals, the situation may not warrant intervention.

References

  1. Berlanda M et al (2011) Magnetic resonance and computed tomographic features of 4 cases of canine congenital thoracic vertebral anomalies. Can Vet J 52(12):1334-1338
  2. Choi J et al (2009) Imaging diagnosis - positive contrast peritoneographic features of true diaphragmatic hernia. Vet Radiol Ultrasound 50(2):185-187
  3. Simpson DJ et al (1999) Benign masses in the pericardium of two dogs. Aust Vet J 77(4):225-229
  4. Sisson D et al (1993) Intrapericardial cysts in the dog. J Vet Intern Med 7(6):364-369
  5. Hay WH et al (1989) Clinical, echocardiographic, and radiographic findings of peritoneopericardial diaphragmatic hernia in two dogs and a cat. J Am Vet Med Assoc 195(9):1245-1248
  6. Banz AC & Gottfried SD (2010) Peritoneopericardial diaphragmatic hernia: a retrospective study of 31 cats and eight dogs. J Am Anim Hosp Assoc 46(6):398-404
  7. Reichle JK & Wisner ER (2000) Non-cardiac thoracic ultrasound in 75 feline and canine patients. Vet Radiol Ultrasound 41(2):154-162
  8. Schmiedt CW et al (2009) Chylothorax associated with a congenital peritoneopericardial diaphragmatic hernia in a dog. J Am Anim Hosp Assoc 45(3):134-137