Case Studies In Small Animal

Cardiovascular Medicine

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Case 25

Peritoneopericardial Diaphragmatic Hernia Section from :Small Animal Cardiovascular Medicine" On-Line

Text from "Small Animal Cardiovascular Medicine"

Peritoneopericardial Diaphragmatic Hernia

Peritoneopericardial diaphragmatic hernia (PPDH) is the most frequent congenital pericardial anomaly reported in dogs and cats. This anomaly consists of a persistent communication between the pericardial and peritoneal cavities allowing abdominal contents to enter the pericardial cavity while the pleural space remains intact. Although usually considered a result of abnormal fusion of the septum transversum with the pleuroperitoneal folds during embryonic development, postnatal injuries may also cause formation of acquired PPDH. The size of the defect may vary from clinically silent, small communications involving herniation of the omentum to very large defects with herniation of other abdominal organs. The liver and gall bladder are herniated most frequently, followed by the small intestines, spleen, and stomach. Hernias in the cranioventral abdominal wall and caudal sternebrae abnormalities commonly occur in association with congenital PPDH. In one report, male dogs were affected more often than females and 18% of the cases were Weimaraners.

Although in the majority of cases the hernia is present from birth, clinical signs may occur at any age or not at all. In reported cases, the age at the onset of clinical signs ranges from 4 weeks to 15 years, with most diagnoses being made within the first year of life. In many instances, the PPDH is identified as an incidental radiographic finding while evaluating other problems or at necropsy. Although clinical signs are most commonly absent when they are present they are primarily related to the gastrointestinal system and the respiratory tract. Clinical signs include vomiting, diarrhea, weight loss, exertional fatigue, dyspnea/tachypnea, and cough. Rarely, PE accompanies the hernia and signs of cardiac tamponade may predominate. Physical findings may be normal with smaller defects. With larger defects findings may include diminished or displaced heart sounds, umbilical or abdominal hernias, caudal sternal deformities, inability to palpate abdominal organs, and rarely, signs of cardiac tamponade and congestive right heart failure.

Electrocardiograms may demonstrate reduced amplitudes due to the addition of abdominal contents into the pericardial sac and the mean electrical axis may be shifted due to cardiac displacement. The diagnosis of PPDH is usually made by radiographic examination. Survey thoracic radiographs characteristically show cardiac enlargement, dorsal displacement of the trachea, and silhouetting of the caudal heart border and the diaphragm. In some cases, regions of the cardiac silhouette may have a heterogeneous density of soft tissue, gas, and/or fat due to the varied contents of the pericardial cavity. The silhouette of the heart may be seen in some cases, especially when it is surrounded by fat. Although thoracic radiographs may be diagnostic, in many cases the findings are merely suggestive. Abdominal radiographs may show a smaller than normal liver. In extreme cases the peritoneal cavity to be devoid of organs. In some cases gastrointestinal gas patterns may be seen extending from the peritoneal cavity into the pericardial cavity. Two-dimensional echocardiography may allow direct visualization of an extracardiac, intrapericardial mass that displaces the heart with or without a small amount of PE. Occasionally, the discontinuity in the diaphragm can be seen and herniated tissue may appear to be continuous with abdominal contents. If echocardiography is not available, fluoroscopy, nonselective angiocardiography, upper gastrointestinal barium studies, and/or pneumopericardiography may also be helpful to establish the diagnosis. A definitive diagnosis can be established by placing an iodinated radiopaque contrast agent (not barium) or a radionuclide tagged substance in the peritoneal cavity, elevating the dog’s caudal body, and determining if the substance flows forward into the pericardial space.

Surgical correction via laparotomy and/or thoracotomy is the recommended treatment. In asymptomatic adult patients in which the PPDH was an incidental finding and in asymptomatic patients with small hernias, treatment may not necessarily be indicated. The postoperative prognosis for most patients is excellent.

Post mortem specimen of another cat

The pericardium has been removed. Note that only liver lobes are present in the pericardial space in this cat (the heart is lying on top of liver lobes in this view).

©Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.