Cross-Sectional CT of Strangulating Intrapericardial Diaphragmatic Hernia

Donald J. Wenzel1,2 and Jackson D. Hamilton3

1 Department of Radiology, Durham Veteran Affairs Medical Center, 508 Fulton St., Durham, NC 27705.
2 3 University of North Carolina at Chapel Hill Medical School, Rm. CB7525, Chapel Hill, NC 27516.

Republished with permission of American Journal of Roentography
Address correspondence to J. D Hamilton.



Diaphragmatic hernias, in which peritoneal contents are found in the thoracic cavity, are well documented in the medical literature. Hernias of this type may be congenital in origin, such as Morgagni's or Bochdalek's hernia, or traumatic in origin. Herniation into the pericardial space is a relatively infrequent occurrence [1,2,3] involving a sacless entry through a rent in the pericardial portion of the diaphragm's central tendon. The contents of the hernia varied among the following 28 cases reported through 1980: 16, stomach; 15, colon; seven, liver; five, jejunum; and one, spleen. Only two patients presented with cardiac tamponade and one patient, with strangulation [1].
As the rarest of adult diaphragmatic hernias, intrapericardial diaphragmatic hernia is often unrecognized or misdiagnosed, both clinically and radiologically [1]. Before the advent of cross-sectional imaging, a preoperative diagnosis was made in only eight of 22 patients in one series [1] and in three of 16 patients in another [2]. Chest radiographs revealed bowel shadows above the diaphragm, but intrapericardial diaphragmatic hernia was infrequently considered. Fagan et al. [3] were the first to report CT findings in an uncomplicated case that was correctly diagnosed preoperatively.
We recently encountered a patient with an intrapericardial diaphragmatic hernia quiescent for 38 years after trauma. To our knowledge, this is the longest delayed presentation recorded. The clinical presentation was subacute cardiac tamponade, whereas the radiologic findings indicated an abdominal herniation.

Case Report
A 78-year-old man presented with progressive shortness of breath and ankle swelling. He had experienced these symptoms for 2 weeks before presentation. His dyspnea was worse for 5 days, especially at night and when he was in the supine position. He experienced pacing behavior, agitation, insomnia, and chest tightness. He reported no chest or abdominal pain nor vomiting or change in bowel habits. A major frontal body trauma that occurred 38 years earlier was not initially revealed.
The patient appeared ill and tachypneic. His vital signs were as follows: blood pressure, 163 over 85 mm Hg; temperature, 98.8°F (37.1°C); and pulse, 106. His heart sounds were distant. Pitting edema was present, and his neck veins were distended at 45°. The patient's WBC was 4.0 x 103/µL and supine arterial blood gas revealed an oxygen saturation of 88% on room air.
Venous Doppler sonography showed elevated systemic venous pressure. Chest radiographs revealed clear lungs, increased cardiomegaly, and a loop of bowel anterior to the heart on examination 4 days before admission (Figs. 1A and 1B). An emergent thoracic CT scan showed abnormal fat containing vascular congestion, edema, effusion in the pericardium (Fig. 1C), and a gaping diaphragmatic defect (Fig. 1D). A CT scan performed 2 years earlier (Fig. 1E) showed excessive precardiac fat that was interpreted as mediastinal lipomatosis. The interpreter failed to recognize its intrapericardial location or the diaphragmatic defect present at a lower level (Fig. 1F).


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Fig. 1A. 78-year-old man with progressive dyspnea caused by enlarging pericardial hernia. Frontal chest radiograph obtained 6 days after onset of symptoms shows cardiac dimensions are increased from prior examination (not shown). Note apparent double density at right heart contour (horizontal arrows), bowel gas projecting over left heart (vertical arrows), and healed displaced right rib fractures (curved arrows).


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Fig. 1B. 78-year-old man with progressive dyspnea caused by enlarging pericardial hernia. Lateral chest radiograph (companion to A) shows bowel loop projecting into anterior mediastinum (straight arrows) and fluid density anterior to subepicardial fat stripe (curved arrows).


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Fig. 1C. 78-year-old man with progressive dyspnea caused by enlarging pericardial hernia. Enhanced helical CT scan 2 weeks after onset of symptoms shows heart is completely surrounded by thick pad of fluid and fat with increased density and heterogeneity. Note engorged vessels (curved arrow), dependent effusion (open arrow), and subepicardial fat (small arrows).


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Fig. 1D. 78-year-old man with progressive dyspnea caused by enlarging pericardial hernia. Enhanced helical CT scan (same as C but at level of diaphragm) shows enlarged enhanced central vessels traverse large left anterior paracentral defect in diaphragm (arrows). Pleural effusion (P) was new, as was liver lesion (M), consistent with metastasis.


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Fig. 1E. 78-year-old man with progressive dyspnea caused by enlarging pericardial hernia. Enhanced helical CT scan 15 months earlier, during asymptomatic period. Excessive intrapericardial fat, identical in density to fat elsewhere, appears confined by only two membranes. No peritoneal sac is seen. Note smooth nonlobular contour of mediastinum.


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Fig. 1F. 78-year-old man with progressive dyspnea caused by enlarging pericardial hernia. Enhanced helical CT scan (same as E but at level of diaphragm). Note smaller (6 x 8 cm) diaphragmatic defect (arrows) and smaller contained vessels.

New epigastric pain in our patient prompted an abdominal CT scan. The scan showed normal-appearing subcutaneous and infradiaphragmatic fat, a normal bowel pattern, a bladder mass (recently diagnosed), and liver metastases.
The patient was believed to have a symptomatic intrapericardial diaphragmatic hernia. Surgical treatment was not considered in light of his condition and cancer prognosis. During a short hospital stay, the patient developed a bandemia of 29%, with a WBC of 8.9 x 103/µL. Blood cultures were negative. He remained agitated and a morphine infusion was begun. While awaiting hospice placement, the patient died. The family declined to have an autopsy performed.

Intrapericardial diaphragmatic hernia results from a posttraumatic and severe compressive injury to the chest and abdomen, usually caused by a motor vehicle crash. Most often the hernia is overlooked and more pressing cardiorespiratory and orthopedic abnormalities are addressed. A delayed presentation may occur from 6 weeks to 33 years after the injury [4]. Of the 60 cases reported through 1991, half of the patients presented in the delayed phase [5]. Chest complaints may be erroneously diagnosed as ischemic heart disease [1, 4].
A previously small defect progressively enlarges to the extent that the individual becomes symptomatic. Chest or abdominal pain (75%), dyspnea (75%), and vomiting (25%) are common symptoms, whereas bowel obstruction and strangulation are not [4]. Two of the 28 cases reported through 1980 presented with cardiac tamponade resulting from herniation of the viscera into the pericardial sac [1]. Because the stomach, spleen, and left kidney offer less protection from sudden increases in abdominal pressure, tears usually occur on the left. The intrapericardial diaphragmatic hernia has no sac. Large tears are initially filled with omentum that prevents healing and initiates stretching of the defect and the pericardial sac, resulting in further herniation and enlargement [1].
Our patient had healed displaced right rib fractures, a high right kidney, and an adjacent deformed diaphragm attributed to a motor vehicle crash that occurred 38 years earlier. During the patient's asymptomatic period, his pericardium accommodated the additional omental fat. More recently, however, the increased cardiomegaly on the chest radiograph was coincident with worsening subacute tamponade caused by fat edema and pericardial effusion. A similar clinical history in another patient with enlarging pericardial liposarcoma and effusion was described in a recent report [6].
Radiologic findings of intrapericardial diaphragmatic hernia reported before 1980 included the following: intrapericardial gas shadows (19/28), cardiomegaly (4/28), and abnormal barium studies (11/28) [1]. Only one of the numerous chest examinations of this patient, including conventional radiography and CT images, showed the bowel as a participant in the hernia. A search of cases reported before 1980 showed only four cases citing omentum as the sole hernia content [1].
All radiologic interpreters failed to distinguish true cardiomegaly from a composite shadow of heart and juxtacardiac fat. The difficulty in recognizing mediastinal masses as fatty has been cited in the literature [7]. A subtle subepicardial fat stripe defined the true anterior heart margin (Fig. 1B).
In describing a case of intrapericardial diaphragmatic hernia diagnosed on CT scanning, Fagan et al. [3] noted posterior displacement of the heart and a mediastinal configuration thought to be diagnostic. They described smooth symmetric nonlobulated mediastinal margins in contradistinction to angular indentations between the hernial contents and the heart and pericardium seen with extrapericardial diaphragmatic hernias and pericardial cysts. Prior CT performed on the patient also showed nonlobulated margins and precardiac fat confined by two membranes, the parietal and visceral pericardia. Cardiac compression was not seen. Fine linear opacities became more readily recognized as vessels as they converged and centralized while traversing a characteristic diaphragmatic defect (Fig. 1F). The opening measured 6 x 8 cm, which appeared larger on the presentation scan (Fig. 1D). The bland fat observed on the previous CT scan had increased in density from edema or inflammatory exudate, completely enveloping the heart. The fat appearance is similar to mesenteric panniculitis, but in this patient the vessels appeared dilated and associated with pericardial effusion. There is also a striking similarity to the appearance of pericardial liposarcoma [6] (Fig. 1D), but without the diaphragmatic opening.
In summary, intrapericardial diaphragmatic hernia is not usually recognized as a mediastinal mass. It has no sac and therefore conforms to the pericardium with nonlobulated margins. The observation of a diaphragmatic defect on cross-sectional imaging is essential to the diagnosis of a pericardial diaghragmatic hernia. Although this hernia may present acutely with cardiorespiratory distress or bowel obstruction, it is often misdiagnosed as heart disease during a latent period. Paramount to a prompt and correct diagnosis is familiarity with the entity and knowledge of trauma in the patient's history.

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