Introduction

The pericardium could be involved in a variety of benign and malignant disorders. Plain radiography has limited value since pericardial disorders may not be differentiated from various types of mediastinal and/or cardiac pathologies on roentgenograms. Nevertheless, in case of pneumopericardium, plain radiography may give the definite diagnosis yet may not reveal the underlying cause.

Computed tomography (CT) is the most widely used modality of choice for the evaluation of the pericardium; however, ultrasound could be easily and rapidly performed to reveal the presence of pericardial effusion which is a crucial finding particularly in trauma patients. Pericardial calcifications, extension of pericardial collections and tumours, pneumopericardium and its underlying cause, pericardial/epipericardial fat necrosis, foreign bodies, and medical devices placed in the pericardial space can be revealed by CT. However, soft tissue infiltration of pericardium could not be differentiated from accompanied pericardial effusion by CT in rare cases such as in Erdheim-Chester disease or inflammatory constrictive pericarditis. In this case, magnetic resonance imaging (MRI) can replace CT due to its superior soft tissue contrast resolution.

 

Normal pericardium anatomy

The pericardium is seen as a linear line (< 2 mm) covering the heart and also the roots of the great vessels (proximal portions of the ascending aorta, pulmonary artery, left pulmonary veins, and superior vena cava) on CT or MRI images.

Absence of the pericardium

Congenital - Absence of the pericardium is a rarely encountered malformation in clinical practice. Its total prevalence still remains unknown. A significant portion (30–50%) of the reported cases with absence of the pericardium were associated with congenital anomalies of the heart, lungs, chest wall, and diaphragm. The absence is typically partial and occurs more commonly on the left side compared to the right or inferior aspects.

Acquired defect - In addition to congenital etiology, the acquired defect of the pericardium could also be seen particularly following pericardial surgery. Pericardial resection is performed either to relieve the compressive effect of constrictive pericarditis or to be able to reach the coronary arteries during coronary artery bypass grafting surgery. The imaging signs that were previously mentioned in the congenital absence of the pericardium are not observed in patients with pericardial resection.

 

Pericardial collections

Pneumopericardium

Among the various causes of pneumopericardium, trauma is the most frequently encountered etiology. Pneumothorax or pneumomediastinum may or may not accompany to pneumopericardium. Intubated patients, particularly the pediatric population, are also at risk for the development of pneumopericardium due to positive pressure ventilation complicated with barotrauma. The clinical symptoms may range from subtle chest pain to acute heart failure. The adjacent air-containing structures could also be questioned for the occurrence of pneumopericardium in the non-traumatic setting. Cardiac tamponade may occur in case of tension pneumocardium as a consequence of direct communication of pericardial space with the gastrointestinal tract. The diagnosis could be made by roentgenograms. However, CT may reveal the underlying cause. MRI is not practical since patients with pneumopericardium usually need emergent care.

Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare multisystem non-Langerhans cell histiocytosis that could be presented with various radiological signs. Pericardial involvement may rarely be encountered in patients with ECD. Presenting symptoms may vary depending on the dissemination of the disease. Pericardial thickening and effusion are the common imaging findings. Pericardium is commonly infiltrated with mass-like soft tissue lesions, and imaging appearances may mimic those of the loculated pericardial effusions on CT . However, MRI may better differentiate the pericardial soft tissue infiltration from pericardial effusion. Infiltration of the epicardium and/or myocardium is frequently encountered in the right atrium and atrioventricular groove with pseudo-tumor appearance.

Medical devices

Radiologists should be aware of medical devices placed in the pericardial space for certain individual indications. Pericardial drainage catheters are used for therapeutic pericardiocentesis to relieve the pressure applied by pericardial fluid collection to heart chambers. The procedure is performed either echocardiographic or CT guided. A pericardial drainage catheter is seen as a tubular structure coursing within the pericardial space and surrounding heart borders. In the setting of loculated pericardial effusion, the position of drainage catheter may vary.

Post-operative changes

Pericardial adhesions which increase the risk of injury to the heart or other major vascular structures during resternotomy could be encountered in the follow-up period of patients who underwent previous cardiac surgery. Pericardial effusion could be seen as areas of nodularity in the setting of adhesions. This appearance may raise suspicion for malignancy due to the irregular pattern of pericardial adhesions. In addition, a pedicled fat flap applied to maintain hemostasis and infection control could be presented with a fatty pseudo-tumor appearance on CT

 

Conclusion

Imaging findings of pericardial disorders could be non-specific for the majority of the cases; therefore, the patient’s clinical history is the most valuable clue for the differential diagnosis. The radiologists should be familiar with the various imaging appearances of pericardial disorders.

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Source

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6441059/