Right-sided Bochdalek Hernia Presenting as a Solitary Pulmonary Nodule.

Bochdalek hernia is a well-known disorder, which represents visceral herniation through a posterior diaphragmatic defect. In this report we present an adult man with a right-sided Bochdalek hernia mimicking a solitary pulmonary nodule. Furthermore, we perform a brief review of the literature, with emphasis on novel imaging techniques that establish the diagnosis. In conclusion, Bochdalek hernia should be considered in the differential diagnosis of a posterior diaphragmatic or paraspinal opacity. Correct diagnosis is of paramount importance and can be easily established by non-invasive imaging techniques.

Introduction

Bochdalek hernia is a well-known disorder, which represents visceral herniation through a posterior diaphragmatic defect. In this report we present an adult man with a right-sided Bochdalek hernia mimicking a solitary pulmonary nodule. Furthermore, we perform a brief review of the literature, with emphasis on novel imaging techniques that establish the diagnosis.

Case Report

A 45-year-old man, with a history of heavy smoking, was admitted to our department complaining of acute right-sided chest pain of moderate intensity that was not related to breathing or body movements. Previously, he had been in good health. Physical examination and routine blood tests were unremarkable. Arterial blood gases were normal. The posteroanterior chest radiograph was normal, but the lateral view disclosed a round opacity, 2 cm in diameter, in contact with the posterior portion of the right hemidiaphragm which remained unchanged in size or shape with the Valsalva or Müller maneuvers (Fig. 1). A conventional CT of the thorax disclosed an opacity adjacent to the right hemidiaphragm (Figure 2A, Figure 2B). During the multislice contrast-enhanced procedure, scanning was interrupted due to a contrast reaction. As several diseases of intrapulmonary origin may have a similar appearance, coronal and sagittal magnetic resonance T1-weighted images (MRI), focusing on the lungs and upper abdomen were obtained, to further characterize the lesion. The MRI study showed that a portion of the liver had herniated posteriorly through a right diaphragmatic muscle defect, confirming the presence of a Bochdalek hernia (Figure 3A, Figure 3B). The patient underwent fiberoptic bronchoscopy, because of his smoking history. No intraluminal lesions were found although some slight mucosal inflammation was present throughout the tracheobronchial tree. The patient's chest pain resolved a few days later and was deemed to be irrelevant to the diaphragmatic hernia. The patient was discharged without any intervention.

Figure 1

45-year-old man with Bochdalek hernia. Lateral chest radiograph shows a small round opacity (red arrow) in contact with the posterior portion of the right hemidiaphragm.

Figure 2A

45-year-old man with Bochdalek hernia. Axial CT image in soft tissue settings demonstrates an ill-defined opacity adjacent to the right hemidiaphragm.

Figure 2B

45-year-old man with Bochdalek hernia. Axial CT image in lung settings shows the posterior right costophrenic poorly marginated lesion.

Figure 3A

45-year-old man with Bochdalek hernia. Coronal T1-weighted MRI reveals a portion of liver herniated through a defect in the posterior right hemidiaphragm.

Figure 3B

45-year-old man with Bochdalek hernia. Sagittal T1-weighted MRI shows the herniated portion of liver.

Discussion

The diaphragm forms from four embryological elements: a) septum transversum, b) mesentery of the esophagus, c) pleuroperitoneal membranes and d) ingrowing muscular tissue from the body wall [1]. During the 7th week of development, the pleuroperitoneal folds fuse with the mesentery of the esophagus and migrate anteriorly to join the septum transversum, closing two large posterolateral openings. Failure of closure results in patency of the Bochdalek's foramen. The abdominal contents return from the yolk sac at about the 10th week of development and if they return prior to closure, or if closure is incomplete, herniation can occur [2].

Posterolateral congenital diaphragmatic hernias are commonly termed “Bochdalek hernias” in recognition of Professor Vincenz Alexander Bochdalek, a prominent Czech anatomist who first described the abnormality in 1848 [3]. Nowadays, the term “congenital diaphragmatic hernia” is preferred for hernias presenting in the neonatal period, as a result of large central diaphragmatic defects, which allows the protrusion of abdominal viscera into the thoracic cavity. These cases may behave as life-threatening emergencies, due to the compressive effects of the abdominal contents on the lungs and the mediastinum [4]. The term “Bochdalek hernia” is preferred for more localized herniations through small diaphragmatic defects, usually occurring later in life without obvious symptoms. Triggering factors that have been suggested, include physical exertion, sexual intercourse, childbirth, Valsalva maneuver, large meals and abdominal trauma (including post-operative events) [5].

Estimations of the prevalence of Bochdalek hernia vary between 0.17% and 6% [3, 6, 7]. The disorder shows a left-sided predominance (2:1-9:1 ratio), attributed to the “protective” effect of the liver [8]. Clinical presentation is variable according to the volume and contents of the hernia sac and the presence or absence of organ strangulation. Patients may be asymptomatic or suffer from nausea, vomiting, abdominal pain, chest pain, cough or respiratory distress. Physical examination is usually unremarkable, but in cases of strangulated viscera, auscultation may reveal abnormal bowel sounds from acute intestinal obstruction [9]. Some authors distinguish between small hernias containing retroperitoneal fat and larger hernias. The small fat-containing hernias have no clinical implication, whereas the large ones containing abdominal viscera are associated with increased morbidity and mortality [7]. Bochdalek hernia is often discovered as an incidental finding, as in the case we present.

The diagnosis of the disorder can be established using radiological techniques. Chest radiograph is usually the first imaging procedure but it is of limited value on depicting the diaphragmatic defect [10]. The hernia may appear either as a soft-tissue opacity at the lung base or as a solitary, smooth, round lesion in the posterior costophrenic recess. Contrast studies of the gastrointestinal tract may confirm the diagnosis in some cases [11]. Radionuclide imaging may also be useful in showing herniation into the chest [12]. Abdominal ultrasound sometimes may depict the disruption of diaphragmatic continuity with the associated herniated organs, distinguishing fatty tissue from liver and loops of bowel [13].

CT is the procedure of choice for demonstrating a Bochdalek hernia. With routine CT scan, Killeen et al. demonstrated sensitivities of 50% for right-sided and 78% for left-sided Bochdalek hernia detection [14]. However, with the advent of multislice CT with multiplanar reformatting of the images, the diagnosis of Bochdalek hernia is simplified, as the diaphragmatic defect and the herniated contents are accurately depicted [10]. Sagittal and coronal reformatted images can exquisitely demonstrate the defect and identify organ entrapment [10, 15]. When the diagnosis remains unclear, magnetic resonance imaging should be considered.

Bochdalek hernia can simulate neoplastic disease, pulmonary sequestration, foreign material aspiration, tension pneumothorax, pneumonia, pleuritis or pulmonary tuberculosis [16, 17, 18]. Extrapleural lipomas may also present with a similar appearance but they are not accompanied by a diaphragmatic defect or displacement of abdominal viscera [19]. The imaging modalities, already mentioned, accurately establish the diagnosis and obviate the need for further investigative procedures. Surgery represents the treatment of choice, particularly in symptomatic cases, with a high success rate [20]. In adulthood, clinically silent hernias rarely progress to life-threatening surgical emergencies [5]. For this reason we decided to keep our patient under observation without further therapeutic interventions.

In conclusion, Bochdalek hernia should be considered in the differential diagnosis of a posterior diaphragmatic or paraspinal opacity. Correct diagnosis is of paramount importance and can be easily established by non-invasive imaging techniques.