Volume 5, Case 14
Craig T. Nakamura, MD
Kapiolani Medical Center For Women And Children
University of Hawaiʻi John A. Burns School of Medicine
This is a 13 month old male brought to the emergency department with wheezing, coughing, and rhinorrhea. He has had these symptoms for the past month. Tonight, he developed fever which prompted his parents to bring him to the E.D. He was seen by his primary care physician three weeks ago. A chest radiograph was obtained on that day, revealing a left lower lobe consolidation. He was treated with albuterol syrup and a ten day course of clarithromycin with some improvement. He was noted to have a poor appetite and lost approximately one kilogram over the course of the month.
Past medical history. He was born at 39 weeks gestation without complications. In the nursery, he was noted to be tachypneic with subcostal retractions. A chest radiograph in the nursery revealed a left lower lobe infiltrate. He was treated with oxygen and intravenous antibiotics. He was then discharged home after one week. Over the first year of his life, he was seen by his pediatrician on seven occasions for upper respiratory tract infections.
Exam in the E.D.: T 37.5 degrees rectally, P 138, RR 52, BP 95/40, oxygen saturation in room air 95%. General appearance: Responsive with diminished activity in mild respiratory distress. HEENT: Normal except for white rhinorrhea. Neck without adenopathy. Lungs clear to auscultation bilaterally. Breath sounds were diminished at the left base. There were no wheezes, rhonchi, or rales. He has mild subcostal retractions and a paroxsymal cough. Heart regular without murmurs. Abdomen benign. Color and perfusion are good
Labs in the E.D.: Hgb 9.6, hct 30.0, WBC 30,600 with a differential of 48% segs, 13% bands, 33% lymphs and 6% monos. Platelet count 518,000. A blood culture is drawn. A chest radiograph is obtained.
View CXR [PA view]
[Lateral view]
The PA view demonstrates a left sided triangular density of the medial left lung base.
On the lateral view, the triangular density is seen posteriorly over the left lung base. Usually, the right diaphragm is higher than the left diaphragm. In this case, the left diaphragm, which is higher than the right diaphragm, can be identified as the diaphragm with the underlying gastric bubble. In this lateral view, the density can be determined to be on the left side.
View density.
The patient is hospitalized and treated with intravenous antibiotics. The history of recurrent pulmonary infections suggests the possibility of a pulmonary anomaly. An aortogram is performed.
View aortogram.
This aortogram shows contrast injected into the aortic arch. There is a large anomalous vessel from the infradiaphragmatic portion of the aorta that supplies the abnormal density at the left lung base. The venous phase (not shown) revealed drainage into the hemiazygous vein (a systemic vein). This abnormal vascular supply is indicative of a pulmonary sequestration.
Discussion
Pulmonary sequestration (PS) as first described by Rektorzik in 1861 is a mass of accessory lung tissue with an anomalous arterial supply. The pulmonary tissue is dysplastic and nonfunctioning without any connection to the tracheobronchial tree (1). The etiology of this defect is thought to be congenital (2).
There are two types of pulmonary sequestration: intralobar and extralobar.
Intralobar PS is three to six times more common than the extralobar type (3). In intralobar PS, the pulmonary tissue is isolated from the normal lung tissue; however, the pleural covering remains contiguous with that of the lung. The left lung is involved in 65% of the cases (4). Typically, the mass is confined to the posterior basilar segments of the lower lobe of the lung. There are rarely associated anomalies or foregut communications. The symptoms typically occur during early childhood with the patient presenting with recurrent pneumonia. The diagnosis is made after the age of 20 years in fifty percent of this type of PS (5). The incidence of intralobar PS is equal in males and females (6). The arterial supply is via a systemic artery and the venous drainage is through the pulmonary veins.
The accessory lung tissue of extralobar PS is contained within its own pleural sac and is separated from the rest of the lung. It may be located between the inferior surface of the lower lobe and diaphragm, below the diaphragm, within the diaphragm, or in the mediastinum. It occurs on the left in greater than 90% of the cases (5). There may be an occasional foregut communication and associated anomalies are quite common. These may consist of a diaphragmatic hernia, cardiovascular malformation, bronchogenic cyst, pectus excavatum, or other lung anomalies (4). In contrast to intralobar PS, extralobar PS is usually diagnosed in infancy secondary to respiratory distress or feeding difficulties. Since the accessory tissue is sequestered within its own pleura, the chances of presentation with an infection are less than that of intralobar PS, unless there is a foregut communication. The arterial supply is from a systemic artery and the venous drainage is typically via the systemic veins, rather than the pulmonary veins as seen in intralobar PS.
Most radiographically visible sequestrations occur in children over one year of age. The appearance of the chest radiograph depends on several factors: 1) whether the lesion is a site of infection, 2) if there is a communication with the airway or contiguous lung tissue, and 3) if there are other associated lung anomalies (7). Intralobar sequestration typically appears as a mass, cystic lesion, or infiltrative shadow with ill-defined borders. The majority of extralobar sequestrations are small lesions and are not visible on chest radiographs. However, they may present as an infiltrate or mass in the region between the lower lobes and the diaphragm (but can also be found in the superior or anterior mediastinum, pericardium, or infradiaphragmatic region).
In the diagnosis of pulmonary sequestration, a CT, MRI, or ultrasound may be diagnostic. However, a normal study does not exclude the diagnosis. The gold standard for identifying a sequestration is angiography (7). Angiography confirms the anatomy, identifies the systemic supply, and shows the venous drainage.
It is now thought that there are many "variants" to the pulmonary sequestration spectrum (8,9) which include: scimitar syndrome, horseshoe lung, cystic adenomatoid malformation, and pulmonary arteriovenous fistula/malformation.
In the scimitar syndrome, the anomalous vein drains into the inferior vena cava or at its junction at the right atrium. This vein has the appearance of a scimitar. This may or may not be accompanied by hypoplasia of the right lung and dextrocardia, anomalies of the lobes of the right lung, hypoplasia of the right pulmonary artery, and an anomalous systemic vascular supply to the lung (10).
The horseshoe lung is a rare congenital anomaly. It is associated with some of the findings of the scimitar syndrome. There is an isthmus of pulmonary tissue which extends from the right lung base across the midline behind the pericardium and then fuses with the left lung base. Likewise, there may be an anomalous systemic supply (1).
The cystic adenomatoid malformation is an abnormality of the pulmonary parenchyma due to an overgrowth of bronchioles (1). There is usually a normal vascular supply, however there may be an aberrant systemic artery.
Lastly, the pulmonary arteriovenous fistula/malformation consists of an abnormal pulmonary artery and venous connection (1). In this condition, there is normal pulmonary parenchyma (1) .
Regardless of which variant is present, a diagnosis is suggested clinically and confirmed with angiography.
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