What caused recurrent pneumonia and hemoptysis in this woman?

A 53-year-old woman presented to the emergency department complaining of substernal chest pain that awoke her from sleep. The chest pain was associated with left shoulder numbness, radiating to her back, and was partially alleviated with sublingual nitroglycerin. During this episode, the patient had a cough productive of yellow phlegm and one instance of cough productive of 1 tbs of bright red blood.

Over the past few months, she had intermittent episodes of chest pain that did not worsen with exertion. She denied dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea, and lower extremity edema. Her history included multiple episodes of pneumonia and bronchitis. For the past 3 years, she had had an intermittent cough productive of yellow phlegm, which had worsened in the past 6 months. She had had 2 other episodes of hemoptysis. The patient took no medications and reported no drug allergies. She had never smoked cigarettes and reported occasional alcohol use.

A physical examination revealed normal heart rate, blood pressure, respiration rate, and temperature. Her oxygen saturation was 99% on room air. Auscultation of her heart revealed a regular rhythm with a grade 2/6 harsh systolic ejection murmur heard best at the left upper sternal border. The patient's chest pain was not reproducible with palpation, and her lungs were clear to auscultation bilaterally. No clubbing or cyanosis was noted in her extremities. Head, neck, abdominal, and neurological examination findings were normal.

An ECG showed left axis deviation with left ventricular hypertrophy without ST elevations or depressions or other evidence of conduction abnormality. Glucose and electrolyte levels and complete blood cell count were normal. Cardiac enzyme test results were negative 3 times within 24 hours, and ECG findings were unchanged during this time. The patient's posteroanterior (PA) and lateral chest radiographs obtained on admission are shown below (Figure 1).

Making the diagnosis

The patient's PA and lateral chest radiographs showed an area of focal confluent opacity within the left retrocardiac region obscuring the descending aortic-lung interface. The heart size was normal, the remaining lung parenchyma was clear, and there were no pleural effusions. The focal confluent opacity within the posterior basilar segment of the left lower lobe could represent an acute process, such as infectious pneumonia or aspi- ration pneumonia. The differential diagnosis also includes chronic processes, such as sequestration and primary or metastatic lung neoplasm.

While the differential diagnosis of a focal confluent radiographic opacity is broad, this patient's negative smoking history and lack of exposures makes neoplasm less likely. She had no known history of gastroesophageal reflux or memory of significant aspiration. She did have a history of recurrent pneumonia, and she had a cough productive of yellow sputum and hemoptysis at the time of presentation. Recurrent pulmonary infec- tions should prompt further evaluation for structural or immunological abnormalities.

Because the patient presented with chest pain radiating to the back, an aortic dissection was a primary concern. Thus, a CT angiogram of the chest was obtained to evaluate the aorta (Figure 2). Findings from the scan excluded aortic dissection. However, the scan allowed for better characterization of the focal left lower lobe abnormality and demonstrated vascular supply to this region from the descending thoracic aorta. This finding is consistent with the diagnosis of pulmonary sequestration.

Sequestration may appear radiographically as a smooth-bordered area of uniform density or as a consolidation with an irregular margin. On a CT scan, the area of sequestration appears as a mass of soft tissue density with smooth or irregular borders, similar to its radiographic appearance. Sequestrations that have been complicated by chronic inflammation and recurrent infection often evolve into predominantly cystic lesions. After administration of intravenous contrast, the lesion may show heterogeneous enhancement. While the systemic artery supplying the sequestered lung is visualized in 80% of cases and allows for definitive diagnosis, failure to identify the artery does not exclude the diagnosis of pulmonary sequestration.

To further characterize the arterial supply and venous drainage of this patient's sequestration, MRI of the chest was performed. Arterial supply was shown to arise from 2 large arteries and 2 small arteries from the lower descending thoracic aorta. No venous drainage into the pulmonary veins was identified. Rather, a dominant vein was found to drain into the azygous system, and at least 2 smaller veins also draining into the azygous system were found more superiorly. The presence of systemic venous drainage is consistent with an extralobar sequestration, an entity that is usually diagnosed much earlier in life, usually during infancy or early childhood.

The patient's symptoms of recurrent pneumonia and hemoptysis are consistent with a sequestration. In the absence of any identified cardiac or GI cause, it is likely that the patient's chest pain was related to chronic inflammation and infection of the sequestration.

Discussion

Pulmonary sequestration was defined by Pryce¹ in 1946as an area of bronchopulmonary tissue with systemic blood supply. There are 2 types of sequestration: intralobar, with the lesion bound by the visceral pleura, and extralobar, which is found external to the visceral pleura and may be ensheathed in its own pleural lining.^2-6 The venous drainage varies depending on the type of pulmonary sequestration. In an intralobar sequestration, the anomalous venous drainage occurs via the inferior pulmonary vein. In an extralobar sequestration, the anomalous venous drainage is systemic, typically flowing through the azygous system, as demonstrated in this case.

Whereas extralobar sequestration is always congenital, 2 hypotheses for the pathogenesis of intralobar sequestration have been proposed. Because intralobar sequestration can occur in the setting of other developmental abnormalities, it has been proposed that the sequestered segment of bronchopulmonary tissue may have originated as an accessory lung bud that developed in the ventral foregut and retained its systemic blood supply as it migrated caudally. Via traction, the anomalous systemic artery causes the detachment of the lung tissue in its vascular territory from adjacent lung tissue, resulting in sequestration.

Because many cases of intralobar sequestration are diagnosed later in life rather than presenting early as congenital problems, an alternative hypothesis has been proposed by Stocker and Malczak⁷:a segment of the lung develops systemic blood supply in the setting of recurrent postobstructive pneumonia. According to this hypothesis, the chronic infection causes the obstruction of the pulmonary vessels that normally supply the infected lung parenchyma. To compensate, small systemic pulmonary ligament arteries arise from the thoracic artery hypertrophy to supply the area of infected lung.

The great majority of sequestrations occur within the lower lobes, more often on the left than on the right. Thickening of the pleura covering the lesion occurs, and there may also be fibrotic adhesions between the sequestered tissue and other structures in the mediastinum. By definition, the sequestered segment does not communicate with the tracheobronchial tree, but a connection can be formed in the setting of tissue breakdown caused by chronic infection and inflammation. This communication between the sequestration and the rest of the lung parenchyma allows blood from hemorrhage in the sequestered segment to spread to the tracheobronchial tree, resulting in hemoptysis.

Histologically, the sequestered bronchopulmonary tissue is characterized by extensive fibrosis, sclerosing of the vessels, inflammation, and replacement of the normal lung parenchyma with cystic structures surrounded by lymphoid cysts.^2,3 The severity of the inflammation typically causes atherosclerosis in the systemic vessels that supply the lesion.^2,3

Intralobar sequestration is commonly diagnosed before age 20 with symptoms of recurrent infections.⁶ Patients may also present with chest pain. The vasculature of the sequestered parenchyma is hypertensive, making patients susceptible to hemoptysis. The hemoptysis can be massive, with patients losing several hundred milliliters of blood. Rarely, necrosis of the anomalous vessel can occur, resulting in sudden-onset massive hemoptysis.

The definitive treatment for pulmonary sequestration is surgical resection of the lesion.⁶ Hemorrhage, the most serious complication of treatment, can be minimized by vessel mapping with magnetic resonance angiography or CT angiography before surgery.⁸

Outcome in this case

The patient was discharged from the hospital and evaluated in the outpatient pulmonary clinic. Pulmonary function testing showed a mild, symmetric decrease in forced expiratory volume in 1 second and forced vital capacity, findings consistent with a restrictive process. The intralobar sequestration was removed surgically. Pathological examination showed abscess formation within the sequestration. Two months after left lower lobectomy, the patient reported marked improvement in her cough, resolution of her chest pain, and no episodes of hemoptysis.

References:

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