Pulmonary sequestration is a result of a disturbance in normal embryonic lung development producing a mass of nonfunctioning lung tissue. The term “sequestration” was derived from the Latin “sequestrare,” to separate, and was first applied to this anomaly by Pryce in 1946. Usually the mass of lung tissue derives its blood supply through one or more anomalous systemic arteries and has its own rudimentary bronchial system, which does not communicate with the normal tracheobronchial tree, therefore lacking any pulmonary function.
Pulmonary sequestration occurs in two types: intralobar and extralobar. Intralobar sequestrations represent a mass of nonfunctioning parenchyma occurring within the visceral pleura of the normal functioning lobes. The mass receives arterial supply through anomalous vessels originating from the aorta, and the venous drainage is into the pulmonary veins. The rudimentary bronchial system within the mass typically does not communicate with the tracheobronchial tree. Despite this, the sequestered intralobar tissue can aerate with surrounding lung parenchyma, probably through the pores of Kohn. With this intercommunication, repeated infection of the sequestered tissue occurs and accounts for the presenting complaint in many of these patients.
In extralobar sequestrations the anomalous lung tissue resides within a distinct visceral pleural investment maintaining complete anatomic and functional separation from adjacent normal lung. The arterial supply is from anomalous systemic vessels; however, the venous drainage is also systemic, usually via the azygos or hemiazygos systems. Bronchial intercommunications are very rare. Therefore, extralobar sequestration rarely presents with pulmonary infections but rather from mass effects on adjacent normal structures. As with intralobar sequestrations, the left lower lobe is the most frequent site of occurrence. Apcalis Oral Jelly
Pulmonary sequestrations are uncommon, with a reported incidence of 1.1 to 1.8 percent of all pulmonary resections. Intralobar sequestrations are more prevalent than extralobar, possibly due to the greater propensity of the intralobar type to cause symptoms. In Savics review of the literature he found 400 reported cases of intralobar with 133 extralobar and six patients presenting with both types simultaneously. Greater than 90 percent of sequestrations occur on the left, with 97.75 percent of reported cases involving the lower lobes. Although a case of intralobar sequestration has been recently reported in the right upper lobe, there have to date been no reported cases of extralobar sequestrations occurring in the right upper thorax.
The majority of extralobar sequestrations are found during the first year of life as incidental findings on chest roentgenograms. However, infants can present with respiratory distress if the sequestration is large enough to impair ventilation. Diagnosis by chest roentgenogram can be difficult, and ultrasound may help to assess the mass, diaphragm, and relationship of the mass to the mediastinum. Males are affected more than females with approximately 4:1 ratio. In contrast, intralobar sequestrations present later, with few recognized during the first year and some not until early adulthood. Males and females are equally affected. Angiography can be helpful in defining anomalous blood supply, and upper GI contrast studies should be undertaken on all patients with suspected sequestration due to the small but definite incidence of coexisting enteric duplications. Results of bronchoscope study are usually normal but may show compressive changes.
The treatment of symptomatic or large asymptomatic sequestrations is surgical resection. While segmental resection will be sufficient in some patients with the intralobar type, lobectomy will be necessary in the majority. Extralobar sequestrations with their separate pleural investments can usually be removed sparing normal lung tissue. In all resections, care should be taken to identify and control all anomalous blood vessels, thereby preventing potentially fatal hemorrhage.
generic tadalafil 20mg
Pulmonary sequestrations are congenital anomalies that can present life-threatening and respiratory distress in a newborn. The clinician must be aware of this condition and its therapy.