Pulmonary sequestration
Encyclopedia
A pulmonary sequestration, also known as a bronchopulmonary sequestration or a cystic lung lesion, is a medical condition where a piece of tissue that develops into lung
tissue is not attached to the pulmonary arterial blood supply (intrapulmonary sequestration drains via pulmonary veins, extra pulmonary sequestration drains to the IVC) and does not communicate with the other lung tissue. Often it gets its blood supply from the thoracic aorta
. Communication is a medical phrase indicating that it is not connected to the standard bronchial airways and that it performs no function in respiration
.
This condition is normally detected in children and is generally held to be congenital in nature. The treatment for this is a segmentectomy via a thoracotomy
. More and more, these lesions are diagnosed by prenatal ultrasound
.
Bronchopulmonary sequestration (BPS) is a rare congenital malformation of the lower respiratory tract.
It consists of a nonfunctioning mass of normal lung tissue that lacks normal communication with the tracheobronchial tree
, and that receives its arterial blood
supply from the systemic circulation.
BPS is estimated to comprise 0.15 to 6.4 percent of all congenital pulmonary malformations, making it an extremely rare disorder.
Sequestration
s are classified anatomically.
Intralobar sequestration (ILS) in which the lesion is located within a normal lobe
and lacks its own visceral pleura.
Extralobar sequestration (ELS) in which the mass is located outside the normal lung and has its own visceral pleura
The blood supply of 75% of pulmonary sequestrations is derived from the thoracic or abdominal aorta
.
The remaining 25% of sequestrations receive their blood flow from the subclavian
, intercostal
, pulmonary, pericardiophrenic, innominate
, internal mammary, celiac
, splenic, or renal arteries.
·Usually presents in adolescence or adulthood as recurrent pneumonia
s.
·Lies within the same visceral pleura as the lobe in which it occurs.
·Males and females are equally affected with ILS.
·In ILS, the arterial supply usually is derived from the lower thoracic or upper abdominal aorta.
·Venous drainage is usually to the left atrium
via pulmonary veins establishing a left to right shunt
.
oAbnormal connections to the vena cava, azygous vein, or right atrium
may occur.
·Two thirds of the time, the sequestration
is located in the paravertebral gutter in the posterior segment of the left lower lobe.
·Unlike extralobar sequestration, it is rarely associated with other developmental abnormalities.
·Patients present with signs and symptoms of pulmonary infection
of a lower lobe mass.
oIt is believed that sequestrations become infected when bacteria
migrate through the pores of Kohn
or if the sequestration is incomplete.
Extralobar sequestration=
·The extralobar variety accounts for 25 percent of all sequestrations.
·ELS usually presents in infancy with respiratory compromise.
· Develops as an accessory lung contained within its own pleura.
·ELS has a male predominance (80%).
·Related to the left hemidiaphragm in 90% of cases.
oELS may present as a subdiaphragmatic or retroperitoneal mass.
·In general, the arterial supply of ELS comes from an aberrant vessel arising from the thoracic aorta.
·It usually drains via the systemic venous system to the right atrium, vena cava, or azygous systems.
·Congenital anomalies occur more frequently in patients with ELS than ILS.
oAssociated anomalies include Congenital cystic adenomatoid malformation (CCAM), congenital diaphragmatic hernia, vertebral anomalies, congenital heart disease, pulmonary hypoplasia, and colonic duplication
·Since it is enveloped in its own pleural sac, it rarely gets infected so almost always presents as a homogeneous soft tissue mass.
·The mass may be closely associated with the esophagus, and fistulae may develop.
Imaging=
.An arteriogram has been considered vital in documenting the systemic blood supply, allowing definitive diagnosis as well as preoperative planning.
·The advent of new noninvasive imaging techniques has changed this thinking.
Chest radiograph=
·Sequestrations typically appear as a uniformly dense mass within the thoracic cavity or pulmonary parenchyma.
·Recurrent infection can lead to the development of cystic areas within the mass.
·Air-fluid levels due to bronchial communication can be seen.
Ultrasound=
·The typical sonographic appearance of BPS is an echogenic homogeneous mass that may be well defined or irregular.
·Some lesions have a cystic or more complex appearance.
·Doppler studies are helpful to identify the characteristic aberrant systemic artery that arises from the aorta and to delineate venous drainage.
CT=
·CT scans have 90% accuracy in the diagnosis of pulmonary sequestration.
·The most common appearance is a solid mass that may be homogeneous or heterogeneous, sometimes with cystic changes.
·Less frequent findings include a large cavitary lesion with an air-fluid level, a collection of many small cystic lesions containing air or fluid, or a well-defined cystic mass.
·Emphysematous changes at the margin of the lesion are characteristic and may not be visible on the chest radiograph.
·CT technique for optimal depiction of lesions by using state-of-the-art volumetric scanning requires a fast intravenous (IV) contrast injection rate and appropriate volume and delay based upon size.
·Multiplanar and 3D reconstructions are helpful.
MRI=
·Contrast-enhanced MRA or even conventional T1-weighted spin-echo (SE) images may help in the diagnosis of pulmonary sequestration by demonstrating a systemic blood supply, particularly from the aorta, to a basal lung mass.
·In addition, MRA may demonstrate venous drainage of the mass and may obviate more invasive investigations.
However, CT allows sharper delineation of thin-walled cysts and emphysematous changes than MRI.
In a few instances, fetuses with sequestrations develop problematic fluid collections in the chest cavity. In these situations a Harrison catheter shunt can be used to drain the chest fluid into the amniotic fluid.
In rare instances where the fetus has a very large lesion, resuscitation after delivery can be dangerous. In these situations a specialized delivery for management of the airway compression can be planned called the EXIT procedure
.
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
tissue is not attached to the pulmonary arterial blood supply (intrapulmonary sequestration drains via pulmonary veins, extra pulmonary sequestration drains to the IVC) and does not communicate with the other lung tissue. Often it gets its blood supply from the thoracic aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
. Communication is a medical phrase indicating that it is not connected to the standard bronchial airways and that it performs no function in respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
.
This condition is normally detected in children and is generally held to be congenital in nature. The treatment for this is a segmentectomy via a thoracotomy
Thoracotomy
Thoracotomy is an incision into the pleural space of the chest. It is performed by a surgeon, and, rarely, by emergency physicians, to gain access to the thoracic organs, most commonly the heart, the lungs, the esophagus or thoracic aorta, or for access to the anterior spine such as is necessary...
. More and more, these lesions are diagnosed by prenatal ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
.
Diagnosis
Bronchopulmonary sequestrationBronchopulmonary sequestration (BPS) is a rare congenital malformation of the lower respiratory tract.
It consists of a nonfunctioning mass of normal lung tissue that lacks normal communication with the tracheobronchial tree
Tracheobronchial tree
The tracheobronchial tree is the structure from the trachea, bronchi, and bronchioles that forms the airways that supply air to the lungs. It is within the neck and the chest. The structure looks like a tree because the trachea splits into the right and left mainstem bronchi, which "branch" into...
, and that receives its arterial blood
Arterial blood
Arterial blood is the oxygenated blood in the circulatory system found in the lungs, the left chambers of the heart, and in the arteries. It is bright red in color, while venous blood is dark red in color...
supply from the systemic circulation.
BPS is estimated to comprise 0.15 to 6.4 percent of all congenital pulmonary malformations, making it an extremely rare disorder.
Sequestration
Sequestration
In law, sequestration may refer to:* Sequestration , the seizure of property* the isolation of a jury in order to ensure they are not prejudiced by external contact* In Scottish law, the term for bankruptcy* In U.S...
s are classified anatomically.
Intralobar sequestration (ILS) in which the lesion is located within a normal lobe
Lobe
Lobe may refer to:* Lobe * Lobation, a characteristic of the nucleus of certain biological cells* Glacial lobe, a lobe-shaped glacier* Sidelobe, an identifiable segment of an antenna radiation pattern...
and lacks its own visceral pleura.
Extralobar sequestration (ELS) in which the mass is located outside the normal lung and has its own visceral pleura
The blood supply of 75% of pulmonary sequestrations is derived from the thoracic or abdominal aorta
Abdominal aorta
The abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta .-Path:...
.
The remaining 25% of sequestrations receive their blood flow from the subclavian
Subclavian
In general, Subclavian means beneath the clavicle, and it can refer to:* Subclavian vein* Subclavian artery* Subclavian nerve...
, intercostal
Intercostal
Intercostal means "between the ribs". It can refer to:* Intercostal muscle* Highest intercostal vein* Intercostal arteries* Intercostal space...
, pulmonary, pericardiophrenic, innominate
Innominate
Innominate can refer to:*The brachiocephalic artery*The brachiocephalic veins*The three large bones which form the hip bone*An innominate contract, a contract not of a type regulated by law...
, internal mammary, celiac
Celiac
Celiac may refer to:* Coeliac disease* Celiac artery* Celiac lymph nodes* Celiac plexus...
, splenic, or renal arteries.
Intralobar sequestration
·The intralobar variety accounts for 75 percent of all sequestrations.·Usually presents in adolescence or adulthood as recurrent pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
s.
·Lies within the same visceral pleura as the lobe in which it occurs.
·Males and females are equally affected with ILS.
·In ILS, the arterial supply usually is derived from the lower thoracic or upper abdominal aorta.
·Venous drainage is usually to the left atrium
Atrium
Atrium may refer to:*Atrium , a large open space within a building usually with a glass roof*Atrium , microscopic air sacs in lungs*Atrium , an anatomical structure of the heart* Atrium of the ventricular system of the brain...
via pulmonary veins establishing a left to right shunt
Shunt
Shunt may refer to:* Shunt - a hole or passage allowing fluid to move from one part of the body to another* Shunt - a device allowing electrical current to pass around a point in a circuit...
.
oAbnormal connections to the vena cava, azygous vein, or right atrium
Atrium
Atrium may refer to:*Atrium , a large open space within a building usually with a glass roof*Atrium , microscopic air sacs in lungs*Atrium , an anatomical structure of the heart* Atrium of the ventricular system of the brain...
may occur.
·Two thirds of the time, the sequestration
Sequestration
In law, sequestration may refer to:* Sequestration , the seizure of property* the isolation of a jury in order to ensure they are not prejudiced by external contact* In Scottish law, the term for bankruptcy* In U.S...
is located in the paravertebral gutter in the posterior segment of the left lower lobe.
·Unlike extralobar sequestration, it is rarely associated with other developmental abnormalities.
·Patients present with signs and symptoms of pulmonary infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
of a lower lobe mass.
oIt is believed that sequestrations become infected when bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
migrate through the pores of Kohn
Kohn
- People :* Alfie Kohn, American lecturer and author* Dan Kohn-Sherbock, Jewish theologian* David Kohn, Russian archaeologist* Donald Kohn, economist* Eugene Kohn, rabbi* Fritz Nathan Kohn, later Kortner, Austrian-born stage and film actor....
or if the sequestration is incomplete.
Extralobar sequestration=
·The extralobar variety accounts for 25 percent of all sequestrations.
·ELS usually presents in infancy with respiratory compromise.
· Develops as an accessory lung contained within its own pleura.
·ELS has a male predominance (80%).
·Related to the left hemidiaphragm in 90% of cases.
oELS may present as a subdiaphragmatic or retroperitoneal mass.
·In general, the arterial supply of ELS comes from an aberrant vessel arising from the thoracic aorta.
·It usually drains via the systemic venous system to the right atrium, vena cava, or azygous systems.
·Congenital anomalies occur more frequently in patients with ELS than ILS.
oAssociated anomalies include Congenital cystic adenomatoid malformation (CCAM), congenital diaphragmatic hernia, vertebral anomalies, congenital heart disease, pulmonary hypoplasia, and colonic duplication
·Since it is enveloped in its own pleural sac, it rarely gets infected so almost always presents as a homogeneous soft tissue mass.
·The mass may be closely associated with the esophagus, and fistulae may develop.
Imaging=
.An arteriogram has been considered vital in documenting the systemic blood supply, allowing definitive diagnosis as well as preoperative planning.
·The advent of new noninvasive imaging techniques has changed this thinking.
Chest radiograph=
·Sequestrations typically appear as a uniformly dense mass within the thoracic cavity or pulmonary parenchyma.
·Recurrent infection can lead to the development of cystic areas within the mass.
·Air-fluid levels due to bronchial communication can be seen.
Ultrasound=
·The typical sonographic appearance of BPS is an echogenic homogeneous mass that may be well defined or irregular.
·Some lesions have a cystic or more complex appearance.
·Doppler studies are helpful to identify the characteristic aberrant systemic artery that arises from the aorta and to delineate venous drainage.
CT=
·CT scans have 90% accuracy in the diagnosis of pulmonary sequestration.
·The most common appearance is a solid mass that may be homogeneous or heterogeneous, sometimes with cystic changes.
·Less frequent findings include a large cavitary lesion with an air-fluid level, a collection of many small cystic lesions containing air or fluid, or a well-defined cystic mass.
·Emphysematous changes at the margin of the lesion are characteristic and may not be visible on the chest radiograph.
·CT technique for optimal depiction of lesions by using state-of-the-art volumetric scanning requires a fast intravenous (IV) contrast injection rate and appropriate volume and delay based upon size.
·Multiplanar and 3D reconstructions are helpful.
MRI=
·Contrast-enhanced MRA or even conventional T1-weighted spin-echo (SE) images may help in the diagnosis of pulmonary sequestration by demonstrating a systemic blood supply, particularly from the aorta, to a basal lung mass.
·In addition, MRA may demonstrate venous drainage of the mass and may obviate more invasive investigations.
However, CT allows sharper delineation of thin-walled cysts and emphysematous changes than MRI.
Complications
Failure to have a pulmonary sequestration removed can leads to a number of complications. These include:- Hemorrhage that can be fatal
- The creation of a left-right shuntShunt (medical)In medicine, a shunt is a hole or a small passage which moves, or allows movement of fluid from one part of the body to another. The term may describe either congenital or acquired shunts; and acquired shunts may be either biological or mechanical.* Cardiac shunts may be described as...
, where blood flows in a shortcut through the feed off the aorta. - Chronic infection. Diseases such as bronchiectasisBronchiectasisBronchiectasis is a disease state defined by localized, irreversible dilation of part of the bronchial tree caused by destruction of the muscle and elastic tissue. It is classified as an obstructive lung disease, along with emphysema, bronchitis, asthma, and cystic fibrosis...
, tuberculosisTuberculosisTuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
, aspergillosisAspergillosisAspergillosis is the name given to a wide variety of diseases caused by fungi of the genus Aspergillus. The most common forms are allergic bronchopulmonary aspergillosis, pulmonary aspergilloma and invasive aspergillosis. Most humans inhale Aspergillus spores every day...
, bronchial carcinoid and bronchogenic squamous cell carcinoma.
Treatments
Usually the sequestration is removed after birth via surgery. In most cases this surgery is safe and effective; the child will grow up to have normal lung function.In a few instances, fetuses with sequestrations develop problematic fluid collections in the chest cavity. In these situations a Harrison catheter shunt can be used to drain the chest fluid into the amniotic fluid.
In rare instances where the fetus has a very large lesion, resuscitation after delivery can be dangerous. In these situations a specialized delivery for management of the airway compression can be planned called the EXIT procedure
EXIT procedure
The EXIT procedure, or ex utero intrapartum treatment procedure, is a specialized surgical delivery procedure used to deliver babies who have airway compression...
.