Pulmonary sequestration is a rare condition involving a portion of lung tissue that develops separately from the rest of the lung. This tissue is non-functional, meaning it does not participate in breathing. It is often discovered unexpectedly during routine prenatal ultrasound appointments. This finding can be concerning for expectant parents, but it is a well-understood condition with established methods for monitoring and treatment.
Understanding Pulmonary Sequestration
Pulmonary sequestration is defined by a mass of lung tissue that lacks a normal connection to the airway system. A key feature of this tissue is its unique blood supply. Instead of receiving blood from the pulmonary arteries, which serve the healthy lungs, the sequestration is fed by a systemic artery, typically branching directly from the aorta. This abnormal circulatory connection is a defining characteristic used in its diagnosis.
There are two distinct types of pulmonary sequestration. Intralobar sequestration (ILS) is found within the lining, or pleura, of a normal lung lobe. This form accounts for around 75% of cases and is often identified later in childhood.
The second type is extralobar sequestration (ELS), where the abnormal tissue is completely separate from the lung and enclosed in its own pleural sac. ELS is the form more commonly diagnosed before birth. It frequently appears in the chest cavity, typically between the lower left lobe of the lung and the diaphragm.
The Role of Prenatal Ultrasound in Detection
The discovery of pulmonary sequestration often occurs during a routine mid-pregnancy anatomy scan, usually performed between 18 and 22 weeks of gestation. During this detailed examination, a sonographer assesses fetal growth and anatomy and might notice an unexpected feature in the fetal chest. A bright, dense-looking area can indicate the presence of a mass.
This initial observation does not confirm a diagnosis but prompts a more focused evaluation of the chest area to understand the nature of the finding. This detailed follow-up examination is what leads to the potential identification of a pulmonary sequestration, where doctors look more closely at the mass and its relationship to surrounding structures.
Key Ultrasound and Doppler Findings
When a potential pulmonary sequestration is examined, it appears on the ultrasound as a solid and bright, or echogenic, mass. It is most often triangular in shape and located in the lower portion of the fetal chest. The mass can vary in size and may sometimes displace the fetal heart from its normal position or push down on the diaphragm.
A definitive diagnosis relies heavily on the use of Color Doppler ultrasound. This specialized imaging technique allows clinicians to visualize blood flow within the fetus, mapping the direction and speed of blood in different vessels. This tool is used to identify the specific blood supply to the mass.
The hallmark finding that distinguishes pulmonary sequestration is the identification of a systemic feeding artery. Using Color Doppler, the sonographer can trace a blood vessel that originates from the fetal aorta and leads directly to the echogenic mass. Visualizing this aberrant artery confirms the diagnosis.
Management During Pregnancy
Once a pulmonary sequestration is diagnosed, the focus of care shifts to monitoring the pregnancy closely with a series of follow-up ultrasounds, often every four weeks. These appointments track the size of the mass and its effect on the fetus.
A primary concern is the potential development of hydrops fetalis, a serious condition characterized by abnormal fluid accumulation in the fetal body. This can occur if a very large sequestration demands a high volume of blood flow, putting strain on the fetal heart, though it develops in a minority of cases.
Fortunately, many sequestrations decrease in size during the third trimester, sometimes shrinking significantly or resolving before birth. This spontaneous regression is thought to be related to changes in blood flow or thrombosis of the feeding artery.
Postnatal Evaluation and Treatment
After the baby is born, the medical team will perform further imaging to confirm the prenatal diagnosis and assess the sequestration in greater detail. A postnatal evaluation is standard procedure, even if the mass appeared to shrink on prenatal ultrasounds. This typically involves a CT scan with contrast or an MRI, which provide a highly detailed view of the mass and its blood supply.
The standard treatment for pulmonary sequestration is surgical removal of the non-functional tissue. This is recommended to prevent future complications, such as recurrent respiratory infections or breathing difficulties. The surgery is performed within the first year of life and removes the abnormal mass while preserving all healthy, functional lung.
Following the procedure, the prognosis for children is positive. The removal of the sequestration is curative, and since the tissue was non-functional, its removal does not impact respiratory capacity. Children go on to live healthy, active lives with normal lung function.