Lung Sequestration

Posterior part of left lung

Posterior part of left lung

The intralobar sequestration (ILS) accounts for 75 percent of all sequestrations.

Usually presents in adolescence or adulthood as recurrent pneumonias.

The lung tissue lies within the same visceral pleura as the lobe in which it occurs.

Males and females are equally affected.

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.

Two thirds of the time, the sequestration is located in the paravertebral gutter in the posterior segment of the left lower lobe.

• Pulmonary sequestration is nonfunctional pulmonary tissue that does not communicate with the tracheobronchial tree and receives its blood supply from one or more anomalous systemic arteries. This abnormality originates during the embryonic period of lung development. It is classified as either extralobar or intralobar.

• Extralobar sequestration is a mass of pulmonary parenchyma anatomically separate from the normal lung, with a distinct pleural investment. Its blood supply is derived from the systemic circulation. The left side is involved in more than 90% of cases.

• Intralobar sequestration is an isolated segment of lung within the normal pleural investment that often receives blood from one or more arteries arising from the aorta or its branches. Intralobar sequestration is usually found within the lower lobes (98%), two-thirds are found on the left side.

• The diagnosis of intralobar sequestration may be established after repeated infections manifested by cough, fever, and consolidation in the posterior basal segment of the left lower lobe.

Ans. is ‘a’ i.e., Left lower lobe

o Bronchogenic sequestration refers to the presence of a discrete mass of lung tissue without any normal connection to the airway system.

o Intralobar sequestrations are found most frequently in the posterior basal segment of the left lower lobe.

o Blood supply to the sequestered area arises not from the pulmonary arteries but from the aorta or its branches.

o Extralobar sequestrations are external to the lung. Found most commonly in infants as abnormal mass lesions, they

may be associated with other congenital anomalies.

o Intralobar sequestrations are found within the lung substance and are usually associated with recurrent localized infection or bronchiectasis.

Ans. is ‘b’ i.e., Pulmonary sequestration

• Sequestrated lung has no connection to airway, so this part does not fill on bronchography.

Pulmonary sequestration

o In this congenital anomaly, there is a discrete mass of lung tissue without any normal connection to the airway system.

o It may be

i)           Intrapulmonary (intralobar) More common

ii)          Extrapulmonary (extralobar)

o Sequestrated tissue receives its arterial supply from the systemic arteries (most commonly aorta).

o It returns blood to the right side of heart through IVC (extrapulmonary sequestration) or pulmonary veins (intrapulmonary sequestration).

o The sequestration functions as a space-occupying lesion within chest, it does not function in gas exchange, and does not contribute to a left to right shunt or dead space.

o Gastric or pancreatic tissue may also be found in sequestrated segment.

o Associated anomalies —> cystic adenomatoid malformation, congenital diaphragmatic hernia, esophageal cysts.

Ans. is ‘b’ i.e., Descending abdominal aorta

Ans. is ‘b’ i.e., Left posterior basal 

Ans. is ‘d’ i.e., Posterior basal segment of lower lobe

Ans. is ‘b’ i.e., Descending aorta

Ans. is ‘a’ i.e., CT

Ans. C: Angiography

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 blood supply and does not communicate with the other lung tissue.

Often it gets its blood supply from the thoracic aorta.

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.

Symptoms can vary greatly, but they include a persistent dry cough.

Sequestrations can be identified in-utero via an abnormal artery on ultrasound.

The gold standard for diagnosis is pulmonary angiography, but it being a very invasive procedure is getting replaced by CT Scan with a contrasting fluid, as the investigation of choice.