Pulmonary sequestration

Clinical History

An 8-month-old girl patient was referred for further imaging of an antenatally detected lung lesion. She was a twin, and on doing a 20-week antenatal US (ultrasound) scan it was confirmed that she had an echogenic left lung with cystic lesions in the left lower lobe. A CT scan of the chest showed an enhancing solid/cystic lesion in the left lower lobe.

Imaging Findings

An 8-month-old girl was referred for further imaging of an antenatally detected lung lesion. She was a twin and her 20-week antenatal US (ultrasound) scan photographs confirmed an echogenic left lung with cystic lesions in the left lower lobe. A provisional diagnosis made suggested pulmonary sequestration or congenital cystic adenomatoid malformation. No other abnormalities were detected. She was born at 33-weeks gestation in the caesarean section. Although she initially required oxygen and CPAP for respiratory distress syndrome, she recovered quickly and was discharged a week later. A CXR performed during the neonatal period was found to be normal with no suggestion of cystic lesions in the lung. The child was referred for further investigations during the neonatal period after recurrent chest infections. A CT scan of the chest showed an enhancing solid/cystic lesion in the left lower lobe supplied by an anomalous artery from the coeliac axis in keeping with a pulmonary sequestration. The barium swallow test results and her echocardiogram were also found to be normal. The pulmonary sequestration was subsequently resected.

Discussion

Pulmonary sequestration is a mass of lung tissue disconnected from the bronchial tree that receives its blood supply from the systemic circulation. They can be divided into two groups depending on their relationship to the pleura. Intralobar sequestration (ILS) is found within the visceral pleura and extralobar sequestration (ELS) outside of the visceral pleura with its own pleural coating. Arterial supply is via an anomalous systemic artery, usually off the thoracic or abdominal aorta. ILS drains via the pulmonary veins and ELS via the azygos or portal venous system. Pulmonary sequestrations are found rarly, accounting for 6% of congenital pulmonary malformations. ILS occurs more commonly than ELS does, with 75% of pulmonary sequestrations being intralobar. ILS occurs in the left lower lobe in 60% of cases, and its lesions tend to be smaller. ILS tends to be discovered incidentally or is found in older children with recurrent chest infections. ELS also commonly occurs in the left lower lobe of which 15% occur within or below the diaphragm and can be confused for neuroblastomas, teratomas, Wilms tumours and accessory spleens. ELS tends to be larger and is discovered antenatally or neonatally with respiratory distress, cyanosis and sometimes cardiac failure if there is significant shunting. ELS has a stronger association with congenital malformations (65%) than ILS. These include foregut, diaphragmatic, cardiac and skeletal abnormalities. Rarely, both types communicate with the GI tract where they are referred to as broncho-pulmonary foregut malformations. This can be demonstrated by perfofming a contrast swallow study. Antenatally diagnosed pulmonary sequestrations are usually of the ELS rather than of the ILS type. On US scans, they typically appear as an echogenic paraspinal lung lesion +/- cystic change. This can change in size and can even appear to resolve with serial antenatal scanning. Postnatally, the CXR can be normal or exhibit a soft tissue opacity in the lower lobes +/- cystic components. Doppler US examinations can often help identify the anomalous blood supply to the sequestration. Although angiography remains the gold standard for detecting the anomalous vessels, it is now rarely used. CT and MR can be used to demonstrate a homogeneous soft tissue mass often having internal cystic areas that enhance at the same time as the aorta. It can identify the anomalous arterial supply but it often does not identify the venous drainage. Classification of whether it is an ILS or an ELS is made after performing a surgery. V/Q scanning will show an area of absent perfusion and ventilation. Pulmonary sequestrations are resected because of the risks of recurrent infection, haemorrhage, pneumothorax and the small potential risk of malignant transformation. After surgery a prognosis is made based on the presence of any accompanying congenital malformation.

Differential Diagnosis List

Final Diagnosis

Pulmonary sequestration.

URL:	https://www.eurorad.org/case/3184
DOI:	10.1594/EURORAD/CASE.3184
ISSN:	1563-4086