Tiruvarur Medical Centre, No 5, Javulikara street, Tiruvarur, Tamil Nadu-610001, India.

Case report

A 24-year-old woman was sent to our unit at 20 weeks of gestation (according to her last menstrual period) for a routine ultrasonographic scan. Her menstrual periods were irregular.

Our examination revealed the following findings:
- fetal biometry corresponded to 16 weeks of pregnancy;
- a wedge shaped echogenic lung mass could be seen on the left side in paravertebral plane (the mass was located basally adjacent to the diaphragm);
- arterial supply of the mass arising from the aorta and venous drainage to the pulmonary veins could be seen.

The findings were consistent with the diagnosis of intralobar pulmonary sequestration.

Images 1, 2: Transverse and longitudinal scans of the fetal chest showing hyperechoic mass located on the left postero-basal region of the lungs.

Images 3, 4, 5, and videos 1, 2, 3: Color Doppler images and videos demonstrating vascular supply of the mass from descending thoracic aorta.

Images 6, 7: Doppler scans showing arterial and venous vascular flow within the lesion.

Image 8, 9: Image 8 demonstrates vascularization of the lung sequestration by color Doppler imaging. The image 9 demonstrates 3D imaging of the lung sequestration that can be seen located paravertebrally at the base of the left lungs.

Definition

Pulmonary sequestration is an aberrant pulmonary tissue that has no normal connection with the bronchial tree or pulmonary arteries. There are two types of sequestration, intra and extralobar.

Sequestrated lung tissue receives its arterial supply from either thoracic or abdominal aorta irrespective of its type. Venous drainage is variable and dependent on the type of the sequestration:

- Intralobar sequestrations have venous drainage commonly via the pulmonary veins, but can occur through the azygous/hemi-azygous system, portal vein, right atrium or the inferior vena cava.
- Extralobar sequestrations have venous drainage most commonly through the systemic veins into the right atrium.

In intralobar sequestration ,the mass is closely connected to the adjacent normal lung and do not have a separate pleura whereas the extralobar sequestration has  its own pleura.

Sequestration preferentially involves the lower lobes. Intralobar sequestrations commonly affect the left lower lobe.

Extralobar sequestrations almost always affect the left lower lobe and  can be sub-diaphragmatic(1).

In pulmonary sequestration with no pleural effusions, expectant management is associated with survival in all cases and in about half of fetuses the lesion regresses antenatally with no need for postnatal surgery. In pulmonary sequestration with pleural effusions the condition may progress to hydrops and perinatal death.

Effective antenatal intervention of the pleural effusion is provided either by placement of thoracoamniotic shunts and consequent resolution of the effusion or by occlusion of the feeding vessel at the hilus of the tumor by ultrasound-guided laser coagulation or injection of a sclerosant agent. In the case of drainage of the effusions, postnatal surgery is usually necessary to remove the tumor, whereas in those treated by antenatal occlusion of the feeding vessel, postnatal surgery was necessary only in half of our cases because in the other half the tumor resolved antenatally. This issue merits further investigation.

Prognosis and prenatal management

In cases of sequestration  without  pleural effusion,  the lesion  may regresses antenatally  whereas  those associated with pleural effusions the condition may progress to hydrops. Prenatal management is provided either by placement of thoracoamniotic shunts or by occlusion of the feeding vessel by ultrasound-guided laser coagulation or injection of a sclerosant agent. If the mass persists postnatally, sequestrectomy is needed (2).

References

1. Lee A Grant, Nyree Griffin.Grainger & Allison's Diagnostic Radiology Essentials. Published 2013 - Chapter 1.10 - Paediatric chest –Bronchopulmonary sequestration, page 124.
2. P. Cavoretto, F. Molina, S. Poggi, M. Davenport and K. H. Nicolaides. Prenatal diagnosis and outcome of echogenic fetal lung lesions. Ultrasound Obstet Gynecol 2008; 32: 769–783 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/uog.6218