Ultrasound images of fetal chest

 Fluid collection in fetal pleural cavity

This early third trimester pregnancy underwent routine sonography. Ultrasound images reveal large, bilateral pleural effusion in the fetus. Both the fetal lungs are virtually floating in the pleural fluid. There is also evidence of mild ascites and scalp edema in the fetus . Polyhydramnios is also present. These ultrasound findings suggest bilateral fetal pleural effusion with hydrops fetalis. Images courtesy of Dr. Prem Chand, Pakistan. These images were taken with a Toshiba Just Vision 200 ultrasound machine.

This is yet another example of Fetal hydrothorax, which is the term used for pleural effusion in the fetus. In this case there is a large pleural effusion or hydrothorax affecting the right lung. Unilateral hydrothorax usually involves the right side. This second trimester fetus shows the pleural effusion or hydrothorax completely encircling the fetal right lung. in this case the large right hydrothorax appears to have caused a complete collapse of the right lung. Such a large hydrothorax if present at birth can be life-threatening. The fluid usually contains chyle.

This ultrasound image is courtesy of Dr Durr-e-Sabih, FRCP.

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  Fetal aortic arch                                      Fetal ductal arch (left) and aortic arch (right)

These ultrasound and color Doppler images show a sagittal section of the fetal thorax with the aortic arch and the descending thoracic aorta seen emerging from the LVOT (left ventricular outflow tract).       

 

The ultrasound image on right shows the sagittal section of the fetal ductal arch. The characteristic appearance of the fetal ductal arch is described as hockey stick whilst the aortic arch is compared to a candy stick or umbrella.

Ultrasound images taken by Joe Antony, MD, using a Toshiba Nemio-XG system.

This sagittal section image  shows the fetal aortic arch. Note the typical shape of the ascending aorta and arch forming the candy stick shape as it descends downwards

 There is a clear hockey stick appearance to the fetal ductal arch as it has a shallow curve from the RVOT (right ventricular outflow tract) and descending downwards as the thoracic aorta. (see the red arrow). Images taken using a Philips HD 15 ultrasound system.

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These ultrasound and Color Doppler images show the normal fetal IVC (Inferior Vena Cava) in sagittal section, entering the fetal right atrium after passing upward through the posterior aspect of the liver. One of the hepatic veins is also seen as it enters the IVC.

 Transverse section fetal chest

This was a 34 week old fetus with a remarkable congenital anomaly seen in the fetal chest. Transverse section ultrasound and color Doppler images show fetal stomach, left lobe of liver and fetal bowel in the left hemithorax. There is also evidence of midline shift of the mediastinal structures including heart to the extreme right of the fetal thorax. In addition, the fetal lungs appear markedly hypoplastic. (ST= stomach ; HRT= heart). The fetal left hemi- diaphragm is not visualized in these ultrasound images. These images are diagnostic of fetal CDH or left sided congenital diaphragmatic hernia. Left diaphagmatic hernia is far more common than hernia on right side. Early ultrasound imaging (2nd trimester) may fail to detect this fetal anomaly if the CDH is small or intermittent. This means that the herniated bowel and stomach may get replaced into their normal position at certain times and again enter the fetal chest at other times. This is a potentially lethal anomaly and may be associated with other fetal anomalies, the most common ones being cardiac defects. One of the diagnostic features of sonography of left CDH is the presence of stomach of the fetus in a transverse section of the fetal chest in the same view as a 4 chamber view of the heart. 

References: http://www.fetalsono.com/teachfiles/CDH.lasso (free excellent article and images of CDH).

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This late second trimester fetus shows a large, well defined mass lesion occupying the left hemithorax with displacement of the heart and mediastinal shift to the right side. Such an ultrasound appearance of an echogenic mass in the region of the left lung is typical of pulmonary sequestration. The main differential diagnosis here is congenital cystic adenomatoid malformation or CCAM as this is commonly known. Pulmonary sequestration may be intralobar (75 %) or extralobar (25%). The presence of a separate pleural cover around the sequestrated lung tissue is indicative of extra lobar pulmonary sequestration. If the pulmonary mass is located within the pleural cover of the lung it is called intralobar pulmonary sequestration. It is often difficult if not impossible to distinguish if the sequestration is intralobar of extra lobar. The presence of a feeder vessel usually arising from the thoracic aorta also goes in favour of the pulmonary lesions being pulmonary sequestration.

Most of the cases of pulmonary sequestration diagnosed during the fetal stage are extra lobe in nature- meaning that this case too, is extra lobar pulmonary sequestration. Likewise, intra-lobar pulmonary sequestration is a disease of adulthood.

Medical literature currently feels that an element of cystic changes with macro cysts may also be present in pulmonary sequestration thus leading to considerable overlap of cystic adenomatoid malformation and pulmonary sequestration.

These ultrasound images of pulmonary sequestration are courtesy of     Dr Sunil Yadav, MD.

references:

1) http://www.ajronline.org/doi/full/10.2214/ajr.180.2.1800433

2)  http://emedicine.medscape.com/article/412554-overview

The normal fetal thymus is seen well in this high resolution ultrasound image of the fetal chest (courtesy of Dr. Mayank Chowdhury, MD). The fetal thymus is shown highlighted within the dotted ring in this image. The normal fetal thymus is a hypoechoic homogenous tissue/ gland occupying the anterior mediastinum and is relatively large though variable in size. It is limited anteriorly by the sternum and posteriorly by the major cardiac vessels (seen here in 3 vessel view- namely the superior vena cava,  ascending aorta and pulmonary artery). The ultrasound machine used here is the powerful Voluson E8 (GE) system.

References:

http://www.fetalultrasound.com/online/text/3-195.HTM