Chest Ultrasound (US)

Ultrasound of the pediatric chest

Cross-sectional imaging modalities like MRI and CT provide images of the chest which are easily understood by clinicians. However, these modalities may not always be available and are expensive. Lung ultrasonography (US) has therefore become an important tool in the hands of clinicians as an extension of the clinical exam, which has been underutilized by the radiologists. Reinforcement of the ALARA principle along with the dictum of "Image gently" have resulted in increased use of modalities which do not require radiation. Hence, ultrasound, which was earlier being used mainly to confirm the presence of pleural effusion as well as evaluate it and differentiate solid from cystic masses, is now being used to evaluate the lung as well. This review highlights the utility of ultrasound of the paediatric chest. It also describes the normal and abnormal appearances of the paediatric lung on ultrasound as well as the advantages and limitations of this modality.

Acute Chest Diseases: Infection and Trauma

Acute chest diseases include clinical situations with infectious and traumatic etiology. Pulmonary infection is the most common indication for performing chest radiography. Radiological imaging often confirms the diagnosis and allows the evaluation of the location and extent of infection. Chest radiography is the primary imaging procedure and the starting point for the evaluation of all children with acute chest disease. Accurate interpretation of pediatric chest films also requires a basic understanding of the physiologic and anatomic differences among adults, neonates, and infants and their most important differences will be referred. Characterization of pulmonary infiltrates is important, because patterns of abnormality suggest specific organisms and aetiologies. Although providing evidence suggestive of the causative agent, the chest radiograph cannot confirm viral infection, confirm or exclude bacterial etiology. In fact, in infancy, pneumonia usually produces a combination of alterations of the airspace and interstitium. However, some aspects may be useful in distinguishing between viral and bacterial pneumonia. Close attention to CT technique is crucial for imaging evaluation of pneumonia in pediatric patients, namely those with persistent symptoms and/or progressive symptoms despite medical or surgical therapy, or in immunocompromised patients. CT with low radiation dose technique should be carefully performed in these cases. CT examination with IV contrast is very useful for the evaluation of complications of chest infection. Thoracic trauma in children is rare, only 4–6 % of children are hospitalized following severe trauma. Only a small number of children with trauma have thoracic injury (14 %), but the injuries tend to be of serious nature. About 25–50 % of thoracic trauma cases occur in combination with other trauma locations. Pulmonary contusion and lacerations, tracheobronchial injuries, pneumothorax, and esophageal rupture are referred as the main consequences of trauma. The decision for the appropriate use of imaging techniques must consider the specific case under review. Chest radiography should be the initial screening method. The decision to use CT is determined by the nature of the trauma, the clinical circumstances, and the prediction of future revaluation, always taking into account the radiation dose applied to the child.

Correlation between US and MRI for prenatal lung volumetry in diaphragmatic hernia, and use of Doppler to identify the ipsilateral lung cap

BACKGROUND

Pulmonary hypoplasia is a common cause of neonatal death.

OBJECTIVE

To describe the correlation between relative fetal lung volume (RFLV) and lung-to-head ratio (LHR) in fetuses with unilateral diaphragmatic hernia. Additionally, to describe identification of the ipsilateral lung cap by power Doppler.

MATERIALS AND METHODS

Single-institution study of consecutive fetuses with diaphragmatic hernia. LHR (by US) and RFLV (by MRI) were correlated in fetuses with and without an ipsilateral lung cap seen at MRI. In four, color/power Doppler was used to follow the pulmonary artery of the ipsilateral lung to identify the compressed cap.

RESULTS

The study included 48 fetuses of 20-38 weeks' gestational age (mean, 26 weeks). Mean LHR was 1.52 (range, 0.6-3) in fetuses with a lung cap and 1.15 (range, 0.6-2.58) in fetuses without (P = 0.043). Mean RFLV was 47.4% (range, 18-80%) in fetuses with and 32.9% (range, 14-57%) in fetuses without a lung cap (P = 0.005). RFLV and LHR correlated (r = 0.41, P = 0.01 in those with a cap; r = 0.50, P = 0.05 in those without). Power Doppler identified the ipsilateral lung cap and pulsed Doppler confirmed pulmonary vascularization in four of four fetuses.

CONCLUSION

LHR underestimates lung volume in fetuses with an ipsilateral lung cap. Power Doppler may be useful for identifying the cap.