neonatal chest radiograph in the exam setting

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The neonatal chest radiograph in the exam setting may strike fear into the heart of many radiology registrars, but it need not!

There are only a limited number of diagnoses that will be presented on such films and they are often highlighted by the history.

Gestation

First of all, have a look to see if the neonate is premature or not - signs of prematurity being reduction in subcutaneous fat and the lack of humeral head ossification (the latter occurs around term).

When the chest radiograph also includes the abdomen, look out for the umbilical clip. These are plastic clips used to clamp the umbilicus before it is cut at birth. The umbilical stump remains in situ for approximately 1-2 weeks and its presence helps to age the baby.

Lines and tubes

In the unwell neonate, it is likely that they will have lines and tubes - its usually worthwhile dealing with these first:

ET tube: estimate the distance from the carina - ensure it's not down the right main bronchus
NG tube: where is the tip? It shouldn't be at or above the GEJ, but rather projected over the stomach
UAC (umbilical arterial catheter): it's the one that dips down into the pelvis and should have a tip above (T6-9) or below (L2-5) the renal arteries and unpaired aortic branches
UVC (umbilical venous catheter): it should enter at the level of the umbilicus and head north with its tip at the RA/IVC junction - not in the hepatic veins (right hand side) or portal vein (left hand side)
peripheral line (PICC): from arm, leg or scalp (!)

Many neonatal chest films have a rather enthusiastically caudal inferior border and umbilical lines can often be seen in full. For more information see the dedicated page on neonatal lines and tubes.

Diagnoses

Common things are common, and the commonest causes for respiratory distress in the immediate post-natal period can be split into causes that present in the preterm or term infant.

Preterm

respiratory distress syndrome (RDS)
- ground-glass
- low volume lungs

Term

transient tachypnea of the newborn (TTN)
- interstitial lines with possible small effusions
- pulmonary edema in the neonate
- usually associated with cesarian section delivery
meconium aspiration
- bilateral patchy airspace shadowing
- commonest cause of respiratory distress in a term/postdates neonate
- large volume lungs
- air trapping with possible pneumothorax/pneumomediastinum
- small pleural effusions

If it's not one of the big-3, then you need to look for other patterns (e.g. cystic change) or predisposing factors, e.g. ventilation.

Ventilated

Ventilation may be evident by the presence of an ET tube, but remember that CPAP can be used on the neonatal unit and be the cause of ventilated associated pathology without the presence of an ET tube.

neonatal pneumothorax
- describe the pneumothorax and explain that the apparent size of the pneumothorax under-estimates the volume of free pleural gas because the infant is supine
- look at the mediastinum and describe whether there is evidence of tension
pulmonary interstitial emphysema (PIE)
- in the ventilated patient, gas lucencies extend to the edge of the film (i.e. they cannot be bronchi)
- look for the associated pneumothorax

In both cases, say that you'll contact the team to let them know.

Cystic changes

One cause of acute breathlessness in a neonatal patient is a mass within the hemithorax causing ipsilateral pulmonary hypoplasia/atelectasis and mediastinal shift.

congenital diaphragmatic hernia (CDH)
- gas locules in the hemithorax
- indistinct hemidiaphragm
congenital pulmonary airway malformation (CPAM)
- multi-cystic mass in the hemithorax
- mass effect with contra-lateral mediastinal shift

Consolidation

Confluent areas of consolidation are not particularly common in neonates, they usually have ground-glass change or patchy opacification. While confluent consolidation is not common, it may appear in an exam film.

pulmonary sequestration
- a bit of lung that has blood supply from the aorta and whose parenchyma isn't connected to the tracheobronchial tree
- it may be consolidated and fluid-filled or undergo cystic change
- extra-lobar sequestration (the less common type) occurs in neonates
neonatal pneumonia
- standard confluent consolidation

Other pathology

If you look at the film and you can't see anything, you need to start thinking laterally. What could they show you on a neonatal film?

esophageal atresia
- distended pouch of gas in the upper mediastinum
- if the examiner is being kind, it will have an NG tube looped in it
- if there is gas in the stomach, there must be an accompanying congenital tracheo-esophageal fistula
- see esophageal atresia in the exam
fractures
- birth related injury, e.g. clavicular fracture or shoulder/humerus injury
- if the child is a little older, rib fractures in non-accidental injury