Neonatal Diversion

The chest film is over-penetrated, as the vertebrae are clearly visible through the heart.  The heart has a somewhat ‘boot-shaped‘ appearance. Both lungs are diffusely, mildly opacified, perhaps more so at the junction of the right mid and upper zones. There is an endotracheal tube, a right-sided intercostal catheter and a nasogastric tube.

Oddly, the nasogastric tube veers to the patient’s right as it enters the abdomen — not to the left, where the stomach is usually positioned…

The reversed position of the nasogastric tube tip is consistent with situs inversus (transposition of the visceral organs such that their positions are a mirror image of normal).

A  heart with a ‘boot-shaped’ appearance is consistent with Fallot’s tetralogy, or a similar congenital heart abnormality. The boot or wooden-shoe appearance (‘coeur en sabot’) results from right ventricular hypertrophy pushing the apex of the heart upwards, and a relatively concave left upper heart border due to an underdeveloped right ventricular outflow tract and right main pulmonary artery. The heart is normally orientated (levocardia).

The tracheal bifurcation cannot be visualised, but when seen the angle of the bifurcation is a clue to the orientation of the lungs. The right lung normally has three lobes (with a horizontal fissure) to the left lung’s two, and the right main bronchus normally has a steeper origin from the tracheal bifurcation.

These findings, in the context of the limited history provided (a neonate returning from OT, intubated with an intercostal catheter), allows the Joseph Bell/ Sherlock Holmes wannabes among us to deduce that this child needed emergency surgery for congenital heart disease associated with situs inversus.

Situs inversus may be associated with dextrocardia ( the apex of the heart at birth is on the right rather than the left) or with levocardia (the apex of the heart is normally positioned, as in this case).

Situs inversus is associated with:

1. Almost any type of congenital heart disease

• most people with situs inversus totalis (reversed positioning of all visceral organs) have completely normal hearts, but congenital heart abnormalities are more common (~5-10%) than in people with situs solitus (a normally positioned heart and viscera).
• dextrocardia without associated situs inversus or levocardia in the presence of situs inversus — in other words, where the heart and the abdominal viscera are oppositely orientated — are much more likely (~95%) to coexist with congenital heart abnormalities such as:
  • single ventricle malformations
  • transposition of the great arteries
  • pulmonary stenosis
  • ASDs, VSDs, and AVSDs
  • anomalous pulmonary venous return
  • tricuspid atresia
  • pulmonary arterial hypoplasia or atresia

2. Kartagener’s syndrome (primary ciliary dyskinesia, PCD)

• Rare autosomal recessive syndrome found in about 1 in 4 cases of situs inversus. It is characterised by bronchiectasis, sinusitis, male infertility and situs inversus totalis.
• Ciliary motility determines the position of the viscera during development; laterality is randomly determined in individuals with PCD, such that 50% of affected people have situs inversus.

When situs cannot be determined (neither left nor right), the terms situs ambiguus, situs indeterminus or heterotaxy are used. Heterotaxy is associated with severe congenital heart abnormalities, vascular abnormalities (such as interruption of the inferior vena cava or duplication of the superior vena cava)  and asplenia-polysplenia syndromes (absent or multiple spleens).