Case 38 - Variants and hernias of the diaphragm simulating injury

Summary

Imaging description

Most blunt diaphragmatic ruptures are longer than 10 cm and occur along the posterolateral aspect of the left hemidiaphragm [1]. Imaging findings of diaphragmatic rupture on chest radiography include an intrathoracic location of abdominal viscera (with or without the “collar sign”) a nasogastric tube above the left hemidiaphragm, distortion or obliteration of hemidiaphragm outline, contralateral mediastinal shift, and marked elevation of the left hemidiaphragm (> 4 cm) compared to the right [1–3]. CT findings of diaphragmatic injuries include segmental diaphragm non-visualization, intrathoracic herniation of viscera, collar sign, dependent viscera sign, and a thickened diaphragm (Figure 38.1) [3]. Although sensitive for injury, focal thickening of the diaphragm in the absence of other signs of diaphragmatic injury is not specific [4].

Diagnostic pitfalls for diaphragmatic injury include hernias (Bochdalek, Morgagni, and hiatal) and discontinuity of the diaphragm between crura and lateral arcuate ligaments [5].

Foramen of Bochdalek hernias

The foramen of Bochdalek is a 2cm opening in the posterior fetal diaphragm that normally closes by the eighth week of gestation. The left foramen closes later than the right. Hence, 85% of Bochdalek hernias occur on the left [6]. Most symptomatic Bochdalek hernias present in the neonatal period whereas asymptomatic foramina and hernias are detected incidentally later in life, during imaging for other reasons.