Diaphragmatic eventration refers to an abnormal contour of the diaphragmatic dome with no disruption to the diaphragmatic continuity. It typically affects only a segment of the hemidiaphragm, compared to paralysis/weakness where the entire hemidiaphragm is typically affected.
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Epidemiology
Associations
Unilateral eventration 5
trisomy 13, 14, 15 or 18
Bilateral eventration 5
cytomegalovirus (CMV)
Clinical presentation
In newborns, eventration of the diaphragm is a recognized cause of respiratory distress. However in adults, it is often asymptomatic 6.
Pathology
Diaphragmatic eventration is thought to be congenital in origin. It occurs due to incomplete muscularisation of the diaphragm with a thin membranous sheet replacing normal diaphragmatic muscle. Over time this region stretches and on inspiration does not contract normally.
Etiology
Congenital
phrenic nerve agenesis
failure of myotomes to migrate to a localized area in the diaphragm leading to abnormal muscularisation
This should be differentiated from trauma/surgery/birth trauma leading to phrenic nerve paralysis
Location
Congenital eventration is frequently seen in the anteromedial portion of the right hemidiaphragm, while acquired eventration is frequently seen in the left hemidiaphragm. Total eventration is most commonly seen in the left hemidiaphragm 6.
Radiographic features
Plain radiograph
Elevation of the affected portion of the diaphragm is usually seen as a smooth hump, while the remainder of the hemidiaphragm contour is normal. The frontal x-ray may show a 'double' diaphragmatic contour, which is easily confirmed on the lateral projection.
CT
There is typically a constricting ridge of muscle at the boundary of the normal portion of the diaphragm with the mushroom-shaped eventration. The posterior diaphragm and costophrenic recess are normal in position and width and this helps to differentiate eventration from phrenic nerve palsy 4.
Differential diagnosis
Possible considerations on plain film include:
-
lung
-
pleura
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subdiaphragmatic region
liver/stomach mass
hemiplegia
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