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.
Unilateral eventration 5
Bilateral eventration 5
In newborns, eventration of the diaphragm is a recognized cause of respiratory distress. However in adults, it is often asymptomatic 6.
Diaphragmatic eventration may be congenital or acquired in nature. 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.
phrenic nerve agenesis
- failure of myotomes to migrate to a localized area in the diaphragm leading to abnormal muscularisation
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.
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.
There may be a sharp border between the eventrated portion and the remainder of the hemidiaphragm 4.
Possible considerations on plain film include:
- 1. Verhey PT, Gosselin MV, Primack SL et-al. Differentiating diaphragmatic paralysis and eventration. Acad Radiol. 2007;14 (4): 420-5. doi:10.1016/j.acra.2007.01.027 - Pubmed citation
- 2. Oh A, Gulati G, Sherman ML et-al. Bilateral eventration of the diaphragm with perforated gastric volvulus in an adolescent. J. Pediatr. Surg. 2000;35 (12): 1824-6. doi:10.1053/jpsu.2000.19271 - Pubmed citation
- 3. Mantoo SK, Mak K. Congenital diaphragmatic eventration in an adult: a diagnostic dilemma. Singapore Med J. 2007;48 (5): e136-7. Singapore Med J (link) - Pubmed citation
- 4. Nason LK, Walker CM, McNeeley MF et-al. Imaging of the diaphragm: anatomy and function. Radiographics. 2012;32 (2): E51-70. doi:10.1148/rg.322115127 - Pubmed citation
- 5. Comstock CH. The antenatal diagnosis of diaphragmatic anomalies. (1986) Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 5 (7): 391-6. doi:10.7863/jum.1918.104.22.1681 - Pubmed
- 6. Andy Adam, Adrian K. Dixon, Cornelia Schaefer-Prokop, Jonathan H. Gillard. Grainger & Allison's Diagnostic Radiology, 2 Volume Set. (2020) ISBN: 9780702075247