E4984. Epidemiology of Eventration
  1. Sadie Walter; Pacific Northwest University of Health Sciences
  2. Elena LeCompte; Pacific Northwest University of Health Sciences
  3. Jocelyn Larsen; Pacific Northwest University of Health Sciences
  4. Ron Walser; Pacific Northwest University of Health Sciences
  5. Wade Justice; Pacific Northwest University of Health Sciences
Diaphragmatic eventration (DE) is broadly defined as an abnormally elevated diaphragmatic contour with preserved continuity that may be attributed to an array of congenital or acquired causes. Most cases of DE, especially in adults, are asymptomatic and diagnosed via incidental radiological findings. Because of this, DE often remains undetected throughout an individual’s lifespan and is therefore typically described as rare. The elusive nature of DE greatly limits accurate reporting of its occurrence, with stated prevalence ranging from about 0.1–0.7% and little reliable published epidemiological data to substantiate these values. Thus, the true prevalence of DE is likely significantly higher than reported. Diaphragmatic asymmetry can be an important chest x-ray (CXR) finding and may be associated with a plethora of differential diagnoses, from benign to life-threatening conditions. Thus, defining the true epidemiology of DE is crucial in mitigating potential diagnostic dilemmas during radiological interpretation. We sought to investigate the commonly encountered DE variant, which is unilateral and partial, affecting the front half of the right diaphragm. This variant, which can lead to further radiologic and/or clinical work-up to exclude subpulmonic fluid, subdiaphragmatic masses, phrenic nerve paralysis, and numerous causes of right pulmonary atelectasis, is often underreported and not recognized as a normal variant. Our clinical experience was suggestive of this type of DE being much more common than 1%. We hypothesize that the prevalence of DE is underreported, owing to the lack of existing reliable literature exploring the true epidemiology of DE.

Materials and Methods:
We surveyed the MIMIC CXR databases of images from hundreds of thousands of adult patients. We chose to review CXRs that were requested as a preoperative evaluation for nonthoracic conditions and were able to assess hundreds of patients. We measured the heights of each diaphragm on the frontal and lateral images to evaluate for DE prevalence, particularly looking for partial elevations of right hemidiaphragms. We identified patients with possible DE if there was a > 2-cm difference between the height of the diaphragms on the frontal projection. This was confirmed or refuted by the appearance of the diaphragms on the lateral projection. As we had four investigators, we used statistical analysis to confirm our measurements were significantly in agreement with each other.

We detected a prevalence of DE of 29%.

The true prevalence of DE is unknown. Many authors have estimated it to be rare; many have stated its prevalence less than 1%. We have shown that the likely prevalence of congenital DE is common and may approach 1/3 of all adult patients. This condition is frequently observed on CXRs and should be appreciated as a normal variation.