What is Eventration of the Right Hemidiaphragm?
Eventration of the right hemidiaphragm is an abnormal permanent elevation of the right diaphragmatic leaf caused by incomplete muscular development (congenital) or muscle weakness/paralysis (acquired), where the diaphragm remains intact but is abnormally thin and elevated. 1, 2
Definition and Pathophysiology
Eventration represents a structural abnormality where the diaphragm is abnormally elevated but remains anatomically continuous without any defect or rupture, distinguishing it from diaphragmatic hernias where there is an actual hole in the diaphragm 2, 3. The condition results from:
- Congenital causes: Incomplete mesenchymal development during the eighth week of gestation in the posterolateral diaphragmatic region, representing a failure of normal muscle fiber formation 1
- Acquired causes: Paralysis or aplasia of muscular fibers leading to weakness and subsequent elevation 3
Epidemiology of Right-Sided Eventration
Right hemidiaphragm eventration is the minority presentation, occurring in only 15-19% of all diaphragmatic eventration cases, while left-sided involvement predominates in 81.5-85% of patients 1. In pediatric series, right-sided eventration represented 22 of 33 cases (67%), though this may reflect referral bias 2.
Clinical Presentation
The abnormally elevated right hemidiaphragm causes compression of the ipsilateral lung and mediastinal shift, leading to:
- Respiratory symptoms (present in all symptomatic cases): tachypnea, dyspnea, cough, respiratory distress, and recurrent pneumonia 2, 3
- Failure to thrive in children due to increased work of breathing 2, 4
- Severe respiratory distress in neonates, particularly after difficult breech delivery or forceps extraction 5
- Asymptomatic presentation is possible, with incidental diagnosis on chest imaging 4
Important caveat: Adult presentation of congenital eventration occurs at a mean age of 40-44 years, meaning this is not exclusively a pediatric condition 1.
Diagnostic Approach
The diagnosis is established through imaging studies:
- Chest radiography shows abnormal elevation of the right hemidiaphragm 2, 4
- Fluoroscopy demonstrates paradoxical or absent diaphragmatic motion during respiration 2, 3
- Ultrasound is particularly useful for confirming the diagnosis and assessing diaphragmatic thickness and motion 4
- CT scan may be needed to differentiate from other pathology 2
Critical pitfall: Diaphragmatic eventration can be easily missed in acute settings due to its rarity and nonspecific radiographic findings 1.
Clinical Significance and Complications
While eventration involves an intact diaphragm, it can cause significant morbidity:
- Pulmonary function decreases by 25-50% due to lung compression 6
- Mortality risk exists, particularly in neonates with severe respiratory distress, with reported mortality of 2 of 33 patients (6%) in one pediatric series 2
- Diaphragm rupture can occur as a complication of the weakened, thinned diaphragmatic tissue 7
Management Principles
Symptomatic eventration requires surgical correction via diaphragmatic plication, while asymptomatic cases can be observed 2, 3, 4. The surgical approach involves:
- Plication technique that replaces the diaphragm in its normal anatomical position, restoring pulmonary parenchymal volume 3
- Thoracotomy or laparotomy as traditional approaches, with modern thoracoscopic/laparoscopic options available 2, 7
- Timing: If neonates cannot be weaned from mechanical ventilation after 7-10 days of respiratory support, surgical correction should be performed 5
Post-plication outcomes: The operated hemidiaphragm typically becomes immobile without paradoxical motion, with immediate symptom remission in most patients and no relapse during follow-up 3.