Diaphragmatic Eventration

Diaphragmatic eventration is abnormal elevation of part or all of a hemidiaphragm because of thinning and weakness of the muscle, while the diaphragm remains continuous and attached normally to the chest wall. It is congenital (failure of muscle development) or acquired (muscle atrophy from phrenic nerve injury or disease).

Congenital eventration is found in about 1 in 1,400 to 1 in 10,000 births, usually on the left side in total eventration, and the right in partial (anteromedial) eventration, with associated anomalies (lung hypoplasia, congenital heart disease, chromosomal abnormalities, Beckwith-Wiedemann syndrome). Acquired disease follows phrenic nerve injury, and occurs in adults, more often on the left.

Pathophysiology. A thin fibroelastic membrane with sparse or no muscle fibres replaces the muscle and rises into the chest, compresses the lung, shifts the mediastinum, and moves paradoxically on inspiration, reducing ventilation and causing atelectasis. In infants, the compliant chest and weak accessory muscles lead to respiratory failure.

Infants: tachypnoea, respiratory distress, feeding difficulty, recurrent pneumonia, and failure to thrive, or detection on antenatal ultrasound or chest radiograph. Adults: most have no symptoms, found on chest radiograph as raised hemidiaphragm. Others have exertional dyspnoea, orthopnoea, cough, recurrent chest infection, gastrointestinal symptoms (early satiety, postprandial fullness, reflux, nausea from gastric volvulus) and chest or epigastric pain.

Severe dyspnoea, respiratory failure, or acute gastric volvulus (pain, vomiting, inability to pass a tube) needs urgent assessment.

• Chest radiograph: smooth elevation of the hemidiaphragm (above the 4th to 5th anterior rib level in adults), with preserved outline, atelectasis and mediastinal shift.
• Ultrasound with real time assessment: reduced or paradoxical movement and thinning of the muscle (under 2 mm), confirming that the diaphragm is intact.
• CT or MRI (coronal views): a thin, intact, elevated diaphragm with no herniated viscera through a defect, and identification of the underlying cause (phrenic nerve compression, mass). It separates from a hernia where there is a defect.
• Spirometry: restriction with FVC reduced by 20 to 30% (greater supine), and ventilation perfusion scan for lung function.
• Barium study when gastric volvulus or herniation is suspected.
• Antenatal ultrasound and echocardiography to screen for associated anomalies.

Differential diagnosis.

• Diaphragmatic hernia (congenital or traumatic)
• Phrenic nerve palsy and paralysis
• Subpulmonic effusion or lobar collapse
• Subphrenic abscess or tumour
• Hepatomegaly or splenomegaly

• Asymptomatic: observation with no intervention, as most are benign. Avoid tight clothing and large meals if gastric symptoms exist. Treat reflux with a proton pump inhibitor (omeprazole 20 mg daily).
• Infants with respiratory distress: respiratory support (oxygen, continuous positive airway pressure, ventilation) and early plication of the diaphragm if ventilation is needed beyond a few weeks, or failure to wean, recurrent infection or feeding problems.
• Adults with symptoms (dyspnoea, reduced exercise capacity, recurrent infection, gastrointestinal symptoms) and impaired lung function: plication by thoracoscopic, robotic, laparoscopic or open approach, with non-absorbable sutures (2-0) placed in several rows to flatten and tension the diaphragm, with or without mesh. It improves FVC and FEV1 by about 15 to 25% and dyspnoea in most, with a more modest benefit in obese patients.
• Treat the cause of acquired eventration (phrenic nerve disease, tumour, infection).
• Perioperative care: lung protective ventilation, regional analgesia (epidural or paravertebral), and early mobilisation.
• Respiratory physiotherapy, vaccination against influenza, pneumococcus and COVID-19, and weight loss in obesity.

Complications and prognosis. Recurrent pneumonia, atelectasis, respiratory failure (especially in infants), gastric volvulus and, after plication, recurrence (under 5%) or diaphragmatic hernia. The surgical outcome is good, with low mortality.

Monitoring. Chest radiograph and spirometry at 3 and 6 months after plication, then yearly, with ultrasound of diaphragm movement for follow up in conservative cases.

Referral and escalation. Refer to a paediatric or thoracic surgeon for symptomatic disease and to neonatal services for infants in distress.