# Diaphragm Surgery: Eventration, Paralysis, and Herniation

## Introduction

The diaphragm is the primary muscle of respiration, responsible for approximately 70-80% of tidal volume generation. Disorders of the diaphragm -- including eventration, paralysis, and herniation -- can cause significant respiratory compromise, particularly when bilateral or when occurring in patients with limited pulmonary reserve. The cardiothoracic surgeon must be adept at diagnosing these conditions and performing diaphragmatic plication, repair, and reconstruction.

## Anatomy and Physiology

The diaphragm is a musculotendinous dome separating the thoracic and abdominal cavities. Motor innervation comes from the phrenic nerves, derived from cervical nerve roots C3, C4, and C5 ("C3, 4, 5 keeps the diaphragm alive"). Blood supply is provided by the phrenic arteries from the aorta, the musculophrenic and pericardiophrenic arteries from the internal mammary artery, and the intercostal arteries. Three major hiatal openings traverse the diaphragm: the aortic hiatus at T12, the esophageal hiatus at T10, and the caval hiatus at T8. During inspiration, diaphragmatic contraction increases thoracic volume and decreases intrapleural pressure, generating negative-pressure ventilation.

## Diaphragmatic Eventration

### Definition and Pathophysiology

Eventration is an abnormal elevation of the diaphragm due to congenital absence or atrophy of diaphragmatic muscle, replaced by a thin membranous sheet. It is distinguished from paralysis in that eventration involves a structural abnormality of the diaphragmatic muscle itself, while paralysis involves phrenic nerve dysfunction with intact muscle. Congenital eventration is more common on the left, and acquired eventration may follow phrenic nerve injury. The condition results in paradoxical upward motion during inspiration, impairing ventilation.

### Clinical Presentation

Eventration is often asymptomatic and discovered incidentally on chest radiograph. Symptomatic patients present with dyspnea on exertion, orthopnea, and exercise intolerance. Recurrent lower lobe atelectasis and pneumonia may develop. Gastrointestinal symptoms such as early satiety and, rarely, gastric volvulus can occur with left-sided eventration. Symptoms are more pronounced in bilateral involvement or in obese patients.

## Diaphragmatic Paralysis

### Etiology

Phrenic nerve injury is the most common cause, with cardiac surgery being the most frequent iatrogenic etiology, occurring in 2-5% of cardiac operations. Other causes include thoracic surgery and birth trauma. Neurological disorders such as cervical spine injury, multiple sclerosis, amyotrophic lateral sclerosis, and Guillain-Barre syndrome can produce paralysis. Malignant invasion from lung cancer or mediastinal tumors may compress or invade the phrenic nerve. Idiopathic cases with no identifiable cause account for up to 20%, possibly related to viral neuritis. Cold injury from topical ice slush used for myocardial protection during cardiac surgery is another recognized mechanism.

### Diagnosis

Chest radiograph reveals an elevated hemidiaphragm, best seen on upright PA film. The fluoroscopic sniff test demonstrates paradoxical upward motion of the affected hemidiaphragm during a forceful sniff maneuver, with greater than 2 cm of excursion considered positive. Ultrasound provides dynamic assessment of diaphragmatic motion and thickness, with the advantages of portability and no radiation exposure. Pulmonary function tests show a restrictive pattern, and an FVC drop exceeding 20% from upright to supine position is highly suggestive of bilateral paralysis. Phrenic nerve conduction studies and EMG differentiate neuropraxia from axonotmesis and guide prognosis for recovery.

![Fluoroscopic sniff test demonstrating paradoxical upward motion of the paralyzed right hemidiaphragm during inspiration](/images/sniff-test-diaphragm.png)

## Diaphragmatic Plication

### Indications

Plication is indicated for symptomatic unilateral diaphragmatic paralysis or eventration causing dyspnea, orthopnea, or recurrent infections. An FVC decline exceeding 20% from upright to supine supports the indication. Conservative management with observation for 6-12 months is recommended first to allow potential phrenic nerve recovery after injury, and surgery is pursued when this fails. Bilateral paralysis may be addressed with staged bilateral plication in selected patients.

### Surgical Technique

VATS plication is the preferred approach, using a three-port technique with a continuous running suture to plicate the redundant diaphragm into a taut, flat surface. Open thoracotomy is reserved for complex cases or when VATS access is limited. Robotic-assisted plication is increasingly utilized and offers excellent visualization and suturing capability. The diaphragm is folded upon itself and sutured with non-absorbable pledgeted sutures using U-stitches or a running mattress pattern to flatten and tighten the dome. The goal is to reduce the diaphragmatic dome by 3-5 cm, restoring its functional position.

### Outcomes

Successful plication yields improvement in FVC of 15-25%. More than 85% of patients report symptomatic improvement in dyspnea, and the results are durable with low recurrence rates. Surgical mortality is low, less than 1% when performed in experienced centers.

## Diaphragmatic Herniation

### Congenital Diaphragmatic Hernia (CDH)

| Type | Location | Proportion of CDH | Typical Side | Presentation | Management |
|------|----------|------------------|-------------|-------------|-----------|
| Bochdalek | Posterolateral | ~85% | Left (80%) | Neonatal respiratory distress | Stabilization → ECMO if needed → delayed repair |
| Morgagni | Anterior/retrosternal | ~5% | Right | Adults: incidental or GI symptoms | Laparoscopic or open repair |
| Traumatic | Variable (blunt/penetrating) | N/A | Left (3:1 ratio) | Acute distress or chronic (delayed) | Acute: laparotomy; chronic: thoracotomy/VATS |

Bochdalek hernia is a posterolateral defect accounting for approximately 85% of congenital diaphragmatic hernias, typically left-sided, and presents in neonates with respiratory distress. Morgagni hernia is an anterior or retrosternal defect comprising about 5% of CDH, more common on the right, and often presents in adults as an incidental finding or with vague gastrointestinal symptoms. CDH in neonates is associated with pulmonary hypoplasia and pulmonary hypertension, with mortality depending on the degree of lung development. Neonatal management involves stabilization, ECMO if severe pulmonary hypertension is present, followed by delayed surgical repair.

### Traumatic Diaphragmatic Hernia

Traumatic diaphragmatic hernia occurs in 1-7% of major blunt thoracoabdominal trauma and up to 15% of penetrating left thoracoabdominal injuries. Left-sided injury is more common by a 3:1 ratio due to the protective effect of the liver on the right. Presentation may be acute with respiratory distress and herniated abdominal viscera, or it may be occult, diagnosed months to years later as a chronic diaphragmatic hernia. Strangulation of herniated bowel is the most feared delayed complication. Diagnosis relies on chest radiograph showing an elevated hemidiaphragm with bowel in the thorax, CT scan as the most sensitive modality, and contrast study for confirmation.

### Surgical Repair of Diaphragmatic Hernia

Acute traumatic hernias are repaired via laparotomy to assess for associated abdominal injuries, or via thoracotomy or VATS. Chronic traumatic hernias are best approached through thoracotomy or VATS, as adhesions between herniated organs and pleura are better managed from the chest. Primary repair uses direct suture closure with non-absorbable mattress sutures for small defects. Prosthetic patch repair with PTFE or biological mesh is used for large defects where primary closure would create excessive tension. Morgagni hernia repair is performed laparoscopically or open, with reduction of contents and patch or primary closure of the defect.

![CT scan of the chest and abdomen showing a left traumatic diaphragmatic hernia with stomach and colon herniated into the thoracic cavity](/images/traumatic-diaphragmatic-hernia-ct.png)

## Phrenic Nerve Reconstruction

Phrenic nerve reconstruction is an emerging technique for diaphragmatic paralysis from phrenic nerve injury. When the injury site is identified, phrenic nerve repair or grafting can be performed through direct neurorrhaphy or interposition nerve grafting. Nerve transfer, specifically intercostal nerve to phrenic nerve transfer, can restore diaphragmatic function in select patients. Results are best when the procedure is performed within 12-18 months of injury, before irreversible muscle atrophy occurs. This approach requires specialized centers with microsurgical expertise.

![Intraoperative photograph of thoracoscopic diaphragmatic plication using running non-absorbable suture technique](/images/diaphragm-plication-vats.png)

## Key Clinical Pearls

A drop in FVC exceeding 20% from upright to supine is a sensitive indicator of significant diaphragmatic dysfunction and helps identify patients who will benefit from plication. After phrenic nerve injury during cardiac surgery, observation for 6-12 months is recommended before plication, as neuropraxia may recover spontaneously. Left-sided traumatic diaphragmatic hernias can present years after injury with bowel strangulation, and this diagnosis should always be considered in a patient with left thoracic pathology and a remote history of trauma. VATS plication has become the standard approach, offering equivalent outcomes to open thoracotomy with less morbidity. Phrenic nerve reconstruction is an exciting emerging option that should be considered early for young patients with documented phrenic nerve injury.

## References

1. Groth SS, Andrade RS. Diaphragmatic eventration. *Thoracic Surgery Clinics*. 2009;19(4):511-519.
2. Freeman RK, Wozniak TC, Fitzgerald EB. Functional and physiologic results of video-assisted thoracoscopic diaphragm plication in adult patients with unilateral diaphragm paralysis. *Annals of Thoracic Surgery*. 2006;81(5):1853-1857.
3. Kaufman MR, Elkwood AI, Rose MI, et al. Surgical treatment of permanent diaphragm paralysis after interposition nerve grafting. *Annals of Thoracic Surgery*. 2015;99(5):1484-1490.
4. Soper NJ, Teitelbaum EN. Laparoscopic repair of Morgagni hernia. *Surgical Laparoscopy, Endoscopy and Percutaneous Techniques*. 2013;23(3):221-225.