Diaphragmatic eventration (DE) is the abnormal elevation of a portion or entire hemidiaphragm due to a lack of muscle or nerve function while maintaining its anatomical attachments. The abnormality can be congenital or acquired, thus presenting in both the pediatric and adult populations. The diaphragm is a dome-shaped muscle that plays a strong role in the inspiratory phase of respiration and acts as a barrier between the thoracic and abdominal cavities. The diaphragm is innervated by the phrenic nerve, which originates from the C3, C4, and C5 spinal nerve roots.
The left and right phrenic nerves provide the motor function to each hemidiaphragm, respectively, and impaired development or injury to this nerve can lead to diaphragmatic paralysis and diminished lung expansion. In both congenital and acquired eventration, a portion of the diaphragm is weakened and thin causing reduced function. Depending on the severity, patients may be asymptomatic or present with respiratory symptoms. Diagnosis is confirmed by radiographic imaging, and treatment usually consists of supportive care and, in some cases, surgical plication.
Congenital causes are due to abnormal diaphragm muscle development. There is a defect in the migration of myoblasts to the septum transversum causing partial or total replacement of the diaphragm muscle with fibroelastic tissue. This creates a thin and weakened hemidiaphragm resulting in a cephalic displacement of the affected side. Eventration can also occur in association with other congenital disorders and infections. These disorders include spondylocostal dysostosis, Kabuki syndrome, Beckwith-Wiedemann syndrome, Poland syndrome, chromosomal defects, pulmonary hypoplasia, spinal muscular atrophy, malrotation, and congenital heart disease. Mitochondrial respiratory chain disorder has been linked to diaphragmatic dysfunction in the neonatal period. Infectious associations include fetal rubella and cytomegalovirus infections.
Acquired cases are more common and are due to etiologies that result in phrenic nerve injury and muscle atrophy. Injury may be due to blunt or penetrating trauma, birth trauma, or thoracic surgery. Phrenic nerve dysfunction or damage may also occur as a complication of other illnesses, including multiple sclerosis, Guillain-Barre syndrome, nerve compression, radiation therapy, and connective tissue diseases. Paralysis or phrenic nerve damage can then lead to muscle atrophy and thinning of the diaphragm with cephalic displacement.
Eventrations of the diaphragm are further divided on an anatomical basis as complete, partial, or bilateral. On embryological bases, congenital eventration could be anterior, posterolateral, and medial.
Due to the rarity of diaphragmatic eventration, there is limited data on the incidence and prevalence of this condition. A limited number of case reports have suggested the incidence is as low as less than 0.05% with male predominance and more commonly affecting the left hemidiaphragm. Others have suggested the incidence to be 1 in 10,000 live births. The incidence is likely higher than reported as most patients are asymptomatic, and many remain undiagnosed.
Neurogenic muscular aplasia of the diaphragm is the term used to describe a stretched-out and aponeurotic scattered muscle fibers in a congenital eventration of the diaphragm. Whereas these changes are lacking in acquired form.
Patients with eventration of the diaphragm have variable presentations. Most patients are asymptomatic and discovered incidentally on chest X-ray; however, some may present with significant respiratory distress or gastrointestinal symptoms. Bilateral congenital diaphragmatic eventration in the neonate may present with acute respiratory failure and cyanosis. Respiratory symptoms in adult and pediatric cases may include dyspnea on exertion, orthopnea, tachypnea, and shallow breathing. In Adults, recurrent respiratory infections or lung atelectasis or chronic productive cough may initial presentation. Adults may also complain of chest pain which may be caused by arrhythmias or palpitations. Gastrointestinal symptoms in the adult population may worsen with increased intraabdominal pressure (e.g., exercise, pregnancy, ascites, infection, fluid sequestration) and present with dyspepsia, dysphagia, gastroesophageal reflux, and/or epigastric pain.
In infants, respiratory symptoms are largely attributed to the shifting of the mediastinal structures to the contralateral side. Gastrointestinal involvement is common and may manifest as vomiting, bloating, constipation, poor weight gain, and poor oral intake. In severe cases, gastric volvulus may be present. All patients should be assessed for a history of trauma and other causes of respiratory distress.
The physical examination findings are variable and often non-specific. Below is a list of physical findings that may be found in adult and pediatric cases (or shared).
Shared findings (Adults and Infants)
Most patients with diaphragmatic eventration are asymptomatic. These patients are often unaware of their condition, and the diagnosis is typically an incidental finding on chest imaging. After a thorough history and physical examination, symptomatic patients should undergo chest imaging. Radiographic findings on chest x-rays confirm the diagnosis of diaphragmatic eventration.
Chest x-ray imaging should include both posterior-anterior (PA) and lateral (LAT) views. X-ray images will show an elevation of the affected portion of the hemidiaphragm and normal cardiomediastinal contours. Computed tomography (CT) chest may be done if the diagnosis is unclear or if the intrathoracic or intraabdominal abnormalities are suspected. CT of the chest will show elevation of the affected portion of the hemidiaphragm as well as a sharp edge of the eventration. Diaphragmatic eventration can be differentiated from hernia due to the normal attachment sites of the diaphragm.
Further evaluation is often reserved for assessing lung volumes and diaphragm function. These tests include pulmonary function testing along with maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), fluoroscopic sniff testing, and ultrasonography. Laboratory testing may be necessary if there is suspicion for associated congenital diseases or infectious etiologies.
Pulmonary function testing shows a restrictive pattern with a reduction in forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). This restrictive pattern is more commonly seen when eventration is bilateral. This has shown to improve with diaphragm plication, which is further discussed in the next section.
The MIP and MEP are a measure of the pressure generated during maximal inspiratory or expiratory effort and are indicative of the strength of the respiratory muscles involved. As the diaphragm plays a role in the inspiratory phase, the MIP is reduced in patients with diaphragm eventration. The MEP is generally normal.
Fluoroscopic sniff testing is used to examine diaphragm function and is done under continuous fluoroscopy. The patient is asked to take hard and fast inspirations (sniffs) and assess the direction and motion of each hemidiaphragm. In diaphragm eventration, only a portion of the hemidiaphragm may show abnormal movement. Sniff testing may aid in distinguishing diaphragm paralysis from eventration as paralysis may have paradoxical motion during sniffing. This is of limited value as diaphragm eventration and paralysis are both treated with plication when conservative measures fail. In infants, the sniff test may be difficult to obtain. Ultrasonography of the diaphragm is often used in place of fluoroscopy to evaluate diaphragm function due to its lack of exposing radiation to patients.
Diagnosis can be made prenatally with a high-resolution fetal ultrasound, CT, or magnetic resonance imaging (MRI). Prenatally, diaphragm eventration is difficult to differentiate from congenital diaphragmatic hernia (CDH) as the lung appears hypoplastic and the fetal stomach or liver is visualized in the same transverse plane as the heart. Postnatally, eventration is suspected when there is an elevation of a portion of the diaphragm on chest radiography when evaluating for respiratory distress. Confirmatory testing for DE includes fluoroscopy, dynamic MRI, or ultrasound to evaluate diaphragm function. Further evaluation should be tailored to the patient's clinical history and physical findings to determine the underlying etiology (e.g., infections, malignancy, developmental and degenerative diseases).
The management of diaphragm eventration mostly dependent on the etiology and severity of the disease. In asymptomatic or mild cases, supportive care is recommended. In cases of hypoxemia, oxygen supplementation should be provided to maintain appropriate oxygen saturation. When supplemental oxygen via nasal cannula is inadequate, patients may require nasal continuous positive airway pressure (nasal CPAP). As infants commonly present with gastrointestinal symptoms and failure to thrive, nutritional support should be optimized. Infants in significant respiratory distress may require gavage feeding or parenteral nutrition to maximize calorie intake, fluid intake, and electrolyte replenishment to meet metabolic demands. Conservative management may also include physical therapy and pulmonary rehabilitation.
In severe cases requiring mechanical ventilation or when patients fail to respond to medical management, surgical plication may be indicated. Diaphragmatic plication is a known surgical treatment for eventration. The procedure involves creating pleats with U-stitches in the weakened hemidiaphragm and then anchored down. This results in a flattened and lowered hemidiaphragm allowing for increased intrathoracic volume and lung expansion. Diaphragm plication can be done via open thoracotomy, video-assisted thoracoscopic surgery (VATS), laparoscopic, or robotic-assisted surgery. After the surgery, a thoracostomy tube is placed for 24 to 48 hours for pleural drainage until the output is less than 200 mL/day. It should be noted that surgical plication does not improve the function of the hemidiaphragm.
The indications for surgical plication are outlined below:
Patients should be monitored postoperatively, and the frequency of follow-up is variable depending on symptoms or complications. Follow-up tests may include PA/LAT chest X-rays and pulmonary function testing. A patient’s quality of life, activity level, and the psycho-social impact can be monitored using the St. George’s Respiratory Questionnaire.
Prognosis is generally good and may be dependent on the severity and etiology of eventration. Most patients are asymptomatic and may not need any intervention. Those with extensive eventration may develop severe respiratory distress requiring mechanical ventilation. Diaphragm plication has shown to significantly improve symptoms and quality of life in patients with extensive eventration. The procedure has also shown to improve the FEV1 and FVC by up to 25% and 30% respectively on follow-up pulmonary function tests.
Eventration of the diaphragm is often an incidental finding and most patients are asymptomatic without a need for extensive management. Patients and parents of children with confirmed eventration of the diaphragm should be educated on recognizing symptoms and when to seek medical treatment. Pulmonary rehabilitation may also be beneficial in teaching patients about diaphragm eventration as well as breathing exercises.
Interprofessional collaboration between primary care physicians and other healthcare professionals is necessary for the diagnosis and management of diaphragmatic eventration. Healthcare professionals that may be involved are neonatologists, primary care physicians, pulmonologists, intensivists, thoracic surgeons, respiratory therapists, nursing staff, physical therapists, and pulmonary rehabilitation specialists. Each of these professionals brings a set of skills and with collaboration can strategically improve healthcare outcomes for patients. A radiologist is necessary for providing details of radiographic findings for diagnosis and follow-up. Patients should be followed by an adult or pediatric pulmonologist for both inpatient and outpatient management.
Thoracic surgeons are involved with individuals who need surgical plication and chest tube management. For those who are on ventilator support require management by an intensivist and a respiratory therapist. Pulmonary rehabilitation specialists and physical therapists also play a strong role in improving outcomes for patients through education and exercises. Nursing care is vital and often seen in the inpatient setting. Prompt and detailed communication between these professionals is vital in promoting positive outcomes and improving safety for patients. Interprofessional collaboration has shown to improve healthcare outcomes and reduce medical errors. [Level 3]
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