Eventration of the right hemidiaphragm is an uncommon anatomical abnormality affecting the primary breathing muscle and the chest cavity. This condition involves a weakness or thinning of the right side of the diaphragm, causing it to ride abnormally high into the chest. The elevated diaphragm reduces the space available for the right lung and impacts respiratory function.
Understanding the Diaphragm and Eventration
The diaphragm is a large, dome-shaped sheet of muscle situated at the base of the chest cavity, separating the chest from the abdomen. It functions as the body’s main muscle for breathing, contracting downward during inhalation to create a vacuum that draws air into the lungs. The diaphragm is divided into two halves, or hemidiaphragms, with the right hemidiaphragm sitting slightly higher than the left due to the presence of the liver beneath it.
Eventration describes a condition where one hemidiaphragm is permanently elevated into the chest cavity. This occurs because the muscle tissue is thin, weak, or replaced by non-muscular, fibrous tissue, preventing effective contraction. Unlike a diaphragmatic hernia, eventration maintains the continuity of the diaphragm’s tissue and its attachments to the rib cage.
The muscle weakness results in a resting position much higher than normal, which is exacerbated during inhalation. Instead of contracting downward, the weakened section is often pulled upward by the negative pressure from the functional side, known as paradoxical motion. This upward movement compresses the underlying lung tissue, reducing the amount of air the lung can hold.
Etiology and Risk Factors
The underlying causes of diaphragmatic eventration are categorized into two main groups: congenital (present from birth) and acquired (developing later in life). Congenital eventration arises from a developmental issue during gestation where muscle-forming cells fail to properly migrate into the diaphragm. This results in the muscular portion being partially or fully replaced by a thin, non-functional fibrous membrane.
Acquired eventration, occurring at any age, typically results from damage to the phrenic nerve, which supplies motor function to the diaphragm. This nerve damage (phrenic nerve palsy) causes the muscle to become paralyzed and atrophic, leading to thinning and elevation. Injury can result from physical trauma, infectious diseases, or iatrogenic injury during surgical procedures.
In many adult cases, the cause of the eventration remains unknown, leading to a diagnosis of idiopathic eventration. The right hemidiaphragm is less frequently affected by complete eventration than the left, though partial eventration often occurs on the right side.
Recognizing Symptoms and Diagnostic Methods
Symptoms of right hemidiaphragm eventration vary significantly, from being entirely asymptomatic to having severe respiratory difficulty. Many adults are unaware of the condition, as the elevated diaphragm is often an incidental finding on a chest X-ray. When symptoms manifest, they usually relate to the compression of the right lung or impaired breathing mechanics.
Common symptoms include shortness of breath (dyspnea), which is often worsened by physical exertion or when lying flat. Infants and young children, whose chest walls are more flexible, may experience more pronounced respiratory distress, recurrent respiratory infections, or poor weight gain due to the impact on lung function. A characteristic finding in symptomatic patients is paradoxical breathing, where the affected side of the diaphragm moves up during inhalation instead of down.
The diagnostic process begins with a simple chest X-ray, which readily shows the abnormally high elevation of the right hemidiaphragm dome. To confirm the diagnosis and distinguish it from other conditions, dynamic imaging studies are necessary. Fluoroscopy, often referred to as a “sniff test,” is a specialized X-ray technique used to visualize the diaphragm’s movement in real-time.
During a sniff test, the patient is asked to sniff sharply, causing the healthy hemidiaphragm to contract downward normally. In eventration, the weakened right hemidiaphragm will either fail to move or move paradoxically upward. Cross-sectional imaging, such as a Computed Tomography (CT) scan, is often used to get a detailed view of the chest and abdomen. The CT scan helps confirm the thin nature of the diaphragm tissue and excludes other potential causes of elevation, such as a tumor or abscess.
Treatment Approaches and Long-Term Outlook
The management of right hemidiaphragm eventration depends on the severity of the patient’s symptoms and the degree of respiratory compromise. For individuals who are asymptomatic or have very mild symptoms, the recommended approach is conservative management, involving observation with periodic clinical follow-ups. This approach assumes the condition will not worsen and will not significantly impact the patient’s quality of life.
Surgical intervention is reserved for patients who experience persistent and significant symptoms, such as debilitating shortness of breath, recurrent pneumonias, or mechanical ventilation dependence. The standard surgical procedure is known as diaphragmatic plication, which involves folding and suturing the weakened, elevated portion of the diaphragm. The goal of plication is to flatten the diaphragm and secure it in a lower, more anatomical position.
This tightening procedure eliminates the paradoxical motion and prevents the diaphragm from compressing the lung, increasing the volume of the chest cavity and improving lung function. Plication is often performed using minimally invasive techniques, such as video-assisted thoracoscopic surgery (VATS), which leads to reduced pain and a quicker recovery time. The long-term prognosis following successful plication is positive, with most patients reporting durable improvement in their breathing and exercise tolerance.