What are the differential diagnoses, diagnostic work‑up, and management options for a patient presenting with dyspnea and an elevated hemidiaphragm on imaging?

Elevated Hemidiaphragm with Dyspnea: Diagnostic and Management Approach

Begin with chest radiography (PA and lateral views) to assess diaphragm position and shape, followed by fluoroscopy or ultrasound to confirm paralysis versus eventration, then proceed to diaphragmatic plication for all symptomatic patients regardless of etiology. 1, 2, 3

Differential Diagnosis

The key distinction is between diaphragmatic paralysis (neuromuscular dysfunction with paradoxical motion) and eventration (congenital or acquired thinning without paradoxical motion). 2, 4, 3

Primary Causes to Consider:

• Phrenic nerve injury from trauma, cardiac surgery, or idiopathic causes (most common in adults) 5, 6
• Neuromuscular disorders affecting diaphragm innervation or contractile function 4, 6
• Congenital eventration (thinned diaphragm without paralysis) 2, 3
• Underlying lung disease that may worsen symptoms (COPD, interstitial lung disease) 1, 4

Diagnostic Workup Algorithm

Step 1: Initial Imaging

Obtain PA and lateral chest radiographs first (not AP portable films, which are lower quality). 1, 2 The lateral view is particularly important because the radius of curvature on lateral radiograph is the most important factor for detecting paralysis—a flattened or inverted contour suggests paralysis, while a smooth dome suggests eventration. 7

Critical measurement: If the hemidiaphragm height-to-anteroposterior diameter ratio (HH/APD) is >0.28 on lateral radiograph, this argues against paralysis. 7

Important caveat: Normal chest radiographs occur in 11-62% of diaphragmatic abnormalities, so maintain clinical suspicion if symptoms persist. 2

Step 2: Functional Assessment

Fluoroscopy with sniff test is the traditional gold standard for differentiating paralysis (paradoxical upward motion during inspiration) from eventration (normal downward motion or no motion). 1, 3

Alternatively, ultrasound is equally effective and has concordant findings with fluoroscopy for assessing diaphragm motion, excursion amplitude, thickness, and contraction, with high sensitivity and specificity for neuromuscular disorders. 1 Ultrasound can identify paradoxical movement during respiration that confirms paralysis. 1

Step 3: Confirmatory Imaging

CT chest without IV contrast serves as the gold standard for confirming diaphragmatic pathology (sensitivity 14-82%, specificity 87%) and can accurately determine the presence, location, and size of defects. 2 CT is particularly useful for identifying complications such as lower lobe atelectasis or recurrent infection. 5

Step 4: Pulmonary Function Testing

Expect a restrictive pattern with reduced FVC and FEV1. 4, 5 A key diagnostic feature is that symptoms, oxygenation, and vital capacity worsen in the supine position—this postural worsening is highly suggestive of diaphragmatic dysfunction. 4

Step 5: Additional Testing if Diagnosis Unclear

• Phrenic nerve stimulation or diaphragm electromyography can confirm the diagnosis when imaging is equivocal 4, 6
• MRI with cine dynamic sequences allows direct visualization of diaphragm motion and comprehensive analysis of chest wall muscle movement, though not widely practiced 1

Management Strategy

For Symptomatic Patients (Unilateral or Bilateral):

Diaphragmatic plication is indicated for ALL symptomatic patients with an elevated diaphragm, regardless of whether the etiology is paralysis or eventration. 3, 6 The goal is to improve lung volumes, decrease paradoxical elevation, and relieve dyspnea. 3, 5

Surgical approach: Most thoracic surgeons perform minimally invasive thoracoscopic plication, which can be approached from either thoracic or abdominal routes. 3

Expected outcomes: Plication is safe with excellent long-term results. 3, 5 In one study with 5.4-year follow-up:

• FVC improved by 43.6% (p<0.001) 5
• FEV1 improved by 27.3% (p<0.001) 5
• Dyspnea scores improved by 3 points in 92% of patients (p<0.0001) 5
• Atelectasis completely resolved in 100% of affected patients 5
• 67% returned to work within 3 months 5

For Asymptomatic Patients (Unilateral Only):

Observation is appropriate for asymptomatic unilateral diaphragm paralysis, especially in the absence of underlying lung disease. 4, 6 Prognosis is good in these cases. 4

For Bilateral Paralysis with Ventilatory Failure:

More aggressive intervention is required: 4, 6

• Continuous positive airway pressure (CPAP) or non-invasive ventilation 4, 6
• Mechanical ventilation with tracheostomy in severe cases 4
• Diaphragmatic pacing in select patients 4, 6
• Prognosis is generally poor, especially with advanced lung disease or chronic demyelinating conditions 4

Critical Pitfalls to Avoid

Do not assume eventration is benign—both eventration and paralysis cause identical symptoms and both require plication if symptomatic. 3

Do not rely solely on chest radiography—up to 62% of diaphragmatic abnormalities may have normal initial radiographs, so proceed to fluoroscopy or ultrasound if clinical suspicion remains high. 2

Do not delay surgical referral in symptomatic patients—plication provides dramatic symptom relief and functional improvement that persists long-term. 3, 5

Recognize that bilateral paralysis is a medical emergency—these patients may develop ventilatory failure and cor pulmonale and should be managed in experienced centers. 4, 6