What are the potential causes and diagnostic approaches for an elevated right hemidiaphragm in a patient with a history of pulmonary, cardiac, or gastrointestinal diseases?

Differential Diagnosis of Elevated Right Hemidiaphragm

An elevated right hemidiaphragm most commonly results from phrenic nerve injury, diaphragmatic paralysis/eventration, subdiaphragmatic pathology (particularly hepatobiliary disease), or cardiac causes including right ventricular enlargement from pulmonary hypertension.

Primary Diagnostic Categories

Neuromuscular Causes

• Phrenic nerve injury or paralysis is the most frequent cause of hemidiaphragmatic elevation, resulting from damage anywhere along the neuromuscular axis 1
• Post-surgical phrenic nerve injury occurs in 31-44% of patients after cardiopulmonary bypass, with left-sided injury being 8 times more common than right due to cold cardioplegia irrigation patterns 2
• Most post-bypass phrenic injuries resolve within 6-12 months, with 80% recovering by 6 months and 90% by one year 2
• Diaphragmatic paralysis presents with dyspnea (particularly on exertion), orthopnea, rapid shallow breathing, and paradoxical inward abdominal motion during inspiration 1

Subdiaphragmatic Pathology

• Acute cholecystitis can cause right hemidiaphragm elevation even without significant mass effect or large collections, and may present with sepsis and vague symptoms rather than classic right upper quadrant pain 3
• This presentation can be misdiagnosed as pneumonia, leading to clinical deterioration from delayed definitive management 3
• Hepatic herniation through diaphragmatic fenestrations (particularly in catamenial/endometriosis-related defects) can mimic a chronically elevated hemidiaphragm and cause persistent ipsilateral chest pain 4
• Massive diaphragmatic fenestrations (up to 10 cm) can allow liver herniation into the thorax, often misattributed to iatrogenic phrenic nerve palsy 4

Cardiac and Pulmonary Vascular Causes

• Right ventricular enlargement from pulmonary arterial hypertension causes characteristic chest X-ray findings including hilar pulmonary artery prominence and right ventricular enlargement that can elevate the hemidiaphragm 5
• Pulmonary hypertension requires both mean pulmonary artery pressure >25 mmHg AND pulmonary vascular resistance >3 Wood units, confirmed by right heart catheterization 6
• Left heart disease (systolic/diastolic dysfunction or valvular disease) is the most common cause of elevated pulmonary artery pressures, with approximately 22% having elevated pulmonary capillary wedge pressures >15 mmHg 6
• Diaphragmatic eventration with cardiac compression can present as cardiac tamponade physiology, particularly when associated with ascites 7

Chronic Thromboembolic Disease

• Chronic thromboembolic pulmonary hypertension (CTEPH) should be considered in patients with history of deep vein thrombosis or pulmonary embolism presenting with progressive exertional dyspnea and right heart failure signs 5
• CTEPH diagnosis requires pulmonary vascular resistance ≥3 Wood units, evidence of arterial obstruction on angiography or V/Q scan despite 3 months of anticoagulation, and exclusion of other causes 5

Diagnostic Approach Algorithm

Initial Evaluation

• Chest radiograph identifies the elevated hemidiaphragm and associated findings (hilar prominence, cardiac silhouette changes, subdiaphragmatic pathology) 5, 3
• Fluoroscopic screening demonstrates paradoxical upward movement of the affected hemidiaphragm during inspiration, confirming paralysis 1
• Look specifically for rapid shallow breathing and paradoxical inward abdominal motion during inspiration on physical examination 1

Targeted Investigation Based on Clinical Context

• In post-surgical patients: Consider phrenic nerve injury, especially after cardiac surgery with cold cardioplegia; most resolve spontaneously within 6-12 months 2
• In patients with sepsis/fever: Obtain CT imaging to evaluate for acute cholecystitis even with vague symptoms, as hemidiaphragm elevation may be the only radiographic clue 3
• In patients with persistent chest pain post-thoracic surgery: Suspect diaphragmatic fenestration with visceral herniation, particularly in women with history of catamenial pneumothorax 4
• In patients with dyspnea and signs of right heart failure: Perform echocardiography to screen for pulmonary hypertension and right ventricular enlargement, followed by right heart catheterization for definitive diagnosis 5, 6

Confirmatory Testing

• Maximal static transdiaphragmatic pressure (Pdimax) confirms diaphragmatic weakness when reduced 1
• Phrenic nerve stimulation with absent compound diaphragm action potential confirms diaphragmatic paralysis 1
• Right heart catheterization is mandatory for definitive pulmonary hypertension diagnosis—echocardiographic estimates alone are insufficient 5, 6

Critical Pitfalls to Avoid

• Do not assume chronic hemidiaphragm elevation is simply phrenic nerve palsy without excluding structural diaphragmatic defects or subdiaphragmatic pathology 4
• Do not misdiagnose acute cholecystitis as pneumonia based solely on elevated hemidiaphragm and fever; obtain cross-sectional imaging 3
• Do not rely on echocardiography alone to diagnose or exclude pulmonary hypertension; invasive hemodynamic assessment is required 5, 6
• Do not overlook the possibility of diaphragmatic eventration causing cardiac compression, particularly in elderly patients with ascites 7