What are the causes, symptoms, and management of an elevated left hemidiaphragm with pleural thickening on a chest X-ray (CXR)?

Elevated Left Hemidiaphragm with Pleural Thickening: Causes, Symptoms, and Management

The combination of elevated hemidiaphragm with pleural thickening requires immediate differentiation between benign asbestos-related disease and malignant pleural mesothelioma through contrast-enhanced CT imaging, as these findings can be indistinguishable on chest X-ray alone. 1

Causes

Malignant Causes (Must Be Excluded First)

• Malignant pleural mesothelioma (MPM): Presents with nodular pleural thickening >1 cm, pleural nodularity, mediastinal pleural involvement, and circumferential pleural thickening 1
• Metastatic pleural disease: Can produce similar imaging findings with pleural thickening and associated effusion 1

Benign Causes

• Benign asbestos-related pleural effusion (BAPE) and diffuse pleural thickening (DPT): Occurs 30-38 years after asbestos exposure, with pleural thickening ≥3 mm measuring >5 cm axially and >8 cm craniocaudally 1
• Diaphragm paralysis/eventration: Results from phrenic nerve injury, thoracic or abdominal pathology, or neuromuscular disease causing apparent hemidiaphragm elevation 2, 3
• Subpulmonic effusion: Can mimic elevated hemidiaphragm with lateral peaking and steep lateral slope on PA radiograph 1
• Post-inflammatory pleural disease: Following empyema, hemothorax, or tuberculosis 1

Symptoms

Common Presentations

• Dyspnea: Most common symptom, particularly with large effusions or significant diaphragm dysfunction 1, 2, 3
• Chest pain: Pleuritic or dull aching pain 1
• Cough: Often non-productive 1
• Influenza-like symptoms: Particularly in BAPE 1
• Asymptomatic: Many cases discovered incidentally on routine imaging 1, 3

Physical Examination Findings

• Decreased or absent breath sounds over affected hemithorax 4
• Dullness to percussion 4
• Decreased tactile fremitus 4

Diagnostic Management Algorithm

Step 1: Initial Imaging Assessment

• PA and lateral chest radiographs: First-line investigation to confirm elevated hemidiaphragm and pleural thickening 1
• Look for: lateral peaking of hemidiaphragm, pleural thickening pattern, costophrenic angle obliteration, and pleural plaques suggesting asbestos exposure 1

Step 2: Differentiate Fluid from Thickening

• Ultrasound: Readily differentiates between pleural fluid and true pleural thickening; detects as little as 20 mL of fluid 1, 4
• Lateral decubitus films: Shows gravitational layering if free fluid present 1, 4

Step 3: Advanced Cross-Sectional Imaging (Essential)

• Contrast-enhanced CT chest: Gold standard for characterizing pleural disease and differentiating benign from malignant causes 1

Malignant features on CT include: 1

• Nodular pleural thickening
• Pleural thickening >1 cm
• Mediastinal pleural involvement (94% specificity)
• Circumferential pleural thickening (100% specificity)
• Parietal pleural thickening >1 cm (88% specificity)

Benign features include: 1

• Smooth pleural thickening <1 cm
• Pleural plaques
• Folded lung/rounded atelectasis
• Absence of nodularity

Step 4: Assess Diaphragm Function

• Fluoroscopy: Differentiates true paralysis (paradoxic motion) from eventration (no paradoxic motion) 1, 3
• Ultrasound diaphragm: High sensitivity/specificity for neuromuscular disorders; evaluates excursion amplitude and paradoxical movement 1

Step 5: Tissue Diagnosis When Indicated

• Ultrasound-guided pleural aspiration: Obtain 25-50 mL for cytology if effusion present; yields fluid in 97% of loculated effusions 1, 4
• Pleural biopsy: Required when malignancy cannot be excluded; full-thickness biopsies to fat level needed 1
• PET-CT: Consider if diagnostic uncertainty persists after biopsy; MPM typically shows higher SUV values than benign disease 1

Step 6: Establish Asbestos Exposure History

• Document occupational exposure (latency period 30-50 years) 1
• Look for concurrent pleural plaques on imaging 1

Management Strategy

For Malignant Disease

• Immediate oncology referral if CT shows features of MPM (nodular thickening >1 cm, mediastinal involvement, circumferential thickening) 1
• Staging with contrast-enhanced CT to assess chest wall, diaphragmatic, and mediastinal invasion 1

For Benign Asbestos-Related Disease

• Multidisciplinary team discussion with 24-month monitoring period without development of malignant features 1
• Serial imaging surveillance given risk of progression to mesothelioma 1
• Symptomatic management of dyspnea and chest pain 1

For Diaphragm Paralysis/Eventration

• Surgical plication indicated for all symptomatic patients with disabling dyspnea 2, 3
• Minimally invasive thoracoscopic approach preferred 3
• Goal: improve lung volumes and decrease paradoxic elevation 3
• Excellent outcomes with significant symptom improvement 3

For Subpulmonic Effusion

• Therapeutic thoracentesis if symptomatic, removing maximum 1-1.5 L per session to avoid re-expansion pulmonary edema 4
• Ultrasound guidance mandatory to reduce pneumothorax risk 4

Critical Pitfalls to Avoid

• Never assume benign disease without contrast-enhanced CT: Chest X-ray cannot reliably differentiate benign from malignant pleural thickening 1
• Do not perform blind thoracentesis: Always use ultrasound guidance to significantly reduce pneumothorax risk 4
• Do not send <25 mL for cytology: Sensitivity drops substantially below this volume 4
• Do not rely on single imaging modality: Supine radiographs underestimate fluid volume; ultrasound differentiates fluid from thickening 1, 4
• Do not delay tissue diagnosis: If CT features suggest malignancy (thickening >1 cm, nodularity, mediastinal involvement), proceed directly to biopsy 1
• Do not overlook asbestos exposure history: 30-50 year latency period means exposure may be remote 1