What is the differential diagnosis (ddx) for a patient with right-sided chest pain that occurs only on expiration?

Differential Diagnosis for Right-Sided Chest Pain Present Only on Expiration

Right-sided chest pain occurring exclusively during expiration is an unusual presentation that most commonly suggests musculoskeletal pathology, but you must systematically exclude life-threatening pulmonary and cardiac causes before settling on a benign diagnosis.

Immediate Life-Threatening Causes to Exclude First

Pulmonary Embolism

• Pulmonary embolism presents with acute dyspnea and pleuritic chest pain, with tachycardia present in >90% of patients 1
• Pain typically worsens with inspiration rather than expiration, but atypical presentations occur 2, 3
• Use validated clinical decision rules to determine pretest probability and guide D-dimer testing 2
• Obtain ECG within 10 minutes and measure cardiac troponin as soon as possible 1

Pneumothorax

• Classic triad includes dyspnea, pleuritic pain on inspiration, and unilateral absence of breath sounds with hyperresonant percussion 2
• Right-sided pneumothorax can present with pain during any phase of respiration 1
• Chest radiography is essential for diagnosis 2, 3
• Consider spontaneous pneumothorax, especially in young patients with vigorous exercise history 4

Acute Coronary Syndrome

• May present with pleuritic pain in 13% of patients, though typically not isolated to expiration 2
• Examination may be completely normal in uncomplicated cases 1
• ECG should be obtained within 10 minutes to evaluate for ST-segment elevation or new ischemic changes 1, 5

Serious But Non-Immediately Fatal Causes

Pericarditis

• Sharp, pleuritic chest pain that worsens when supine and improves when leaning forward 5, 2
• Friction rub on examination and fever are characteristic findings 1
• ECG shows widespread ST-elevation with PR depression 2

Pneumonia

• Presents with localized pleuritic pain, fever, productive cough, regional dullness to percussion, and egophony 1, 2
• Pleural friction rub may be present 1
• Chest radiography is diagnostic 2, 3

Pleural Effusion

• May develop in 46% of pulmonary embolism cases and cause ongoing pleuritic discomfort 2
• Unilateral decreased breath sounds suggest large pleural effusion 2

Most Likely Diagnosis: Musculoskeletal Causes

Costochondritis/Tietze Syndrome

• Tenderness of costochondral joints on palpation with pain reproducible with chest wall pressure is the hallmark 5, 2
• Pain affected by palpation, breathing, turning, twisting, or bending 5
• However, 7% of patients with reproducible chest wall tenderness still have acute coronary syndrome, so do not rely on this finding alone 2

Intercostal Muscle Strain

• Pain localized to a very limited area, affected by specific movements 5
• History of recent trauma, vigorous exercise, or repetitive motion 6

Critical Pitfalls to Avoid

• Do not assume reproducible chest wall tenderness excludes serious pathology—7% of patients with palpable tenderness have acute coronary syndrome 2
• Do not use nitroglycerin response as a diagnostic criterion, as esophageal spasm and other non-cardiac conditions also respond to nitroglycerin 5, 6
• Do not dismiss chest pain in women, elderly patients, or patients with diabetes, as they frequently present with atypical symptoms 5, 6
• Sharp, pleuritic pain does not exclude cardiac ischemia completely 2

Mandatory Initial Evaluation

History

• Exact onset, duration, quality, and severity of pain 6
• Radiation pattern and precipitating factors 6
• Associated symptoms including diaphoresis, dyspnea, nausea, syncope, or palpitations 5
• Relationship to respiratory cycle—confirm pain truly occurs only on expiration 2

Physical Examination

• Focused cardiovascular examination for murmurs, friction rub, S3, pulse differentials, and blood pressure differentials 6
• Unilateral breath sounds assessment 1, 2
• Chest wall palpation for reproducible tenderness 5, 2
• Vital signs including heart rate and respiratory rate 2

Essential Testing

• ECG within 10 minutes of presentation to identify STEMI, pericarditis patterns, or signs of pulmonary embolism 1, 5, 2
• Chest radiography to evaluate for pneumothorax, pneumonia, pleural effusion, or widened mediastinum 2, 7
• Cardiac troponin measured as soon as possible in acute presentations to exclude myocardial injury 1, 2

Management Algorithm

1. If ECG shows ST elevation or new ischemic changes, immediate transfer by EMS is required 5
2. If chest X-ray reveals pneumothorax, pneumonia, or pleural effusion, manage accordingly 2, 3
3. If cardiac testing is negative and chest wall tenderness is present, treat as costochondritis with anti-inflammatory medications 2
4. If symptoms persist despite negative workup, consider evaluating for gastrointestinal causes such as esophageal reflux 1, 2
5. For recurrent episodes without physiological cause, consider referral to cognitive-behavioral therapy 2

High-Risk Features Requiring Immediate Action

• Age >75 years with accompanying dyspnea, syncope, acute delirium, or unexplained fall 5, 6
• Hemodynamic instability 5
• Elevated cardiac troponin levels 6
• Pulse differentials or blood pressure differentials >20 mmHg 6
• New murmurs on examination 6