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Figure 2.

Differential Diagnosis

  • Glenohumeral joint osteoarthritis
  • Acromioclavicular joint separation
  • Pneumothorax
  • Pneumoperitoneum


The correct diagnosis is pneumoperitoneum as the imaging reveals air under the right hemidiaphragm. Although musculoskeletal causes of shoulder pain are common, other non-orthopedic causes should be in the differential, including gastrointestinal, cardiopulmonary, and neurologic sources.

What to Look For

  • Free air under the diaphragm on upright chest or abdominal x-ray
  • Pneumomediastinum, pleural effusion, pneumothorax and subcutaneous emphysema may also occasionally be seen on x-ray
  • Patient may present with abdominal and/or chest pain along with shoulder pain

Pearls for Urgent Care Management

  • If no recent trauma, pneumoperitoneum is usually the result of a gastrointestinal tract perforation
  • This requires immediate transfer to the emergency department for further evaluation and management
  • Fluid resuscitation is the initial treatment
25-Year-Old With Shoulder Pain