What are the possible causes of stabbing, cramping pain posterior to the left rib cage about 8 inches below the axilla, and does this require urgent evaluation?

Stabbing and Cramping Pain Behind Left Rib 8" Below Armpit

This pain pattern most likely represents a musculoskeletal condition such as costochondritis, intercostal muscle strain, or slipping rib syndrome, but you must first exclude life-threatening cardiac and pulmonary causes before settling on this diagnosis. 1, 2

Immediate Evaluation Required

Obtain an ECG immediately to exclude acute coronary syndrome, even though the lateral location and stabbing quality make cardiac ischemia less likely. 1 Sharp, stabbing chest pain that is positional or reproducible with palpation markedly reduces the probability of ACS, but cardiac causes must still be ruled out first. 1

Red Flags Requiring Emergency Evaluation

• Sudden onset "ripping" or "tearing" quality suggests aortic dissection and requires immediate CT angiography 1, 3
• Pain with inspiration plus dyspnea suggests pulmonary embolism or pneumothorax 1
• Associated diaphoresis, nausea, or radiation to jaw/arm increases concern for ACS despite atypical location 1
• Unilateral absence of breath sounds indicates pneumothorax 1

Most Likely Diagnoses (After Excluding Emergencies)

Musculoskeletal Causes (Most Common)

Costochondritis or intercostal muscle strain accounts for the majority of lateral chest wall pain. 1, 2 The location 8 inches below the armpit corresponds to ribs 8-10, which are the most common sites for:

• Slipping rib syndrome: Hypermobility of ribs 8-10 causing the cartilaginous tip to slip under the rib above, impinging the intercostal nerve 2, 4
• Intercostal myofascial injury: Damage to connective tissues between ribs causing localized pain 2
• Rib fracture: Can occur without trauma from violent muscle contractions, particularly in ribs 3-8 2, 5

Clinical Examination Findings

Reproduce the pain by palpating the costal margin firmly - if this recreates the exact pain, it confirms musculoskeletal origin. 6 The painful rib syndrome consists of three features: pain in the lower chest, a tender spot on the costal margin, and reproduction of pain on pressing the tender spot. 6

Check for the "hooking maneuver": Hook your fingers under the lower costal margin and pull anteriorly - reproduction of pain confirms slipping rib syndrome. 4

Diagnostic Algorithm

1. ECG within 10 minutes if any concern for cardiac cause 1
2. Chest radiograph if dyspnea present or trauma history to exclude pneumothorax, pneumonia, or rib fracture 2
3. Ultrasound of the rib cage if fracture suspected - more sensitive than plain radiographs for costochondral junction injuries 2
4. No further imaging needed if pain is reproducible on palpation and ECG/vital signs are normal 6

Management Approach

For confirmed musculoskeletal pain:

• NSAIDs (ibuprofen 400-600 mg three times daily) for pain control 2
• Ice application to the affected area 5
• Avoid activities that reproduce the pain for 2-4 weeks 5, 6
• Reassurance that this is benign - 70% of patients continue to have intermittent pain but learn to live with it 6

Avoid the trap of extensive unnecessary testing - 43% of patients with painful rib syndrome undergo extensive investigations before diagnosis, and 33% get referred again despite a firm diagnosis being given. 6

When to Refer

Refer to surgery if:

• Pain persists beyond 3-6 months despite conservative management 4
• Slipping rib syndrome confirmed and significantly affecting quality of life - resection of slipping rib cartilages provides good pain relief 4

Refer back to ED if:

• New dyspnea, fever, or hemodynamic instability develops 1
• Pain quality changes to "ripping" or "tearing" 1, 3

Critical Pitfalls to Avoid

Do not dismiss as non-cardiac without obtaining an ECG first - atypical presentations of ACS can occur, particularly in women, diabetics, and elderly patients. 1, 7

Do not rely solely on chest radiographs - they miss up to 50% of rib fractures and 90% of costochondral junction injuries. 2

Do not order extensive GI workup unless clear GI symptoms present - only 10-20% of chest pain has a gastrointestinal cause, and empiric evaluation is only reasonable after cardiac and pulmonary causes are excluded. 1