What are the possible causes of a deep, aching, boring pain on the left side, located deep behind the ribs about 12 inches (30 cm) below the left axilla?

Deep Aching Boring Pain Behind Left Ribs Below Armpit

The most likely diagnosis is twelfth rib syndrome (also called slipping rib syndrome when involving ribs 8-10), which presents as deep, aching, boring pain in the flank or lower chest and is confirmed by localized tenderness over the affected rib with immediate relief from trigger-point injection. 1, 2

Primary Diagnostic Consideration: Twelfth Rib Syndrome

Clinical Characteristics

• Twelfth rib syndrome causes chronic chest, back, flank, and abdominal pain from irritation of the 12th intercostal nerve, presenting as deep, continuous, dull, and gravitative pain at the bottom of the chest that is relieved by rest and exacerbated by effort and certain postures. 2, 3
• This condition is frequently overlooked and leads to months or years of unnecessary testing and ineffective treatments before diagnosis, resulting in significant morbidity, psychiatric comorbidities, and increased healthcare costs. 2
• The pain location you describe—deep behind the ribs approximately 12 inches below the left armpit—corresponds anatomically to the region of the 12th rib and lower false ribs (8th-10th). 1, 2

Diagnostic Approach

• Diagnosis is clinical and based on localized tenderness over the twelfth rib on physical examination, with the "hooking maneuver" (pulling the anterior edge of the rib margin forward) reproducing the pain. 2, 4, 5
• Dynamic ultrasound can identify abnormalities in rib and cartilage anatomy and soft tissue swelling, providing confirmation in difficult cases. 4, 5
• All other serious causes must be excluded first, including cardiac, pulmonary, and gastrointestinal pathology. 2

Critical Life-Threatening Differentials to Exclude First

Cardiac Causes

• Musculoskeletal causes are the most common etiology of chest pain, but cardiac causes must be ruled out initially, particularly in patients with risk factors. 6
• Obtain a 12-lead ECG to exclude acute coronary syndrome, especially if you have cardiovascular risk factors (hypertension, diabetes, smoking, family history). 6
• Cardiac ischemia can present with atypical pain patterns, though the boring, positional nature of your pain and specific anatomic location make this less likely. 6

Pulmonary Causes

• Pulmonary embolism, pneumonia, and pneumothorax are less frequent but potentially serious respiratory causes that typically present with dyspnea in addition to chest pain. 6
• Pleuritis can cause sharp pain worsened by breathing and should be considered if pain changes with respiration. 1

Gastrointestinal Causes

• Gastroesophageal reflux disease is the most common gastrointestinal cause of recurring chest pain, presenting as squeezing or burning pain lasting minutes to hours, often occurring after meals or at night. 6
• Esophageal motility disorders can present as squeezing retrosternal pain often accompanied by dysphagia, but would not typically cause the specific flank location you describe. 6
• Renal pathology should be considered given the flank location, though the deep boring quality and rib-associated nature point more toward musculoskeletal origin. 1

Treatment Algorithm for Twelfth Rib Syndrome

First-Line Conservative Management

• Conservative treatment includes local heat or ice packs, rest, and oral over-the-counter analgesics (NSAIDs) as initial therapy. 2
• Physical therapy targeting the affected area can provide significant symptom improvement. 1, 2
• Transcutaneous electrical nerve stimulation (TENS) has been described with some success. 2

Second-Line Interventional Options

• Trigger-point injections with local anesthetic at the end of the free cartilage provide immediate pain relief and serve both diagnostic and therapeutic purposes. 1, 3
• Intercostal nerve blocks are usually effective in the immediate term, though there is limited evidence for long-term efficacy. 2, 4
• Twelfth intercostal nerve cryotherapy has been described with some success. 2
• Botulinum toxin injections and prolotherapy are emerging treatment options. 4

Surgical Management for Refractory Cases

• Surgical removal of all or part of the 12th rib (and possibly the 11th rib) is the next line of therapy for refractory pain and may provide long-lasting relief. 2, 5
• Rib stabilization is an emerging option for recurrent symptoms after initial resection. 5
• Surgery consistently shows good results for pain relief in patients who fail conservative management. 5

Critical Pitfalls to Avoid

• Do not assume musculoskeletal pain without first excluding cardiac, pulmonary, and other serious causes, particularly if you have risk factors or if the pain pattern changes. 6
• Do not delay seeking emergency evaluation if you develop new symptoms such as severe shortness of breath, syncope, diaphoresis, or radiation of pain to the jaw, neck, or arm. 6
• Do not accept a diagnosis of anxiety or psychosomatic pain until comprehensive workup is negative, as twelfth rib syndrome is frequently misdiagnosed due to lack of familiarity with the condition. 2
• Do not expect standard imaging (X-rays, CT) to diagnose twelfth rib syndrome—this is a clinical diagnosis confirmed by physical examination findings. 2, 5

Immediate Next Steps

• Seek evaluation by a physician who can perform a focused physical examination looking for localized tenderness over the 12th rib and perform the hooking maneuver. 2, 4, 5
• If serious causes are excluded and twelfth rib syndrome is confirmed, begin with conservative management and escalate to interventional options if symptoms persist. 2
• Consider referral to a pain specialist or thoracic surgeon if conservative measures fail after 6-12 weeks. 2, 5