What could be the cause of dull pain from the lower rib or costal margin to the loin lasting 2 days?

Differential Diagnosis: Dull Pain from Lower Rib/Costal Margin to Loin in a 21-Year-Old

The most likely diagnosis is musculoskeletal chest wall pain, specifically either painful rib syndrome (costal margin tenderness), twelfth rib syndrome, or slipping rib syndrome, given the age, pain location, and 2-day duration. 1, 2

Immediate Clinical Assessment Required

Systematically palpate the costal margin firmly to reproduce the pain - this single maneuver is diagnostic for painful rib syndrome and requires no further investigation if positive. 3 The key diagnostic features to assess include:

• Pain reproduction with direct palpation of the lower costal margin or affected rib - if present, this confirms musculoskeletal etiology 1, 3
• Pain worsening with lateral flexion, trunk rotation, or rising from sitting - classic for twelfth rib syndrome 4
• Mobile or "popping" rib sensation with palpation suggests slipping rib syndrome 2, 5
• Pain characteristics: dull, localized to chest wall, varies with breathing or body position - all favor benign musculoskeletal cause 1

Most Likely Diagnoses (in order of probability)

1. Painful Rib Syndrome (Most Common)

• Accounts for 3% of general medical referrals, predominantly affects women (70%), mean age 48 years but occurs in young adults 3
• Three diagnostic features: pain in lower chest/upper abdomen, tender spot on costal margin, reproduction of pain with pressure on tender spot 3
• This is a safe clinical diagnosis requiring no investigation when criteria are met 3

2. Twelfth Rib Syndrome

• More common in women (3:1 ratio), presents as constant dull ache or sharp stabbing pain lasting hours to weeks 4
• Pain aggravated by lateral flexion, trunk rotation, and rising from sitting position 4
• Diagnosis requires exact reproduction of symptoms by manipulation of the affected rib 4

3. Slipping Rib Syndrome

• Occurs when ribs sublux from joint connections, causing reproducible pain with palpation 2, 5
• Commonly associated with popping/clicking sensation during activity 5
• Dynamic ultrasound detects this with 89% sensitivity and 100% specificity 1

4. Costo-Iliac Impingement Syndrome

• Occurs when lowest rib impinges against iliac crest, causing back and loin pain 6
• Typically associated with height loss or vertebral osteoporosis (unlikely in 21-year-old) 6

Red Flags to Exclude (Low Probability but Must Rule Out)

• Cardiac causes: Extremely unlikely at age 21 without exertional component, dyspnea, or radiation to arm/jaw 7, 8
• Pulmonary embolism/pneumothorax: Would present with dyspnea, sudden onset, or respiratory distress 7, 2
• Renal pathology: Consider if flank tenderness, urinary symptoms, or fever present (not mentioned in history)

Diagnostic Algorithm

Step 1: Physical Examination (No imaging needed initially) 1, 3

• Firm systematic palpation of entire costal margin bilaterally
• Assess for reproducible tenderness at specific point
• Test for rib mobility/popping sensation
• Observe pain with trunk movements (flexion, rotation)

Step 2: If Physical Exam Positive for Musculoskeletal Pain 1, 3

• No imaging required - this is a clinical diagnosis
• Proceed directly to treatment

Step 3: If Physical Exam Equivocal or Concerning Features Present 1, 2

• Chest radiography as first-line imaging (though misses 50% of rib fractures) 1
• Consider ultrasound for suspected slipping rib syndrome or costochondral injury 1, 2
• CT chest reserved only for suspected malignancy or pulmonary disease 1

Management Approach

First-Line Treatment 1, 2

• Regular acetaminophen as primary analgesic
• NSAIDs as second-line for severe pain (consider GI protection)
• Avoid movements/postures that worsen pain
• Reassurance that this is benign and self-limited

Expected Course 3

• 70% of patients have persistent pain at 4-year follow-up, but most learn to live with it
• No serious complications or mortality associated with this condition

Critical Pitfalls to Avoid

• Over-investigation: Painful rib syndrome patients are frequently over-investigated with extensive workups that are unnecessary 3
• Surgical misadventures: Eight patients in one series had non-curative cholecystectomies before correct diagnosis 3
• Missing the diagnosis: This syndrome is "common but underdiagnosed" - failure to palpate the costal margin systematically leads to missed diagnosis 3
• Relying on imaging alone: Standard radiographs miss up to 50% of rib pathology 1

In this 21-year-old patient, if systematic costal margin palpation reproduces the exact pain, no further investigation is needed and treatment with NSAIDs plus reassurance is appropriate. 1, 3