What is the appropriate management for a patient with right lower quadrant (RLQ) pain radiating down the right leg accompanied by weakness?

Right Lower Quadrant Pain with Radicular Symptoms and Weakness

This patient requires urgent neurological and musculoskeletal evaluation, not abdominal imaging, as the combination of RLQ pain radiating down the leg with weakness suggests lumbar radiculopathy, hip pathology, or psoas abscess rather than primary intra-abdominal pathology.

Critical Distinction from Typical RLQ Pain

The provided evidence addresses intra-abdominal causes of RLQ pain (appendicitis, diverticulitis, gynecologic pathology), but this clinical presentation is fundamentally different 1, 2. The key distinguishing features are:

• Radiation down the leg indicates nerve root involvement (L2-L4 distribution for anterior/medial thigh, L5-S1 for posterior leg) rather than visceral pain patterns
• Associated weakness is a red flag for neurological compromise that does not occur with uncomplicated appendicitis or other common intra-abdominal pathology 1
• Visceral abdominal pain typically does not radiate in dermatomal patterns or cause motor deficits

Primary Differential Diagnoses to Consider

Neurological/Musculoskeletal Causes (Most Likely)

• Lumbar radiculopathy from disc herniation (L2-L4 affecting hip flexion/knee extension, L5-S1 affecting ankle dorsiflexion/plantarflexion)
• Psoas abscess can present with RLQ pain, hip flexion weakness, and pain radiating to the groin/anterior thigh
• Hip pathology (septic arthritis, avascular necrosis, fracture) with referred pain
• Femoral neuropathy causing anterior thigh pain and quadriceps weakness

Intra-abdominal Causes (Less Likely Given Radicular Pattern)

• Appendicitis with retrocecal location causing psoas irritation (but would not typically cause true weakness) 1, 2
• Gynecologic pathology (ovarian torsion, ruptured cyst) in women of reproductive age 2

Immediate Diagnostic Approach

Essential Clinical Assessment

• Detailed neurological examination: Test hip flexion strength (L2-L3), knee extension (L3-L4), ankle dorsiflexion (L5), ankle plantarflexion (S1), and sensory distribution
• Straight leg raise test to assess for nerve root tension
• Patrick's test (FABER) to evaluate hip pathology
• Psoas sign: Pain with hip extension or resisted hip flexion suggests psoas involvement
• Fever assessment: Presence suggests infectious etiology (psoas abscess, septic arthritis, appendicitis) 1, 2

Laboratory Studies

• Complete blood count to assess for leukocytosis suggesting infection 2
• Inflammatory markers (ESR, CRP) if psoas abscess or septic arthritis suspected
• Urine pregnancy test in women of reproductive age before imaging 2
• Urinalysis to exclude urinary tract infection or nephrolithiasis 2

Imaging Strategy

CT abdomen and pelvis with IV contrast is the initial imaging study of choice, as it can simultaneously evaluate for:

• Psoas abscess or hematoma (most critical diagnosis requiring urgent drainage) 1
• Appendicitis with psoas irritation 1, 2
• Gynecologic pathology in women 2
• Lumbar spine pathology (though MRI is superior for disc herniation)

CT has 95% sensitivity and 94% specificity for appendicitis and excellent visualization of the psoas muscle and retroperitoneum 1, 2.

MRI lumbar spine should be obtained urgently if:

• CT abdomen/pelvis is negative for intra-abdominal pathology
• Neurological examination strongly suggests radiculopathy
• Progressive weakness is present (concern for cauda equina syndrome)

Hip radiographs should be obtained if hip pathology is suspected based on examination findings.

Management Algorithm

If Psoas Abscess Identified

• Immediate broad-spectrum IV antibiotics (coverage for Staphylococcus aureus, gram-negative organisms, and anaerobes)
• Urgent CT-guided or surgical drainage 1
• Blood cultures before antibiotics

If Appendicitis Confirmed

• Immediate appendectomy with IV antibiotics 2, 3

If Lumbar Radiculopathy Confirmed

• Urgent neurosurgery or spine surgery consultation if progressive weakness or cauda equina symptoms
• Conservative management with NSAIDs and physical therapy for stable radiculopathy without red flags

If Gynecologic Pathology (Ovarian Torsion)

• Emergency gynecologic surgery 2

Critical Pitfalls to Avoid

• Do not assume this is simple appendicitis without explaining the radicular symptoms and weakness—these features demand broader evaluation 1, 2
• Do not delay neurological consultation if weakness is progressive, as this may represent surgical emergency (cauda equina, epidural abscess)
• Do not miss psoas abscess, which can be subtle on examination but causes significant morbidity if untreated
• Do not forget pregnancy test in women of reproductive age before CT imaging 2