What is the diagnosis and management for a 38-year-old female with chronic lateral right buttock pain (5/10), numbness on the lateral thigh, infrequent electric shock-like sensations, and incomplete bladder emptying, who has a history of a fall and experiences relief with warm compression or lateral decubitus position?

Diagnosis: Meralgia Paresthetica with Possible Neurogenic Bladder Dysfunction

This patient most likely has meralgia paresthetica (lateral femoral cutaneous nerve compression) from her fall, but the incomplete bladder emptying is a red flag that requires urgent evaluation to exclude cauda equina syndrome or other neurogenic bladder pathology. 1

Immediate Diagnostic Priorities

Rule Out Cauda Equina Syndrome First

• Urinary retention has 90% sensitivity for cauda equina syndrome (CES) and is the most frequent finding 1
• The patient reports incomplete bladder emptying that improves with warm compression—this is an atypical presentation but warrants urgent evaluation 1
• Obtain post-void residual (PVR) volume immediately using bladder scanner or in-and-out catheterization to quantify retention 2
• If PVR >150 mL or if urinary symptoms worsen, urgent MRI lumbar spine without IV contrast is mandatory to exclude CES 1
• The absence of saddle anesthesia, fecal incontinence, bilateral radiculopathy, or foot drop makes CES less likely but does not exclude it 1

Clinical Pitfall to Avoid

• Do not assume bladder symptoms are unrelated to the fall or buttock pain—delayed diagnosis of CES can result in permanent bladder dysfunction 1
• Without urinary retention, the probability of CES is approximately 1 in 10,000, but this patient has reported incomplete emptying which changes the risk calculation 3, 1

Primary Diagnosis: Meralgia Paresthetica

Clinical Features Supporting This Diagnosis

• Lateral thigh numbness with electric shock-like sensations is classic for lateral femoral cutaneous nerve (LFCN) compression 4
• History of fall to right buttock provides mechanism for nerve compression or injury 4
• Relief with lateral decubitus position suggests positional nerve compression 4
• Normal straight leg raise and cross-leg testing excludes lumbar radiculopathy 3, 5
• L3 radiculopathy would cause symptoms on ventral thigh and knee, not lateral thigh 5
• L4 radiculopathy distinctive region is lateral shin, not lateral thigh 5

Diagnostic Confirmation

• Clinical diagnosis is sufficient when presentation is typical 4
• Electrodiagnostic studies (nerve conduction studies/EMG) should be obtained to confirm LFCN involvement if diagnosis is uncertain or symptoms persist beyond 6-8 weeks 4
• Imaging is rarely helpful for meralgia paresthetica itself 4

Management Algorithm

Step 1: Bladder Function Assessment (Within 24-48 Hours)

• Measure PVR volume with bladder scanner 2
• If PVR <150 mL and symptoms stable: proceed with conservative management for meralgia paresthetica 2
• If PVR ≥150 mL or progressive urinary symptoms: urgent MRI lumbar spine and urology referral 1, 2
• Obtain urinalysis to exclude urinary tract infection as cause of incomplete emptying 3

Step 2: Conservative Treatment for Meralgia Paresthetica (First 6-12 Weeks)

• Physical therapy focused on stretching and reducing pain-spasm cycle is the mainstay of conservative treatment 4
• Avoid prolonged sitting and positions that compress the LFCN (tight clothing, belts) 4
• NSAIDs for pain control 4
• Local nerve block injection at the anterior superior iliac spine can provide diagnostic confirmation and therapeutic benefit 4
• Continue warm compression as it provides symptomatic relief 4

Step 3: Reassessment at 6-8 Weeks

• If symptoms improving: continue conservative management 4
• If symptoms persist or worsen: obtain electrodiagnostic studies to confirm diagnosis and exclude alternative pathology 4
• Repeat PVR measurement to ensure bladder function remains stable 2

Step 4: Refractory Cases (After 3-6 Months of Conservative Failure)

• Consider repeat local injections 4
• Surgical decompression of LFCN is reserved as last resort after failure of all conservative modalities 4
• Piriformis syndrome can coexist and may require separate evaluation if buttock pain persists 4

Monitoring for Neurogenic Bladder

Ongoing Surveillance Required

• All patients with incomplete bladder emptying require thorough urodynamic evaluation if symptoms persist beyond initial assessment 6
• Monitor for development of detrusor overactivity, abnormal compliance, or detrusor-external sphincter dyssynergia (DESD) 7, 6
• Clean intermittent catheterization may be required if PVR remains elevated or symptoms progress 3, 2

Red Flags Requiring Immediate Re-evaluation

• Development of urinary retention (inability to void) 1
• New onset saddle anesthesia or perineal numbness 1
• Bilateral leg symptoms or progressive motor weakness 1
• Fecal incontinence or loss of rectal tone 1
• Any of these findings mandate urgent MRI and neurosurgical consultation 1

Critical Clinical Pearls

• The combination of lateral buttock pain with lateral thigh numbness after trauma suggests meralgia paresthetica, but incomplete bladder emptying is NOT part of this syndrome 4
• Bladder dysfunction in peripheral neuropathy typically presents as diabetic cystopathy, detrusor overactivity, or urge incontinence—not isolated incomplete emptying 8
• The temporal relationship between fall and both symptoms suggests possible dual pathology: LFCN injury AND occult spinal/sacral nerve involvement 1, 4
• Do not delay PVR measurement—this single test determines whether urgent neuroimaging is needed 2
• Physical therapy effectiveness for meralgia paresthetica is enhanced by local injections 4