What are the potential causes and management options for an adult patient with a history of physical activity or pre-existing musculoskeletal conditions presenting with left-sided mid and lower back pain?

Left-Sided Mid and Lower Back Pain: Evaluation and Management

Immediate Red Flag Assessment

First, exclude serious pathology that requires urgent intervention before attributing pain to benign musculoskeletal causes. 1, 2, 3

Critical Red Flags to Rule Out:

• Cauda equina syndrome: Check for urinary retention, fecal incontinence, saddle anesthesia, and motor deficits at multiple levels—this requires immediate MRI and neurosurgical consultation 1, 2, 3
• Cancer: Consider in patients with history of malignancy, unexplained weight loss, age >50 years, or failure to improve after 1 month (likelihood ratio 14.7 with cancer history) 3, 4
• Infection: Suspect with fever, IV drug use, or recent infection 5
• Vertebral compression fracture: Especially in patients with osteoporosis, steroid use, or significant trauma with midline tenderness 2, 3
• Inflammatory spondyloarthropathy: In patients <45 years with pain >3 months that improves with exercise, worsens at night, and causes morning stiffness >30 minutes—this requires MRI and rheumatology referral 5

Physical Examination Priorities:

• Neurologic examination: Assess motor strength (knee extension, great toe/foot dorsiflexion, foot plantarflexion), reflexes (knee, ankle), and sensory distribution in dermatomal patterns 1
• Straight leg raise test: 91% sensitivity for herniated disc if pain radiates below the knee 1
• Midline tenderness: Strongly suggests vertebral fracture in trauma or high-risk patients 2
• Costovertebral angle tenderness: Evaluate for renal pathology given left-sided location 2

Imaging Strategy

Do not order imaging for nonspecific back pain without red flags—it provides no clinical benefit and leads to unnecessary interventions. 3

When to Image:

• Immediate MRI: Severe or progressive neurologic deficits, suspected cauda equina syndrome, suspected cancer or infection 1, 3
• Plain radiographs first: If trauma mechanism with midline tenderness (concern for fracture) 2
• MRI after 4-6 weeks: Only if symptoms persist despite conservative management AND patient is a surgical candidate 1, 3
• Key caveat: Disc abnormalities appear in 29-43% of asymptomatic patients, and most disc herniations reabsorb by 8 weeks 3

Initial Management Approach

First-Line Pharmacologic Treatment:

NSAIDs are the primary medication with the strongest evidence for moderate pain relief in acute back pain. 5, 3

• Topical NSAIDs with or without menthol gel: First-line for acute musculoskeletal pain (strong recommendation, moderate-certainty evidence) 5
• Oral NSAIDs: Moderate-certainty evidence for pain reduction and improved function 5, 3
• Acetaminophen: Fair evidence as adjunctive therapy, though less effective than NSAIDs 5, 3
• Skeletal muscle relaxants: Consider adding for short-term relief in acute phase, though carries sedation risk 5, 3

Avoid These Interventions:

• Opioids (including tramadol): Conditional recommendation AGAINST—no better than NSAIDs but more adverse effects 5, 3
• Epidural steroid injections: Strong recommendation AGAINST for chronic radicular pain 1
• Bed rest: Contraindicated—leads to deconditioning and worse outcomes 1, 3

First-Line Non-Pharmacologic Treatment:

• Advise patients to remain active: More effective than bed rest for acute or subacute low back pain 1, 3
• Superficial heat: Good evidence for moderate benefits in acute phase 1
• Spinal manipulation: Fair evidence for small to moderate short-term benefits if performed by appropriately trained providers 1, 3
• Physical therapy: May be considered after acute phase (>4 weeks), not effective during acute phase 3

Management Algorithm by Clinical Presentation

If Radicular Pain (Pain Radiating Down Left Leg):

More than 90% of symptomatic disc herniations occur at L4/L5 and L5/S1 levels. 1

• Conservative management first: NSAIDs, activity modification, physical therapy for at least 6 weeks 1
• Most patients improve within 4 weeks with noninvasive management 1, 3
• MRI indicated: Only if symptoms persist >6 weeks despite conservative therapy OR severe/progressive neurologic deficits 1
• Specialist referral: Within 3 months for non-severe radicular pain; within 2 weeks if severe and disabling 1

If Nonspecific Mechanical Low Back Pain (>85% of Cases):

• No imaging needed unless red flags present or symptoms persist >4-6 weeks 3
• NSAIDs or acetaminophen as first-line medication 3
• Activity as tolerated within pain limits 3
• Reassess at 4-6 weeks if symptoms persist 3

If Inflammatory Pattern Suspected:

• Age <45 years, pain >3 months, improves with exercise, worse at night, morning stiffness >30 minutes 5
• MRI with STIR sequences of cervicothoracic, thoracolumbar spine, and sacroiliac joints 5
• Rheumatology referral: Early diagnosis prevents long-term disability 5
• NSAIDs more effective than simple analgesia, but use cautiously if IBD present 5

Common Pitfalls to Avoid

• Ordering routine imaging for uncomplicated acute back pain: Exposes patients to unnecessary radiation (single lumbar x-ray = daily chest x-ray for >1 year in gonadal radiation) without clinical benefit 3
• Rushing to epidural steroid injections: Strong recommendation AGAINST this for radicular pain based on most recent high-quality evidence 1
• Missing cancer in patients with prior malignancy: Posttest probability jumps from 0.7% to 9% in this population 3
• Overlooking inflammatory causes in younger patients: Delays access to highly effective TNF-blocking agents 3
• Prescribing bed rest: Leads to deconditioning and worse outcomes 1, 3
• Using opioids as first-line therapy: Equal effectiveness to NSAIDs but more adverse effects 5, 3

Follow-Up Strategy

• Reevaluate at 4-6 weeks if symptoms persist without improvement 3
• Consider imaging at that point only if patient is potential surgical candidate 3
• Immediate reevaluation if any neurologic symptoms develop 2
• Screen for yellow flags (depression, passive coping, job dissatisfaction) that predict chronicity using STarT Back tool at 2 weeks 3