Low Back Pain Algorithm and Differential Diagnosis

Table of Contents

General Red Flags for Low Back Pain

General Approach

Begin work-up by ruling out emergent/urgent conditions and evaluating/charting the absence of red flags that can signal the presence of an emergent condition
Then consider other visceral causes of low back pain
If no red flags are present and patient does not need further work-up, then the likely default diagnosis is benign mechanical (lumbar strain) LBP

Age

<20 years old
- Increased incidence of congenital, developmental, bony abnormalities, and malignancy
>50 years old
- Increased incidence of serious causes (AAA, vertebral fracture, pancreatitis…)

Duration of Symptoms

Acute (0-6wks); Subacute (6-12wks); Chronic (>12wks), and recurrent
Non acute (>6wks)
- Red flag because 80-90% sx should resolve by 4-6wks (Emerg Med Clin North Am 1999;17:877- 93)

Atypical pain features

Awaken from sleep
Intractable pain
- Consider: infection, tumor, fracture, nerve impingement, or non-musculoskeletal causes

The Causes of Lower Back Pain — Low Back Pain: Causes and Differential Diagnosis

Low Back Pain - Differential Diagnosis — Low Back Pain: Causes and Differential Diagnosis

Emergent Conditions of Low Back Pain

1. Abdominal Aortic Aneurysm (AAA) / Aortic Dissection

Abdominal Aortic Aneurysm (AAA)

Presentation
- Usually asymptomatic until rupture
- Acute epigastric and back pain
- Wide pulsatile abdominal mass
- Renal colic mimic (back pain, hematuria)
AAA Risk factors (age, male, smoking, CAD/PVD, Family History)

Abdominal Aortic Aneurysm - Clinical Findings and Complications — Abdominal Aortic Aneurysm – Clinical Findings and Complications

Aortic Dissection

Presentation
- Sudden-onset, severe, “tearing” pain
- Pulse/neuro deficit
- New Aortic Insifficiency murmur
- Limb ischemia
Risk factors: HTN (Hypertension), Marfan’s, vasculitis, pregnancy, coarctation, bicuspid aortic valve, trauma, cocaine/meth

2. Epidural Compression

Causes of Epidural Compression

Spinal cord compression,
Conus medullaris syndrome,
Cauda Equina syndrome

Clinical Presentation of Epidural Compression

History of cancer ?
Multiple myotomes/dermatomes may be involved
Focal Neurologic deficit:
- Bilateral Lower Extremity weakness, sciatica change, gait disturbance
- Bowel/bladder incontinence caused by urinary retention (PVR (post-void residual urine volume) >100-200ml)
- Decreased rectal tone
- Motor > Sensory loss
- Sensory loss: saddle anesthesia, sensory level
Age (JAMA 1992;268;760-5)
- Age > 50 or history of Cancer or unexplained weight loss or failure of conservative therapy → Sens 100% for detecting metastasis to spine

Work-up for Epidural Compression

Overflow incontinence
- Cause (J Bone Joint Surg Am 1986;68:386)
  - Urinary retention (sensitivity 90%, specificity 95% for epidural compression)
- Abnormal PVR (post-void residual urine volume)
  - Absence of large PVR (>100ml) has NPV (Negative predictive value) 99.99%
  - In absence of significant neurologic deficit → normal PVR rules out compression
- Post-void US: Volume = Length x Width x Height x (0.52)
- Anal sphincter tone diminished in 60-80%
- Saddle anesthesia has sensitivity 75%
MRI
- Diagnose site of compression

Special Case: Patient with history of Cancer (Emerg Med Clin N Am 2010;28:811)

Group I: New/progressive neurologic symptoms
- Steroids (Dexamethasone 10mg IV)
- Xrays, emergent MRI
Group II: Stable neurologic symptoms
- Steroids
- Xrays, urgent MRI (24h)
Group III: No neurologic signs/symptoms
- Conservative therapy
- Xrays, outpatient MRI

Treatment of Epidural Compression

Emergent Neurosurgical Consult
Steroids/Radiation if due to metastasis

3. Spinal Epidural Abscess (SEA)

Other infectious causes of low back pain

Epidural abscess
Osteomyelitis
Discitis
Transverse Myelitis

Clinical Presentation of Spinal Epidural Abscess

Spinal Epidural Abscess (SEA) Triad
Fever
Spine pain
Neurologic deficit

Classic Triad (Fever, Spine pain, neuro deficit)
- Triad present in only 13% patients with SEA and is usually a late finding
- Must consider risk factor screening for rulling out epidural abscess. (J Emerg Med 2004;26:285-91)
Progression of symptoms:
- Back pain → Radiculopathy → Sensory changes/motor weakness → Bowel-bladder dysfunction → Paralysis
Risk Factors:
- Intravenous drug abuse
- immunocompromised
- alcohol abuse
- spine procedure
- distant infection
- Diabetes Mellitus
- Chronic Kidney Failure (CKD)
- Cancer
- indwelling catheter
- spine fracture
Risk factor screening sensitivity 98%, for one or more risk factors

Work-up for Spinal Epidural Abscess

ESR (Erythrocyte sedimentation rate) (J Neurosurg Spine 2011;14:765-770)
- Used as screening test for value of >20mm/h (sens 100%)
- Useful as screening tool for ED patients with spine pain, risk factor for Spinal Epidural Abscess and no neurologic deficits
Emergent MRI

Treatment of Spinal Epidural Abscess

Broad spectrum antibiotics (Staph/Strep/gm neg)
Emergent Neurosurgical consultation

4. Vertebral Fracture

Clinical Presentation of Vertebral Fracture

Usually elderly with osteoporosis
Trauma
Point Vertebral Tenderness
Steroid use
- A person with Lower Back Pain on long-term steroids is considered to have a compression fracture until proven otherwise (Spec 99%)

Work-up for Vertebral Fracture

• Xrays / CT Spine

Visceral Causes of Low Back Pain

1. UTI / Pyelonephritis

Definitions

Uncomplicated UTI: young, healthy, non-pregnant women with structurally and functionally normal urinary tracts
Complicated UTI: UTI associated with an underlying condition that increases the risk of failing therapy
Complicated pyelonephritis: progression of upper UTI to emphysematous pyelonephritis, renal corticomedullary abscess, perinephric abscess, or papillary necrosis

Pathogenesis of Urinary Tract Infection (UTI)

Risk Factors for Complicated UTI
□ Pregnancy
□ Diabetes
□ Male gender
□ Immunosuppression (AIDS, chemotherapy…)
□ Functional GentioUrinay abnormality (catheter, neurogenic bladder…)
□ Structural GU abnormality (stones, fistula, PCKD, transpant…)

Risk Factors for UTIs (Urinary Tract Infections)

Clinical Presentation

Cystitis
- Urinary frequency and urgency, dysuria, and hematuria
- Suprapubic pain, low back pain
- New or increased incontinence in older patients or Altered Mental Status / Delirium
Pyelonephritis
- Flank or abdominal pain, CVA (costovertebral angle) tenderness on exam
- Fever/chills, Nausesa / Vomitus
- Complicated Pyelonephritis (Sepsis, Renal failure)

Diagnosis

Urine Dipstick / Urine Analysis (UA)
- Either nitrite OR leukocyte esterase (LE) positive: 75% sensitive, 82% specific
- Nitrite AND leukocyte esterase positive: 35-84% sensitive, 98-100% specific
- Nitrite alone (95-98%) more specific than leukocyte esterase alone (59-96%) but S. saprophyticus, pseudomonas, and enterococci do not reduce nitrate
- False positive LE (leukocyte esterase) with vaginitis or cervicitis
- Pyuria and bacteruria may be absent if obstruction of the collecting system or ureters is present

Urine Microscopy
- White blood cell casts are diagnostic of upper urinary tract infection

Urine culture
- Helpful in guiding antibiotic therapy in pyelonephritis or failed antibiotic treatment
- Positive: single organism isolated with ≥ 100,000 CFU

Imaging
- Not routinely necessary
- CT abdomen/pelvis with/without IV contrast consider to/if :
  - rule out infected/obstructed ureteral stone
  - rule out pyelonephritis complication (abscess…):
    - Consider if failure of response to therapy in 48-72 hours
  - Recurrence of symptoms within a few weeks of therapy
  - Suspicion for obstruction, gas, hemorrhage, masses
- Ultrasound:
  - Rule out hydronephrosis / obstruction / stone

Proposed algorithm for evaluating women with symptoms of acute urinary tract infection (UTI)

Treatment

Antibiotics
- Base antibiotic selection on previous culture data, local resistance patterns, patients history and medical problems
Adjunctive pain control option: Phenazopyridine PO TID (urinary analgesic).
See Current Guidelines (Clinical Infectious Diseases 2011;52(5):e103)

Complications

Pyonephrosis
- Infection + obstruction (pus under pressure)
- Pyelonephritis with an obstructing stone, mass, or other obstruction
- Therapy: emergent urology/interventional radiology consult for percutaneous nephrostomy tube or stenting

Renal abscess
- Diagnosis: CT with IV contrast; can be visualized on Ultrasound
- Therapy: Resuscitation, antibiotics, percutaneous drainage (depending on size and response to antibiotics)

Emphysematous UTI
- Definition: necrotizing infection with gas formation in bladder (cystitis), renal pelvis (pyelitis) or kidney parenchyma (pyelonephritis)
- High mortality (20% to 40%) even with treatment
- 95% of cases occur in patients with DM
- Major risk factor is infected obstructing stone

Papillary necrosis
- Definition: coagulative necrosis of the renal medullary pyramids and papillae

Disposition

Outpatient therapy appropriate if:
- Uncomplicated pyelonephritis
- Normal vitals, normal renal function, no urinary obstruction
- Pain control and hydration status adequate
- Able to tolerate Oral medications

2. Renal Colic

Clinical Presentation of Renal Colic

Renal colic
- Mechanism of Action: obstruction of urinary tract → ↑ pressures → renal capsular distention (visceral pain/N/V) → ↑ peristalsis of ureter (colicky pain)
- Unilateral flank pain → radiating to groin
- Migration of pain (depending on location of stone):
  - Back pain → flank pain → lower quadrant abdominal pain → penile / labial / testicular pain
- Colic pain: intermittent, waxes/wanes, patient writhing, unable to sit still
Urinary symptoms: urgency, frequency, dysuria, gross hematuria
Nausea/vomiting
Physical Exam : CVA (costovertebral angle) tenderness or lower abdominal tenderness

Diagnosing Renal Colic

Urinalysis
- Microscopic hematuria only 85% sensitive for urolithiasis
- Use to rule-out infection/UTI and infected stone
- UA negative?: Patient may still have urine infection proximal to obstructing stone

KUB (kidney, ureter, and bladder X-ray)
- 85-90% of stones are radioopaque (calcium, struvite, cystine) but KUB only 40-62% sensitive and 60-67% specific
- Little diagnostic utility; consider in patient with known history of radiopaque stones and typical presentation

Ultrasound
- Ureteral calculi
  - Sensitivity 45% and specificity 94%
  - More likely to see larger stones (>4mm), at the UVJ (ureterovesical junction), or proximal near the renal pelvis.
- Hydronephrosis
  - Sensitivity 85-90% and specificity 90-100%
  - Not visualize stone itself but can demonstrate obstructive sequelae
  - Presence/absence of hydronephrosis is neither diagnostic nor prognostic
- Preferred initial test in pregnancy, children → no radiation
- Use to evaluate abdomen/pelvis for alternative diagnoses (gallstones, appy etc…)

CT (Non-contrast):
- Study of choice to evaluate urolithiasis
- Indications:
  - 1st time diagnosis of urolithiasis
  - Atypical presentation
  - Rule out infection
  - Not improving with conservative treatment
- Sensitivity 96-98% and specificity ~100%
- Useful in prognosis (size/location of stone, obstruction/hydronephrosis, perinephric stranding)

No imaging ?:
- Pt with known kidney stone, typical presentation, well appearing, no risks for complications and good follow/up
- May treat empirically (pain control, hydration)

Treatment of Renal Colic

Conservative treatment
- Pain control, hydration, expectant stone passage.

NSAIDs
- Inhibits prostaglandin-mediated process in urolithiasis
- As effective as opioids and fewer side effects of nausea and vomiting
- Ketorolac IV or Ketorolac + Opiate combination

Opiates
- In addition to NSAID or if contraindications to NSAID

Hydration & Diuresis
- No evidence that increased hydration or forced diuresis improves pain scores or rate of passage ⇒ Use: replete volume in dehydrated patients or those with elevated creatinine only

Medical Expulsion Therapy:
- CCBs (e.g nifedipine) or α-antagonists (e.g. tamsulosin)
- Mechanism of Action: relax ureteral smooth muscle → allow passage of stone
- Conclusion: Trial of tamsulosin (0.4 mg qd x4 weeks) in stones <10mm is reasonable

Emergent urology consult
- Urosepsis, obstruction with proximal infection, AKI, anuria, intractable pain/vomiting, stones >10mm

Renal Stents
- Use:
  - Facilitate drainage of upper urinary tract and relieve obstruction
  - Temporizing while await stone passage or definitive urological procedure.
- Complications: pain, hematuria, urgency and frequency (more common), upward migration, infection, sepsis (rare)

Infected kidney stone
- Treatment: decompression, emergently by urology or IR
- Admission, hydration, IV antibiotics
- UTI + non-obstructing stone: if well appearing, outpatient antibiotics, urology follow-up

Size of stone	Rate of passage
1 mm	87 %
2-4 mm	76 %
5-7 mm	60 %
7-9 mm	48 %
>9 mm	25 %

Disposition

Admit
- Obstructing stone with a proximal infection, urosepsis, acute renal failure, anuria, or intractable pain, nausea, or vomiting
- Urology consult
Discharge Home
- Stable, tolerating po, pain controlled, nausea/vomiting controlled, outpatient urology follow-up
- Outpatient Urology follow-up:
  - Stone >10mm, failure to pass stone after conservative treatment, pain not controlled

Journal Club: Tamsulosin in ureteral stones

RCT (Arch Intern Med 2010;170:2021)

Study: multicenter, placebo-controlled, randomized, double-blind study of tamsulosin vs placebo (good)
No difference in expulsion delay within 42 days; (P = .30)
No difference in surgical procedure or other secondary end points between groups
Conclusion: “Tamsulosin did not accelerate the expulsion of distal ureteral stones in patients with ureteral colic”

Systematic review (Ann Emerg Med. 2007;50:552)

Previous review suggested increase stone passage rate and decreased time to stone passage with tamsulosin
Critique: Review had poor quality, unblinded studies, poor follow up

Mechanical Low Back Pain

1. Sciatica (ischialgia)

Definition

Peripheral radiculopathy caused by compression of nerve root, usually caused by disc herniation or spinal stenosis

Clinical Presentation of Sciatica

Back pain + neuropathy (paresthesia, sensory loss) down one leg
Unilateral symptoms that extend distal to knee
Sensory > Motor
Single myo/dermatome involved
SLR (Straight leg raise) called Lasègue test or Lazarević’s sign
- Pain when the straight leg is raised to an angle of between 30 and 70 degrees
- Pain must extend below knee
- Sensitivity 91%, Specificity 26% (Spine 25 (9): 1140–7)
Crossed SLR: Raising the opposite leg causes pain on affected side (sensitivity 29%, specificity 88%)

Treatment of Sciatica

90% of acute sciatica responds to conservative treatment
Conservative management: Tylenol / NSAIDS / continue daily activities
Treat similar to lumbar strain except consider Xrays to rule out other causes of nerve compression (tumor, fracture, spondylolisthesis, infection…)
Emergent/Urgent Surgery
- Significant motor deficit (foot drop, unable to ambulate)
- Intractable pain
Indications for outpatient surgery
- Definite herniation on imaging study +
- Corresponding pain syndrome +
- Corresponding neurologic deficit +
- No response to 4-6 weeks conservative treatment

2. Lumbar Strain

General

Diagnosis of exclusion
No further work-up needed