Differentials
Spinal stenosis
SIGNS / SYMPTOMS
Numbness, weakness in lower extremities, pain radiating to buttock and leg (especially if the pain radiates beyond the knees), and neurogenic claudication. Spinal stenosis is often bilateral.
INVESTIGATIONS
Lumbar MRI, CT, or myelography shows spinal canal narrowing.
Electromyogram shows elevated insertional activity, fibrillation/sharp waves, and lower recruitment.
Radiculopathy/sciatica
SIGNS / SYMPTOMS
Numbness, weakness in lower extremities, pain radiating to buttock and leg (especially if the pain radiates beyond the knees). Radiculopathy/sciatica is often unilateral.
INVESTIGATIONS
Abnormal or asymmetric patellar, hamstring, or ankle reflex.
Positive straight-leg raise test.
Lumbar MRI or myelography shows disk protrusions or foraminal narrowing that impinges on nerve root(s).
Lumbar CT shows foraminal narrowing; may not be able to see acute herniation because nerves or disk not visible.
Electromyogram shows elevated insertional activity, fibrillation/sharp waves, and lower recruitment.
Cauda equina syndrome
SIGNS / SYMPTOMS
Signs and symptoms include gastrointestinal/genitourinary incontinence or retention, saddle anesthesia, and sudden unexplained bilateral lower-extremity weakness.
INVESTIGATIONS
MRI is the best test to show compression of cauda equina.
If urinary retention is absent the likelihood of cauda equina is <1/10,000.[80]
Spinal neoplasia
SIGNS / SYMPTOMS
May be suspected when nocturnal pain and weight loss occurs, particularly if lower back pain does not improve after 6 weeks of conservative treatment.
INVESTIGATIONS
Spine x-ray may demonstrate lysis of the vertebral body or posterior elements; metastases may cause destruction of the pedicle resulting in the winking owl sign.
Spine MRI may show either a lytic or blastic lesion with varying T2 signal intensity.
Erythrocyte sedimentation rate may be elevated.
Bone scan can identify area of turnover possibly representing primary or metastatic disease.
Abscess, osteomyelitis, or septic diskitis
SIGNS / SYMPTOMS
Patients may present with recent urinary tract or skin infection, immunosuppression, or fever.
INVESTIGATIONS
MRI can identify abscess, osteomyelitis, or diskitis.
Erythrocyte sedimentation rate and CRP may be elevated.
Ankylosing or psoriatic spondylitis, or reactive arthritis
SIGNS / SYMPTOMS
Morning stiffness lasting >60 minutes, improvement of symptoms with physical activity, and awakening at night due to lower back pain may suggest these inflammatory arthritides.
INVESTIGATIONS
A positive Schober test showing a lack of spinal flexibility suggests ankylosing spondylitis, although this is nonspecific.
Erythrocyte sedimentation rate and CRP levels may be elevated.
A positive result for the human leukocyte antigen (HLA)-B27 test suggests these conditions.
Pelvic and spine x-ray can show sacroilitis and bamboo spine.
Spinal compression fracture
SIGNS / SYMPTOMS
Spine tenderness on palpation, particularly in older patients with a history of steroid treatment and/or osteoporosis.
INVESTIGATIONS
Lumbosacral x-ray can show fractures.
Spine CT can more clearly define bony pathology.
Abdominal aortic aneurysm
SIGNS / SYMPTOMS
Sudden onset of intermittent or continuous abdominal pain, radiating to the back; patient may collapse.
INVESTIGATIONS
Ultrasound/CT of the abdomen can show the presence of abdominal aortic aneurysm.
Nephrolithiasis
SIGNS / SYMPTOMS
Pain typically radiates toward the groin.
INVESTIGATIONS
CT urogram and renal ultrasound results are diagnostic.
Pyelonephritis
SIGNS / SYMPTOMS
Patients may present with costovertebral angle tenderness and urinary symptoms of dysuria, frequency, and hesitancy; flank pain may radiate to back; fever, chills, fatigue may be present.
INVESTIGATIONS
Positive urinalysis and/or urine culture.
Sacroiliac (SI) pathology
SIGNS / SYMPTOMS
In addition to lower back pain, pain is also common in the buttocks and upper thighs.
INVESTIGATIONS
Tenderness to palpation at the SI joint and positive result for the FABER (flexion, abduction, and external rotation) and Gaenslen (maximal hip flexion plus contralateral hip extension) tests may suggest SI joint dysfunction.
Pelvic and lumbar spine x-ray can show sclerotic changes and joint widening.
Pelvic and lumbar spine CT can show sclerosis, spurring, and subluxation.
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