BACK PAIN, LOW   42A

A 45-year-old man presents to the urgent care clinic complaining of low back pain. He was moving heavy boxes at work the day before when he had a sudden onset of low back pain that radiates down into his left buttock and left posterior thigh. His medical history is unremarkable, and he takes no medications. He denies bowel and bladder incontinence. On physical examination, he has decreased sensation on the posterior left thigh, decreased strength on left ankle dorsiflexion, and an absent left ankle jerk deep tendon reflex. He has no saddle anesthesia and normal rectal tone. His straight-leg raise test result positive, with pain reproduced on passive elevation of the right (contralateral) leg.

What are the salient features of this patient’s problem? How do you think through his problem?

Salient features: Acute onset of low back pain; radiation down the left buttock and posterior thigh with decreased sensation and loss of ankle jerk reflex; positive straight-leg raise test result (suggestive of disc herniation); no warning signs of cauda equina syndrome

How to think through: Acute low back pain is common in both primary care and emergency medicine settings. The challenge is to identify the high-risk patient who needs urgent further evaluation from the low-risk patient who may be equally uncomfortable but for whom a trial of conservative management is appropriate. Even with an apparent mechanical cause, key risk factors must be assessed. What are the major causes of high-risk back pain? (Infection [vertebral osteomyelitis, epidural abscess], metastatic cancer, rheumatologic spondylitis, cauda equina syndrome, fracture.) This patient has no notable medical history, history of cancer, corticosteroid use, or osteoporosis. What additional risk factor must be assessed? (Injection drug use.) What are the key “red flag” symptoms to elicit? (Fever, weight loss, nocturnal pain, change in bowel or bladder function, lower extremity or sphincter weakness.) What is the most likely cause of this patient’s pain? (An L5–S1 radiculopathy, likely caused by disk herniation. Less likely causes, given his age, include pyriformis syndrome, osteoarthritis, and fracture.) What examination finding specifically supports the diagnosis of disk herniation? (Positive contralateral straight-leg raise.) Should he receive imaging? (No. He is very likely to improve with conservative management, including nonsteroidal antiinflammatory drugs [NSAIDs], heat, and physical therapy, within 6 weeks.)

BACK PAIN, LOW   42B

What are the essentials of diagnosis and general considerations regarding low back pain?

Essentials of Diagnosis

A precise diagnosis cannot be made in the majority of cases even when anatomic defects are present because such defects are common in asymptomatic patients.

Most patients with acute onset of low back pain will improve in 1 to 4 weeks and need no evaluation beyond the initial history and physical examination.

General Considerations

Low back pain is exceedingly common; it is experienced at some time by up to 80% of the population.

Chronic low back pain from degenerative joint disease is rare before age 40 years.

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