Worsening Back Pain in an Injection Drug User

December 31, 2006

For several weeks, a 29-year-old woman has had worsening left lower backpain that is aggravated by sitting and walking. The pain is most severe aboveher left buttock; it radiates into the buttock and very slightly into the leg. Overthe-counter analgesics have been ineffective. Assuming a supine position providessome relief, but the pain still occasionally awakens her at night. She deniesweakness, other neurologic symptoms, and any symptoms of bowel orbladder dysfunction.

For several weeks, a 29-year-old woman has had worsening left lower backpain that is aggravated by sitting and walking. The pain is most severe aboveher left buttock; it radiates into the buttock and very slightly into the leg. Overthe-counter analgesics have been ineffective. Assuming a supine position providessome relief, but the pain still occasionally awakens her at night. She deniesweakness, other neurologic symptoms, and any symptoms of bowel orbladder dysfunction.HISTORY
Medical history is noncontributory. However, the patient uses both cocaineand intravenous heroin and supports her habit through prostitution. Shereports that the results of an HIV test performed within the last year or sowere negative.PHYSICAL EXAMINATION
The patient appears well-nourished. Temperature is 38.3oC (101oF), heartrate is 92 beats per minute, and blood pressure is normal. There are no oral lesionsor neck adenopathy. Chest is clear, and heart rate and rhythm are regular,with a soft systolic ejection murmur along the left sternal border. The liverand spleen are not enlarged. Palpatory percussion of the left sacroiliac and buttockregion reveals diffuse tenderness. Range of motion in the left leg is somewhatlimited by pain, but there are no definite neurologic deficits or findings.Anal sphincter tone is intact.LABORATORY RESULTS
Results of a serum chemistry panel and urinalysis are normal. Hemoglobinlevel is 10.3 g/dL, and white blood cell count is 11,100/μL, with a normaldifferential.Which of the following is the most appropriate initial managementstrategy?A. Consult immediately with a neurosurgeon for evaluation and likelysurgical intervention.B. Prescribe bed rest and NSAIDs and discharge the patient; reevaluatein 3 weeks.C. Evaluate thoroughly for systemic causes of back pain.D. Order plain lumbosacral radiographs, and refer to ananesthesiologist/pain specialist for a course of epidural corticosteroidtherapy for spinal stenosis.CORRECT ANSWER: C
Low back pain is one of the most common clinical problemsseen in medical practice. In the United States,it also consistently ranks high as a source of health-relatedexpenditures and as a cause of workplace disability.1In the workup, first focus on the symptoms of typicallow back problems (eg, back pain only, sciatica, claudication);then differentiate between simple and "complicated"back pain based on the associated clinical findings. Thetiming, aggressiveness, and specific nature of the evaluationwill follow from such an approach.Most causes of back pain are benign and self-limited.In 80% of patients with back pain who are seen in theacute phase, the pain resolves within 2 weeks.1 Studieshave shown that in most patients with back pain--eventhose with suspected disk disease--a conservative approachto diagnosis and treatment yields excellent results.2Thus, even if radiculopathy resulting from mechanicalback disease were the sole cause of this patient'ssymptoms (and, as will be discussed below, there is ampleevidence it is not), immediate referral for a neurosurgicalevaluation (choice A) is likely too aggressive at this time.Most patients with disk disease do not require neurosurgeryand should first be offered conservative therapy unlessthe symptoms are bilateral or are associated with urinaryretention (which suggests cauda equina syndrome).On the other hand, reassuring this patient and allowingher to return home with a prescription for NSAIDs(choice B) is likely not aggressive enough. In patientsyounger than 50 years who have no neurologic deficit andno systemic disease and/or risk factors (eg, history orfindings on examination that suggest neoplasm, active infection,or injection drug use), simple conservative therapyfor 6 weeks, without diagnostic testing, is a reasonablestrategy. However, this patient's history of current injectiondrug use and symptoms of at least several weeks'duration suggest that further evaluation is indicated.Spinal stenosis is an increasingly common cause ofback pain, especially in patients older than 65 years. Thispatient is too young for this entity. Moreover, unlike thepain of spinal stenosis, her pain worsens--rather than improves--when she sits. In addition, she has no claudication;her symptoms are focused in the sacroiliac joint andbuttock and do not affect the legs. Even if spinal stenosiswere a reasonable possibility, plain radiographs would notbe the optimal diagnostic study. The compromise of centralneural tissue that is characteristic of spinal stenosis isbetter detected by myelography, CT, or MRI; currently,MRI is preferred because it is more sensitive and less invasive.Thus, choice D (order plain radiographs and referfor therapy for spinal stenosis) is incorrect on 2 counts.Thorough evaluation for systemic causes of backpain (choice C) is the optimal strategy for this patient. Shehas a history of injection drug use, a fever, and leukocytosis.These findings strongly suggest "complicated" backpain; additional "red flags" include age older than 50years, weight loss, cancer, hematuria, and other systemicsigns and/or symptoms.3 In patients with any one of thesefindings, there is an increased probability (1% to 10%) thatserious systemic disease, such as tumor or infection, isthe cause of their back symptoms3; thus, a more aggressivemanagement strategy is warranted.Most clinicians would begin by obtaining radiographsand usually an MRI scan. Here, because the history suggeststhat infection is the most likely cause of the patient'ssymptoms, blood cultures and an echocardiogram shouldbe ordered as well. In older patients, studies that screenfor malignancy might be the appropriate next step.Outcome of this case. The patient revealed that shehad been admitted 18 months earlier for similar symptomsand that intravenous antibiotics had been administered.She left the hospital against medical advice afterabout 2 weeks because she felt better (her physicians hadsuggested 4 to 6 weeks of treatment).During her latest admission, an MRI scan revealedfindings consistent with sacroiliac joint infection and continuousosteomyelitis in the iliac and sacral bones. Bloodculture results were positive for Staphylococcus aureus sensitiveto methicillin, quinolones, and clindamycin. A 6-week course of antibiotics is planned.

References:

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