A 68-year-old woman with end-stage renal disease receiving intermittent hemodialysis comes to the office due to back pain. She says that she may have "pulled a muscle" while getting out of her car a week ago; since then she has had progressively worsening back pain. She has no leg numbness or weakness but reports malaise and fatigue. The patient also has hypertension and type 2 diabetes mellitus and was treated several weeks ago for staphylococcal bacteremia associated with the dialysis catheter. Her temperature is 38 C (100.4 F). On examination, she has tenderness over the upper lumbar vertebrae without overlying skin changes. The straight leg raise test is negative. Which of the following is the best next step in management of this patient?

Question

A 68-year-old woman with end-stage renal disease receiving intermittent hemodialysis comes to the office due to back pain.  She says that she may have "pulled a muscle" while getting out of her car a week ago; since then she has had progressively worsening back pain.  She has no leg numbness or weakness but reports malaise and fatigue.  The patient also has hypertension and type 2 diabetes mellitus and was treated several weeks ago for staphylococcal bacteremia associated with the dialysis catheter.  Her temperature is 38 C (100.4 F).  On examination, she has tenderness over the upper lumbar vertebrae without overlying skin changes.  The straight leg raise test is negative.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Although this patient believes her back pain may be due to a muscle sprain, her presentation (localized bony back pain, low-grade fever, recent staphylococcal bacteremia) suggests vertebral osteomyelitis. Bacteria can access the spine by hematogenous spread from a distant infection (eg, skin or soft tissue, intravenous catheter), direct invasion from trauma or local spinal procedures (eg, lumbar puncture, spinal surgery), or direct spread from adjacent soft tissue infection. Hematogenous spread is most common as the adult vertebral bone has a very rich and vascular marrow. Increasing age can cause the nutrient arteries to develop a "corkscrew" anatomy, which allows bacteria to more easily penetrate the marrow cavity and cause local infection. Bacteremia due to intravascular devices (eg, hemodialysis catheters) increases risk of health care-related vertebral osteomyelitis. Offending organisms include Staphylococcus (most common is S aureus or coagulase-negative staphylococci) and various gram-negative organisms (eg, Pseudomonas). Vertebral osteomyelitis should be suspected in patients with new or worsening back pain, fever, and recent endocarditis or bacteremia (especially S aureus). It should also be suspected if there are new neurologic findings and fever, with or without back pain. Initial evaluation includes blood cultures and MRI of the spine, which is the most sensitive imaging method for diagnosing vertebral osteomyelitis. (Choice A) Analgesics and close follow-up are recommended for musculoskeletal causes of low back pain, but this patient's clinical findings (fever, localized bony tenderness, recent bacteremia) are concerning for more serious etiologies and require further evaluation. (Choice B) CT myelogram, which can diagnose spinal stenosis or other vertebral pathology (including osteomyelitis), is performed by injecting contrast into the lumbar spine prior to CT imaging. However, it is more invasive than MRI and usually reserved for patients who cannot undergo MRI (eg, those with pacemaker, metallic implants). (Choice C) Lumbar puncture is typically used for diagnosing meningitis and has a low yield for diagnosing vertebral osteomyelitis. CT-guided bone biopsy is usually preferred for isolating the organism after imaging confirms the diagnosis of vertebral osteomyelitis. (Choice E) Serum protein electrophoresis is typically done to evaluate for monoclonal gammopathies (eg, multiple myeloma). Although multiple myeloma can present with back pain, this patient's fever and recent bacteremia make vertebral osteomyelitis more likely. Educational objective: Vertebral osteomyelitis should be suspected in patients with new or worsening back pain, fever, and recent endocarditis or bacteremia (especially Staphylococcus aureus). It should also be suspected if there are new neurologic findings and fever with or without back pain. MRI of the spine is preferred for diagnosis. __________ References: 2015 Infectious Diseases Society of America (IDSA) Clinical Practice Guidelines for the Diagnosis and Treatment of Native Vertebral Osteomyelitis in Adults. (http://www.ncbi.nlm.nih.gov/pubmed/26229122) Health care associated hematogenous pyogenic vertebral osteomyelitis: a severe and potentially preventable infectious disease (http://www.ncbi.nlm.nih.gov/pubmed/25621677)

A 68-Year-Old Woman with End-Stage Renal Disease Receiving Intermittent Hemodialysis