Question

A 68-year-old man is admitted to the hospital due to a 4-week history of progressively worsening lower back pain. The pain is localized to the lower lumbar area, is dull and constant, and frequently awakens him from sleep. It is not relieved by rest or over-the-counter ibuprofen. He has a history of type 2 diabetes mellitus and benign prostatic hyperplasia. Six weeks ago, he underwent a transurethral resection of the prostate. His temperature is $38.2^\circ\text{C}$ ($100.8^\circ\text{F}$), blood pressure is $135/85\text{ mmHg}$, pulse is $88/\text{min}$, and respiratory rate is $14/\text{min}$. Physical examination reveals exquisite point tenderness over the L4 and L5 spinous processes. Neurological examination of the lower extremities shows 5/5 motor strength, normal sensation, and 2+ symmetric deep tendon reflexes. Anal sphincter tone is normal. Laboratory studies show a leukocyte count of $11,500/\text{mm}^3$, an erythrocyte sedimentation rate of $85\text{ mm/h}$, and a C-reactive protein level of $72\text{ mg/L}$. Magnetic resonance imaging of the lumbar spine reveals fluid in the L4-L5 intervertebral disc space with T2 hyperintensity and gadolinium enhancement of the adjacent vertebral endplates. Blood cultures are drawn on admission. Forty-eight hours later, the blood cultures show no growth, and the patient's clinical status remains unchanged. Which of the following is the most appropriate next step in management?