A 74-year-old man comes to urgent care due to persistent back pain at L1 to L4 spinal levels. The patient's symptoms started suddenly while he was having breakfast yesterday. The pain is constant, deep, and dull. He reports no trauma or having had similar pain previously. The symptoms do not change with climbing stairs or lumbar flexion/extension activities. The patient had difficulty falling asleep last night because of increased pain in his lower back. Medical history is significant for hypertension. The patient has a 40 pack-year smoking history, but he does not use alcohol. Medications include amlodipine and enalapril. He is afebrile; blood pressure is 140/90 mm Hg and pulse is 88/min. BMI is 27 kg/m2. Physical examination shows normal range of motion of the spine without point tenderness. Straight leg raise test is normal. The abdomen is soft. Mild tenderness is present with deep palpation from the epigastric to supraumbilical regions. Bowel sounds are normal. Femoral, popliteal, and pedal pulses are symmetric. Erythrocyte sedimentation rate is normal. X-ray of the spine reveals no vertebral abnormalities, but prevertebral calcifications are present. Which of the following is the best next step in management of this patient?
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Patients age >60 years, smokers, men, and those with a history of atherosclerosis or connective tissue diseases are at increased risk for abdominal aortic aneurysm (AAA), which typically causes few symptoms until it markedly expands or ruptures. Pain is the most common initial manifestation and can vary according to aneurysm location. Proximal aneurysms tend to present with upper abdominal, flank, or back pain, whereas distal lesions present with lower abdominal or groin pain. In the event of rupture, hemorrhage usually occurs into the retroperitoneum; because the expanding hematoma may be temporarily contained within the retroperitoneum, patients may remain hemodynamically stable and have a delayed presentation, as in this case.
Other clues to the diagnosis of AAA include a pulsatile abdominal mass (present in slightly over half of patients) and prevertebral aortic calcification on plain x-ray, consistent with extensive atherosclerosis. In symptomatic patients who are hemodynamically stable, the diagnosis should be confirmed with abdominal CT. Hemodynamically unstable patients require emergency surgical repair with confirmation obtained by rapid bedside ultrasound if necessary.
(Choice B) Patients with evidence of musculoskeletal back pain (eg, inciting event, worsened with movement) or lumbar radiculopathy (eg, positive straight leg raise) can be managed conservatively with ibuprofen and rest. However, this patient's unprovoked, sudden-onset lower back pain in the setting of prevertebral calcifications and multiple risk factors for AAA necessitates further investigation.
(Choice C) Spinal MRI is indicated for patients with acute lower back pain and "red flag" features (eg, focal weakness, bowel or bladder incontinence, fever) that suggest serious pathology of the vertebral column (eg, cord compression, epidural abscess).
(Choice D) Serum amylase and lipase are useful in diagnosing acute pancreatitis, which classically presents with epigastric pain radiating to the back (rather than back pain alone). On physical examination, severe epigastric tenderness is expected and hypoactive bowel sounds are commonly present.
(Choice E) Serum protein electrophoresis is used to diagnose multiple myeloma, which may present with bone pain in the back or chest. However, an elevated erythrocyte sedimentation rate is expected and plain x-rays often reveal lytic lesions.
Educational objective:
Pain is the most common manifestation of abdominal aortic aneurysm (AAA), and it can vary according to aneurysm location. Proximal AAA tends to cause upper abdominal, flank, or back pain. In symptomatic, hemodynamically stable patients, the diagnosis is best made by abdominal CT.