A 55-year-old man with prior remote anterior cervical neck surgery presented with two months of intermittent back pain and one month of generalized fatigue and chest swelling. He reported throwing his back out around two months before and had had intermittent back pain since then, but the pain had worsened in the past month. He had also noted increased swelling to his left anterior neck and upper chest that had gradually worsened, and was associated with some decreased appetite and fatigue. The patient had not seen a doctor in 15 years.
He was lying in bed comfortably. His vital signs were notable for a heart rate of 112 bpm, a blood pressure of 93/78 mm Hg, a respiratory rate of 16 bpm, an SPO2 of 95%, and a temperature of 36.8°C. He had nonreproducible back pain, with 2+ radial pulses and 1+ DP pulses bilaterally. He had no focal abdominal pain. The patient also had a 4 cm area of induration from the left upper chest to the proximal left neck, but had clear breath sounds bilaterally.
Lab results were notable for a WBC count of 24.4, a hemoglobin of 11.4 gm/dL, a sodium of 118 mEq/L with a glucose of 600 mg/dL, and a lactate of 3.0 mmol/L. Blood cultures were sent, and the patient was started on broad-spectrum antibiotics and fluids. A CT head without contrast and neck, chest, abdomen, and pelvis CT scans with contrast were ordered. What is the diagnosis?
Find that and the case discussion on the next page.
Diagnosis: Mycotic Aortic Aneurysm
A mycotic aortic aneurysm, defined as an aortic aneurysm caused by infection, most commonly develops through microbial inoculation of the diseased aortic endothelium during bacteremia. (Clin Med Insights Cardiol. 2018;12:1179546818759678; http://bit.ly/2Q29bkv.) Its spread into the arterial wall is most common in immunocompromised patients such as those with diabetes, as was the case with our patient. Bacterial endocarditis is a frequent etiology in these patients, and commonly involves gram-positive cocci as the causative agent. Symptoms can often be insidious with vague complaints, particularly when it involves the aorta. (Ann Vasc Dis. 2010;3:7; http://bit.ly/3cHbPWx.)
The diagnosis of mycotic aneurysm is complicated and typically involves a combination of fever, leukocytosis, positive blood cultures, and suggestive radiology findings including saccular outpouching of the aorta, a multilobular appearance, calcification, and mural thrombosis. Treatment typically involves surgical repair with open or endovascular repair and graft placement. The mortality rate remains high, however, even with repair, which ranges from 15-50 percent. (Clin Imaging. 2016;40:256.)
Our patient's CT was notable for a 6.6 cm abdominal aortic aneurysm that had ruptured into the retroperitoneum along with a 4 cm chest wall abscess of the left chest under the area of the mass. He went to the OR directly from the emergency department for endovascular repair of the aortic aneurysm with an aortic endograft, as well as incision and drainage of the chest wall abscess. Initial blood cultures grew 2/2 positive for Streptococcus pneumoniae, and a transthoracic echocardiogram on postoperative day one demonstrated an aortic valve vegetation concerning for endocarditis. These findings, combined with the radiographic findings, suggested that this was a mycotic aneurysm.
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Dr. Noackis a third-year emergency medicine resident at Denver Health Medical Center.