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Clostridium septicum infection is a rare cause of aortic dissection, and the mortality rate for the condition is high. Only 26 cases of C. septicum aortitis have been reported; all of those patients were elderly, and 20 of them had an associated colonic neoplasm. Herein, we present the case of a 22-year-old man whose C. septicum aortitis resulted in aortic dissection that involved the entire length of the aorta. Upon autopsy, no neoplasm or other predisposing condition was identified in this patient. To the best of our knowledge, this is the 1st report of C. septicum aortitis, fatal or otherwise, in a young individual.
Infection is an uncommon cause of aortic aneurysm or dissection, accounting for approximately 2.6% of such cases.1 Staphylococcus aureus and Salmonella are the 2 most common organisms found in mycotic aortic aneurysms.2 Clostridium septicum infection is a very rare cause of aortitis, aneurysm, or dissection; it is typically seen in elderly patients who also have colonic neoplasms, and the mortality rate is high.3,4 In younger individuals, aortic dissection is most commonly associated with inherited connective-tissue defects such as Marfan syndrome; a clostridial cause has not been reported in the medical literature. Here, we report the unusual case of a 22-year-old man who presented with C. septicum aortitis and, soon thereafter, aortic dissection.
In July 2003, a 22-year-old morbidly obese man with a history of hypertension (unmedicated for 2 months) presented at an emergency department with acute onset of pain and loss of sensory and motor function in his lower extremities. He had lower abdominal and rectal pain, but no chest pain. He described the pain severity as 4 to 5 on a scale of 10. Upon initial examination, his feet were cool and mottled, and no pedal pulses were palpable. His legs and feet were swollen. His family history included deep vein thrombosis and “easy clotting.” The patient was believed to have arterial insufficiency, and a continuous heparin infusion was administered. He was transferred to our facility within 4 hours of initial presentation.
Upon the patient's arrival, his vital signs were blood pressure, 144/49 mmHg; heart rate, 157 beats/min; respiration rate, 22 breaths/min; and temperature, 35.4°C. His oxygen saturation fell to below 90% on room air. Physical examination confirmed the findings at the other hospital: both legs were cool, with decreased sensation and strength. Upon Doppler ultrasonography of the femoral arteries and their distal distributions, no pulse was detected in either leg. Laboratory evaluation showed marked leukocytosis (27.3 ×109/L) with a left shift (23% bands), a myoglobin level of >2,000 ng/mL (reference range, 0–110 ng/mL), a bicarbonate level of 18 mEq/L (reference range, 23–29 mEq/L), a lactic acid level of 8.9 mMol/L (reference range, 0.7–2.1 mMol/L), an international normalized ratio of 1.3, and a partial thromboplastin time of 85 sec (on heparin). On the basis of the physical findings and the absence of chest pain, computed tomographic (CT) angiography of the abdomen was ordered. It revealed occlusive thrombosis of the distal aorta, approximately 3 cm below the origin of the inferior mesenteric artery and likely extending into the bilateral common iliac arteries (Fig. 1). Infarction of the lower pole of the right kidney and a small pericardial effusion were noted; however, there was no evidence of bowel ischemia, and the descending thoracic and abdominal segments of the aorta were of normal diameter (2 cm). The patient was taken to the surgical intensive care unit, where bedside echocardiography was performed. Angiographic thrombolysis and an evaluation for inherited hypercoagulable conditions were planned for the patient, with long-term anticoagulation the anticipated treatment. However, while the echocardiographic results were pending, and before the patient was transferred to interventional cardiology, he experienced cardiopulmonary arrest. Despite resuscitative efforts, the patient's cardiac rhythm showed pulseless electrical activity and deteriorated to an agonal rhythm. He was pronounced dead within 8 hours of initial presentation.
Postmortem examination revealed acute aortic dissection that involved the entire length of the aorta, with the distal portion occluded by a large blood clot in the false lumen (Fig. 2). The aortic valve had 3 cusps, and the valve and root were dilated (aortic valve circumference, 11.1 cm vs an expected 6–8.5 cm). There was a 5.5-cm transverse intimal tear in the dilated ascending aorta, rupture into the pericardial sac, and massive hemopericardium. No signs of Marfan syndrome were present. There was no aortic atherosclerosis. No malignancy was seen. The gastrointestinal tract was normal. Microscopic sections showed acute aortitis that involved the outer media and adventitia, with gram-positive rods in the aortic wall (Figs. 3 and and4).4). There was no evidence of basophilic degeneration of the aortic wall, which indicated that the aortic infection was the cause of the aneurysmal dilation. No other site of infection was present, and no portal of entry was found. A postmortem anaerobic blood culture grew C. septicum. The echocardiogram was suboptimal, but the ascending aorta appeared aneurysmal at 6 cm in diameter. The abdominal CT angiogram, performed 2 hours before the patient's death, was reviewed; it revealed an enlargement of the aortic root at and above the aortic valve. On the basis of a Hounsfield unit of 62, there was blood in the pericardial sac (estimated volume, 80–100 mL). No dissection flap was identified.
Clostridium septicum is a gram-positive, spore-forming, highly motile, obligate anaerobe. Spontaneous infection often manifests itself as gas gangrene, atraumatic myonecrosis, or fulminant sepsis.5 The organism produces exotoxins, and the α-toxin is responsible for hemolysis and myonecrosis. Although C. septicum accounts for only 1.3% of all clostridial infections,3 it is clinically important, in part because of its strong association with gastrointestinal and hematologic malignancies (up to 85%).5 It has been postulated that the low pH and reduced oxidation–reduction potential in necrotic tumors provides a favorable environment in which clostridia can thrive, and that a compromised bowel mucosa provides a portal of entry into the bloodstream.6,7
Our review of the medical literature revealed only 26 cases of C. septicum aortitis,4,8–13 and all of those patients were older, with a median age of 75 years (range, 55–91 yr). Aortic aneurysms were found in 22 patients, and the abdominal aorta was involved in 15 (68.2%). Aortic dissection was present in 2 patients—1 occurrence involved the ascending aorta and the aortic arch, and the other involved the entire aorta, as in our patient. Existing aortic atherosclerosis has been suggested as the site of clostridial colonization,8,14 and this partly explains the occurrence of aortitis in the elderly. Colonic carcinoma was present in 18 of the 26 patients (69.2%), and polyps were present in 2 other patients. The prognosis for persons who have C. septicum aortitis is generally poor: 14 patients (53.8%) died of the aortitis or its complications.
The typical presentation of C. septicum aortitis includes fever, lower abdominal or back pain, and leukocytosis. Upon physical examination, an abdominal mass may be palpated. At this point, abdominal CT scanning is often performed, and it may show aortic aneurysm, inflammatory changes, or a tumorous mass. When periaortic gas formation is noted, C. septicum aortitis should be strongly suspected, and appropriate treatment should be initiated.
The treatment of C. septicum aortitis is chiefly surgical, including resection and repair of the involved aortic segment, débridement of necrotic tissue, and prolonged antibiotic therapy.4,12 All of the patients who initially survived the disease underwent vascular surgery (in situ graft replacement or extra-anatomic bypass, depending on the location of the aortitis).4,10,12 Reducing the risk of death requires early diagnosis, antibiotic therapy, and appropriate surgical intervention. Unfortunately, the correct diagnosis—which ultimately relies on the results of a bacterial culture—was delayed in almost every reported instance. Without appropriate surgery, the condition is almost always fatal. A postmortem examination can establish or confirm the diagnosis.
In our patient, the physical findings, the lack of chest pain, and the family medical history led to a clinical diagnosis of distal aortic thrombosis, which was presumed to be due to an underlying inherited hypercoagulable condition. Unfortunately, the course of his disease was rapidly fatal, and its true nature was identified only upon autopsy.
We believe that this is the 1st report of C. septicum aortitis, fatal or otherwise, in a young individual.
Address for reprints: No reprints will be available from the authors.
This case was presented in poster format during the College of American Pathologists' 2007 Annual Meeting (Chicago).