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Contiguous arterial infections are extremely rare, and their actual rate of occurrence is not known. These infections occur as a result of direct invasion of an artery from an adjacent septic focus. Reaching the diagnosis of infected aorta is very difficult when there are contiguous infections from spondylitis or psoas abscess, because the clinical features are nonspecific. Although computed tomography is the most useful diagnostic tool in the detection of aortic infections, the most frequent findings mimic those of other diseases, such as retroperitoneal fibrosis, lymphoma, and periaortic lymphadenopathy. Diagnosis becomes even more challenging when an infected aorta is of normal diameter.
Herein, we report the case of a 64-year-old man who experienced nonaneurysmal abdominal aortic rupture due to spondylitis and psoas abscess. Despite appropriate surgical management, the patient later died. We review the relevant medical literature and examine specific considerations that surround the diagnosis and treatment of this rare condition.
The overall incidence of primary infection of an abdominal aortic aneurysm is approximately 2% to 3%.1–3 The most common culprit organisms are Staphylococcus aureus and Salmonella.4 Contiguous arterial infections are extremely rare, and their exact incidence is not known. Most are secondary to the adjacent osteomyelitis. We report the case of a patient who experienced a nonaneurysmal rupture of the abdominal aorta secondary to spondylitis, and we discuss the diagnosis and treatment of this rare condition.
In January 2008, a 64-year-old man was admitted to our emergency department with back pain, fever, and fatigue. Initial laboratory analysis revealed a white blood cell count of 17,000/mm3, a hemoglobin level of 10.1 g/dL, a creatinine level of 1.2 mg/dL, and a C-reactive protein level of 32 mg/L. Other hematology and chemistry test results were normal. Computed tomography and lumbar magnetic resonance imaging showed lumbar spondylitis that involved the corpus of the L3, L4, and L5 vertebral bones, and bilateral psoas muscle abscesses with filling of pre- and paravertebral spaces (Figs. 1 and and2).2). The abscesses were percutaneously drained. Cultures obtained from the abscess cavity were positive for methicillin-sensitive Staphylococcus aureus (MSSA), and the patient was started on appropriate intravenous antibiotic therapy. The patient became afebrile, and his white blood cell count gradually decreased. He was discharged from the hospital after 21 days, without any evidence of infection, on a regimen of oral antibiotics.
Four days later, the patient was readmitted due to lethargy and confusion. He was mildly hypotensive, and he had right-leg swelling and cyanosis. The distal pulses of the right leg were absent. Laboratory analysis revealed leukocytosis, anemia, and elevated creatinine and potassium levels (white blood cell count, 20,000/mm3; hemoglobin level, 7.2 g/dL; creatinine level, 4 mg/dL; blood urea nitrogen, 91 mg/dL; and potassium, 7 mg/dL). Emergency hemodialysis was performed. A Doppler ultrasonographic study showed deep vein thrombosis of the right leg. Computed tomography, which was performed in order to look for the possible cause of anemia, detected the rupture of a nonaneurysmal aorta at the level of the aortic bifurcation (Figs. 3 and and44).
The patient was taken for emergency surgery. A midline laparotomy was performed, and the retroperitoneum was exposed. Proximal and distal control of the abdominal aorta was obtained by use of nylon tapes, and heparin was administered. The proximal aorta was cross-clamped just below the renal artery orifices. The retroperitoneal space was fully entered. Fresh and old thrombi, necrotic tissues, and pus were evacuated. A large perforation was identified at the posterior wall of the aorta at the bifurcation. An aortic segment that was still infected with MSSA was resected. Necrotic and infected tissues were débrided; cultures obtained from these tissues showed infection with MSSA. In situ reconstruction was performed with use of a Dacron 16/8-mm aorto-biiliac Y graft. The graft and suture lines were covered with omentum for protection against graft infection. The laparotomy was closed in standard fashion. The patient's hemodynamic levels were stable, and he was transferred to the intensive care unit. In the postoperative period, the patient developed renal failure that required hemodialysis, and he died of multiorgan failure 21 days after the operation.
In cases of aortic rupture, the incidence of aortic infection has been very low, due to the use of wide-spectrum antibiotics. Early diagnosis, extensive surgical intervention, and appropriate antibiotic therapy are the mainstay of treatment.3,5,6 However, the mortality rate associated with aortic infection is still 20% to 40%.6,7 The virulence of the infecting organism, the severity of the infection, and the patient's severe state of shock are the primary determinants of clinical outcome.8 Immunocompromised men aged 50 to 70 years who have an atheromatous or aneurysmal aorta are most susceptible to aortic infections.2
Reaching the diagnosis of infected aorta is very difficult when there are contiguous infections from spondylitis or psoas abscess. A high index of suspicion is necessary, because clinical features are nonspecific: fever, back or abdominal pain, leukocytosis, and (rarely) pulsatile abdominal mass.8 Computed tomography is the most useful diagnostic tool in the detection of aortic infections; the most frequent findings are periaortic gas accumulation, lymph node enlargement, disruption of mural calcification, retroaortic sparing, periaortic soft-tissue-density enhancement, and renal infarcts.9,10 However, these findings can be confused with those of other diseases, such as retroperitoneal fibrosis, lymphoma, and periaortic lymphadenopathy.11
Diagnosis becomes even more challenging when an infected aorta is of normal diameter, because this circumstance is very rare, and the clinical symptoms are nonspecific. Furthermore, aortic involvement with the infection is not usually suspected until an aneurysm develops or ruptures.
In our patient, the diagnosis of spondylitis and psoas abscess was made easily, on the basis of the magnetic resonance imaging findings. Antibiotic treatment was started immediately, but aortic rupture occurred nonetheless, 3 weeks later.
Salmonella and S. aureus are well-known causes of vascular infections.2,12 However, mycobacterium tuberculosis is the microorganism that is most frequently found to cause contiguous arterial infections.13 Long and colleagues13 reviewed 39 cases of tuberculous mycotic aortic aneurysms and concluded that 30 of them were secondary to a contiguous septic focus.
McHenry and associates14 studied 70 cases of vertebral osteomyelitis and contiguous arterial infections and reported that the most commonly involved microorganisms were Salmonella (in 27% of the cases) and mycobacterium (in 24%). Aortic infection due to Streptococcus has been reported by Worrell and colleagues.15 The incidence of anaerobes is probably underestimated because of the isolation difficulties in culture media. Antibiotic agents should be given for at least 6 weeks to patients who have Salmonella infections, due to high recurrence rates.2
The treatment for contiguous aortic infections is primarily surgical. Surgical management involves resection of the involved arterial segment, extensive débridement of infected tissue, and drainage of abscesses. Alternative surgical approaches are possible for reconstruction of the resected aortic segment: extra-anatomic bypass grafting with aortic stump closure, or in situ replacement with deep leg veins, homografts, or prosthetic grafts.16–18 Extra-anatomic reconstruction does not eliminate the risk of graft infection or aortic stump blowout, especially in patients with spondylitis.2 In our experience, arterial homografts are not totally safe alternatives for in situ replacement, due to the high occurrence of rupture—we previously used 3 cryopreserved aortic homografts for prosthetic-graft infections of the abdominal aorta, and 2 of the homografts ruptured, 3 and 4 months after the operation, respectively. Acceptable long-term results have been reported by Hollier19 and Fichelle20 and their associates for in situ prosthetic replacement. Fichelle and co-authors20 reported some criteria for successful in situ reconstruction of the aorta: preoperative diagnosis, complete resection of the aorta and surrounding infected tissues, and omental coverage of prosthetic graft and suture lines. Because we were able to meet these operative criteria, we chose to perform an in situ replacement. Because of the delay in diagnosis, the patient died, despite appropriate surgical management.
In conclusion, the combination of contiguous arterial infection and ruptured nonaneurysmal aorta is seen very rarely. A high index of suspicion and frequent follow-up imaging are essential in order to detect the infection, because early diagnosis before rupture can avert an adverse outcome.
Address for reprints: Hakan Posacioglu, MD, Department of Cardiovascular Surgery, Ege University Medical Faculty, 35100 Bornova–Izmir, Turkey. E-mail: moc.oohay@ulgoicasop