Evolution of the infected abdominal aortic aneurysm: CT observation of early aortitis

Features of infective native aortic aneurysms on computed tomography

Background

Infective native aortic aneurysm (INAA) is a rare clinical diagnosis. The purpose of this study was to describe the CT findings of INAAs in detail.

Methods

This was a retrospective single-center study of INAA patients at a major referral hospital between 2005 and 2020. All images were reviewed according to a protocol consisting of aneurysm features, periaortic findings, and associated surrounding structures.

Results

One hundred and fourteen patients (mean age, 66 years [standard deviation, 11 years]; 91 men) with 132 aneurysms were included. The most common locations were infrarenal (50.8%), aortoiliac (15.2%), and juxtarenal (12.9%). The mean transaxial diameter was 6.2 cm. Most INAAs were saccular (87.9%) and multilobulated (91.7%). Calcified aortic plaque was present in 93.2% and within the aneurysm in 51.5%. INAA instability was classified as contained rupture (27.3%), impending rupture (26.5%), and free rupture (3.8%). Rapid expansion was demonstrated in 13 of 14 (92.9%) aneurysms with sequential CT studies. Periaortic inflammation was demonstrated as periaortic enhancement (94.7%), fat stranding (93.9%), soft-tissue mass (92.4%), and lymphadenopathy (62.1%). Surrounding involvement included psoas muscle (17.8%), spondylitis (11.4%), and perinephric region (2.8%). Twelve patients demonstrated thoracic and abdominal INAA complications: fistulas to the esophagus (20%), bronchus (16%), bowel (1.9%), and inferior vena cava (IVC) (0.9%).

Conclusion

The most common CT features of INAA were saccular aneurysm, multilobulation, and calcified plaques. The most frequent periaortic findings were enhancement, fat stranding, and soft-tissue mass. Surrounding involvement, including psoas muscle, IVC, gastrointestinal tract, and bronchi, was infrequent but may develop as critical INAA complications.

Acute non-traumatic disease of the abdominal aorta

Acute pathology in the abdominal aorta is associated with significant morbidity and mortality. The most feared complication of abdominal aortic disease is acute rupture in the setting of atherosclerotic abdominal aortic aneurysm. Although frank rupture often is easily diagnosed on CT, other findings such as a hyperattenuating crescent, discontinuous intimal calcium, and draping of the aorta are subtle signs of aneurysm instability. A true aneurysm should be distinguished from a rapidly growing, saccular pseudoaneurysm in the setting of infectious aortitis, as treatment strategy differs. Acute aortic syndrome involving the abdominal aorta, such as dissection and intramural hematoma, often is an extension of thoracic aortic disease, whereas penetrating atherosclerotic ulcers occasionally involve only the abdominal aorta. The goal of treating acute aortic pathology is to repair and prevent rupture, as well as restore and maintain perfusion of the lower extremities, kidneys, and mesentery. However, both open and endovascular repair of the abdominal aorta may become acutely complicated, resulting in compromise of these goals. Examples include aortoenteric fistula, endoleak, anastomotic pseudoaneurysm, graft infection, and thrombosis or kinking of a stent graft resulting in ischemia of the limbs and mesentery.

A Case of Superior Mesenteric Artery Aneurysm Mimicking an Abdominal Aortic Aneurysm and Presenting as a Pulsating Abdominal Mass

A 62-year-old male with a smoking history of 30 pack-years presented with a 1-year history of a periumbilical pulsating mass. He had been treated for hypertension for 2 years. Physical examination revealed a huge pulsating mass in the periumbilical abdomen. Femoral and popliteal arterial pulses were palpable. Computed tomography showed arterial dissection in the proximal segment of the superior mesenteric artery, a huge aneurysm (52×50 mm) with mural thrombus and two smaller aneurysms (20×20 mm) in the right ileocolic and ileal branches, along with atherosclerotic changes. Interposition using the great saphenous vein was performed after aneurysmal isolation and ligation of jejunal branches in the sac. Distal flow was reestablished by end-to-end and end-to-side anastomoses of the right ileocolic and ileal branches, respectively. No complications were observed at 1-year follow-up.

An immunosuppressed man with an aortic rupture secondary to Salmonella aortitis successfully treated with endovascular aortic repair

A 75-year-old immunosuppressed man presented with fever and central abdominal pain 3 weeks after having positive blood cultures for Salmonella enteritidis. A computed tomography scan demonstrated a contained perforation of a nonaneurysmal abdominal aorta. Salmonella aortitis was suspected, and given his recent history of coronary artery stent insertion, endovascular aortic repair was performed, with lifelong antibiotic therapy. At 6 months, there were no remaining clinical or radiological concerns for aortitis or aneurysmal development. This case highlights the high index of suspicion required for aortitis in immunosuppressed patients and verifies endovascular aortic repair, an appropriate alternative in patients with severe comorbidities.

Escherichia coli primary aortitis presenting as sequelae of incompletely treated urinary tract infection

We report a rare case of nonaneurysmal infectious aortitis (IA) with the causative microorganism being Escherichia coli. The patient was a 78-year-old man who presented with a 3-week history of abdominal pain, fevers, and anorexia after treatment for a urinary tract infection. The patient had positive blood cultures and a computed tomography scan that had signs of IA. He was treated with intravenous antibiotics and extra-anatomic revascularization with excision and debridement of the infected aortic segment with a good outcome. IA is an uncommon condition with a high mortality rate; however, if diagnosed early, it can be successfully treated.

Pseudoaneurysmal formation in abdominal aorta associated with Escherichia coli infection

Early and accurate diagnosis of infective aortic aneurysms (IAA) is critical for adequate treatment to optimize patient outcome. We report the case of an 84-year-old man who complained of severe back pain with high fever and was finally diagnosed as Escherichia coli-related IAA. Computed tomography showed a periaortic soft tissue density and irregular fringe adjacent to the non-dilated abdominal aorta suggesting the presence of pseudoaneurysm. In addition to intravenous antibiotic injection, an aneurysmectomy with extensive debridement and an in situ graft, were successfully performed. The case emphasizes the potential for rapid IAA change and the need for frequent radiologic follow-up.

Infected (mycotic) aneurysms: spectrum of imaging appearances and management

Infected aneurysms are uncommon. The aorta, peripheral arteries, cerebral arteries, and visceral arteries are involved in descending order of frequency. Staphylococcus and Streptococcus species are the most common causative pathogens. Early clinical diagnosis of infected aneurysms is challenging owing to their protean manifestations. Clinically apparent infected aneurysms are often at an advanced stage of development or are associated with complications, such as rupture. Nontreatment or delayed treatment of infected aneurysms often has a poor outcome, with high morbidity and mortality from fulminant sepsis or hemorrhage. Current state-of-the-art imaging modalities, such as multidetector computed tomography and magnetic resonance imaging, have replaced conventional angiography as minimally invasive techniques for detection of infected aneurysms in clinically suspected cases, as well as characterization of infected aneurysms and vascular mapping for treatment planning in confirmed cases. Doppler ultrasonography allows noninvasive assessment for infected aneurysms in the peripheral arteries. Imaging features of infected aneurysms include a lobulated vascular mass, an indistinct irregular arterial wall, perianeurysmal edema, and a perianeurysmal soft-tissue mass. Perianeurysmal gas, aneurysmal thrombosis, aneurysmal wall calcification, and disrupted arterial calcification at the site of the infected aneurysm are uncommon findings. Imaging-guided endovascular stent-graft repair and embolotherapy can be performed in select cases instead of open surgery. Familiarity with the imaging appearances of infected aneurysms should alert the radiologist to the diagnosis and permit timely treatment, which may include endovascular techniques.

Evolution of bacterial arteritis into a mycotic aortic aneurysm

Arteritis and mycotic aneurysms have been well described for more than 100 years. The authors report a case of bacterial arteritis that presented with pneumatosis of the aortic wall and that evolved over 1 week into an infected abdominal aortic aneurysm. This case documents the rapid progression from arteritis to mycotic aneurysm, highlighting the need for close radiologic follow-up and aggressive medical and surgical management.

Rupture of a nonaneurysmal aorta secondary to Staphylococcus aortitis

Infectious aortitis has become increasingly uncommon and, when diagnosed, typically occurs in an immunocompromised elderly male with a history of Staphylococcus or Salmonella infection and underlying atheromatous cardiovascular disease. The authors report a case of a 74-year-old man with aortitis complicated by rupture secondary to Staphylococcus aureus infection. The patient presented with worsening abdominal pain and fever after being discharged from the emergency room 2 weeks before with back pain and leukocytosis diagnosed as urinary tract infection and bronchitis. Computed tomography (CT) imaging of the retroperitoneum on the first visit appeared normal. Repeat CT scan on the subsequent visit revealed a contained rupture of a nonaneurysmal aorta at the level of the diaphragm. The patient was taken to the operating room emergently for repair. An infected periaortic hematoma and a 1 cm perforation in the posterior aorta were found. The aorta was excised and the area debrided. Revascularization was performed using a 22 mm extruded polytetrafluoroethylene (ePTFE) interposition graft placed in situ. This case demonstrates that a high index of suspicion is required in diagnosing infectious aortitis and that the diagnosis may be delayed in many cases. Additionally, it may not be uncommon for the infected aorta to rupture without prior aneurysm formation.

To biopsy or not to biopsy: an 82-year-old patient with a retroperitoneal mass and severe low back pain

An 82-year-old patient was admitted to our ward due to disabling severe low back pain. Computed tomography of the spine revealed a retroperitoneal space-occupying lesion encroaching on two adjacent lumbar vertebrae and causing destruction of the cortex of their anterior aspect. The patient was scheduled for a biopsy of the mass. Magnetic resonance (MR) of the lumbar spine, however, suggested that the mass was most probably an aortic aneurysm. The biopsy was cancelled and the patient was referred for surgical intervention. MR is indicated in the evaluation of a solid mass causing vertebral destruction in order to achieve an accurate preoperative diagnosis and prevent a hazardous invasive procedure.

Delayed rupture of abdominal aortic false aneurysm following blunt trauma

Blunt injury of the abdominal aorta resulting in pseudoaneurysm formation is very rare. Such a pseudoaneurysm may rupture at any time, usually with fatal outcome. We report the case of a 32-year-old man with a clinically unsuspected ruptured abdominal aorta pseudoaneurysm, which had probably formed 3 years earlier, and emphasize the CT features.

Infected abdominal aortic aneurysm presenting with sudden appearance: diagnostic importance of serial computed tomography

The case of an 86-year-old man with an infected abdominal aortic aneurysm (AAA) that developed suddenly over 3 weeks is presented here. Previous reports on the diagnosis of infected AAA have focused mainly on the findings of single computed tomography (CT). These include the presence of a saccular aneurysm with an irregular lumen, perianeurysmal fluid, gas and/or hematoma, osteomyelitis in adjacent vertebral bodies, disruption of intimal calcification, and obscuring of the aortic wall. Our case report presents a useful diagnostic technique for the diagnosis of infected AAA, emphasizing the importance of serial CT for suspected cases, even if the initial scan does not demonstrate the findings listed above.