Infected abdominal aortic aneurysm: early CT findings

Clinical and microbiological characteristics and challenges in diagnosing infected aneurysm: a retrospective observational study from a single center in Japan

Background

It is challenging to diagnose infected aneurysm in the early phase. This study aimed to describe the clinical and microbiological characteristics of infected aneurysm, and to elucidate the difficulties in diagnosing the disease.

Methods

Forty-one cases of infected aneurysm were diagnosed in Nagasaki University Hospital from 2005 to 2019. Information on clinical and microbiological characteristics, radiological findings, duration of onset, and type of initial computed tomography (CT) imaging conditions were collected. Factors related to diagnostic delay were analyzed by Fisher’s exact test for categorical variables or by the Wilcoxon rank-sum test for continuous variables.

Results

Pathogens were identified in 34 of 41 cases; the pathogens were Gram-positive cocci in 16 cases, Gram-negative rods in 13 cases, and others in five cases. Clinical characteristics did not differ in accordance with the identified bacteria. At the time of admission, 16 patients were given different initial diagnoses, of which acute pyelonephritis (n = 5) was the most frequent. Compared with the 22 patients with an accurate initial diagnosis, the 19 initially misdiagnosed patients were more likely to have been examined by plain CT. The sensitivities of plain CT and contrast-enhanced CT were 38.1% and 80.0%, respectively.

Conclusions

In cases of infected aneurysm, diagnostic delay is attributed to non-specific symptoms and the low sensitivity of plain CT. Clinical characteristics of infected aneurysm mimic various diseases. Contrast-enhanced CT should be considered if infected aneurysm is suspected.

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.

Genuine impact of 18F-fluorodeoxyglucose positron emission tomography with contrast-enhanced computed tomography in clinching the diagnosis and follow-up response assessment of vascular graft infections

Vascular graft infection (VGI) is a rare and severe complication after vascular surgery associated with significant morbidity and mortality, but the diagnosis is not always straightforward due to its variable and nonspecific clinical signs. Computed tomography (CT) scan is considered to be the diagnostic tool of choice for advanced VGI, but there is a high incidence of false-negative results, especially in low-grade infections. ¹⁸F-Fluorodeoxyglucose positron emission tomography with contrast-enhanced CT (¹⁸F-FDG PET-CT) imaging can serve as an effective alternative tool for assessment of suspected VGI and also provide accurate anatomic localization of the infective focus. Here, we describe three cases of VGI with various clinical presentations where the site of infection was diagnosed, confirmed, and documented with the help of ¹⁸F-FDG PET-CT imaging.

Long-Term Outcomes of Surgical Treatment by In Situ Graft Reconstruction for Infected Abdominal Aortic Aneurysm

Objectives: The optimal surgical management for primary infected abdominal aortic aneurysm (IAAA) is controversial. Here, we report the early and long-term results of surgical treatments with the resection of the IAAA and in situ graft reconstruction with pedicled omental coverage that was performed at out hospital.

Methods: Between 2010 and 2017, 27 consecutive patients (26 males, 1 female, median age 69 years) with IAAA were surgically treated with the resection of the IAAA, in situ graft reconstruction and covered with a pedicled omental flap. Perioperative and long-term outcomes were reviewed retrospectively by medical records.

Results: Clinical manifestations, including pyrexia, fever and abdominal pain, were observed during the treatment of the patients. Aneurysm excision and in situ graft reconstruction with omental coverage were performed for all cases. In 13 cases (48.1%), tissue culture was positive. The antibiotic was administered intravenously for 9 to 47 days (median 18 days) postoperatively, and after confirming the reduction of the inflammatory response, it was administered as oral agents for 24 to 443 days (median 169 days).There was no perioperative death or re-infection. Perioperative complications were found in 8 cases (29.6%) of minor spinal cord infarction, ileus, chylous ascites, and cholangitis due to choledochlithiasis. During the observation period of median 1,147 days, there was no recurrence of infection, graft infection, or disease-related death. There were six deaths due to other diseases. And the overall survival rate was 76.2%.

Conclusion: According to our study, the long-term outcomes of surgical treatment with in situ graft reconstruction for IAAA were considered satisfactory. (This is a translation of Jpn J Vasc Surg 2019; 28: 35–40.)

Aortoenteric fistula secondary to an Inflammatory Abdominal Aortic Aneurysm

Primary aortoenteric fistulas are rare, with the annual incidence of such fistulas estimated to be 0.007 per million. The most common predisposing conditions for primary aortoenteric fistulas are atherosclerotic abdominal aortic aneurysms or penetrating atherosclerotic ulcers. We illustrate a rare case of an inflammatory aortic aneurysm causing a primary aortic fistula, with a direct fistulous jet from the aorta to the bowel with resultant catastrophic bleeding. In contrast to atherosclerotic aneurysms, most inflammatory aneurysms are symptomatic and show dense perianeurysmal fibrosis and periaortic wall thickening. A direct jet of contrast extravasation from the aorta into a bowel loop, while rarely seen, remains the most specific sign of a primary aorta-enteric fistula. A comprehensive literature review of the clinical presentation, imaging features, and differential diagnosis of a primary aortoenteric fistula are also discussed.

Outcomes of Open Repair of Mycotic Aortic Aneurysms with In Situ Replacement

Background

Mycotic aortic aneurysms are rare and life-threatening. Unfortunately, no established guidelines exist for the treatment of patients with mycotic aortic aneurysms. The purpose of this study was to evaluate the midterm outcomes of the open repair of mycotic thoracic and thoracoabdominal aneurysms and suggest a therapeutic strategy.

Methods

From 2006 to 2016, 19 patients underwent open repair for an aortic aneurysm. All infected tissue was extensively debrided and covered with soft tissue. We recorded the clinical findings, anatomic location of the aneurysm, bacteriology results, antibiotic therapy, morbidity, and mortality for these cases.

Results

The median age was 62±7.2 years (range, 16 to 78 years), 13 patients (68%) were men, and the mean aneurysm size was 44.5±4.9 mm. The mean time from onset of illness to surgery was 14.5±2.4 days. Aortic continuity was restored in situ with a Dacron prosthesis (79%), homograft (16%), or Gore-Tex graft (5%). Soft-tissue coverage of the prosthesis was performed in 8 patients. The mean follow-up time was 43.2±11.7 months. The early mortality rate was 10.5%, and the 5-year survival rate was 74.9%±11.5%.

Conclusion

This study showed acceptable early and midterm outcomes of open repair of mycotic aneurysms. We emphasize that aggressive intraoperative debridement with soft-tissue coverage results in a high rate of success in these high-risk patients.

Infected Abdominal Aortic Aneurysms Treated with Extra-anatomic Prosthesis Bypass in the Retroperitoneum

BACKGROUND

Infected abdominal aortic aneurysms (iAAAs) are rare but life-threatening diseases. The purpose of the present study was to report our experience of extra-anatomic prosthesis bypass in the retroperitoneum as a treatment for iAAAs.

METHODS

Data of 8 consecutive patients diagnosed with iAAAs and treated by an extra-anatomic prosthesis bypass in the retroperitoneum were retrospectively collected. Operative details were as follows: one side of the retroperitoneal space was selected to build a track, and a bifurcated expanded polytetrafluoroethylene prosthesis was placed through the track. The proximal end of the prosthesis was sutured with the normal segment of abdominal aorta proximal to the infected aneurysm by end-to-end anostomosis. The 2 distal ends of the prosthesis were, respectively, sutured with the external iliac artery distal to the aneurysm. The anastomoses were then consolidated with the nearby connective tissue. After the closure of the retroperitoneum, the infected aneurysm was incised, and the infected tissue was debrided. Drainage tubes were placed in the aneurysm sac, which was packed with an omentum flap. All patients received perioperative antibiotic therapy for a period of time. All 8 patients were regularly followed up by outpatient observation.

RESULTS

Eight patients with iAAAs underwent an extra-anatomic prosthesis bypass in the retroperitoneum and debridement of the infected aneurysm. An emergency operation was performed for 1 patient who underwent concomitant gastrointestinal procedures for aortoduodenal fistula. All 8 patients were definitively diagnosed by one or more sequential computed tomography scans combined with other methods. The blood or tissue cultures of all cases were positive in the perioperative period, with Salmonella (5 cases) being the most common pathogens. Other pathogens included Burkholderia pseudomallei (2 cases) and Escherichia coli (1 case). All patients survived and were discharged in 4-5 weeks after their operations. All patients were free from graft infection during the follow-up period.

CONCLUSIONS

The extra-anatomic prosthesis bypass in the retroperitoneum for treating iAAAs was safe and effective. Our experience with the procedure may provide a new approach for the treatment of this disease.

Detection of unexpected emergency diseases using FDG-PET/CT in oncology patients

PURPOSE

To evaluate the frequency of emergency diseases that were detected unexpectedly using FDG-PET/CT.

MATERIALS AND METHODS

Interpretation reports for 11,663 FDG-PET/CT studies in our hospital were retrospectively reviewed. Patients with major emergency diseases were extracted according to the following exclusion criteria: (1) relevant findings had been recognized prior to the PET/CT; (2) an intervention or operation that may have been relevant to the present findings was performed within 1 month prior to the PET/CT; and (3) the clinical course could not be investigated sufficiently (e.g., in cases where the patients were introduced from other hospitals).

RESULTS

Forty-one patients (0.35%) with unexpected emergency diseases were identified. The most frequent disease was pneumothorax (8 patients), followed by chronic subdural hematoma (CSH) (7 patients), ureteral stone (7 patients), and abdominal aortic aneurysm (AAA) with a dirty fat sign or a high-attenuation crescent sign visualized on CT (4 patients). Nine patients (2 pneumothorax, 3 CSH, 1 cerebral hemorrhage, 1 acute cholecystitis, 1 acute pancreatitis, and 1 acute appendicitis) were hospitalized and/or underwent therapeutic intervention within 1 week after the PET/CT.

CONCLUSION

Although rare, an unexpected emergency disease requiring urgent management can be detected using FDG-PET/CT in oncology patients.

18F-Fluorodeoxyglucose positron emission tomography/CT scanning in diagnosing vascular prosthetic graft infection

Vascular prosthetic graft infection (VPGI) is a severe complication after vascular surgery. CT-scan is considered the diagnostic tool of choice in advanced VPGI. The incidence of a false-negative result using CT is relatively high, especially in the presence of low-grade infections. ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) scanning has been suggested as an alternative for the diagnosis and assessment of infectious processes. Hybrid ¹⁸F-FDG PET/CT has established the role of ¹⁸F-FDG PET for the assessment of suspected VPGI, providing accurate anatomic localization of the site of infection. However, there are no clear guidelines for the interpretation of the uptake patterns of ¹⁸F-FDG as clinical tool for VPGI. Based on the available literature it is suggested that a linear, diffuse, and homogeneous uptake should not be regarded as an infection whereas focal or heterogeneous uptake with a projection over the vessel on CT is highly suggestive of infection. Nevertheless, ¹⁸F-FDG PET and ¹⁸F-FDG PET/CT can play an important role in the detection of VPGI and monitoring response to treatment. However an accurate uptake and pattern recognition is warranted and cut-off uptake values and patterns need to be standardized before considering the technique to be the new standard.

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.

MR Imaging of the Aorta

Recent advances in noninvasive imaging methods, such as CT and MR imaging, have replaced most of invasive angiographic procedures in the diagnosis of acquired aortic disease, decreasing the cost and morbidity of diagnosis. This article reviews and illustrates present MR imaging methods for evaluation of the aorta. Common diseases of the aorta also are discussed with a focus on their unique morphologic and functional features and characteristic MR imaging findings. Knowledge of pathologic conditions of common aortic diseases and proper MR imaging techniques enables accurate and time-efficient aortic evaluation.

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.

Clinically occult isolated right iliac mycotic aneurysm with duodenal involvement in a diabetic elderly man: multislice CT diagnosis

A diabetic old man presented with vague abdominal discomfort and intermittent tarry stools for 2 days and gastric ulcers with bleeding was diagnosed after endoscopy. Multislice computed tomography (MSCT) clearly depicted an isolated right iliac mycotic aneurysm with retroperitoneal extension and duodenal involvement. Timely operation and effective antibiotic treatment resulted in complete recovery. To our knowledge, this is the first report of an isolated mycotic iliac artery aneurysm (IAA) complicated with an aneurysmo-duodenal fistula induced by Klebsiella pneumoniae.

Successful endoluminal repair of an infected thoracic pseudoaneurysm caused by methicillin-resistant Staphylococcus aureus

PURPOSE

To report the successful endoluminal repair of an infected thoracic aneurysm secondary to methicillin-resistant Staphylococcus aureus (MRSA).

CASE REPORT

A 76-year-old man presented with an infected thoracic pseudoaneurysm 9 weeks after an elective infrarenal aneurysm repair. Blood cultures were positive for MRSA. Computed tomography (CT) showed an 11.5-cm false aneurysm of the descending thoracic aorta just proximal to the celiac axis. An Excluder stent-graft was used to successfully repair the lesion. Recovery was uneventful, and the patient was treated with linezolid for 6 weeks. Follow-up CT scans at 3 and 12 months confirmed exclusion of the aneurysm and progressive shrinkage of the aneurysm sac with no evidence of graft infection.

CONCLUSIONS

Endoluminal repair is an alternative to open surgery for the treatment of infected aneurysms of the thoracic aorta.

Mycotic aneurysms of the thoracic and abdominal aorta and iliac arteries: experience with anatomic and extra-anatomic repair in 33 cases

OBJECTIVE

A mycotic aneurysm of the aorta and adjacent arteries is a dreadful condition, threatening life, organs, and limbs. With regard to the aortic segment involved, repair by either in situ replacement or extra-anatomic reconstruction can be quite challenging. Even when surgery has been successful, the prognosis is described as very poor because of the weakened health status of the patient who has developed this type of aneurysm. The aim of our study was to find out whether any progress could be achieved in a single center over a long time period (18 years) through use of surgical techniques and antiseptic adjuncts.

MATERIAL AND METHODS

From January 1983 to December 1999, a total of 2520 patients with aneurysms of the thoracic and abdominal aorta and iliac arteries underwent surgery for aortic or iliac replacement at our institution. During that period, 33 (1.31%) of these patients (mean age, 64.3 years) were treated for mycotic aneurysms of the lower descending and thoracoabdominal (n = 13), suprarenal (n = 4), and infrarenal (n = 10) aorta and iliac arteries (n = 6). Twenty (61%) of these 33 patients had histories of various septic diseases; in the other 13 (39%), the etiology remained uncertain. Preoperative signs of infection, such as leukocytosis and elevated C-reactive protein, were found in 79% of the patients, and fever was apparent in 48%; 76% of the patients complained of pain. At the time of surgery, eight (24%) mycotic aneurysms were already ruptured, and 20 (61%) had penetrated into the periaortic tissues, forming a contained rupture. Five (15%) aneurysms were completely intact. The predominant microorganisms found in the aneurysm sac were Staphylococcus aureus and Salmonella species. Careful debridement of all infected tissue was essential. In the infrarenal aortic and iliac vascular bed, in situ reconstruction was performed only in cases of anticipated "low-grade" infection. Alternative revascularization with extra-anatomic procedures (axillobifemoral or femorofemoral crossover bypass graft) was carried out in eight of 16 cases. All four suprarenal and all 13 mycotic aneurysms of the thoracoabdominal aortic segment were repaired in situ. Antibiotics were administered perioperatively, and all patients were subsequently treated with long-term antibiotics.

RESULTS

In-hospital mortality was 36% (n = 12). Because of the smallness and heterogeneity of the sample, we could not demonstrate significant evidence for any influence of aneurysm location or type of reconstruction on patients' outcome. However, survival was clearly influenced by the status of rupture. During long-term follow-up (mean, 30 months; range, 1-139 months), 10 patients (48%) died-one (4.8%) probably as a consequence of the mycotic aneurysm, the others for unrelated reasons. Eleven patients (52%) are alive and well today, with no signs of persistent or recurrent infection.

CONCLUSIONS

A mycotic aneurysm of the aortic iliac region remains a life-threatening condition, especially if the aneurysm has already ruptured by the time of surgery. Although the content of the aneurysm sac is considered septic, as was proved by positive cultures in 85% of our patients, in situ reconstruction is feasible and, surprisingly, was not more closely related to higher morbidity and mortality in our series than ligation and extra-anatomic reconstruction, although most of the aneurysms repaired in situ were located at the suprarenal and thoracoabdominal aorta. We assume that our operative mortality rate of 36%, which relates to a rupture rate of 85%, could be substantially lowered if the diagnosis of mycotic aneurysm were established before rupture.