F-18 FDG PET/CT in the Management of Infected Abdominal Aortic Aneurysm Due To Salmonella

Coexistence of FDG-Avid and FDG-Negative Aneurysms in a Patient With Fever of Unknown Origin

ABSTRACT

A 68-year-old man with intermittent fever of unknown origin for 5 months underwent 18F-FDG PET/CT to detect causative lesion. An 18F-FDG-avid lesion was revealed in the left pelvic iliac vessel region and was highly suggestive of malignancy. One and a half months later, a giant left internal iliac artery aneurysm was identified by CT angiography, corresponding to the 18F-FDG-avid lesion. Combined with elevated inflammatory markers, he was finally diagnosed as having inflammatory internal iliac artery aneurysm. An abdominal aortic aneurysm with low 18F-FDG uptake was also identified.

Ciprofloxacin accelerates aortic enlargement and promotes dissection and rupture in Marfan mice

OBJECTIVE

Aortic aneurysm and dissection are major life-threatening complications of Marfan syndrome. Avoiding factors that promote aortic damage is critical in managing the care of these patients. Findings from clinical and animal studies raise concerns regarding fluoroquinolone use in patients at risk for aortic aneurysm and dissection. Therefore, we examined the effects of ciprofloxacin on aortic aneurysm and dissection development in Marfan mice.

METHODS

Eight-week-old Marfan mice (Fbn1C1041G/+) were given ciprofloxacin (100 mg/kg/d; n = 51) or vehicle (n = 59) for 4 weeks. Mice were monitored for 16 weeks. Aortic diameters were measured by using ultrasonography, and aortic structure was examined by using histopathologic and immunostaining analyses.

RESULTS

Vehicle-treated Fbn1C1041G/+ mice showed progressive aortic enlargement, with aortic rupture occurring in 5% of these mice. Compared with vehicle-treated Fbn1C1041G/+ mice, ciprofloxacin-treated Fbn1C1041G/+ mice showed accelerated aortic enlargement (P = .01) and increased incidences of aortic dissection (25% vs 47%, P = .03) and rupture (5% vs 25%, P = .005). Furthermore, ciprofloxacin-treated Fbn1C1041G/+ mice had higher levels of elastic fiber fragmentation, matrix metalloproteinase expression, and apoptosis than did vehicle-treated Fbn1C1041G/+ mice.

CONCLUSIONS

Ciprofloxacin accelerates aortic root enlargement and increases the incidence of aortic dissection and rupture in Marfan mice, partially by suppressing lysyl oxidase expression and further compromising the inherited defect in aortic elastic fibers. Our findings substantiate that ciprofloxacin should be avoided in patients with Marfan syndrome.

Patient-tailored approach for diagnostics and treatment of mycotic abdominal aortic aneurysm

OBJECTIVE

The existing literature on mycotic aortic aneurysm is scarce and focuses on treatment. This study evaluates the clinical characteristics, diagnostics, treatment and outcome of patients with a mycotic abdominal aortic aneurysm treated in a tertiary referral center.

METHODS

A retrospective cohort study was conducted including all patients with a proven mycotic abdominal aortic aneurysm admitted between May 2010 and July 2020. Primary outcome was mortality and secondary outcome included complications such as vascular graft/endograft infection.

RESULTS

Twenty-four patients with a mycotic abdominal aortic aneurysm were included. Patients had a mean age of 68 ± 9 years and 20 (83%) were male. Thirteen patients (57%) had positive preoperative blood cultures. Streptococcus pneumoniae was most frequently isolated by blood culturing, pus, and vascular or perivascular tissue cultures (17%). In 19 (83%) patients the mycotic abdominal aortic aneurysm was located infrarenally, in three (13%) patients suprarenally, and in one (4%) patient juxtarenally. Median follow-up was 20 (7-42) months. In eight patients (33%) vascular graft and or endograft infection was diagnosed after surgical repair. Ten (42%) patients died during the follow-up period. The main causes of death were vascular graft/endograft infection-related (n=4) and rupture of the mycotic abdominal aortic aneurysm (n=3). No patient characteristics could be identified as predictive for mortality.

CONCLUSION

This study shows a large variation in presentation, diagnostic approaches, and surgical and antibiotic treatment of mycotic abdominal aortic aneurysm. The detailed information about the diagnostic approaches to this rare disease and its antibiotic/other treatment contributes to existing knowledge of mycotic abdominal aortic aneurysm. Because of the individual variation patients should be discussed in a multidisciplinary team with a vascular surgeon, infectious disease specialist, and clinical microbiologist.

PET-Based Imaging with 18F-FDG and 18F-NaF to Assess Inflammation and Microcalcification in Atherosclerosis and Other Vascular and Thrombotic Disorders

Positron emission tomography (PET) imaging with ¹⁸F-fluorodeoxyglucose (FDG) represents a method of detecting and characterizing arterial wall inflammation, with potential applications in the early assessment of vascular disorders such as atherosclerosis. By portraying early-stage molecular changes, FDG-PET findings have previously been shown to correlate with atherosclerosis progression. In addition, recent studies have suggested that microcalcification revealed by ¹⁸F-sodium fluoride (NaF) may be more sensitive at detecting atherogenic changes compared to FDG-PET. In this review, we summarize the roles of FDG and NaF in the assessment of atherosclerosis and discuss the role of global assessment in quantification of the vascular disease burden. Furthermore, we will review the emerging applications of FDG-PET in various vascular disorders, including pulmonary embolism, as well as inflammatory and infectious vascular diseases.

18F-fluorodeoxyglucose positron emission tomography/ computed tomography in the diagnosis of a rare mycotic aneurysm of the thoracic aorta in a patient with fever of unknown origin

Fever of unknown origin (FUO) is a condition with high mortality that often presents a diagnostic challenge to clinicians. We present the case of a patient with FUO who was discovered to have a rare mycotic aneurysm of the thoracic aorta by ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography imaging. Mycotic aneurysm, also known as an infected aneurysm, is a highly lethal condition due to the risk of sepsis and aneurysmal rupture. While unusual to present in this manner, it is of utmost importance to promptly recognize a mycotic aneurysm as a potential diagnosis because initiation of treatment is critical in reversing the natural history of the disease.

Gallium-67 Scan with Single Photon Emission Computed Tomography for the Evaluation and Monitoring of Infected Abdominal Aortic Aneurysms: A 10-Year Case Series

Purpose

This study aimed to evaluate the role of gallium-67 single photon emission computed tomography (SPECT) with contrast computed tomography (CT) in the evaluation and monitoring of infected abdominal aortic aneurysms (IAAA).

Methods

Materials and A retrospective cohort analysis was performed using prospectively collected data of consecutive patients with IAAA in Princess Margaret Hospital in Hong Kong between January 2010 and December 2020. The patients were identified using the Radiology Information System.

Results

All five patients had proven IAAA on CT and/or metabolic imaging. Among them, three were further supported by positive blood culture results. Gallium-67 SPECT with contrast CT was useful in the detection of residual disease, monitoring, and detection of recurrence.

Conclusion

Gallium-67 SPECT with contrast CT is helpful for evaluating IAAA. It serves an important role in guiding management, especially during long-term follow-up.

The value of 18F-FDG-PET-CT in the management of infective native aortic aneurysms

OBJECTIVE

The objective of this systematic literature review was to explore the value of positron emission tomography combined with low-dose computed tomography (18F-FDG-PET-CT) in the diagnostics of infective native aortic aneurysm (INAA).

METHODS

A systematic literature review was performed using the search terms mycotic- and infected aortic aneurysms in Medline and Sciencedirect databases, published between 1 January 2000 and 1 January 2020. Using the PRISMA statement, articles were scrutinized according to a predefined protocol including: timing of 18F-FDG-PET-CT examination, the maximum standardized uptake value (SUVmax), additional findings on examination, and findings on repeated scanning of 18F-FDG-PET-CT.

RESULTS

Four studies were included in the analysis, comprising a total of 11 patients. Two studies were single case reports, and two were small case series, all were graded to be of low quality with high risk of bias. All patients were examined with a preoperative 18F-FDG-PET-CT, and 10 (91%) had increased 18F-FDG uptakes. The median SUVmax value was 6.53, range 4.46-9.23. The mean duration of antibiotic therapy prior to 18F-FDG-PET-CT was not known. Two patients were examined with repeated 18F-FDG-PET-CT examinations after treatment, where a decrease in SUVmax values could be demonstrated after successful treatment.

CONCLUSION

The literature on 18F-FDF-PET/CT for diagnosing infective native aortic aneurysms is scarce. However, there might be a role for 18F-FDF-PET/CT in the management of the disease, in particular for patients with clinical suspicion of INAA without convincing findings on CT. SUVmax values ranging from 4.5 to 6.5 could be guiding and suggestive of metabolic activity in agreement of INAA. However, further conclusions on its usefulness, robustness and specific SUVmax values are premature, and a definitive cut-off value is probably not attainable.

Vascular findings on FDG PET/CT

Since its introduction into clinical practice, 2-deoxy-2-[18F]flu-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) has become firmly established in the field of oncological imaging, with a growing body of evidence demonstrating its use in infectious and inflammatory vascular pathologies. This pictorial review illustrates the utility of FDG PET/CT as a diagnostic tool in the investigation of vascular disease and highlights some of the more common incidental vascular findings that PET reporters may encounter on standard oncology FDG PET/CTs, including atherosclerosis, large vessel vasculitis, complications of vascular grafts, infectious aortitis and acute aortic syndromes.

Aortic sarcoma mimicking a mycotic aneurysm in the thoracoabdominal aorta

Aortic sarcoma is a rare primary tumor with dismal prognosis. Here, we report a case involving a 74-year-old female patient with aortic sarcoma masquerading as a mycotic aneurysm in the thoracoabdominal aorta. She underwent aortic resection with Dacron prosthetic graft replacement because of rapid growth. The postoperative pathological findings of the resected specimen confirmed the diagnosis of aortic mural sarcoma, which was an unexpected result based on repeat computed tomography angiography performed within 2 months preoperatively. The preoperative diagnosis of aortic sarcoma is often difficult because of its rarity, and this case demonstrates some of the diagnostic pitfalls.

Role of PET/CT in the Evaluation of Aortic Disease

Positron emission tomography (PET) /computed tomography (CT) has been established as a standard imaging modality in the evaluation of malignancy. Although PET/CT has played a major role in the management of oncology patients, its clinical use has also increased for various disorders other than malignancy. Growing evidence shows that PET/CT images have many advantages in aortic disease as well. This review article addresses the potential role of PET/CT in diseases involving the aorta, emphasizing its usefulness with regard to acute thoracic aortic syndromes, aortic aneurysm, atherosclerotic lesions, aortitis and aortic tumors.

Effect of Ciprofloxacin on Susceptibility to Aortic Dissection and Rupture in Mice

Importance

Fluoroquinolones are among the most commonly prescribed antibiotics. Recent clinical studies indicated an association between fluoroquinolone use and increased risk of aortic aneurysm and dissection (AAD). This alarming association has raised concern, especially in patients with AAD with risk of rupture and in individuals at risk for developing AAD.

Objective

To examine the effect of ciprofloxacin on AAD development in mice.

Design, Setting, and Participants

In a mouse model of moderate, sporadic AAD, 4-week-old male and female C57BL/6J mice were challenged with a high-fat diet and low-dose angiotensin infusion (1000 ng/min/kg). Control unchallenged mice were fed a normal diet and infused with saline. After randomization, challenged and unchallenged mice received ciprofloxacin (100 mg/kg/d) or vehicle through daily gavage during angiotensin or saline infusion. Aortic aneurysm and dissection development and aortic destruction were compared between mice. The direct effects of ciprofloxacin on aortic smooth muscle cells were examined in cultured cells.

Results

No notable aortic destruction was observed in unchallenged mice that received ciprofloxacin alone. Aortic challenge induced moderate aortic destruction with development of AAD in 17 of 38 mice (45%) and severe AAD in 9 (24%) but no rupture or death. However, challenged mice that received ciprofloxacin had severe aortic destruction and a significantly increased incidence of AAD (38 of 48 [79%]; P = .001; χ2 = 10.9), severe AAD (32 of 48 [67%]; P < .001; χ2 = 15.7), and rupture and premature death (7 of 48 [15%]; P = .01; χ2 = 6.0). The increased AAD incidence was observed in different aortic segments and was similar between male and female mice. Compared with aortic tissues from challenged control mice, those from challenged mice that received ciprofloxacin showed decreased expression of lysyl oxidase, an enzyme that is critical in the assembly and stabilization of elastic fibers and collagen. These aortas also showed increased matrix metalloproteinase levels and activity, elastic fiber fragmentation, and aortic cell injury. In cultured smooth muscle cells, ciprofloxacin treatment significantly reduced lysyl oxidase expression and activity, increased matrix metalloproteinase expression and activity, suppressed cell proliferation, and induced cell death. Furthermore, ciprofloxacin-a DNA topoisomerase inhibitor-caused nuclear and mitochondrial DNA damage and the release of DNA into the cytosol, subsequently inducing mitochondrial dysfunction, reactive oxygen species production, and activation of the cytosolic DNA sensor STING, which we further showed was involved in the suppression of lysyl oxidase expression and induction of matrix metalloproteinase expression.

Conclusions and Relevance

Ciprofloxacin increases susceptibility to aortic dissection and rupture in a mouse model of moderate, sporadic AAD. Ciprofloxacin should be used with caution in patients with aortic dilatation, as well as in those at high risk for AAD.

Clinical experience of positron-emission tomography in infective aortic disease

Background

Fluorine-18-fluorodeoxyglucose positron-emission tomography with computed tomography has revolutionized medical diagnosis by adding functional activity to anatomic imaging. We report our experience with this technique in patients with mycotic aortic pathology and aortic vascular graft infection.

Methods

We conducted a retrospective review of a prospective database of patients who underwent 18F-fluorodeoxyglucose positron-emission tomography with computed tomography for suspected infective aortic disease. From 2012 to 2016, 13 patients underwent 18F-fluorodeoxyglucose positron-emission tomography. Of these, 9 (69%) had a vascular graft infection (5 infrarenal aorta, 1 para-visceral, 2 descending, and 1 arch; 2 had previous open surgery and 7 had endovascular interventions) and 4 (31%) had a mycotic aneurysm (2 aortic arch, 1 infrarenal aorta, and 1 distal aorta and common iliac; 3 had endografts). The indications for imaging, location of pathology, 18F uptake, and clinical outcomes were analyzed.

Results

Eight (62%) patients had a single scan and 5 (38%) had serial scans performed. Among the 5 patients who had serial imaging, 3 showed decreased 18F uptake and 2 had increased uptake. Only one patient underwent subsequent endograft removal; the others were treated with lifelong antibiotics. There were 5 (38%) deaths on follow-up.

Conclusion

18F-fluorodeoxyglucose positron-emission tomography with computed tomography could be a valuable adjunct in the diagnosis and surveillance of patients with aortic infection. Serial scans may be useful for monitoring disease activity and response to antibiotic therapy.

Metabolic Imaging as a Novel Strategy in Evaluation of Mycotic Abdominal Aortic Aneurysm: A Case Report and Brief Clinical Review

Abdominal aortic aneurysm (AAA) is an uncommon entity with high mortality. Etiologically, they are classified as inflammatory and infective (mycotic), the latter being less common. Clinical presentation, laboratory investigations, and treatment for these may considerably overlap. However, choice of management and the need for surgical intervention depends on factors such as size and progression of aneurysm, persistent symptoms, and presence or absence of distant pathology. Although computed tomography (CT) is the gold standard for AAA, in selected cases, especially in infected AAA, fluorodeoxyglucose positron emission tomography-CT can provide valuable information.

Cross-sectional imaging of aortic infections

Aortic infections are uncommon clinical entities, but are associated with high rates of morbidity and mortality. In this review, we focus on the cross-sectional imaging appearance of aortic infections, including aortic valve endocarditis, pyogenic aortitis, mycotic aneurysm and aortic graft infections, with an emphasis on CT, MRI and PET/CT appearance. Teaching Points • Aortic infections are associated with high morbidity and mortality. • CT, MRI and FDG PET/CT play complementary roles in aortic infection imaging. • Radiologists should be vigilant for aortic infection manifestations to ensure timely diagnosis.

Fluorine-18-fluorodeoxyglucose positron emission tomography-computed tomography for diagnosis of infected aortic aneurysms

BACKGROUND

Infected aortic aneurysms are diagnosed on the basis of a positive bacterial blood culture, clinical evidence of inflammation, and morphologic findings on computed tomography (CT). However, preoperative diagnosis is often difficult because blood cultures are frequently negative and patients can be asymptomatic. Because therapeutic approaches differ significantly, it is vital to determine whether an aortic aneurysm is infected prior to surgery.

METHODS

From June 2007 to July 2012, we investigated 11 cases of suspected infected aortic aneurysm using fluorine-18-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG-PET/CT). In addition to contrast-enhanced CT examination, blood culture and histologic examinations were performed to aid diagnosis.

RESULTS

Patients with a final diagnosis of infected aortic aneurysms showed a maximum standard uptake value (SUVmax) of >4.46, whereas infection-free cases had an SUVmax of <2.59 (mean 6.5 ± 1.8 vs. 1.9 ± 0.5; P < 0.001).

CONCLUSION

FDG-PET/CT examination is useful in the diagnosis of infected aortic aneurysms.

Thoracic endovascular aortic repair as emergency therapy despite suspected aortic infection

OBJECTIVES

To evaluate thoracic endovascular aortic repair (TEVAR) as emergency therapy despite suspected aortic infection.

METHODS

Within a 5-year period, we treated 6 patients with a strategy of primary TEVAR despite suspected aortic infection in patients with symptomatic or already ruptured thoracic aortic pathology.

RESULTS

In-hospital mortality was 16.7%. The reason for death was septic multiorgan failure. During follow-up, 2 patients were converted to secondary open surgery in a stable elective setting. The median follow-up was 42.5 months. All surviving patients are not receiving continuing antibiotic therapy. Freedom from infection is 100% to date.

CONCLUSIONS

TEVAR as emergency therapy despite suspected aortic infection is feasible and may well serve as a definite treatment option in selected cases. As recurring infection cannot be entirely excluded, life-long clinical and morphological surveillance remains mandatory.

Infected aortic aneurysm and inflammatory aortic aneurysm--in search of an optimal differential diagnosis

Infected aortic aneurysm and inflammatory aortic aneurysm each account for a minor fraction of the total incidence of aortic aneurysm and are associated with periaortic inflammation. Despite the similarity, infected aortic aneurysm generally shows a more rapid change in clinical condition, leading to a fatal outcome; in addition, delayed diagnosis and misuse of corticosteroid or immunosuppressing drugs may lead to uncontrolled growth of microorganisms. Therefore, it is mandatory that detection of aortic aneurysm is followed by accurate differential diagnosis. In general, infected aortic aneurysm appears usually as a saccular form aneurysm with nodularity, irregular configuration; however, the differential diagnosis may not be easy sometimes for the following reasons: (1) symptoms, such as abdominal and/or back pain and fever, and blood test abnormalities, such as elevated C-reactive protein and enhanced erythrocyte sedimentation rate, are common in infected aortic aneurysm, but they are not found infrequently in inflammatory aortic aneurysm; (2) some inflammatory aortic aneurysms are immunoglobulin (Ig) G4-related, but not all of them; (3) the prevalence of IgG4 positivity in infected aortic aneurysm has not been well investigated; (4) enhanced uptake of 18F-fluorodeoxyglucose (FDG) by 18F-FDG-positron emission tomography may not distinguish between inflammation mediated by autoimmunity and that mediated by microorganism infection. Here we discuss the characteristics of these two forms of aortic aneurysm and the points of which we have to be aware before reaching a final diagnosis.

PET/CT imaging in infectious conditions

New aggressive pathogens are responsible for the increasing incidence and difficult management of infections. Modern epidemics such as diabetes are frequently complicated by severe infections with subsequent high morbidity. Diagnosis (essentially early detection of infection) and also management decision making pose clinical challenges. Many resources are invested in developing precise, noninvasive diagnostic tests and efficient therapies for infectious processes. Nuclear medicine procedures are part of the evaluation armamentarium of patients with suspected or confirmed infection. Their strength relies on the fact that they are noninvasive tests that provide both functional as well as metabolic information early in the course of disease. Their limitations relate to the need for specific radiotracers and the rather low resolution of images. These limitations have been largely overcome by the hybrid PET/CT and SPECT/CT technology. PET/CT, primarily using FDG, is redefining the diagnostic work up and is currently leading to changes in the management of patients with suspected or known infections. The main indications for FDG PET/CT in infection, as well as updated literature results, are presented in the following review.

Imaging of Abdominal Aortic Aneurysm: the present and the future

Abdominal Aortic Aneurysm (AAA) is a common, progressive, and potentially lethal vascular disease. A major obstacle in AAA research, as well as patient care, is the lack of technology that enables non-invasive acquisition of molecular/cellular information in the developing AAA. In this review we will briefly summarize the current techniques (e.g. ultrasound, computed tomography, and magnetic resonance imaging) for anatomical imaging of AAA. We also discuss the various functional imaging techniques that have been explored for AAA imaging. In many cases, these anatomical and functional imaging techniques are not sufficient for providing surgeons/clinicians enough information about each individual AAA (e.g. rupture risk) to optimize patient management. Recently, molecular imaging techniques (e.g. optical and radionuclide-based) have been employed to visualize the molecular alterations associated with AAA, which are discussed in this review. Lastly, we try to provide a glance into the future and point out the challenges for AAA imaging. We believe that the future of AAA imaging lies in the combination of anatomical and molecular imaging techniques, which are largely complementary rather than competitive. Ultimately, with the right molecular imaging probe, clinicians will be able to monitor AAA growth and evaluate the risk of rupture accurately, so that the life-saving surgery can be provided to the right patients at the right time. Equally important, the right imaging probe will also allow scientists/clinicians to acquire critical data during AAA development and to more accurately evaluate the efficacy of potential treatments.

Diagnosis and management of aortic mycotic aneurysms

We reviewed all papers most recently reported in the literature (January-December 2008) with regard to infected arterial aneurysms (IAAs) affecting the aorta. Most of the recently reported knowledge is limited to case reports and small series of aortic mycotic aneurysms. Most patients are elderly men and have comorbidities at presentation. Aneurysms were most commonly associated to Salmonella and Staphylococcus. However, several cases of aortic IAAs caused by atypical pathogens were also reported, likely due to an increase in immunosuppressive illnesses, increased life expectancy, improved diagnostic methods, and increasing medical awareness. Open surgical therapy of IAAs remains the gold standard. Some have reported successful outcomes with endovascular methodologies for patients medically compromised or for particular challenging clinical or anatomical scenarios. However, at this time, conclusive evidence is lacking and it should be in general considered a bridge to open repair. The latter should be planned at the earliest possible, when medically permissible.