Common and uncommon CT findings in rupture and impending rupture of abdominal aortic aneurysms

Computed Tomography Attenuation Values of the High-Attenuating Crescent Sign Can Discriminate Between Rupture, Impending Rupture, and Non-Rupture of Aortic Aneurysms

BACKGROUND

Although the high-attenuating crescent (HAC) sign can indicate aortic aneurysm (AA) impending rupture, the relation of its computed tomography (CT) value to the aneurysmal status remains unclear. This study compared the HAC sign CT-attenuation values among rupture, impending rupture, and non-rupture AA cases.Methods and Results:This included 76 patients (mean age: 77.0 years) diagnosed with HAC sign-associated AA between January 2005 and July 2015. The CT-attenuation values of the HAC sign (H) and aortic lumen (A) using region-of-interest methodology were measured and the H/A ratio was calculated. The study classified patients into the rupture group (R-G, n=36), impending rupture group (IR-G, n=16), and non-rupture group (NR-G, n=24); the H and the H/A ratio were compared among them. Additionally, the H and the H/A ratio cut-offs between the IR-G and NR-G groups were evaluated. The H and the H/A ratio were significantly higher in the R-G and IR-G than in the NR-G (both P<0.001); the H/A ratio was significantly higher in the R-G than in the IR-G (P=0.038). The optimal cut-off for H between the IR-G and NR-G was 50.3 Hounsfield units (area under the curve [AUC]=0.875; sensitivity=87.5%; specificity=87.5%), and that for the H/A ratio was 1.3 (AUC=0.909; sensitivity=91.7%; specificity=87.5%).

CONCLUSIONS

Among patients with AA, the H and the H/A ratio were significantly higher in cases of rupture and impending rupture than in those of non-rupture.

Signs of impending rupture in abdominal aortic and iliac artery aneurysms by computed tomography: Outcomes in 41 patients

OBJECTIVES

This study aimed to determine the prevalence of signs of impending rupture (SIR) in asymptomatic patients with abdominal aortic and iliac artery aneurysms, and to evaluate whether these signs were associated with rupture in asymptomatic patients.

METHODS

This was a retrospective study of patients with abdominal aortic and iliac artery aneurysms identified on computed tomography (CT) over a 10-year period in a single center. The CT scans were reviewed by two reviewers, and patients with SIR were assigned to one of three groups: (1) early symptomatic (ES), (2) late symptomatic (LS), and (3) always asymptomatic (AA). The four main SIR described in the literature were investigated: 1) crescent sign, 2) focal wall discontinuity of circumferential calcifications, 3) aortic bulges or blebs, and 4) aortic draping.

RESULTS

From a total of 759 aortic and iliac aneurysm reports on 2226 CT scans, we identified 41 patients with at least one SIR, and a prevalence of 4.14% in asymptomatic patients. Focal wall discontinuity of circumferential calcifications was the most common sign, and it was present in 46.3% of these patients (19/41); among these, 26 were repaired (ES: 9, LS: 2, AA: 15). Eleven asymptomatic patients underwent follow-up CT. The aneurysm increased in size in 6 of the 11 (54.5%) patients, and three ruptured (all with discontinuity of calcifications), one of which had no increase in diameter.

CONCLUSIONS

The presence of focal wall discontinuity of circumferential calcifications was the most common SIR. There was a prevalence of all signs in less than 5% of asymptomatic patients. In unrepaired patients, the signs could be observed on follow-up CT scans with an increase in aneurysm size, indicating that the presence of SIR alone in the absence of other clinical factors or aneurysm characteristics is an insufficient indication for surgery.

Clinical features, management, and outcome of iliopsoas abscess associated with cardiovascular disorders: a hospital-based observational case series study

BACKGROUND

Iliopsoas abscess (IPA) is a rare clinical entity and is difficult to diagnose due to its insidious onset and nonspecific symptoms. The association between IPA and cardiovascular disorders (CVD) has been rarely reported. Computed tomographic (CT) scan can provide a definitive diagnosis of IPA and associated foci of adjacent structures. IPA is a life-threatening condition, especially when associated with CVD.

MATERIALS AND METHODS

We conducted a hospital-based observational study of IPA associated with CVD. Data were collected from the electronic clinical database of Taichung Veterans General Hospital (1520-bed tertiary referral hospital in central Taiwan) between July 2007 and December 2017. The diagnosis of IPA associated with CVD was confirmed by classical findings on CT and transesophageal echocardiography with compatible clinical presentation and cultures from pus/tissue and blood.

RESULTS

Fifteen patients of IPA associated with CVD were studied. They included 12 males (80%) and 3 females (20%), with a mean age 63.2 ± 16.9 years (31-85 years). CVD included stent-graft/endograft infection of abdominal aortic aneurysm (AAA) (40%), primary mycotic AAA (33.3%), and infective endocarditis (26.7%). Staphylococcus aureus is the most common microorganism in pus/tissue cultures (n = 3, 37.5%) and in blood cultures (n = 6, 40%). The average length of hospital stay was 33.1 ± 20.5 days (range, 3-81 days; median, 33 days). Hospital stay lasted 42.6 ± 19.2 days in the survival group and 19.0 ± 14.1 days (P = 0.018) in the non-survival group. Incidence of patients staying in the intensive care unit (ICU) with intubation > 3 days was 33% in the survival group and 100% (P = 0.028) in the non-survival group. Intra-hospital mortality rate was 40%. Poor prognostic factors in the non-survival group were hypoalbuminemia, hyponatremia, involved disc/vertebral body and/or epidural abscess, and ICU stay with intubation > 3 days. Cumulative survival rate was 25% under conservative treatments and 66.3% under aggressive treatments (P = 0.038).

CONCLUSION

Due to high mortality rates, clinicians should keep a high suspicion index for IPA associated with CVD through clinical presentation, physical examination, and imaging study. Timely empiric antibiotics for common bacteria, drainage for IPA, endovascular repair, or vascular reconstruction by graft replacement or bypass with intensive care should be mandatory to shorten the hospital stay, reduce medical costs, and lower mortality rate.

Vascular CT and MRI: a practical guide to imaging protocols

Non-invasive cross-sectional imaging techniques play a crucial role in the assessment of the varied manifestations of vascular disease. Vascular imaging encompasses a wide variety of pathology. Designing vascular imaging protocols can be challenging owing to the non-uniform velocity of blood in the aorta, differences in cardiac output between patients, and the effect of different disease states on blood flow. In this review, we provide the rationale behind—and a practical guide to—designing and implementing straightforward vascular computed tomography (CT) and magnetic resonance imaging (MRI) protocols.

Teaching Points

• There is a wide range of vascular pathologies requiring bespoke imaging protocols.

• Variations in cardiac output and non-uniform blood velocity complicate vascular imaging.

• Contrast media dose, injection rate and duration affect arterial enhancement in CTA.

• Iterative CT reconstruction can improve image quality and reduce radiation dose.

• MRA is of particular value when imaging small arteries and venous studies.

Abdominal Pain in the Presence of Small Abdominal Aortic Aneurysms: If in Doubt, Cut It Out!

Although small (<5 cm) abdominal aortic aneurysms (AAA) have been associated with symptoms and indication for intervention scarcely, the clinicians should never exclude such potential association especially in the absence of other overt pathological findings. In such cases, a surgical exploration with consequent intervention, if feasible, should be justified to prevent a detrimental evolution in a dubious scenario. In this article, we present 2 cases of patients with small AAA presenting with severe abdominal pain. In the absence of other solid clinical and radiological pathological findings, both patients underwent laparotomy where an inflammatory small AAA was identified and subjected either to resection and restoration with a tube graft or secondary endovascular repair because the periaortic fibrosis precluded the open repair. The characteristics and rationale of treatment modalities are exemplified and discussed.

MDCT evaluation of acute aortic syndrome (AAS)

Non-traumatic acute thoracic aortic syndromes (AAS) describe a spectrum of life-threatening aortic pathologies with significant implications on diagnosis, therapy and management. There is a common pathway for the various manifestations of AAS that eventually leads to a breakdown of the aortic intima and media. Improvements in biology and health policy and diffusion of technology into the community resulted in an associated decrease in mortality and morbidity related to aortic therapeutic interventions. Hybrid procedures, branched and fenestrated endografts, and percutaneous aortic valves have emerged as potent and viable alternatives to traditional surgeries. In this context, current state-of-the art multidetector CT (MDCT) is actually the gold standard in the emergency setting because of its intrinsic diagnostic value. Management of acute aortic disease has changed with the increasing realization that endovascular therapies may offer distinct advantages in these situations. This article provides a summary of AAS, focusing especially on the MDCT technique, typical and atypical findings and common pitfalls of AAS, as well as recent concepts regarding the subtypes of AAS, consisting of aortic dissection, intramural haematoma, penetrating atherosclerotic ulcer and unstable aortic aneurysm or contained aortic rupture. MDCT findings will be related to pathophysiology, timing and management options to achieve a definite and timely diagnostic and therapeutic definition. In the present article, we review the aetiology, pathophysiology, clinical presentation, outcomes and therapeutic approaches to acute aortic syndromes.

Unstable abdominal aortic aneurysms: a review of MDCT imaging features

Abdominal aortic aneurysms are commonly encountered during abdominal CT imaging, and size-based parameters for surgical or endovascular repair are well established. Aneurysms greater than 5 cm in diameter are recognized as representing an increased rupture risk and meriting intervention. Increasingly, additional interest has been generated in recognizing imaging features which may herald instability and portend a higher chance for potentially catastrophic rupture. This article will review and illustrate such signs, including hyperattenuation of mural thrombus, rapid expansion, low thrombus to lumen ratio, intimal calcification disruption, posterior mural draping, and saccular outpouching. Other features of complicated abdominal aneurysms including perianeurysmal inflammation, aortocaval and aortoenteric fistula formation will also be addressed. Heightened awareness of these features and their prognostic implications, as well as timely communication with the clinical service, is critical for the interpreting radiologist.

Assessing the potential risk of rupture of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) involve complex interplays between inflammatory and biomechanical factors that can be elucidated with anatomical and functional imaging. Although AAA size has been well-established in the literature to correlate with risk of rupture (and subsequent need for vascular intervention), there are other less-well-known characteristics about AAAs that also contribute to higher risk of rupture. This review focuses on biomechanical, radiological, and epidemiological characteristics of AAAs that are associated with higher rupture risk. For clinicians, knowing and considering a wide variety of risk factors in addition to AAA size is important to initiate early and proper intervention for AAA repair. Although there is no official quantitative risk score of AAA rupture risk that takes other non-size-related variables into account, if clinicians are aware of these other parameters, it is hoped that intervention can be appropriately performed for higher-risk AAAs that have not met the size-threshold for elective repair.