CT of abdominal aortic aneurysms

The interdependent hemodynamic influence between abdominal aortic aneurysm and renal artery stenosis

Cardiovascular diseases remain a leading cause of morbidity and mortality worldwide with abdominal aortic aneurysm (AAA) and renal artery stenosis (RAS) standing out as significant contributors to the vascular pathology spectrum. While these conditions have traditionally been approached as distinct entities, emerging evidence suggests a compelling interdependent relationship between AAA and RAS, challenging the conventional siloed understanding. The confluence of AAA and RAS represents a complex interplay within the cardiovascular system, one that is often overlooked in clinical practice and research. Here, we reveal a bidirectional consequential impact between these two diseases. The location of the AAA sac was investigated for its specific influence on the risk of RAS development. Although studies have shown a higher coincidence between the suprarenal AAA and RAS, our findings demonstrated that the presence of a suprarenal AAA correlated with the lowest risk of RAS development among the three investigated AAA locations. Notably, we also highlighted that the pre-existence of stenosis in the renal artery poses an elevated risk for the formation of suprarenal AAA, assessed by an increased wall shear stress gradient on the aortic wall. Our findings prompt a paradigm shift in the understanding and treatment of AAA and RAS in clinical practice.

Chronic Ruptured Abdominal Aortic Aneurysm

Chronic rupture of Abdominal Aortic Aneurysm is a rare presentation although AAA and its frank rupture is well known phenomenon. Chronic rupture of AAA can be misdiagnosed due to non-specific presentation and absence of haemorrhagic shock. This case report discusses the presentation scenarios as well radiologic findings which may help diagnose a Chronic Ruptured AAA (CR-AAA) and will be helpful in prompt recognition and early management of the situation.

Disaster Diagnoses in Geriatric Patients with Abdominal Pain

Care of geriatric patients with abdominal pain can pose significant diagnostic and therapeutic challenges to emergency physicians. Older adults rarely present with classic signs, symptoms, and laboratory abnormalities. The incidence of life-threatening emergencies, including abdominal aortic aneurysm, mesenteric ischemia, perforated viscus, and other surgical emergencies, is high. This article explores the evaluation and management of several important causes of abdominal pain in geriatric patients with an emphasis on high-risk presentations.

Saccular Kommerell aneurysm, a potential pitfall on MDCT imaging - A review of imaging features and potential mimics

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Kommerell aneurysm is an outpouching from a kommerell diverticulum.

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Mimics include saccular aneurysm of the thoracic aorta, ductus diverticulum and dilated Kommerell diverticulum.

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Kommerell aneurysm has the tendency to rupture, therefore, accurate diagnosis is critical.

Saccular Kommerell aneurysm represents a potential pitfall on Multidetector CT (MDCT) imaging, mimicking conditions such as saccular aneurysm of the thoracic aorta, ductus diverticulum and dilated Kommerell diverticulum. Accurate diagnosis of this condition is critical in the management of this potentially fatal condition. This paper reviews the MDCT imaging features of Kommerell aneurysms and its mimics and demonstrates how to make an accurate diagnosis through a series of four cases. MDCT features of Kommerell aneurysms, either saccular or fusiform types arising from a Kommerell diverticulum with atherosclerotic plaque and mural thrombus are discussed.

"To-and-fro" waveform in the diagnosis of arterial pseudoaneurysms

Medical ultrasound imaging with Doppler plays an essential role in the diagnosis of vascular disease. This study intended to review the clinical use of “to-and-fro” waveform at duplex Doppler ultrasonography (DDU) in the diagnosis of pseudoaneurysms in the arterial vessels of upper and lower extremities, abdominal aorta, carotid and vertebral arteries as well as to review our personal experiences of “to-and-fro” waveform at DDU also. After receiving institutional review board approval, an inclusive literature review was carried out in order to review the scientific foundation of “to-and-fro” waveform at DDU and its clinical use in the diagnosis of pseudoaneurysms in various arterial vessels. Articles published in the English language between 2000 and 2013 were evaluated in this review study. Pseudoaneurysms in arterial vessels of the upper and lower extremities, abdominal aorta, carotid and vertebral arteries characterized by an extraluminal pattern of blood flow, which shows variable echogenicity, interval complexity, and “to-and-fro” flow pattern on color Doppler ultrasonography. In these arterial vessels, Duplex ultrasonography can demonstrate the degree of clotting, pseudoaneurysm communication, the blood flow patterns and velocities. Spectral Doppler applied to pseudoaneurysms lumen revealed systolic and diastolic turbulent blood flow with traditional “to-and-fro” waveform in the communicating channel. Accurate diagnosis of pseudoaneurysm by spectral Doppler is based on the documentation of the “to-and-fro” waveform. The size of pseudoaneurysm determines the appropriate treatment approach as surgical or conservative.

Chronic Contained Abdominal Aortic Aneurysm Rupture Mimicking Vertebral Spondylodiscitis: A Case Report

A 63-year-old Caucasian male presented with a 4-month history of low back pain associated with bilateral intermittent claudication. A contrast enhanced CT scan demonstrated a 4 cm abdominal aortic aneurysm (AAA), along with severe bilateral aorto-iliac disease, a right psoas collection, and extensive vertebral erosion. An MRI of the lumbar spine suggested spondylodiscitis at L4-L5. After an unsuccessful and prolonged course of antibiotics, a decision was ultimately made to repair the aneurysm and bypass the aorto-iliac disease. Intra-operatively, a chronic contained rupture (CCR) involving the posterior aortic wall was encountered and repaired with an aorto-bifemoral bypass graft.

Abdominal emergencies in the geriatric patient

Abdominal pain is one of the most frequent reasons that elderly people visit the emergency department (ED). In this article, we review the deadliest causes of abdominal pain in this population, including mesenteric ischemia, abdominal aortic aneurysm, and appendicitis and potentially lethal non-abdominal causes. We also highlight the pitfalls in diagnosing, or rather misdiagnosing, these clinical entities.

Aorto-left renal cyst fistula: a rare complication of abdominal aortic aneurysm rupture

Abdominal aortic aneurysm (AAA) rupture can occur in different ways, such as closed rupture into the retroperitoneum, open rupture into the peritoneal cavity, rupture into surrounding hollow structures, and chronic contained or sealed rupture. Here, we report an unusual case of spontaneous rupture of AAA into a renal cyst that presented with hematuria, abdominal pain and shock, and which was diagnosed with multidetector computed tomography. We also review the literature on unusual patterns of AAA rupture.

Comprehensive reviews of the interfascial plane of the retroperitoneum: normal anatomy and pathologic entities

The retroperitoneum is conventionally divided into three distinct compartments: posterior pararenal space, anterior pararenal space, and perirenal space, bounded by the posterior parietal peritoneum, transversalis fascia, and perirenal fascia. But more recent work has demonstrated that the perirenal fascia is not made up of distinct unilaminated fascia, but a single multilaminated structure with potential space. These potential spaces are represented by retromesenteric plane, retrorenal plane, lateral conal plane, and combined fascial plane. The purpose of this review was to demonstrate embryogenesis, anatomy of interfascial plane, and spreading pathways of various pathologic entities with computed tomography imaging.

Superior mesenteric artery syndrome caused by huge mycotic abdominal aortic aneurysm

A 92-year-old man who had been hospitalized for dementia developed sudden-onset bilious vomiting accompanied by a fever of 40 degrees C. Physical examination revealed an 8 cm diameter pulsatile mass in the upper abdomen. Computed tomography of the abdomen demonstrated a huge infrarenal saccular aneurysm with a lobulated appearance. We considered this to be a mycotic abdominal aortic aneurysm compressing the third portion of the duodenum and causing proximal duodenal dilatation and superior mesenteric artery (SMA) syndrome.

Effects of thoracic and hiatal clamping in repair of ruptured abdominal aortic aneurysms

The purpose of this study was to determine the effects of hiatal and thoracic clamping on postoperative outcome and morbidity and factors affecting mortality and morbidity. The records of 102 patients who had undergone ruptured abdominal aortic aneurysm repair between 1993 and 2005 were evaluated retrospectively. Hiatal clamping and thoracic clamping were performed in 72 patients and 30 patients, respectively. Postoperative complications and survival were evaluated comparatively between the two groups by univariate and multivariate statistical analyses. Overall mortality and hospital mortality rates were 63 (61.8%) and 24 (23.5%) patients, respectively; and there was no difference between the two groups. Postoperative respiratory complications, gastrointestinal complications, and blood requirement were higher in the thoracic clamping group. Preoperative shock and renal ischemia time (>30 min) were found to be significant predictors of hospital mortality. Postoperative renal failure was the only independent postoperative predictor of mortality. In the follow-up period, cardiac event was an independent predictor of late mortality. If hospital mortalities were excluded, 5-year and 10-year cumulative survivals were 57.82 +/- 5.85% and 38.16 +/- 6.97%, respectively. Cross-clamp level did not have a significant effect on long-term survival. Although both thoracic and hiatal clamping had no effect on mortality, postoperative respiratory complications, blood requirement, and intestinal ischemia were more pronounced in patients operated with thoracic clamping. Hiatal clamping is preferable for a safe postoperative period.

Abdominal Pain

Evaluation of the elderly patient with acute abdominal pain is sometimes difficult. Various factors can obscure the presentation, delaying or preventing the correct diagnosis and leading to adverse patient outcomes. Clinicians must consider multiple diagnoses, especially those life-threatening conditions that require timely intervention to limit morbidity and mortality. This article reviews abdominal pain in the elderly, discusses the clinical approach, and highlights key diagnostic considerations.

CT Criteria for Differentiating Abdominal Hemorrhage: Anticoagulation or Aortic Aneurysm Rupture?

OBJECTIVE

The purpose of our study was to test the hypothesis that CT criteria would allow accurate diagnosis of the specific cause of abdominal hemorrhage in patients with coagulopathy or abdominal aortic aneurysm.

CONCLUSION

Attention to specific CT criteria allows accurate diagnosis of the specific cause of spontaneous abdominal hemorrhage even in patients who have both coagulopathy and an abdominal aortic aneurysm.

Abdominal Pain in the Elderly

Elderly patients who have abdominal pain remain one of the most challenging patient populations. Signs and symptoms of serious disease are often nonspecific. Atypical presentations are common in elderly patients. In addition, the higher incidence of serious pathology in this population requires emergency physicians to be vigilant and thorough in their work-up. Vascular catastrophes are more likely to be seen in this population, and a broad differential diagnosis needs to be considered.

Alternative diagnoses to stone disease on unenhanced CT to investigate acute flank pain

Acute flank pain is a common problem in emergency medicine. The most frequent cause is urolithiasis, but many other entities can cause the same clinical presentation. In many institutions unenhanced computed tomography (CT) of the abdomen is used in this setting. One of the major advantages of unenhanced CT is its ability to detect other pathologies causing flank pain. In this pictorial review, we present the CT findings of pathologies other than stone disease in patients with acute flank pain.

Emergencies in the retroperitoneum: assessment of spread of disease by helical CT

Acute pancreatitis, leaking abdominal aortic aneurysm, and renal trauma frequently occur in the setting of patients with abdominal nontraumatic and traumatic injury; it represents the most urgent conditions that may determine the presence of fluid collections or haematoma in the retroperitoneum. Single spiral CT and multidetector-row CT (MDCT) play an important role in diagnosis of retroperitoneal emergencies, providing useful informations on the type, site, extent and management of the fluid collections. An accurate CT assessment requires the awareness of the existence of dissectable retroperitoneal fascial planes. Fluid collections or haematoma tends to escape the retroperitoneal site of origin into planes extend from the diaphragm to the pelvic floor. We assess the multicompartimental anatomy of the retroperitoneum and the pathway of spread of the most frequent retroperitoneal fluid collections or haematoma by helical CT.

Abdominal surgical emergencies in the elderly

The evaluation of abdominal pain can be considerably more challenging in elderly patients. A higher likelihood of life-threatening pathology combined with a myriad of diagnostic pitfalls in this population mandate a more cautious approach with greater use of diagnostic resources and specialist consultation.

CT of acute abdominal aortic disorders

Aortic aneurysm rupture, aortic dissection, PAU, acute aortic occlusion, traumatic aortic injury, and aortic fistula represent acute abdominal aortic conditions. Because of its speed and proximity to the emergency department, helical CT is the imaging test of choice for these conditions. MR imaging also plays an important role in the imaging of aortic dissection and PAU, particularly when the patient is unable to receive intravenous contrast material. In this era of MDCT, conventional angiography is used as a secondary diagnostic tool to clarify equivocal findings on cross-sectional imaging. Ultrasound is helpful when CT is not readily available and the patient is unable or too unstable to undergo MR imaging.

Helical CT evaluation of aortic aneurysms and dissection: a pictorial essay

The relative noninvasive nature, easy accessibility, convenience and accuracy of helical CT in the rapid evaluation of not only the aorta and its branches, but the entire thorax/abdomen, makes it the best suited imaging modality for use in evaluation of aortic aneurysms and dissection. Excellent vascular opacification, the advantage of reconstructing overlapping scans without respiratory misregistration, multiplanar reconstruction and 3D rendering of the vessels highlight the benefits of helical CT. Helical CT evaluation combines the advantages of conventional CT, giving true information about the exact transverse and longitudinal extent of the aneurysm, the vessel wall, luminal thrombus and structures around the aorta, and those of aortography in the form 3D volumetric information display. The purpose of this essay is to present a spectrum of aortic aneurysms and dissection to highlight the role of helical CT in their evaluation.

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.

Acute aortic abnormalities

Aneurysm and type B dissections account for most acute abdominal aortic abnormalities. The postsurgical aorta deserves special attention owing to the risk of complications. Most aortic abnormalities presenting acutely are emergencies that carry a high risk of mortality, and imaging plays a critical role in patient evaluation. Modern helical CT scanners provide excellent spatial resolution, are readily available, and allow for rapid imaging. For these reasons, helical CT angiography is the imaging modality of choice for initial evaluation of the acute aorta.

Aortic prosthetic graft infections: radiologic manifestations and implications for management

Prosthetic graft infections are an uncommon complication of aortic bypass. These infections may have serious sequelae such as limb loss and can be lethal. They are hard to eradicate and, under certain circumstances, difficult to diagnose. Usually, computed tomography (CT) is the most efficacious imaging method for diagnosis of graft infections due to its quick availability. The sensitivity of magnetic resonance imaging in detection of perigraft infection has not been thoroughly investigated but is probably similar to that of CT. After the early postoperative period, persistent or expanding perigraft soft tissue, fluid, and gas are the CT findings of graft infection. Aortoenteric fistula should be considered a subset of aortic graft infection; however, perigraft air is more likely to be seen with an aortoenteric fistula. Other conditions associated with graft infection include pseudoaneurysm, hydronephrosis, and osteomyelitis. Adjunctive studies such as sinography, ultrasonography, gallium scanning, and labeled white blood cell scanning can be quite useful in diagnosis, determination of the extent of disease, and selection of the treatment modality. White blood cell scanning is an important complementary test to CT in ambiguous cases, such as in the early postoperative period, and may be more sensitive in detection of early graft infection.

Tailored helical CT evaluation of acute abdomen

Helical computed tomography (CT) allows rapid, cost-effective evaluation of patients with acute abdominal pain. Tailoring the examination to the working clinical diagnosis by optimizing constituent factors (eg, timing of acquisition, contrast material used, means and rate of contrast material administration, collimation, pitch) can markedly improve diagnostic accuracy. Rapid (>/=3 mL/sec) intravenous injection of contrast material is required for optimal assessment of acute pancreatitis, ischemic bowel, aortic aneurysm, and aortic dissection. Narrow collimation and small reconstruction intervals can help detect calculi in the biliary system and genitourinary tract. Tailored helical CT in patients with acute pyelonephritis usually involves several acquisitions through the kidneys during various phases of renal enhancement. In patients with suspected renal infarction, CT protocol must include an acquisition during the corticomedullary phase. Helical CT with 5-mm collimation through the lower abdomen and pelvis is used to evaluate patients with suspected diverticulitis. Use of both oral and intravenous contrast material can help localize small bowel perforation and characterize related complications. Tailored helical CT for assessment of abdominal hemorrhage consists of initial unenhanced CT followed by optional contrast material-enhanced CT. Clear communication between the radiologist, the patient, and the referring physician is essential for narrowing the differential diagnosis into a working diagnosis prior to helical CT.

Abdominal aortic aneurysm: pretherapy assessment with dual-slice helical CT angiography

OBJECTIVE

The purpose of this study was to evaluate dual-slice helical CT in the pretherapy assessment of abdominal aortic aneurysms.

SUBJECTS AND METHODS

Dual-slice helical CT angiography was performed in 47 consecutive patients (mean age, 59 years) with abdominal aortic aneurysm to determine whether we could then evaluate the extent of aneurysm and see associated renal, celiac, mesenteric, and iliofemoral artery disease. Results were compared with those of digital subtraction angiography (n = 47) and surgery (n = 37).

RESULTS

The proximal and distal extents of abdominal aortic aneurysm correlated well with surgical findings. Dual-slice helical CT showed all main (n = 102) and accessory (n = 13) renal arteries with a sensitivity of 91% and a specificity of 100% for revealing associated renal artery stenosis exceeding 50%. Sensitivity and specificity of dual-slice helical CT for revealing stenosis exceeding 75% in celiac and superior mesenteric arteries were both 100%. Three of four iliofemoral artery stenoses and two occlusions of the common iliac artery were revealed by dual-slice helical CT.

CONCLUSION

Helical CT angiography with dual-slice scanning is a useful and minimally invasive technique that can provide with high accuracy all the necessary information for treatment of abdominal aortic aneurysm.

Pseudoaneurysm of the abdominal aorta diagnosed by color duplex Doppler sonography

A pseudoaneurysm of the abdominal aorta is rare, accounting for only 1% of all abdominal aneurysms. More than 1 imaging method may be needed to demonstrate an abdominal aortic pseudoaneurysm. We report a case in which the presence of continuous bidirectional flow in the neck of a pseudoaneurysm on color duplex Doppler sonography confirmed the diagnosis.

Spiral CT angiography of the abdominal aorta. Comparison of iodixanol and ioversol

RATIONALE AND OBJECTIVES

Enhancement characteristics of a nonionic, dimeric, isotonic contrast medium (iodixanol [Visipaque]) were compared with a nonionic, monomeric contrast medium (ioversol [Optiray]) of the same iodine concentration in spiral computed tomography angiography (CTA) of the abdominal aorta.

METHODS

Spiral CTA was performed in 78 patients referred for suspected renal artery stenosis (n = 35) and abdominal aortic aneurysm (n = 43). A test bolus was used to time the scan delay, and all patients were injected with 150 ml contrast medium (320 mgI/ml) of either iodixanol (n = 40) or ioversol (n = 38). Contrast enhancement was measured in the aorta, renal arteries, and renal parenchyma.

RESULTS

All mean aortic enhancement was slightly higher with iodixanol than ioversol, measured at three different levels (celiac trunk 315 Hounsfield units [HU] versus 300 HU, renal arteries 325 HU versus 312 HU, aortic bifurcation 276 HU versus 266 HU). However, none of them were statistically significant (e.g., P = 0.26 at the celiac trunk level). Similar results were observed in renal artery and parenchyma enhancements.

CONCLUSIONS

Iodixanol and ioversol had similar enhancement characteristics in the early arterial phase. Both substances were well tolerated and seem to be well suited for spiral CTA.

US, CT, and MR evaluation of accessory renal arteries and proximal renal arterial branches

RATIONALE AND OBJECTIVES

The purpose of this study was to compare color Doppler ultrasound (US), computed tomographic (CT) angiography, and magnetic resonance (MR) angiography for the evaluation of accessory renal arteries and proximal branches of the main renal artery.

MATERIALS AND METHODS

Fifty-six subjects who had undergone conventional arteriography of the renal arteries participated in a prospective comparison of Doppler US (45 patients), CT angiography (52 patients), and nonenhanced MR angiography (28 patients). Conventional arteriography depicted 28 accessory renal arteries and 21 proximal branches of the main renal artery within 2 cm of the aorta.

RESULTS

US depicted five of 24 accessory renal arteries seen at arteriography but no proximal arterial branches. CT angiography depicted 24 of 26 accessory renal arteries and 13 of 17 proximal arterial branches, as well as 15 additional accessory renal arteries not seen at conventional arteriography. MR demonstrated 11 of 15 accessory arteries, as well as four additional accessory arteries not seen at conventional arteriography. MR did not depict any of nine proximal arterial branches seen at conventional arteriography.

CONCLUSION

When compared with US or nonenhanced MR angiography, CT is the preferred method for evaluation of accessory renal arteries and proximal branches of the renal artery.

The value of late computed tomographic scanning in identification of vascular abnormalities after abdominal aortic aneurysm repair

PURPOSE

The purpose of this study was to determine the prevalence of late arterial abnormalities after aortic aneurysm repair and thus to suggest a routine for postoperative radiologic follow-up examination and to establish reference criteria for endovascular repair.

METHODS

Computed tomographic (CT) scan follow-up examination was obtained at 8 to 9 years after abdominal aortic aneurysm (AAA) repair on a cohort of patients enrolled in the Canadian Aneurysm Study. The original registry consisted of 680 patients who underwent repair of nonruptured AAA. When the request for CT scan follow-up examination was sent in 1994, 251 patients were alive and potentially available for CT scan follow-up examination and 94 patients agreed to undergo abdominal and thoracic CT scanning procedures. Each scan was interpreted independently by two vascular radiologists.

RESULTS

For analysis, the aorta was divided into five defined segments and an aneurysm was defined as a more than 50% enlargement from the expected normal value as defined in the reporting standards for aneurysms. With this strict definition, 64.9% of patients had aneurysmal dilatation and the abnormality was considered as a possible indication for surgical repair in 13.8%. Of the 39 patients who underwent initial repair with a tube graft, 12 (30.8%) were found to have an iliac aneurysm and six of these aneurysms (15.4%) were of possible surgical significance. Graft dilatation was observed from the time of operation (median graft size of 18 mm) to a median size of 22 mm as measured by means of CT scanning at follow-up examination. Fluid or thrombus was seen around the graft in 28% of the cases, and bowel was believed to be intimately associated with the graft in 7%.

CONCLUSION

Late follow-up CT scans after AAA repair often show vascular abnormalities. Most of these abnormalities are not clinically significant, but, in 13.8% of patients, the thoracic or abdominal aortic segment was aneurysmal and, in 15.4% of patients who underwent tube graft placement, one of the iliac arteries was significantly abnormal to warrant consideration for surgical repair. On the basis of these findings, a routine CT follow-up examination after 5 years is recommended. This study provides a population-based study for comparison with the results of endovascular repair.

Three-dimensional CT angiography: renal applications

CT angiography has become an effective noninvasive imaging modality for evaluating the renal vasculature. The current clinical applications for CT angiography and three-dimensional (3D) imaging related to the kidneys and renal vasculature include evaluation of renal artery stenosis, renal diseases related to aortic diseases, living-related renal donor candidates, and preoperative evaluation of renal masses for possible nephron sparing surgeries. Imaging parameters need to be individually prescribed for renal CT angiography depending on the diagnostic goal of the examination. Methods for optimizing spiral CT protocols including patient preparation, contrast administration, image acquisition parameters, and image reconstruction will be covered.

The value of computed tomography in the assessment of suspected ruptured abdominal aortic aneurysm

OBJECTIVE

The objective of this study was to determine the diagnostic value of computed tomography (CT) in patients with suspected ruptured abdominal aortic aneurysm.

STUDY DESIGN

The study was an interrogation of a prospectively gathered computerized database.

SETTING

The study was performed at a regional vascular surgery unit.

SUBJECTS

Six hundred fifty-two consecutive patients were admitted to this unit with suspected ruptured abdominal aortic aneurysm between January 1, 1989, and December 31, 1996. Seventy-four patients (11.3%) in whom the diagnosis was in doubt on clinical grounds alone underwent urgent CT. A total of 47 men and 27 women with a median age of 73 years (range, 52 to 86 years) were evaluated.

MAIN OUTCOME MEASURES

CT and operative findings were compared.

RESULTS

CT correctly diagnosed rupture in 22 of 28 patients who underwent operation and correctly excluded rupture in 30 of 39 patients who underwent operation. The sensitivity and specificity of CT when compared with operative findings were therefore 79% and 77%, respectively.

CONCLUSIONS

These data indicate that CT has little additional diagnostic value. If in the opinion of an experienced vascular surgeon rupture cannot be excluded on clinical grounds alone, and the patient has no medical contraindications to abdominal aortic aneurysm repair, then the patient should be taken directly to the operating department.

Intravascular ultrasonography allows accurate assessment of abdominal aortic aneurysm: an in vitro validation study

OBJECTIVE

The objective of this study was to acquire insight into the interpretation of intravascular ultrasound images of the abdominal aorta and to assess to what extent this technique can provide useful parameters for the endovascular treatment of patients with abdominal aortic aneurysm.

STUDY DESIGN

This was a descriptive study.

METHODS

Fifteen abdominal aortic specimens (normal, atherosclerotic, or aneurysmal) were studied. Ultrasonic images and corresponding histologic sections were compared for vessel wall characteristics, lesion morphologic characteristics, and lumen diameter. The length of the aneurysm and the length of the proximal and distal neck were measured and compared with external measurements. Tomographic images were reconstructed to a three-dimensional format.

RESULTS

Normal aortic wall was seen as a two- or three-layered structure corresponding with intima, media, and adventitia. A distinction could be made among fibrous lesion, calcified lesion, and thrombus and between normal and aneurysmal aorta. Correlation between the histologic specimens and intravascular ultrasonography for lumen diameter measurements was high (r = 0.93; p < 0.001). In a similar fashion, correlation between external measurements and intravascular ultrasound measurements on the length of the aneurysm and its proximal and distal neck was high (r = 0.99; p < 0.001). Three-dimensional analysis enhanced interpretation of the tomographic images by visualizing the spatial position of anatomic structures and contributed to understanding the shape and dimensions of the aneurysm.

CONCLUSIONS

Intravascular ultrasonography provides accurate information on the vessel wall, lesion morphologic characteristics, and quantitative parameters of the abdominal aorta. Spatial information supplied by three-dimensional analysis contributes to a more realistic interpretation of the tomographic images.

Pre-operative classification of abdominal aortic aneurysms with spiral CT: the axial source images revisited

OBJECTIVE

The differentiation of supra-, juxta- and high infrarenal abdominal aortic aneurysms (AAA), which is essential for good surgical management, remains problematic. This prospective study assessed the value of highly overlapping vs. contiguous axial spiral computed tomography (CT) reconstructions in the pre-operative assessment of AAA.

PATIENTS AND METHODS

Thirty-five patients with abdominal aortic aneurysms were studied with spiral CT (10 mm collimation, pitch 1). Axial reconstructions were performed at 2 and 10 mm increments and compared with surgical findings. Using each protocol, the aneurysms were classified as infra-, juxta- or suprarenal. Observers also assessed visualization of main and accessory renal artery origins and identification of other surgically relevant vascular anomalies.

RESULTS

The 2 mm protocol correctly identified 29/31 infrarenal, 3/3 juxtarenal and 1/1 suprarenal aneurysms; two infrarenal aneurysms were overestimated as suprarenal. The 10 mm protocol correctly classified 25/31 infrarenal, 3/3 juxtarenal and 1/1 suprarenal aneurysms; five infrarenal aneurysms were overestimated as juxtarenal (n = 3) or suprarenal (n = 2) and one case was equivocal. Correct classification was thus 94% using the 2 mm protocol and 83% with the 10 mm protocol (P = 0.063). All 70 main renal artery origins were visualized with the 2 mm protocol, while the 10 mm protocol missed six (P = 0.03) The 2 mm protocol identified 10 accessory renal arteries, four of which were missed by the 10 mm protocol. Both protocols demonstrated five surgically relevant venous anomalies.

CONCLUSION

Spiral CT with highly overlapping axial reconstructions correctly classified 94% of abdominal aortic aneurysms; overlapping reconstructions were particularly useful in differentiating high infrarenal from juxtarenal aneurysms.

Helical computed tomography in the assessment of abdominal aortic pathology

A pilot study was undertaken to evaluate the role of helical computed tomography in the assessment of abdominal aortic pathology. A total of 17 patients underwent intra-arterial digital subtraction of angiography (IADSA) and helical computed tomography, with eight patients undergoing subsequent operative intervention. A comparison of radiological findings between IADSA and helical computed tomography (CT) was made and, where applicable, a comparison was made with operative findings. Pathology included abdominal aortic aneurysm (AAA) (n = 12), thoraco-abdominal aneurysm (n = 2) and dissection (n = 1), graft distension following AAA repair (n = 1) and plaque haemorrhage in the distal aorta following percutaneous transluminal angioplasty (PTA) of the iliac artery (n = 1). Planned operative management as based on pre-operative helical CT imaging findings, in particular with reference to the type of graft used (straight or bifurcated) was not changed at operation. Our findings on helical CT in regards to AAA, thoroco-abdominal aneurysm and dissection correlated well with angiography and surgery findings.

Risk factors associated with rapid growth of small abdominal aortic aneurysms

BACKGROUND

Approximately 50% of patients who have a ruptured abdominal aortic aneurysm will die. To identify those patients who may be at high risk for rupture, we determined the risk factors for the rapid expansion of the aorta.

METHODS

The growth of 514 aneurysmal aortas was followed in this study. The size of each was measured by ultrasonography at 6- to 12-month intervals until a critical size was reached or a rapid expansion of the aorta occurred. Possible risk factors for rapid expansion were determined from both initial evaluation and clinical laboratory results.

RESULTS

The initial size varied from 2.5 cm to 6.0 cm. The expansion rate of the aorta was 0.5 cm/yr or less in 401 patients (78%), between 0.5 and 1.0 cm/year in 50 patients (10%), and 1.0 cm/year or more (rapid expansion) in 63 patients (12%). Elective repair of aneurysms was done before rupture. Multivariate analysis indicated that the risk factors associated (p < 0.03) with rapid expansion were advanced age, severe cardiac disease, previous stroke, and history of cigarette smoking. The incidence for rapid expansion increased (p < 0.01) in older patients with aneurysms larger than 3 cm and in younger patients with aneurysms larger than 4 cm.

CONCLUSIONS

Risk factors associated with rapid expansion of the aorta have been determined and may help identify the patient at high risk for rupture. Ultrasonographic surveillance should be performed more frequently in these patients to help prevent rupture.

Gadolinium-enhanced magnetic resonance angiography of abdominal aortic aneurysms

PURPOSE

The objective of this study was to assess the usefulness of gadolinum-enhanced magnetic resonance angiography (MRA) for defining anatomic features relevant to performing aortic surgery for aneurysmal disease.

METHODS

Anatomic data defined by MRA, including abdominal aortic aneurysm (AAA) size and character, as well as the status of the celiac, mesenteric, renal, and iliac arteries, were correlated with angiography, ultrasonography, computed tomography, or operative data in 43 patients. Five MRA sequences were obtained in an hour-long examination optimized for aortoiliac, splanchnic, and renal artery imaging at 1.5 T in a body coil. Four of the sequences were performed during or after infusion of gadolinium to improve image quality.

RESULTS

MRA correctly defined the maximum aneurysm diameter, as well as its proximal and distal extent in all patients. MRA detected 33 of 35 significant stenoses among 153 splanchnic, renal, or iliac branches examined (sensitivity = 94% and specificity = 98%). MRA did not resolve the degree of aortic branch stenotic disease sufficiently to precisely grade its severity. MRA did not reliably define the status of the inferior mesenteric artery, lumbar arteries or internal iliac arteries. One ruptured AAA and one inflammatory AAA were correctly diagnosed by MRA. No patient had a contrast reaction or contrast-induced renal toxicity related to administration of gadolinium.

CONCLUSION

Gadolinium-enhanced MRA of AAA provides appropriate, essential anatomic information for aortic reconstructive surgery in a 1-hour examination devoid of contrast-related renal toxicity or catheterization-related complications attending conventional arteriography.