Spectrum Of Ct Findings In Rupture And Impendinging Rupture Of AAA

Spectrum of CT Findings in Rupture and Impeding Rupture of Abdominal Aortic Aneurysms Presented by EKKASIT SRITHAMMASIT, MD. Dmitry Rakita, MD et al Department of Radiology, Division of Body Imaging and Division of Interventional Radiology, Long Island Jewish Medical Center RadioGraphics 2007; 27:497-507

An aortic diameter of 3 cm or more is used to define an AAA. Most involve the aortic segment below the renal arteries. Introduction

Most AAA are true aneurysms. Introduction

Strong risk factors of AAA Concurrent coronary artery disease Concurrent peripheral vascular disease A family history of AAA Introduction Prevalence: 2%–4% of the population older than 50 years. More men than women are affected.

Table of content Imaging Tecniques Finding of Aneurysm Rupture Findings Predictive of Impending Rupture Infected Aneurysms Aortic Fistulas Inflammatory Aneurysms US CT MRI

Imaging Tecniques CT Speed Availability MRI Much longer acquisition time Less available. CT is the modality of choice for evaluation of acute aortic syndrome

Imaging Tecniques CT angiography has become routine for imaging of a suspected rupture. (R/O appendicitis, pancreatitis, or bowel obstruction ) Unenhanced CT may help detect an aneurysm rupture by depicting an AAA with surrounding retroperitoneal hemorrhage. Contrast-enhanced CT provides additional information about the size of the aneurysmal lumen , presence of active extravasation, and relationship of the aneurysm to the celiac a, SMA, renal a, and IMA. CT is the modality of choice for evaluation of acute aortic syndrome

Imaging Tecniques Unenhanced scanning at 5-mm collimation. CT angiography at 1-mm collimation Delayed imaging in the portal venous phase (80 seconds) at 5-mm collimation. CT protocol (on a four– or 16–detector row scanner) Contrast injection rates of 3–4 mL/sec are optimal. A total of 90 mL of nonionic intravenous contrast material is sufficient to reliably produce diagnostic-quality images. Oral contrast material is not administered.

Imaging Tecniques May be an effective alternative option for patients who have a contraindication to the use of iodine. Requires a high dose of Gadolinium (0.3– 0.5 mmol/kg). Best performed with a MDCT scanner with 16 channels or more to allow rapid acquisition. However, the use of high-dose gadolinium as a substitute for iodinated contrast material is controversial in patients at risk for nephrotoxic effects or with preexisting renal insufficiency. Gadolinium-enhanced CT angiography

Imaging Tecniques Bowel gas, body habitus, operator dependent. Unstable patients to transfer for CT. Ultrasonography (limited role in the assessment of acute aortic abnormalities) US may help determine the size of the aneurysm and help identify hemoperitoneum . However, the utility of US for identifying an impending rupture or a contained rupture of an aneurysm is limited.

Table of content Imaging Tecniques Finding of Aneurysm Rupture Findings Predictive of Impending Rupture Infected Aneurysms Aortic Fistulas Inflammatory Aneurysms

Finding of Aneurysm Rupture M/C finding: A retroperitoneal hematoma adjacent to an AAA. Common occurrence: Extension of hemorrhage into the perirenal and pararenal spaces, psoas muscles,and peritoneum( immediate/delayed finding). Active extravasation of contrast material is frequently demonstrated on CECT.

CT angiographic images A 80-year-old woman with abdominal pain and hypotension.

CT angiographic images A 67-year-old man with abdominal pain and hypotension.

CT angiographic images a 68-year-old man with abdominal and right hip pain.

Posttreatment angiogram a 68-year-old man with abdominal and right hip pain. Endovascular repair has gained increasing acceptance for elective use in patients who are at high risk for complications from open surgery and for relatively stable patients.

Gadolinium-enhanced CT angiography A 75-year-old man with chronic renal insufficiency and abdominal pain after endovascular repair.

Finding of Aneurysm Rupture Draped aorta sign : an important imaging feature that may be seen in a contained rupture of an AAA. the posterior wall of the aorta either is not identifiable as distinct from adjacent structures or when it closely follows the contour of adjacent vertebral bodies.

CT angiographic images ; Draped aorta sign a 55-year-old man with a known abdominal aortic aneurysm and recent vague back pain.

Another patient who presented with backpain . There was no evidence of aneurysm leakage, but we see a draped aorta . www . radiologyassistant . nl

Findings Predictive of Impending Rupture Increased Aneurysm Size Thrombus and Calcifications Hyperattenuating Crescent Sign

Findings Predictive of Impending Rupture 1. Increased Aneurysm Size: A patient with a very large AAA (diameter of 7 cm) who presents with symptoms of acute aortic syndrome has a high likelihood of aneurysm rupture. Furthermore, an enlargement rate of 10 mm or more per year is also used as an indication for surgical repair. The most common finding predictive of rupture and, thus, the most common indicator for elective surgical management, is the maximum diameter of the aneurysm.

Unenhanced CT images a 68-year-old man with an acute onset of right flank pain radiating to the back.

Findings Predictive of Impending Rupture 2. Thrombus and Calcification : A thick circumferential thrombus is protective against rupture . Nonruptured aneurysms generally contain more thrombus than do ruptured aneurysms, and the thrombus-to-lumen ratio decreases with increasing aneurysm size. A focal discontinuity in circumferential wall calcifications is more commonly observed in unstable or ruptured aneurysms. This finding is most helpful when a previous CT study is available and its comparison with the current CT study shows that an area of discontinuity in mural calcifications is new.

CT images from two examinations of the same patient in 2003 (a) and 2005 (b) Discontinuity of aortic wall calcifications in an abdominal aortic aneurysm in a 60-yearold woman.

Findings Predictive of Impending Rupture 3. Hyperattenuating Crescent Sign : UECT A well-defined peripheral crescent of increased attenuation within the thrombus of a large abdominal aortic aneurysm is a CT sign of acute or impending rupture. It is one of the earliest and most specific imaging manifestations of the rupture process.

Unenhanced CT images ; a and b are the same section with different window settings a 66-year-old man with back pain, who underwent imaging for suspicion of renal colic.

Axial unenhanced (a) and axial contrast-enhanced (b) CT images A 57-year-old man with a known abdominal aortic aneurysm and increasing abdominal pain.

Infected Aneurysms Uncommon (0.7%–2.6% of aortic aneurysms) Most often pseudoaneurysms. Most commonly caused by endocarditis. The direct spread of infection from adjacent vertebral osteomyelitis and from renal and psoas abscesses also has been documented. Majority occur in the thoracic or suprarenal abdominal aorta. Prone to rupture (a rupture rate of 53%–75% at surgical repair)

Infected Aneurysms Saccular shape and Lobular contours . Periaortic inflammation, abscess, and mass. Other findings include Periaortic gas. Adjacent vertebral body abnormalities due to the spread of infection. CT findings of infected aneurysms

Sagittal and axial contrast-enhanced CT images A 45-year-old man with back and abdominal pain, fever, and an elevated white blood cell count.

Axial, sagittal, and coronal contrast-enhanced CT images. A 74-year-old man with abdominal pain and an elevated white blood cell count.

Aortic Fistulas Most fistulas involve the duodenum , most commonly its third and fourth portions . Symptoms include abdominal pain, hematemesis, and melena. Primary aortoenteric fistulas complication of atherosclerotic aortic aneurysms Secondary aortoenteric fistulas a complication of aortic reconstructive surgery

Aortic Fistulas Primary aortoenteric fistulas A diagnostic dilemma for the clinician, especially in the absence of gastrointestinal tract bleeding. Upper gastrointestinal tract endoscopy may help rule out other causes of bleeding but rarely helps diagnose a fistula . CT Findings AAA ; often with signs of rupture. Intraluminal and periaortic extraluminal gas. Contrast material extravasation from the aorta into the involved portion of the bowel (if a patent fistula is present) Surgical exploration is usually necessary to confirm the diagnosis and for treatment.

Axial, and coronal CT angiographic images a 71 -year-old woman with a known abdominal aortic aneurysm, abdominal pain, and a guaiac-positive stool test.

Aortic Fistulas Secondary aortoenteric fistulas Much more common. Must be distinguished from graft infection perigraft gas may be seen in both conditions both entities may occur as delayed complications of aortic aneurysm repair. Aortoenteric fistulas have been reported to occur between 2 weeks and 8 years after surgery

Inflammatory Aneurysms The term inflammatory aneurysm was initially used in 1972 to describe aortic aneurysm disease with significant perianeurysmal inflammation and adhesions to surrounding structures. 3%–10% of aortic aneurysms Predominantly found in men.

Inflammatory Aneurysms Cause ; slow aneurysmal leakage was initially thought to be its. The etiology ; poorly understood but is thought to be related to periaortic retroperitoneal fibrosis and various autoimmune diseases (rheumatoid arthritis, systemic lupus erythematosus, and giant cell arteritis).

Inflammatory Aneurysms Symtoms & Signs : fever, weight loss, and an elevated erythrocyte sedimentation rate , hydronephrosis or renal failure(20-30%). Inflmmatory Aneurysm Symptomatic Increased risk of rupture irrespective of their size Artherosclerotic Aneurysm Asymptomatic Increased risk of rupture respective of their size

Inflammatory Aneurysms CT imaging features include Inflammatory or fibrotic changes in the periaortic regions of the retroperitoneum.

contrast-enhanced CT images (a at a level higher than b) A 50-year-old man with a known abdominal aortic aneurysm, abdominal pain, and an elevated erythrocyte sedimentation rate.

Summary Imaging findings of aortic aneurysm rupture vary along a spectrum from impending rupture to contained rupture and from small aortic leaks with subtle infiltration of retroperitoneal fat to frank retroperitoneal or intraperitoneal extravasation. Aortic aneurysms most commonly occur as a consequence of atherosclerotic disease of the aorta. Alternatively, they may be associated with infectious seeding of the native or surgically repaired vessel.

Term Acute aortic syndrome (AAS) describes a range of severe, painful, potentially life-threatening abnormalities of the aorta. These include aortic dissection , intramural thrombus , and penetrating atherosclerotic aortic ulcer. AAS can be caused by a lesion on the wall of the aorta that involves the tunica media, often in the descending aorta. It is possible for AAS to lead to acute coronary syndrome. The term was introduced in 2001.

Spectrum Of Ct Findings In Rupture And Impendinging Rupture Of AAA

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Spectrum Of Ct Findings In Rupture And Impendinging Rupture Of AAA