Spectrum Of Ct Findings In Rupture And Impendinging Rupture Of AAA

Spectrum of CT Findings inSpectrum of CT Findings in Rupture and Impeding Rupture ofRupture and Impeding Rupture of

Abdominal Aortic Abdominal Aortic AneurysmsAneurysms

Presented by EKKASIT SRITHAMMASIT, MD.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 An aortic diameter of 3 cm or more3 cm or more is used is used to define an AAA.to define an AAA.

• Most involve the Most involve the aortic segment aortic segment below the renal below the renal arteries.arteries.

IntroductionIntroduction

• Most AAA are true aneurysms.Most AAA are true aneurysms.


Strong risk factors of Strong risk factors of AAAAAA

– Concurrent coronary artery disease

– Concurrent peripheral vascular disease

– A family history of AAA


•Prevalence: 2%–4% of the Prevalence: 2%–4% of the population older than 50 population older than 50 years. years. •More men than women are More men than women are affected.affected.

Table of contentTable of content

Imaging Tecniques Finding of Aneurysm Rupture Findings Predictive of

Impending Rupture Infected Aneurysms Aortic Fistulas Inflammatory Aneurysms

US CT MRI

Imaging TecniquesImaging Tecniques

CTCT

• Speed

• Availability

MRIMRI

• Much longer acquisition time

• Less available.

CT is the modality of choice for evaluation of acute aortic syndrome


• 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


• 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.


• 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


• 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.

Finding of Aneurysm Finding of Aneurysm RuptureRupture

• 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 imagesA 80-year-old woman with abdominal pain and hypotension.

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

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

Posttreatment angiograma 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 angiographyA 75-year-old man with chronic renal insufficiency and abdominal pain after

endovascular repair.

Finding of Aneurysm Finding of Aneurysm RuptureRupture

Draped aorta sign :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.

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

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Findings Predictive of Findings Predictive of Impending RuptureImpending Rupture

1.1. Increased Aneurysm SizeIncreased Aneurysm Size

2.2. Thrombus and CalcificationsThrombus and Calcifications

3.3. Hyperattenuating Crescent SignHyperattenuating Crescent Sign


1. Increased Aneurysm Size: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 imagesa 68-year-old man with an acute onset of right flank

pain radiating to the back.


2. Thrombus and Calcification :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.


3. Hyperattenuating Crescent Sign :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 settingsa 66-year-old man with back pain, who underwent imaging for suspicion of

renal colic.

Axial unenhanced (a) and axial contrast-enhanced (b) CT imagesA 57-year-old man with a known abdominal aortic aneurysm and

increasing abdominal pain.

Infected AneurysmsInfected 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 AneurysmsInfected Aneurysms

1. Saccular shape and Lobular contours.

2. 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 FistulasAortic Fistulas

• Most fistulas involve the duodenum, most commonly its third and fourth portions.

• Symptoms include abdominal pain, hematemesis, and melena.

Primary Primary aortoenteric fistulasaortoenteric fistulas

• complication of atherosclerotic aortic aneurysms

SecondarySecondaryaortoenteric fistulasaortoenteric fistulas

• a complication of aortic reconstructive surgery


Primary aortoenteric fistulasPrimary 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 FindingsCT Findings1. AAA ; often with signs of rupture.

2. Intraluminal and periaortic extraluminal gas.

3. Contrast material extravasation from the aorta into the involved portion of the bowel (if a patent fistula is present)

Surgical exploration is usually necessary t o 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.


Secondary aortoenteric fistulasSecondary 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 Inflammatory AneurysmsAneurysms

• 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.


• 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).


Symtoms & SignsSymtoms & Signs : fever, weight loss, and an elevated erythrocyte sedimentation rate , hydronephrosis or renal failure(20-30%).

Inflmmatory AneurysmInflmmatory Aneurysm

• Symptomatic• Increased risk of rupture

irrespective of their size

Artherosclerotic AneurysmArtherosclerotic Aneurysm

• Asymptomatic• Increased risk of rupture

respective of their size


CT imaging features includeCT 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.

SummarySummary

• 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.

The end.The end.

The end….The end….

TermTerm

• Acute aortic syndrome (AAS)Acute aortic syndrome (AAS) describes a range of describes a range of severe, painful, potentially life-threatening severe, painful, potentially life-threatening abnormalities of the aorta.abnormalities of the aorta.– These include These include aortic dissectionaortic dissection, , intramural thrombusintramural thrombus, and , and

penetrating atherosclerotic aortic ulcer.penetrating atherosclerotic aortic ulcer.– AAS can be caused by a lesion on the wall of the aorta that AAS can be caused by a lesion on the wall of the aorta that

involves the tunica media, often in the descending aorta.involves the tunica media, often in the descending aorta.– It is possible for AAS to lead to acute coronary syndrome.It is possible for AAS to lead to acute coronary syndrome.– The term was introduced in 2001.The term was introduced in 2001.

Spectrum Of Ct Findings In Rupture And Impendinging Rupture Of AAA

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