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Acute Vascular Pathology: Distinguishing Abdominal Pseudoaneurysms from Aneurysms and Implications for Patient Management

F Verde, MD

Objectives

Review the pathophysiology of abdominal aneurysms and pseudoaneurysms
Describe optimal CT technique
- Understand value of arterial and venous phase imaging
- Recognize importance of multiplanar review for detection and characterization
Illustrate distinguishing features between pseudoaneurysms and true aneurysms
Demonstrate CT appearance of splenic, celiac, SMA, GDA and renal aneurysms and pseudoaneurysm
Discuss the management of these lesions

MDCT Protocol Design

Optimization of protocol in the emergent setting not always possible
Symptoms overlap with other entities
Scan may have been performed with positive oral contrast in venous phase only
Recognize advantages of PO water
Increases conspicuity vascular lesions and active bleeding

Limitation of Oral Contrast

Where is the pseudoaneurysm??

Limitation of Oral Contrast

Limitation of Oral Contrast

Post traumatic mesenteric artery pseudoaneurysm (red arrow). More conspicuous on follow up study with oral contrast only in colon (B) and on coronal MPR (C), which shows mesenteric stranding (yellow arrow).

Limitation of Oral Contrast

Dual Phase MDCT Pearls

Some pseudoaneurysms and large aneurysms require time to fully opacify

Pseudoaneurysm may have delayed enhancement if supplied by smaller arteries
Enhancement of a large aneurysm may not be confirmed until a delayed acquisition
Active bleed may not be seen on early arterial phase

Two phases (arterial and venous) increase accuracy in characterization

GDA Pseudoaneurysm: Delayed Enhancement

GDA pseudoaneurysms are fed by small branches and may enhance more on venous phase.

GDA Pseudoaneurysm:Delayed Enhancement

GDA Pseudoaneurysm: Delayed Enhancement

GDA pseudoaneurysms are fed by small branches and may enhance more on venous phase.

GDA Pseudoaneurysm:Delayed Enhancement

Volumetric Post Processing

Standard coronal and sagittal reformats
High resolution dataset for interactive 2D/3D
- 2D multiplanar reformats (MPR)
- Maximum Intensity Projections (MIP)
- Volume rendering (VR)
Maximizes detection rate of subtle vascular abnormality
Evaluation of extent of disease

MPRs for Mesenteric Vasculature

Axial CT and 3D compared in 41 patients
Mesenteric arterial pathology missed on axial images
- Axial and 3D equivalent in 24% (10/41)
- Axial CT partially agreed w/3D CT in 10% (4/41)
- Axial CT false negative in 66% (27/41).
Mesenteric lesions required management in 15% (6/41) of the subjects.

Imaging TechniqueRole of multi-planar reconstructions

Carefully review vasculature in all three standard imaging planes
MPRs, MIPs, and 3D rendering depict the aneurysm in relation to the vessel
- Helpful for treatment planning

Imaging TechniqueRole of multi-planar reconstructions

Coronal MPRS and 3D rendering helpful for small aneurysms
Where is the pathology in this case?
Left renal artery aneurysm

PathophysiologyTrue aneurysm vs Pseudoaneurysm

True aneurysms
- arise from ballooning and weakening of all three arterial layers without rupture
- Usually from atherosclerosis or other vascular diseases.
Pseudoaneurysm
- Contained hematoma usually secondary to trauma or inflammation, not involving all three arterial layers.
- Extravasated blood is contained by one or two layers, adjacent parenchyma or clot, forming the pseudoaneurysm

True Aneurysm vs Pseudoaneurysm – Presentation

True Aneurysm vs Pseudoaneurysm - Common Etiologies

True Aneurysm vs Pseudoaneurysm - Imaging Summary

Mesenteric True AneurysmVessel Distribution

Splenic artery: 60%–80%
Hepatic artery: 20%
SMA: 5.5%
Celiac artery: 4%
Gastric/gastroepiploic: 4%
GDA/pancreatic: 6%
Jejunal and ileocolic: 3%
IMA: <1%

True Aneurysms:Splenic Artery Aneurysm

54-year-old woman with history of autoimmune hepatitis. Axial contrast-enhanced MDCT image shows 1.8-cm aneurysm (arrow) arising from splenic artery. Note lack of surrounding hemorrhage and other traumatic or inflammatory changes, consistent with a true aneurysm.

True Aneurysms:Splenic Artery Aneurysm

Splenic Artery Aneurysm Management

If small and asymptomatic, follow with serial imaging
Surgical intervention at 2 cm
More aggressive management may be warranted in high risk clinical settings: women of childbearing age & cirrhosis
Other considerations
- Location, age
- clinical status, operative risk

Surgical approaches

Aneurysms located in the proximal or middle third of the splenic artery
- simple excision
- proximal and distal ligation of the artery
- splenic preservation (through the short gastric vessels).
For aneurysms located in the distal third, resection with splenectomy is most often performed

True Aneurysms:Hepatic Artery Aneurysm

60-year-old man with long history of hepatitis Axial CT (A) image shows 1.6-cm aneurysm (arrow) of common hepatic artery. Aneurysm is completely depicted with axial 3D rendering (B). Note lack of supporting findings so one may confidently diagnose a true aneurysm.

True Aneurysms:Hepatic Artery Aneurysm

True Aneurysms: SMA Aneurysm

65-year-old man presenting with abdominal pain. Coronal thick slab MIP imaging demonstrating incidental small distal branch SMA aneurysm. Aneurysm is completely depicted in relation to vessels with this reconstruction (arrow). Setting a shortcut for MIPs in PACS is a great tool to quickly evaluate the vessels.

True Aneurysms: SMA Aneurysm

True Aneurysms:Celiac Artery Aneurysm

63-year-old man presenting with abdominal pain. Axial IV contrast enhanced CT (A) with incidental celiac artery fusiform aneurysms are noted and completely depicted in relation to vessels with 3D rendering (arrows) (B and C).3Ds are not necessary for diagnosis but helpful for non-radiologists.

True Aneurysms:Celiac Artery Aneurysm

Celiac Artery AneurysmManagement

Rupture or impending rupture are made apparent by signs and symptoms
- pain
- gastrointestinal bleeding
Size threshold for surgical repair of celiac artery aneurysms is 3 cm in asymptomatic cases.

True Aneurysms:Gastroduodenal Artery Aneurysm

66 year old woman for routine follow-up of cholangiocarcinoma resection. IV contrast enhanced CT in axial (A), coronal (B) and coronal 3D rendering (C) demonstrating focal fusiform 8 mm of the GDA (arrows). 3D rendering best depicts the aneurysm. Note lack of surrounding hemorrhage or mural thrombus.

True Aneurysms:Gastroduodenal Artery Aneurysm

True Aneurysms:Renal Artery Aneurysm

61-year-old male with fever and pain at incision site of previous hip surgery. IV contrast enhanced CT of the abdomen in axial (A) and coronal (B) planes in arterial phase demonstrating 1.5 cm saccular aneurysm at main renal artery bifurcation (most common location). Note lack of surround hemorrhage or mural thrombus.

True Aneurysms:Renal Artery Aneurysm

Visceral Arterial AneurysmsGeneral Management

Treatment options include surgical vs endovascular approaches based on location
For many cases, ligation or coil embolization is the treatment of choice
Stents are used primarily in cases of aneurysms of major branches, where preservation of arterial flow is required

PseudoaneurysmsGeneral

Much higher risk of rupture
- Small and large pseudoaneurysms can rupture
Most common setting is arterial erosion secondary to pancreatitis
- frequently affects the splenic or gastroduodenal arteries
On CT, the wall may be less well defined than a true aneurysm and perianeurysmal hemorrhage is common.
Risk of rupture of a splenic artery pseudoaneurysm can be as high as 37%
Untreated mortality rate approaches 90% to 100%

Splenic Artery Pseudoaneurysms

Two patients. 45-year-old man with pancreatitis (A). Axial contrast enhanced CT demonstrates > 2 cm splenic pseudoaneurysm (red arrow) with an irregular wall surrounded by large amounts of hemorrhage (*). 18-year-old trauma patient (B). Axial contrast enhanced CT demonstrates 1 cm pseudoaneurysm (white arrow) surrounded by hemorrhage as well as splenic laceration (arrow head).

Splenic Artery Pseudoaneurysms

GDA Pseudoaneurysm

50 year old man with pancreatitis. IV contrast enhanced CT in coronal thin section (A) and MIP (B) demonstrates a 2 cm enhancing mass with a minimal hypodense halo, consistent with pseudoaneursym from a GDA/GDA branch in the pancreatic head (arrows). Incidental PV clot noted (arrowhead).

GDA Pseudoaneurysm

Hepatic Artery Pseudoaneurysm

69-year-old woman with pancreatic status post Whipple procedure. Postoperatively, Jackson Pratt drain had continued high output, which became serosanguinous. CT performed with axial image (A) and coronal MPR revealing a hepatic artery pseudoaneurysm. Trauma by any source, is by far the most common etiology for hepatic pseudoaneurysm formation. Note adjacent hemorrhage.

Renal Artery Pseudoaneurysm

57-year-old woman status post right robot assisted laparoscopic partial nephrectomy readmitted with abdominal pain and emesis. Coronal (A) and axial images (B) show a right perinephric hematoma and a large pseudoaneurysm (arrow) arising from lower pole renal artery. Note all the features of pseudoaneurysm formation: history, mural hemorrhage, and associated findings.

Renal Artery Pseudoaneurysm

Coil Embolization of Renal Artery PSA

Conclusions

Distinguishing true aneurysms from pseudoaneurysms is important for decreasing morbidity and mortality
All pseudoaneurysms must be treated emergently, usually by coil embolization

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Acknowledgements:

M Lu, BA
PT Johnson, MD
CR Weiss, MD
EK Fishman, MD
F Verde, MD