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Nontraumatic Emergent Abdominal Vascular Conditions: Advantages of Multi–Detector Row CT and Three-Dimensional Imaging¹

¹ From the Institute of Diagnostic Radiology, University Hospital of Zurich, Raemistrasse 100, 8091 Zurich, Switzerland. Presented as an education exhibit at the 2002 RSNA scientific assembly. Received August 22, 2002; revision requested November 25, 2002, and received May 21, 2003; accepted July 2. Supported by the NCCR CO-ME of the Swiss National Science Foundation. Address correspondence to S.W. (e-mail: simon.wildermuth@usz.ch).

	Abstract

Top Abstract Introduction CT Scanning Technique Emergent Vascular Conditions Conclusions References

 
In the past decade, great strides have been made in the development of helical computed tomography (CT) that have led to shorter scanning time and higher spatial resolution. A wide range of traumatic and nontraumatic emergent conditions may be quickly and accurately diagnosed with multi–detector row CT. Multi–detector row CT angiography is the preferred method for imaging in emergent abdominal vascular conditions because it enables the acquisition of high-spatial-resolution volumetric image data during a single breath hold. Unlike catheter angiography, multi–detector row CT angiography not only depicts the vessels but also allows assessment of perfusion in adjacent organs. To make the most effective diagnostic use of multi–detector row CT angiography and three-dimensional image postprocessing, radiologists must be familiar with the optimal CT angiographic protocols and with the typical CT findings in various emergent vascular conditions. This article describes the protocols used in 11 patients with conditions including ruptured abdominal aortic aneurysm, secondary aortoduodenal fistula, splanchnic segmental arterial mediolysis, and Wegener-type vasculitis with visceral involvement. All of the diagnoses in these 11 cases were made in the emergency department, and the delay between imaging and diagnosis was decreased considerably by avoiding the transfer of patients for catheter angiography.

© RSNA, 2004

Index Terms: Aorta, dissection, 94.74, 89.74 • Arteries, mesenteric, 95.73, 95.76, 95.77 • Computed tomography (CT), angiography, 95.12916, 98.12916 • Mesentery, ischemia, 95.76, 96.76, 98.76 • Veins, mesenteric, 98.73, 98.76, 98.77 • Wegener granulomatosis, 89.622

	Introduction

Top Abstract Introduction CT Scanning Technique Emergent Vascular Conditions Conclusions References

 
Computed tomography (CT) is an important imaging modality for noninvasive assessment of the vascular system (1). Multi–detector row CT offers a number of advantages over single-section CT in the work-up of patients with emergent conditions (2). The shorter scanning time with multi–detector row CT scanners permits better visualization of blood vessels and improved contrast material enhancement of the adjacent organ parenchyma. Furthermore, faster data acquisition makes it possible to perform multiple consecutive CT examinations in the same patient in a short time (2).

The development of multi–detector row CT, in combination with advances in computer hardware, software, and display technology, has facilitated three-dimensional (3D) image reconstruction (3). Shaded surface display, maximum intensity projection (MIP), and volume rendering (VR) are the three most commonly used 3D reconstruction techniques. In vascular imaging, MIP and VR of image data from multi–detector row CT angiography can enable visualization that is equal or superior to that obtained with catheter angiography. Postprocessing can be performed quickly and easily to obtain a two-dimensional MIP image, and a 3D effect can be achieved with stepwise rotation of the object. VR has a high diagnostic accuracy and is the method most often used for reconstruction of CT angiographic image data because it enables 3D visualization not only of the vascular system but also of adjacent organs.

These techniques therefore are increasingly the initial or the only imaging methods used for surgical planning in emergent vascular conditions. Their use often obviates that of catheter angiography or digital subtraction angiography and thus leads to a reduction in costs (4). Multi–detector row CT angiography and 3D reconstruction are the preferred methods for planning of angiographic interventional treatments at our institution. For example, they are used for vessel segmentation to enable determination of the optimal stent-graft dimensions prior to treatment of aortic aneurysm. Follow-up of patients after aortic stent-graft placement also is performed with multi– detector row CT angiography for detection and localization of displaced stent-grafts and various endoleaks. Three-dimensional reconstructions have increased the options available for visualization of emergent vascular conditions and are gaining acceptance among clinicians.

Assessment of emergent abdominal vascular conditions is possible today with the exclusive use of multi–detector row CT angiography. To achieve correct diagnosis and avoid unnecessary intervention, however, it is essential to be familiar with the anatomy and physiology of abdominal vascular lesions, as well as with the techniques of image acquisition, postprocessing, and interpretation. In this article, we describe the protocols used at our institution and present axial source images and three-dimensional reconstructions from multi–detector row CT angiography in 11 patients. These images illustrate the typical findings in various nontraumatic emergent abdominal vascular conditions, such as ruptured abdominal aortic aneurysm, secondary aortoduodenal fistula, splanchnic segmental arterial mediolysis, and Wegener-type vasculitis with visceral involvement.

	CT Scanning Technique

Top Abstract Introduction CT Scanning Technique Emergent Vascular Conditions Conclusions References

 
Optimal scanning protocols are mandatory for complete and accurate assessment of emergent vascular conditions with CT, and the intravenous contrast material injection protocol must be specific to the vascular region that is being assessed. At our institution, different protocols for each anatomic area and for traumatic and nontraumatic emergent conditions are preprogrammed on the CT scanner and the automated injection system.

For optimal assessment, the scanning and protocol must be tailored to the area of interest in a certain anatomic region. If a pathologic condition such as aortoduodenal fistula is suspected to be present, no oral contrast material should be given; contrast material extravasation into the gastrointestinal tract would not be visible with the presence of orally administered contrast material in the bowel, which would obscure the location of the fistula.

CT assessment of patients who have emergent abdominal vascular conditions is performed at our institution with a multi–detector row scanner (Somatom Volume Zoom; Siemens Medical Solutions, Forchheim, Germany). The scanning protocol includes arterial phase imaging with a collimation of 4 x 1 mm (pitch of 0.85) and venous phase imaging with a collimation of 4 x 2.5 mm (pitch of 1.2). Reconstruction of the source image data is performed with section thicknesses of 1.25 and 3 mm, respectively. Prior to CT angiography, 150 mL of a nonionic contrast material containing 370 mg of iopromide per milliliter (Ultravist; Schering, Berlin, Germany) is injected intravenously at a rate of 3–4 mL per second. The CARE bolus technique (Siemens Medical Solutions, Forchheim, Germany) is used to trigger image acquisition at a predefined level of attenuation for optimal arterial depiction in the region of interest. The region of interest for the measurements of attenuation is placed in the abdominal aorta. Arterial phase and venous phase images of the entire abdomen are acquired to characterize blood supply and drainage. If necessary, 3D postprocessing techniques such as multiplanar reformation (MPR), shaded surface display, MIP, or VR are used for better visualization of pathologic changes and for preoperative or preinterventional planning. Commercially available software (ProVision 2.2; Algotec Systems, Raanana, Israel) was used in the reconstruction of most of the 3D images that appear in this article.

	Emergent Vascular Conditions

Top Abstract Introduction CT Scanning Technique Emergent Vascular Conditions Conclusions References

 
Rupture of Abdominal Aortic Aneurysm
Aneurysmal dilatation of the infrarenal aorta is defined as a diameter of more than 29 mm. Based on this criterion, 9% of all people older than 65 have an abdominal aortic aneurysm (5). Rupture of an abdominal aortic aneurysm is one of the most urgent vascular conditions and requires rapid intervention. In autopsy studies reported by Lederle et al (6), the 1-year incidence of abdominal aortic aneurysm rupture according to initial diameter was 9.4% for diameters of 5.5–5.9 cm, 10.2% for diameters of 6.0–6.9 cm (19.1% for the subgroup of 6.5–6.9 cm), and 32.5% for diameters of 7.0 cm or more. Other investigators (7,8) have reported similar rupture rates.

A diagnosis of ruptured abdominal aortic aneurysm may be made on the basis of a nonenhanced CT scan that shows an aortic aneurysm with adjacent periaortic hemorrhage that extends into the perirenal and pararenal spaces of the retroperitoneum (2). Multi–detector row CT angiography may depict active bleeding (Fig 1); extension of the aneurysm into the common, external, and internal iliac arteries; the presence and extent of mural thrombosis; the anatomy of arteries that supply blood to the kidneys, including the accessory renal arteries; and stenosis or occlusion of the vessels. This additional information is important for the choice of treatment. Open surgical repair is increasingly being replaced by endovascular repair, which is more efficient and has lower associated morbidity and mortality (9,10). Lee et al (11) found that patient eligibility for endovascular repair depends on the anatomy of the proximal aneurysm neck. Great effort has been put into the development of specialized software for planning endoluminal treatment of abdominal aortic aneurysm. Most of the measurements required for determination of the optimal dimensions and type of aortic stent-graft now are obtained with multi–detector row CT and 3D reconstruction.

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 1a. Ruptured infrarenal aortic aneurysm in a 72-year-old man. (a, b) Axial source image (a) and coronal oblique MPR image (b) show a ruptured aneurysm (diameter, 7 cm) with active bleeding (arrowhead) caudad to the aneurysm neck; a resultant large hematoma has displaced the kidney ventrally. (c, d) Coronal MIP (c) and VR (d) images show the anatomic location and configuration of the aneurysm and the bleeding (arrowhead)—important information for treatment planning.

View larger version (145K): [in this window] [in a new window] [Download PPT slide]   Figure 1b. Ruptured infrarenal aortic aneurysm in a 72-year-old man. (a, b) Axial source image (a) and coronal oblique MPR image (b) show a ruptured aneurysm (diameter, 7 cm) with active bleeding (arrowhead) caudad to the aneurysm neck; a resultant large hematoma has displaced the kidney ventrally. (c, d) Coronal MIP (c) and VR (d) images show the anatomic location and configuration of the aneurysm and the bleeding (arrowhead)—important information for treatment planning.

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 1c. Ruptured infrarenal aortic aneurysm in a 72-year-old man. (a, b) Axial source image (a) and coronal oblique MPR image (b) show a ruptured aneurysm (diameter, 7 cm) with active bleeding (arrowhead) caudad to the aneurysm neck; a resultant large hematoma has displaced the kidney ventrally. (c, d) Coronal MIP (c) and VR (d) images show the anatomic location and configuration of the aneurysm and the bleeding (arrowhead)—important information for treatment planning.

View larger version (164K): [in this window] [in a new window] [Download PPT slide]   Figure 1d. Ruptured infrarenal aortic aneurysm in a 72-year-old man. (a, b) Axial source image (a) and coronal oblique MPR image (b) show a ruptured aneurysm (diameter, 7 cm) with active bleeding (arrowhead) caudad to the aneurysm neck; a resultant large hematoma has displaced the kidney ventrally. (c, d) Coronal MIP (c) and VR (d) images show the anatomic location and configuration of the aneurysm and the bleeding (arrowhead)—important information for treatment planning.

View larger version (172K): [in this window] [in a new window] [Download PPT slide]   Figure 2a. Ruptured aneurysm in a 77-year-old man who presented with acute abdominal pain. Coronal VR image (a) and axial source image (b) show an infrarenal aortic aneurysm with a diameter of 4.5 cm and a right common iliac artery aneurysm with a diameter of 8.5 cm (arrowheads in b), as well as a retroperitoneal hematoma (arrows in b). These findings were diagnostic. Note that the mural thrombus and the remaining lumen are evident, but no active bleeding can be seen.

View larger version (167K): [in this window] [in a new window] [Download PPT slide]   Figure 2b. Ruptured aneurysm in a 77-year-old man who presented with acute abdominal pain. Coronal VR image (a) and axial source image (b) show an infrarenal aortic aneurysm with a diameter of 4.5 cm and a right common iliac artery aneurysm with a diameter of 8.5 cm (arrowheads in b), as well as a retroperitoneal hematoma (arrows in b). These findings were diagnostic. Note that the mural thrombus and the remaining lumen are evident, but no active bleeding can be seen.

Findings of a contrast-enhanced double lumen and an intimal flap in the aorta are diagnostic. The frequency of occlusion caused by dissection of the abdominal aortic branch vessels has been estimated as 27% (15). Infradiaphragmatic ischemic complications related to the main abdominal arterial branches are best detected with arterial phase imaging. Sebastià et al (16) described two types of branch-vessel occlusion—static and dynamic. In static occlusion, the intimal flap extends into the wall of the branch vessel. In dynamic occlusion, the intimal flap prolapses across the branch-vessel origin and covers the lumen like a curtain. In the presence of ischemia resulting from compression of the true lumen by the false lumen, endovascular fenestration is one option for minimally invasive treatment. Reliable identification of true lumen and false lumen are important for treatment planning (Fig 3). Le Page et al (17) described the beak sign—a triangular area of high attenuation—and a large cross-sectional area on contrast-enhanced CT images as the most useful indicators of the false lumen in acute and chronic aortic dissection. Less common and less reliable identifiers of the true and false lumina are patterns of eccentric calcification (ie, calcification in the dissection membrane facing only one lumen), intraluminal thrombus, and the cobweb sign (ie, thin linear intraluminal filling defects).

View larger version (50K): [in this window] [in a new window] [Download PPT slide]   Figure 3a. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

View larger version (43K): [in this window] [in a new window] [Download PPT slide]   Figure 3b. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

View larger version (54K): [in this window] [in a new window] [Download PPT slide]   Figure 3c. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

View larger version (52K): [in this window] [in a new window] [Download PPT slide]   Figure 3d. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

View larger version (97K): [in this window] [in a new window] [Download PPT slide]   Figure 3e. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

View larger version (96K): [in this window] [in a new window] [Download PPT slide]   Figure 3f. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

View larger version (98K): [in this window] [in a new window] [Download PPT slide]   Figure 3g. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

View larger version (119K): [in this window] [in a new window] [Download PPT slide]   Figure 3h. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

View larger version (119K): [in this window] [in a new window] [Download PPT slide]   Figure 3i. Type B aortic dissection in a 54-year-old woman with acute onset of thoracic and abdominal pain. (a, b) Anterior (a) and posterior (b) shaded surface display images show the true lumen (arrows) and the false lumen (arrowheads), as well as adjacent vessels. (c, d) VR image obtained with a cutting plane (c) and MIP image (d) also depict the two lumina (arrows) but do not permit clear differentiation between them because the entire length of the dissection flap (*) is not visible. (e-i) Contrast-enhanced arterial phase axial source images obtained at successively lower levels show the characteristic signs enabling differentiation between the false (F) and true (T) lumina. In e, the outer, false lumen is wrapped around the inner, true lumen, and the cobweb sign (arrow) is visible. In f and g, the false lumen is clearly larger in diameter than the true lumen and contains a thrombus (arrowheads in g), which is also evident in h (arrows). In h, note the eccentric calcification (arrowhead) alongside the flap facing the true lumen, and, in i, the beak sign (arrowheads) created by the curvature of the flap toward the false lumen.

Active Renal Bleeding Caused by Anticoagulant Drugs
Hemorrhage is common in patients who have received anticoagulant drug therapy. It may occur spontaneously or result from minor trauma and may affect any organ system (18). Renal hemorrhage may occur in suburothelial, intraparenchymal, subcapsular, or perinephric locations, or in a combination of these (19). Acute hemorrhage is best depicted with nonenhanced CT (Fig 4a). However, an additional examination with contrast-enhanced CT should always be performed to exclude other pathologic renal conditions that may cause hemorrhage and may require specific therapy. The presence of perinephric hemorrhage is confirmed by bridging septa of the perinephric fat, which determine the location of bleeding.

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 4a. Spontaneous subcapsular renal hemorrhage in a 70-year-old man who presented, subsequent to oral anticoagulation therapy, with pain in the right side and acute anemia of unknown origin. Nonenhanced axial source image (a), contrast-enhanced coronal MPR (b), and coronal (c) and sagittal (d) VR images depict a subcapsular hematoma (arrowheads) in the right kidney.

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 4b. Spontaneous subcapsular renal hemorrhage in a 70-year-old man who presented, subsequent to oral anticoagulation therapy, with pain in the right side and acute anemia of unknown origin. Nonenhanced axial source image (a), contrast-enhanced coronal MPR (b), and coronal (c) and sagittal (d) VR images depict a subcapsular hematoma (arrowheads) in the right kidney.

View larger version (163K): [in this window] [in a new window] [Download PPT slide]   Figure 4c. Spontaneous subcapsular renal hemorrhage in a 70-year-old man who presented, subsequent to oral anticoagulation therapy, with pain in the right side and acute anemia of unknown origin. Nonenhanced axial source image (a), contrast-enhanced coronal MPR (b), and coronal (c) and sagittal (d) VR images depict a subcapsular hematoma (arrowheads) in the right kidney.

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 4d. Spontaneous subcapsular renal hemorrhage in a 70-year-old man who presented, subsequent to oral anticoagulation therapy, with pain in the right side and acute anemia of unknown origin. Nonenhanced axial source image (a), contrast-enhanced coronal MPR (b), and coronal (c) and sagittal (d) VR images depict a subcapsular hematoma (arrowheads) in the right kidney.

View larger version (101K): [in this window] [in a new window] [Download PPT slide]   Figure 5a. Angiomyolipoma in a 68-year-old man with hemostatic shock, acute anemia, and right-sided abdominal pain. (a-e) Contrast-enhanced axial source image (a), coronal (b) and sagittal (c) MPR images, posteroanterior MIP image (d), and posterior VR image (e) show contrast material extravasation (arrowheads) from the upper right renal pole into a large retroperitoneal hematoma. The lesion (arrow) in the upper renal pole has attenuation characteristic of angiomyolipoma. Note that the MIP image shows only the vessels and extravasation, whereas the VR image depicts adjacent organs as well as the lesion. (f) Angiogram from catheter angiography performed after therapeutic embolization helps confirm the cessation of bleeding at the lesion site (arrow).

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 5b. Angiomyolipoma in a 68-year-old man with hemostatic shock, acute anemia, and right-sided abdominal pain. (a-e) Contrast-enhanced axial source image (a), coronal (b) and sagittal (c) MPR images, posteroanterior MIP image (d), and posterior VR image (e) show contrast material extravasation (arrowheads) from the upper right renal pole into a large retroperitoneal hematoma. The lesion (arrow) in the upper renal pole has attenuation characteristic of angiomyolipoma. Note that the MIP image shows only the vessels and extravasation, whereas the VR image depicts adjacent organs as well as the lesion. (f) Angiogram from catheter angiography performed after therapeutic embolization helps confirm the cessation of bleeding at the lesion site (arrow).

View larger version (157K): [in this window] [in a new window] [Download PPT slide]   Figure 5c. Angiomyolipoma in a 68-year-old man with hemostatic shock, acute anemia, and right-sided abdominal pain. (a-e) Contrast-enhanced axial source image (a), coronal (b) and sagittal (c) MPR images, posteroanterior MIP image (d), and posterior VR image (e) show contrast material extravasation (arrowheads) from the upper right renal pole into a large retroperitoneal hematoma. The lesion (arrow) in the upper renal pole has attenuation characteristic of angiomyolipoma. Note that the MIP image shows only the vessels and extravasation, whereas the VR image depicts adjacent organs as well as the lesion. (f) Angiogram from catheter angiography performed after therapeutic embolization helps confirm the cessation of bleeding at the lesion site (arrow).

View larger version (92K): [in this window] [in a new window] [Download PPT slide]   Figure 5d. Angiomyolipoma in a 68-year-old man with hemostatic shock, acute anemia, and right-sided abdominal pain. (a-e) Contrast-enhanced axial source image (a), coronal (b) and sagittal (c) MPR images, posteroanterior MIP image (d), and posterior VR image (e) show contrast material extravasation (arrowheads) from the upper right renal pole into a large retroperitoneal hematoma. The lesion (arrow) in the upper renal pole has attenuation characteristic of angiomyolipoma. Note that the MIP image shows only the vessels and extravasation, whereas the VR image depicts adjacent organs as well as the lesion. (f) Angiogram from catheter angiography performed after therapeutic embolization helps confirm the cessation of bleeding at the lesion site (arrow).

View larger version (95K): [in this window] [in a new window] [Download PPT slide]   Figure 5e. Angiomyolipoma in a 68-year-old man with hemostatic shock, acute anemia, and right-sided abdominal pain. (a-e) Contrast-enhanced axial source image (a), coronal (b) and sagittal (c) MPR images, posteroanterior MIP image (d), and posterior VR image (e) show contrast material extravasation (arrowheads) from the upper right renal pole into a large retroperitoneal hematoma. The lesion (arrow) in the upper renal pole has attenuation characteristic of angiomyolipoma. Note that the MIP image shows only the vessels and extravasation, whereas the VR image depicts adjacent organs as well as the lesion. (f) Angiogram from catheter angiography performed after therapeutic embolization helps confirm the cessation of bleeding at the lesion site (arrow).

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 5f. Angiomyolipoma in a 68-year-old man with hemostatic shock, acute anemia, and right-sided abdominal pain. (a-e) Contrast-enhanced axial source image (a), coronal (b) and sagittal (c) MPR images, posteroanterior MIP image (d), and posterior VR image (e) show contrast material extravasation (arrowheads) from the upper right renal pole into a large retroperitoneal hematoma. The lesion (arrow) in the upper renal pole has attenuation characteristic of angiomyolipoma. Note that the MIP image shows only the vessels and extravasation, whereas the VR image depicts adjacent organs as well as the lesion. (f) Angiogram from catheter angiography performed after therapeutic embolization helps confirm the cessation of bleeding at the lesion site (arrow).

View larger version (159K): [in this window] [in a new window] [Download PPT slide]   Figure 6a. Aortoduodenal fistula in a 70-year-old man who presented with anemia caused by intestinal bleeding of unknown origin, 10 years after aortoiliac graft implantation. (a, b) Contrast-enhanced axial source image (a) and coronal MPR image (b) show extravasation of contrast material (arrowheads) into the horizontal or inferior duodenum. (c, d) Coronal MIP image (c) and coronal VR image (d) from venous phase imaging show the advantage of two-phase CT: On an arterial phase image, only a small amount of contrast material is evident in the duodenum, whereas the venous phase images show active bleeding (arrow) into the duodenum. (Blood is depicted in yellow.) (e, f) Axial VR image (e) and sagittal MPR image (f) show the exact location of the fistula (arrow).

View larger version (170K): [in this window] [in a new window] [Download PPT slide]   Figure 6b. Aortoduodenal fistula in a 70-year-old man who presented with anemia caused by intestinal bleeding of unknown origin, 10 years after aortoiliac graft implantation. (a, b) Contrast-enhanced axial source image (a) and coronal MPR image (b) show extravasation of contrast material (arrowheads) into the horizontal or inferior duodenum. (c, d) Coronal MIP image (c) and coronal VR image (d) from venous phase imaging show the advantage of two-phase CT: On an arterial phase image, only a small amount of contrast material is evident in the duodenum, whereas the venous phase images show active bleeding (arrow) into the duodenum. (Blood is depicted in yellow.) (e, f) Axial VR image (e) and sagittal MPR image (f) show the exact location of the fistula (arrow).

View larger version (163K): [in this window] [in a new window] [Download PPT slide]   Figure 6c. Aortoduodenal fistula in a 70-year-old man who presented with anemia caused by intestinal bleeding of unknown origin, 10 years after aortoiliac graft implantation. (a, b) Contrast-enhanced axial source image (a) and coronal MPR image (b) show extravasation of contrast material (arrowheads) into the horizontal or inferior duodenum. (c, d) Coronal MIP image (c) and coronal VR image (d) from venous phase imaging show the advantage of two-phase CT: On an arterial phase image, only a small amount of contrast material is evident in the duodenum, whereas the venous phase images show active bleeding (arrow) into the duodenum. (Blood is depicted in yellow.) (e, f) Axial VR image (e) and sagittal MPR image (f) show the exact location of the fistula (arrow).

View larger version (159K): [in this window] [in a new window] [Download PPT slide]   Figure 6d. Aortoduodenal fistula in a 70-year-old man who presented with anemia caused by intestinal bleeding of unknown origin, 10 years after aortoiliac graft implantation. (a, b) Contrast-enhanced axial source image (a) and coronal MPR image (b) show extravasation of contrast material (arrowheads) into the horizontal or inferior duodenum. (c, d) Coronal MIP image (c) and coronal VR image (d) from venous phase imaging show the advantage of two-phase CT: On an arterial phase image, only a small amount of contrast material is evident in the duodenum, whereas the venous phase images show active bleeding (arrow) into the duodenum. (Blood is depicted in yellow.) (e, f) Axial VR image (e) and sagittal MPR image (f) show the exact location of the fistula (arrow).

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 6e. Aortoduodenal fistula in a 70-year-old man who presented with anemia caused by intestinal bleeding of unknown origin, 10 years after aortoiliac graft implantation. (a, b) Contrast-enhanced axial source image (a) and coronal MPR image (b) show extravasation of contrast material (arrowheads) into the horizontal or inferior duodenum. (c, d) Coronal MIP image (c) and coronal VR image (d) from venous phase imaging show the advantage of two-phase CT: On an arterial phase image, only a small amount of contrast material is evident in the duodenum, whereas the venous phase images show active bleeding (arrow) into the duodenum. (Blood is depicted in yellow.) (e, f) Axial VR image (e) and sagittal MPR image (f) show the exact location of the fistula (arrow).

View larger version (186K): [in this window] [in a new window] [Download PPT slide]   Figure 6f. Aortoduodenal fistula in a 70-year-old man who presented with anemia caused by intestinal bleeding of unknown origin, 10 years after aortoiliac graft implantation. (a, b) Contrast-enhanced axial source image (a) and coronal MPR image (b) show extravasation of contrast material (arrowheads) into the horizontal or inferior duodenum. (c, d) Coronal MIP image (c) and coronal VR image (d) from venous phase imaging show the advantage of two-phase CT: On an arterial phase image, only a small amount of contrast material is evident in the duodenum, whereas the venous phase images show active bleeding (arrow) into the duodenum. (Blood is depicted in yellow.) (e, f) Axial VR image (e) and sagittal MPR image (f) show the exact location of the fistula (arrow).

A CT scanning protocol that includes two successive (arterial phrase and portal phase) acquisitions is important for the depiction of small fistulas with a minimal flow volume (Fig 6b and 6c) (29). The appearance of contrast enhancement in the duodenum is diagnostic of aortoduodenal fistula. The delay between the start of arterial phase imaging and the start of venous phase imaging should be about 60 seconds. It is important that oral contrast material not be used when a fistula is suspected, because its use would obscure the source of bleeding. The finding of periaortic air also is specific for the diagnosis of secondary aortoduodenal fistula (30).

Acute Mesenteric Ischemia
Three categories of acute mesenteric ischemia are recognized: arterial occlusion, nonocclusive ischemia, and venous thrombosis (31). Nonspecific findings at radiography may include the sentinel loop sign or paralytic ileus, as well as pneumatosis coli and portal venous air (Fig 7). Secondary to submucosal hemorrhage or edema, bowel wall thickening with a "thumbprinting" appearance may be seen (32).

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 7a. Nonocclusive mesenteric ischemia in a 51-year-old woman with a history of left-sided heart failure. (a) Abdominal radiograph shows signs of pneumatosis coli (arrowheads). (b-d) Coronal VR image (b), sagittal MPR image (c), and curved MPR image (d) show air in the wall of the small bowel and ascending colon (arrowheads). (e, f) Axial source images show air collections in the intrahepatic vessels (arrows in e) and in the portal confluence (arrow in f) and an intraaortic balloon pump device in the aortic lumen (arrowhead in f). The device is shown in a to be in the correct position, and no occlusion is visible in the mesenteric arteries (arrow in d). The absence of occlusion was confirmed at pathologic analysis. The ischemia from low cardiac output probably was exacerbated by a reduction in peak systolic pressure caused by the intraaortic balloon pump.

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 7b. Nonocclusive mesenteric ischemia in a 51-year-old woman with a history of left-sided heart failure. (a) Abdominal radiograph shows signs of pneumatosis coli (arrowheads). (b-d) Coronal VR image (b), sagittal MPR image (c), and curved MPR image (d) show air in the wall of the small bowel and ascending colon (arrowheads). (e, f) Axial source images show air collections in the intrahepatic vessels (arrows in e) and in the portal confluence (arrow in f) and an intraaortic balloon pump device in the aortic lumen (arrowhead in f). The device is shown in a to be in the correct position, and no occlusion is visible in the mesenteric arteries (arrow in d). The absence of occlusion was confirmed at pathologic analysis. The ischemia from low cardiac output probably was exacerbated by a reduction in peak systolic pressure caused by the intraaortic balloon pump.

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 7c. Nonocclusive mesenteric ischemia in a 51-year-old woman with a history of left-sided heart failure. (a) Abdominal radiograph shows signs of pneumatosis coli (arrowheads). (b-d) Coronal VR image (b), sagittal MPR image (c), and curved MPR image (d) show air in the wall of the small bowel and ascending colon (arrowheads). (e, f) Axial source images show air collections in the intrahepatic vessels (arrows in e) and in the portal confluence (arrow in f) and an intraaortic balloon pump device in the aortic lumen (arrowhead in f). The device is shown in a to be in the correct position, and no occlusion is visible in the mesenteric arteries (arrow in d). The absence of occlusion was confirmed at pathologic analysis. The ischemia from low cardiac output probably was exacerbated by a reduction in peak systolic pressure caused by the intraaortic balloon pump.

View larger version (101K): [in this window] [in a new window] [Download PPT slide]   Figure 7d. Nonocclusive mesenteric ischemia in a 51-year-old woman with a history of left-sided heart failure. (a) Abdominal radiograph shows signs of pneumatosis coli (arrowheads). (b-d) Coronal VR image (b), sagittal MPR image (c), and curved MPR image (d) show air in the wall of the small bowel and ascending colon (arrowheads). (e, f) Axial source images show air collections in the intrahepatic vessels (arrows in e) and in the portal confluence (arrow in f) and an intraaortic balloon pump device in the aortic lumen (arrowhead in f). The device is shown in a to be in the correct position, and no occlusion is visible in the mesenteric arteries (arrow in d). The absence of occlusion was confirmed at pathologic analysis. The ischemia from low cardiac output probably was exacerbated by a reduction in peak systolic pressure caused by the intraaortic balloon pump.

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 7e. Nonocclusive mesenteric ischemia in a 51-year-old woman with a history of left-sided heart failure. (a) Abdominal radiograph shows signs of pneumatosis coli (arrowheads). (b-d) Coronal VR image (b), sagittal MPR image (c), and curved MPR image (d) show air in the wall of the small bowel and ascending colon (arrowheads). (e, f) Axial source images show air collections in the intrahepatic vessels (arrows in e) and in the portal confluence (arrow in f) and an intraaortic balloon pump device in the aortic lumen (arrowhead in f). The device is shown in a to be in the correct position, and no occlusion is visible in the mesenteric arteries (arrow in d). The absence of occlusion was confirmed at pathologic analysis. The ischemia from low cardiac output probably was exacerbated by a reduction in peak systolic pressure caused by the intraaortic balloon pump.

View larger version (157K): [in this window] [in a new window] [Download PPT slide]   Figure 7f. Nonocclusive mesenteric ischemia in a 51-year-old woman with a history of left-sided heart failure. (a) Abdominal radiograph shows signs of pneumatosis coli (arrowheads). (b-d) Coronal VR image (b), sagittal MPR image (c), and curved MPR image (d) show air in the wall of the small bowel and ascending colon (arrowheads). (e, f) Axial source images show air collections in the intrahepatic vessels (arrows in e) and in the portal confluence (arrow in f) and an intraaortic balloon pump device in the aortic lumen (arrowhead in f). The device is shown in a to be in the correct position, and no occlusion is visible in the mesenteric arteries (arrow in d). The absence of occlusion was confirmed at pathologic analysis. The ischemia from low cardiac output probably was exacerbated by a reduction in peak systolic pressure caused by the intraaortic balloon pump.

Systemic embolism is often caused by bacterial endocarditis, paradoxical embolism, or atrial fibrillation. One of the most common and severe clinical manifestations of systemic embolism is neurologic deficit caused by cerebral embolism and infarction. Splenic infarction also is common, and embolism due to cardiac thrombus caused by wall motion abnormalities is well known (33). We describe the case of a patient with cardiac aneurysm and thrombus who had multiple symptomatic arterial emboli and infarction. Infarction usually occurs in the kidneys or spleen (Fig 8a and 8b) and is more rarely seen in the liver. Infarcts are typically wedge shaped, nonenhancing, and peripheral (ie, close to the capsule) and are easily differentiated from normal parenchyma (34). The typical CT findings in intestinal ischemia are similar and may include bowel wall thickening with associated submucosal edema or hemorrhage, pneumatosis coli, mesenteric infiltration, and paralytic ileus. In the previously described patient, thromboembolism of the left iliac artery also was seen (Fig 8e).

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 8a. Cardiac pseudoaneurysm and thrombus in a 59-year-old man who presented with diffuse abdominal pain, vomiting, and diarrhea accompanied by hematochezia. (a, b) Axial source image (a) and coronal VR image (b) depict pseudoaneurysm with thrombus (arrow) in the left cardiac apex, as well as extensive infarction in the spleen (arrowhead in a). (c, d) Ax- ial source image (c) and VR image (d) depict atrophy of the left kidney (arrows) with chronic infarction and partial occlusion of the left common iliac artery (arrowheads in d). (e) Axial source image shows ileal wall thickening caused by ischemia (arrowheads) and partial occlusion of the left common iliac artery (arrow).

View larger version (147K): [in this window] [in a new window] [Download PPT slide]   Figure 8b. Cardiac pseudoaneurysm and thrombus in a 59-year-old man who presented with diffuse abdominal pain, vomiting, and diarrhea accompanied by hematochezia. (a, b) Axial source image (a) and coronal VR image (b) depict pseudoaneurysm with thrombus (arrow) in the left cardiac apex, as well as extensive infarction in the spleen (arrowhead in a). (c, d) Ax- ial source image (c) and VR image (d) depict atrophy of the left kidney (arrows) with chronic infarction and partial occlusion of the left common iliac artery (arrowheads in d). (e) Axial source image shows ileal wall thickening caused by ischemia (arrowheads) and partial occlusion of the left common iliac artery (arrow).

View larger version (148K): [in this window] [in a new window] [Download PPT slide]   Figure 8c. Cardiac pseudoaneurysm and thrombus in a 59-year-old man who presented with diffuse abdominal pain, vomiting, and diarrhea accompanied by hematochezia. (a, b) Axial source image (a) and coronal VR image (b) depict pseudoaneurysm with thrombus (arrow) in the left cardiac apex, as well as extensive infarction in the spleen (arrowhead in a). (c, d) Ax- ial source image (c) and VR image (d) depict atrophy of the left kidney (arrows) with chronic infarction and partial occlusion of the left common iliac artery (arrowheads in d). (e) Axial source image shows ileal wall thickening caused by ischemia (arrowheads) and partial occlusion of the left common iliac artery (arrow).

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 8d. Cardiac pseudoaneurysm and thrombus in a 59-year-old man who presented with diffuse abdominal pain, vomiting, and diarrhea accompanied by hematochezia. (a, b) Axial source image (a) and coronal VR image (b) depict pseudoaneurysm with thrombus (arrow) in the left cardiac apex, as well as extensive infarction in the spleen (arrowhead in a). (c, d) Ax- ial source image (c) and VR image (d) depict atrophy of the left kidney (arrows) with chronic infarction and partial occlusion of the left common iliac artery (arrowheads in d). (e) Axial source image shows ileal wall thickening caused by ischemia (arrowheads) and partial occlusion of the left common iliac artery (arrow).

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