Nontraumatic abdominal hemorrhage: MDCTA

Abdominal Imaging

ª Springer Science+Business Media, Inc. 2005 Published online: 7 December 2005

Abdom Imaging (2006) 31:17–24 DOI: 10.1007/s00261-005-0357-x

UPDATE

Nontraumatic abdominal hemorrhage: MDCTA A. A. Lemos,1 J. M. Sternberg,2 L. Tognini,3 R. Lauro,4 P. R. Biondetti1 1

Department Department 3 Department 4 Department 2

of Radiology, Policlinico Ospedale Maggiore IRCCS, Via F. Sforza 35, Milan 20122, Italy of Radiology, Rush-Presbyterian St. Luke’s Medical Centre, 1653 West Congress Parkway Chicago, IL 60612, USA of Endoscopy, Ospedale Maggiore IRCCS, Via F. Sforza 35, Milan 20122, Italy of Surgery, Ospedale Caduti Bollatesi, Via Piave 20, Bollate, Italy

Multidetector row computed tomographic angiography (MDCTA) plays a crucial role in the evaluation of patients with suspected abdominal hemorrhage in the emergency setting. It offers several advantages over single-detector CT in the assessment of patients with emergent conditions [1]. The shorter scanning time with multidetector row CT allows better visualization of blood vessels and more consistent contrast enhancement of the adjacent organ parenchyma. Further, faster data acquisition makes it possible to obtain multiple consecutive phases in a short time. The development of multidetector CT in combination with advances in computer hardware, software, and display technology has facilitated three-dimensional (3D) image reconstruction [1]. Shaded surface display, volume rendering (VR), and maximum intensity projection (MIP) are the three most commonly used 3D reconstruction techniques. In patients with suspected abdominal hemorrhage, MIP and VR of image data from MDCTA can enable vascular visualization that is equal or superior to that obtained with catheter angiography. In our experience, MDCTA allows the detection of not only organ injuries but also vascular anomalies such as rupture of arterial aneurysms and, in some cases, the active bleeding (AB) sign. The AB sign (also called the ‘‘contrast blush’’ or ‘‘blush sign’’) is an active pooling of contrast material caused by vascular or visceral organ injuries [2, 3]. In the absence of a previous traumatic event, detection of the AB sign is of paramount importance because this finding may indicate a life-threatening condition. The AB sign is considered a rare finding on conventional CT images of patients with abdominal trauma. The prevalence of this sign was only 0.2% in a study

Correspondence to: A. A. Lemos; email: alessandrolemos@hotmail. com

conducted by Taylor et al. [4]. Therefore, the prevalence of the AB sign in patients without trauma should be even lower than in patients who had sustained abdominal trauma. This assumption is supported by the fact that, to our knowledge, no data are available to assess the prevalence of the AB sign in patients without trauma by using MDCTA. This article describes our experience in the evaluation of patients without trauma but with suspected abdominal hemorrhage by using MDCTA.

MDCTA technique Optimal scanning protocols are mandatory for complete and accurate assessment of nontraumatic abdominal hemorrhage with MDCTA, and the intravenous contrast material injection protocol must be specific to the vascular region or organ 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 automatic injection system. For optimal assessment, the scanning and protocol must be tailored to the area of interest in a certain anatomic region. No oral agent should be given because it would obscure the location of the AB sign. CT assessment of patients with suspected abdominal hemorrhage is performed at our institution with a multidetector row CT scanner (LightSpeed Q/Xi, GE Medical Systems, Milwaukee, WI, USA). The scanning protocol includes nonenhanced and enhanced series. Enhanced series include arterial and venous phases. For the arterial phase, the Smart Prep bolus technique (GE Medical Systems) 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 interest is placed in the abdominal aorta.

18

A. A. Lemos et al.: Nontraumatic abdominal hemorrhage

Arterial and venous phases are generally acquired with a collimation of 4 · 2.5 mm (pitch of 6). Reconstruction of the source image data is performed retrospectively with a section thickness of 1.25 mm. Before CTA, 150 mL of nonionic contrast material (Iopamidolo, Bioindustria L. I., Milan, Italy; 300 mg/mL) is injected intravenously at a rate of 3 to 4 mL/s. Arterial and venous phase images of the entire abdomen are acquired to detect the AB sign. If necessary, 3D postprocessing techniques such as multiplanar reformation, shaded surface display, MIP, or VR are used for better visualization of pathologic changes and for preoperative or preinterventional planning. Commercially available software (Advantage Windows 3.1, GE Medical Systems) was used in the reconstruction of all 3D images that appear in this article.

Detection of the AB sign The AB sign is defined as multidetector CT evidence of contrast material pooling, with attenuation similar to that of the aorta or major adjacent arteries and greater than that of a surrounding parenchymal organ [2]. The pathologic appearance on multidetector CT images can be assessed by using the following classifications for active hemorrhage that were derived from previous studies performed in patients who had sustained trauma [2, 3]: type 1, presence of a focal highdensity area of extravasated contrast material surrounded by hematoma; type 2, presence of a diffuse high-density area surrounded by hematoma; and type 3, presence of a focal jet of extravasated contrast material. A ‘‘jet’’ was defined as a fountain-like extravasation of contrast material in continuity with a vessel or an abdominal organ. To determine the CT attenuation values (measured in Hounsfield units) of the AB sign, a region-of-interest cursor should be placed over three different localizations of extravasated contrast material. The mean of these measurements are compared with the multidetector CT attenuation values measured with a region of interest of equal area placed over three different locations of the abdominal aorta or adjacent major arteries and over the surrounding hematoma (hemoperitoneum with clot).

Nontraumatic abdominal hemorrhage from vascular conditions Rupture of abdominal aortic aneurysm Aneurysmal dilatation of the abdominal aorta is defined as a diameter larger than 29 mm. Based on this criterion, 9% of all people older than 65 years have an abdominal aortic aneurysm. Rupture of an abdominal aortic aneurysm is one of the most urgent vascular conditions and requires rapid intervention. In an autopsy studies reported by Lederle et al. [4], the 1-year incidences of aortic abdominal

Fig. 1. Rupture of an abdominal aortic aneurysm in a 75year-old man. A Coronal oblique MIP image shows a ruptured aneurysm with the AB sign (type 1; arrows) with a resultant large retroperitoneal hematoma (arrowheads). B Virtual angioscopy demonstrates a dilated aortic wall (black arrows), aortic wall tear (black arrowheads), and aortic lumen (white arrowheads).

aneurysm rupture according to initial diameter were 9.4% for diameters of 5.5 to 5.9 cm, 10.2% for diameters of 6.0 to 6.9 cm (19.1% for the subgroup of diameters of 6.0 to 6.9 cm), and 32.5% for diameters of at least 7.0 cm. A diagnosis of ruptured abdominal aortic aneurysm may be made on the basis of a nonenhanced CT scan that shows the aneurysm with adjacent periaortic hemorrhage that extends into the perirenal and pararenal spaces of the retroperitoneum. MDCTA 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, anatomy of renal vessels including accessory renal arteries, and stenosis or occlusion of the vessels. This additional information is important for the choice of treatment (open vs. endovascular repair).

A. A. Lemos et al.: Nontraumatic abdominal hemorrhage

Fig. 2. Rupture of a hepatic artery pseudoaneurysm in a 56year-old man. A Axial image during the arterial phase shows two high-density images suggestive of active bleeding (arrowheads). B Digital subtraction angiography confirms the diagnosis of rupture of hepatic artery pseudoaneurysm (arrowheads) with contrast medium extravasation (arrows). C

19

Coronal VR 3D reconstruction clearly demonstrates the hepatic artery pseudoaneurysm (arrowheads) with contrast medium extravasation (arrows). These findings suggest the presence of an arterial-venous shunt. D Digital subtraction angiographic image shows successful embolization of the hepatic artery pseudoaneurysm with metallic coils.

20

A. A. Lemos et al.: Nontraumatic abdominal hemorrhage

Rupture of hepatic artery pseudoaneurysm Hepatic artery pseudoaneurysms are most often mycotic and may occur at the anastomotic site after liver transplantation. Occasionally, these may be intrahepatic or peripheral in location secondary to focal parenchymal infection, pancreatitis, or percutaneous interventions [5]. The clinical presentation is often late, with hepatic failure or acute shock if the pseudoaneurysm ruptures. Fistula formation between the aneurysm and biliary tree or portal or hepatic veins can occur. Surgical correction is required, but there have been cases treated successfully with stent placement and/or embolization (Fig. 2D). MDCTA visualizes a periportal or intrahepatic cystic structure usually in juxtaposition to the course of the hepatic artery (Fig. 2A). Our experience suggests that all newly diagnosed cystic masses in or around the liver should undergo nonenhanced and enhanced series with density measurements to avoid mistaking a pseudoaneurysm for a benign collection. On unenhanced CT, a pseudoaneurysm may be indistinguishable from a hemorrhagic pseudocyst; however, pseudoaneurysms can be diagnosed with contrastenhanced CT (Fig. 2A,C). The pseudoaneurysm usually demonstrates homogeneous enhancement, the intensity of which is maximal during the arterial phase of a contrast-enhanced CT scan obtained with a rapid bolus injection (Fig. 2A).

Rupture of splenic artery pseudoaneurysm Splenic pseudoaneurysms are relatively uncommon complications of acute pancreatitis that occur in approximately 10% of cases. Vascular complications of acute pancreatitis include occlusion, erosion of the vessel wall, and pseudoaneurysm. Pseudoaneurysms most commonly affect the splenic artery, although the gastroduodenal, pancreaticoduodenal, gastric, and hepatic arteries (in descending order of frequency) may also be involved [6]. The CT appearance of splenic pseudoaneurysm is similar to that described for hepatic artery pseudoaneurysms: maximal and homogeneous enhancement during the arterial phase of contrast-enhanced CT scan obtained with a rapid bolus injection (Fig. 3A). Rupture of pseudoaneurysm may result in fatal hemorrhage into the gastrointestinal tract or other adjacent anatomic structures. Fatal bleeding may be preceded by self-limiting episodes of ‘‘herald bleeding.’’ Embolization with metallic coils is a well-recognized treatment for splenic and other visceral pseudoaneurysms [7].

Primary aortoduodenal fistula Primary aortoduodenal fistula is an uncommon cause of massive upper gastrointestinal hemorrhage, usually due

Fig. 3. Ruptured splenic artery pseudoaneurysm in a 56year-old woman. A Axial image during the arterial phase demonstrates a rounded high-density image in the left abdominal flank suggestive of a ruptured splenic artery pseudoaneurysm (arrowheads) with resultant hematoma (arrow). The AB sign is not seen. B Shaded surface display 3D reconstruction clearly visualizes the splenic artery pseudoaneurysm.

to pressure erosion of an abdominal aneurysm into the third portion of the duodenum or complex atherosclerotic disease of the abdominal aorta, with a chronic inflammation and foreign body reaction against atheromatous plaque formation (Fig. 4A,B). Symptoms of abdominal pain, gastrointestinal bleeding, and sepsis occur in 30% of patients with this condition. Because primary aortoduodenal fistulas occur less commonly than other complications, the sensitivity of CT specifically for the detection of these fistulas has not been determined. For the initial diagnostic assessment of patients with gastrointestinal bleeding, endoscopy is the modality of

21

A. A. Lemos et al.: Nontraumatic abdominal hemorrhage

Fig. 4. Primary aortoduodenal fistula in a 80-year-old man. A MDCTA (axial) shows contrast medium extravasation from the aorta into the duodenum. The AB sign (type 3) is also visible. B MIP reconstruction (sagittal) clearly demonstrates contrast medium extravasation (arrows).

choice. If the rate of blood loss exceeds 0.5 mL/min and the source of gastrointestinal bleeding cannot be identified with upper gastrointestinal endoscopy or colonoscopy, selective angiography is performed for this purpose [8, 9]. MDCTA is also recommended because it can be performed easily and rapidly and it provides more complete information, especially with regard to coexistent pathologic conditions, which may be useful in treatment planning. A CT scanning protocol that includes two successive (arterial and portal phase) acquisitions is important for the depiction of small fistulas with a minimal flow volume. The appearance of contrast enhancement in the duodenum is diagnostic of aortoduodenal fistula (Fig. 4A,B). The delay between the start of the arterial phase and the start of the venous phase should be about 60 s. It is important that oral contrast material not be used when a fistula is suspected because its use would obscure the AB sign. The finding of periaortic air also is specific for the diagnosis of primary aortoduodenal fistula [1].

Nontraumatic abdominal hemorrhage from nonvascular conditions Acute bleeding in renal angiomyolipoma Renal angiomyolipomas are a commonly occurring type of renal hamartoma. They are usually asymptomatic and are detected incidentally, often in patients with systemic diseases such as tuberous sclerosis. Renal angiomyolipomas are composed of aberrant or anomalous blood vessels, smooth muscle, and fat in various quantities [10]. CT diagnosis of these lesions is based on the presence of fat (i.e., attenuation values