DOI: 10.1148/rg.274065095
RadioGraphics 2007;27:1055-1070
© RSNA, 2007
Acute Gastrointestinal Bleeding: Emerging Role of Multidetector CT Angiography and Review of Current Imaging Techniques1
Christopher J. Laing, MD,
Terrence Tobias, MD,
David I. Rosenblum, DO,
Wade L. Banker, MD,
Lee Tseng, MD, and
Stephen W. Tamarkin, MD
1 From the Department of Radiology, MetroHealth Medical Center, Case Western Reserve University, 2500 MetroHealth Dr, Cleveland, OH 44109. Presented as an education exhibit at the 2005 RSNA Annual Meeting. Received May 8, 2006; revision requested September 11 and received October 16; accepted October 16. All authors have no financial relationships to disclose.
Address correspondence to C.J.L. (e-mail: utmaddoc{at}hotmail.com).
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Abstract
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Acute gastrointestinal bleeding is a common cause of hospitalization, morbidity, and mortality in the United States. The evaluation and treatment of acute gastrointestinal bleeding are complex and often require a multispecialty approach involving gastroenterologists, surgeons, internists, emergency physicians, and radiologists. The multitude of pathologic processes that can result in gastrointestinal bleeding, the length of the gastrointestinal tract, and the often intermittent nature of gastrointestinal bleeding further complicate patient evaluation. In addition, there are multiple imaging modalities and therapeutic interventions that are currently being used in the evaluation and treatment of acute gastrointestinal hemorrhage, each with its own strengths and weaknesses. Initial experience indicates that multidetector computed tomographic angiography is a promising first-line modality for the time-efficient, sensitive, and accurate diagnosis or exclusion of active gastrointestinal hemorrhage and may have a profound impact on the evaluation and subsequent treatment of patients who present with acute gastrointestinal bleeding.
© RSNA, 2007
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Introduction
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Gastrointestinal bleeding is a common cause of both morbidity and mortality in the United States, resulting in approximately 300,000 hospital admissions annually (1). The management of gastrointestinal bleeding often involves a multispecialty approach in which radiologists play a key role, providing several specialized diagnostic examinations with a variety of imaging modalities as well as endovascular therapeutic interventions. The role of the radiologist (when he or she is consulted) is to localize, characterize, and, when indicated, treat the bleeding lesion. Thus, to optimize patient care, the radiologist must be familiar with the common causes of gastrointestinal bleeding, the strengths and weaknesses of the various available imaging examinations, and the most commonly used treatment options.
In this article, we discuss and illustrate the emerging role of computed tomographic (CT) angiography in the evaluation and localization of acute, active gastrointestinal hemorrhage. In addition, we discuss the role of other imaging modalities (radionuclide imaging, catheter-directed angiography, endoscopy) that are commonly used for the diagnosis and treatment of acute gastrointestinal bleeding. We also provide pertinent information to help direct the imaging evaluation and treatment of affected patients in a multispecialty setting.
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Gastrointestinal Bleeding
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Gastrointestinal bleeding is typically categorized as either upper or lower gastrointestinal bleeding depending on the anatomic location of the bleeding site.
Upper gastrointestinal bleeding occurs proximal to the ligament of Treitz and may involve the esophagus, stomach, and duodenum. Upper gastrointestinal bleeding is the reason for hospitalization in approximately 0.1% of hospitalized patients each year and carries a mortality rate of approximately 10% (2). Common causes of upper gastrointestinal bleeding are listed in Table 1.
Lower gastrointestinal bleeding occurs distal to the ligament of Treitz and may involve the small bowel, colon, and rectum. Lower gastrointestinal bleeding is less common than upper gastrointestinal bleeding and accounts for approximately 30% of all gastrointestinal bleeding (3). It is the reason for hospitalization in up to .02% of hospitalized patients each year (4) and carries a mortality rate of 3.6% (5). Lower gastrointestinal bleeding tends to affect elderly patients and is 200 times more likely to occur in an 80-year-old than in a 20-year-old (1). Common causes of lower gastrointestinal bleeding are listed in Table 2.
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Vascular Considerations
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The celiac axis and the superior mesenteric artery (SMA) are the first two branches of the abdominal aorta and provide a rich and well-collateralized network of branch vessels that supply blood to the upper gastrointestinal tract. Extensive collateralization between the celiac artery and the SMA protects the upper gastrointestinal tract from ischemic insult and permits surgical and embolization procedures to be carried out with a relatively low risk of ischemic injury. Similarly, branch vessels of both the SMA and the inferior mesenteric artery (IMA) form a series of interconnected arcades that provide a means of collateral flow throughout the lower gastrointestinal tract. Although descriptions of classic mesenteric vascular anatomy can be found elsewhere (7–10), it is important to realize that anatomic variants are commonly encountered. In fact, in a study by Nelson et al (11), the classically described branching pattern of the celiac artery, SMA, and IMA was present in only 22%, 24%, and 16% of dissected cadavers, respectively.
Gastrointestinal bleeding can also have venous sources. Venous bleeding within the upper gastrointestinal tract is typically due to gastric or esophageal varices arising from the coronary vein or the short gastric veins in the setting of portal hypertension. However, 
approximately 30% of patients with portal hypertension and coexistent varices who present with upper gastrointestinal bleeding will have an arterial source of bleeding (1). Venous bleeding within the lower gastrointestinal tract is commonly due to hemorrhoids involving either the internal or external rectal venous plexus.
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Clinical Considerations
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The rate of blood loss and the patient’s comorbidities dictate the clinical presentation. Patients may remain asymptomatic until blood loss exceeds 100 mL per day. Tachycardia and hypotension commonly occur when acute blood loss exceeds 500 mL, and systemic shock typically ensues upon loss of 15% or more of the circulating blood volume (12). In approximately 75% of cases of upper gastrointestinal bleeding and 80% of cases of lower gastrointestinal bleeding, the bleeding will cease spontaneously with supportive measures alone; in the remaining 20%–25% of cases, further intervention is required, often involving surgeons, gastroenterologists, and interventional radiologists (1,8,13). The effects of acute blood loss can also manifest as derangements in the cardiac, renal, neurologic, and pulmonary systems, resulting in significant morbidity and mortality, especially in patients in whom bleeding does not cease spontaneously. Indeed, most deaths attributable to gastrointestinal bleeding occur in elderly patients and are associated with comorbid conditions exacerbated by blood loss (14).
Initial clinical evaluation and management is directed toward restoration of euvolemia, treatment of any coagulopathy, and, secondarily, clinical localization of the bleeding site to the upper or lower gastrointestinal tract. However, clinical localization is not always accurate. For example, rapid upper gastrointestinal bleeding can manifest with hematochezia due to the cathartic properties of blood. Conversely, the colonic transit time and bleeding rate may be slow enough that right colon bleeding manifests with melena or a combination of melena and dark red blood from the rectum. In addition, the aspiration of stomach contents through a nasogastric tube may fail to help detect duodenal bleeding (15). Therefore, consultation and subsequent imaging evaluation is often undertaken with the primary goal of localizing the bleeding lesion.
In many cases, gastrointestinal bleeding occurs intermittently or ceases spontaneously, presenting a major diagnostic and, therefore, treatment dilemma. It is crucial that patients are imaged while they are actively bleeding clinically to maximize detection capabilities.
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Current Imaging Strategies
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Radionuclide Imaging
Noninvasive imaging with technetium-99m–labeled red blood cell (RBC) or Tc-99m sulfur colloid scintigraphy can be used to detect and localize gastrointestinal bleeding. Tc-99m RBC scintigraphy is 93% sensitive and 95% specific for detecting a bleeding site with active arterial or venous bleeding rates as low as 0.04 mL/min (16) anywhere within the gastrointestinal tract. The capacity for imaging over prolonged periods of time can be extremely useful in the setting of intermittent gastrointestinal bleeding. However, the limited resolution of scintigraphy does not allow precise anatomic localization of gastrointestinal bleeding.
The role of Tc-99m RBC scintigraphy in the evaluation of upper gastrointestinal bleeding is limited due to the widespread use of endoscopy as a first-line modality for such bleeding. However, Tc-99m RBC scintigraphy can be useful when endoscopy is not readily available or in patients in whom endoscopy is difficult or impossible. Tc-99m RBC scintigraphy plays a larger role in the evaluation of lower gastrointestinal bleeding due to the limited sensitivity of endoscopy within the lower gastrointestinal tract and has typically been used as a screening examination to identify patients who require angiography or surgery. The cost, advantages, and disadvantages of radionuclide imaging for gastrointestinal bleeding are shown in Table 3.
Catheter-directed Angiography
Angiography is an invasive examination that can be used for accurate localization as well as treatment of both upper and lower gastrointestinal bleeding. Referrals for angiographic evaluation typically occur in the setting of an acutely unstable patient, after a negative or failed endoscopic evaluation, or as a first-line examination for lower gastrointestinal hemorrhage.
Bleeding rates as low as 0.5 mL/min can be detected with selective catheter angiography (6). Angiography has a sensitivity of 63%–90% and 40%–86% for upper and lower gastrointestinal bleeding, respectively, and a specificity of up to 100% for both (1,19–21). The use of carbon dioxide (CO2) as the contrast agent and provocative measures such as direct arterial infusion of vasodilators, thrombolytics, or anticoagulants may increase the sensitivity of selective catheter angiography. Extravasation of contrast material into the bowel lumen is pathognomonic for active gastrointestinal hemorrhage. Indirect signs include detection of pseudoaneurysm, arteriovenous fistula, hyperemia, neovascularity, and extravasation of contrast material into a confined space (1). Although the cause of a bleeding lesion can occasionally be determined, the angiographic appearance of gastrointestinal bleeding is often non-specific, and further diagnostic testing may be required following transcatheter localization and treatment.
Embolization of the bleeding vessel is the mainstay of transcatheter treatment for nonvariceal gastrointestinal bleeding, and high technical success rates (angiographic cessation of bleeding) of 91%–100% have been reported (22–25). Clinical success rates (cessation of bleeding for 30 days) of 68%–82.5% for upper gastrointestinal bleeding (24,25) and 81%–91% for lower gastrointestinal bleeding (22–24) have been reported. Microcoil embolization is typically preferred within the lower gastrointestinal tract, whereas controversy exists regarding the optimal agent within the upper gastrointestinal tract. In fact, combinations of different embolic agents may be more effective than embolization with a single agent in the upper gastrointestinal tract (25). Common embolic agents include microcoils, polyvinyl alcohol particles, gelfoam, n-butyl cyanoacrylate glue, and enbucrylate tissue adhesive. Direct intraarterial infusion of platelets and vasopressin has also been used successfully in the transcatheter treatment of gastrointestinal hemorrhage.
The cost, advantages, and disadvantages of catheter-directed angiography for gastrointestinal bleeding are shown in Table 3.
Endoscopy
EGD and colonoscopy are currently considered the first-line diagnostic and therapeutic procedures of choice for both upper and lower gastrointestinal bleeding. Endoscopic evaluation allows relatively safe, direct localization and characterization of bleeding lesions within the majority of the upper gastrointestinal tract as well as in the colon and distal ileum. The distal duodenum and the majority of the small bowel cannot be adequately assessed with conventional endoscopy. Visual characterization of a bleeding lesion can provide important prognostic information regarding the risk of recurrent bleeding and may prompt tissue sampling if a neoplasm is suspected.
The reported sensitivity and specificity of EGD for upper gastrointestinal bleeding are 92%–98% and 30%–100%, respectively (1). Occasionally, rapid hemorrhage obscures endoscopic visualization of the bleeding site and precludes intervention. Bowel preparation is required prior to colonoscopy, which can be completed in 3–4 hours, typically by administering a polyethylene glycol–based solution orally or via a nasogastric tube (5). In a study by Angtuaco et al (26), urgent colonoscopy was successful in identifying a definitive bleeding source in only 13% of patients and a probable bleeding source in 67%, despite adequate colon preparation.
Endoscopic interventions can be performed if the bleeding lesion is adequately visualized. Endoscopic therapeutic treatments may be (a) by injection (epinephrine, alcohol), (b) thermal (heater probe, electrocoagulation, laser), or (c) mechanical (clips, bands). Injection sclerotherapy with epinephrine achieves primary hemostasis rates of 96.7% for ulcers and 80%–90% for variceal bleeding (5,27). Although all of the aforementioned therapeutic modalities demonstrate similar efficacies in randomized trials, they have shown increased effectiveness when used in combination (5). Approximately 15%–20% of patients with treated upper gastrointestinal bleeding will develop recurrent bleeding after endoscopic treatment, usually within 72 hours (5).
WCE has proved beneficial in patients in whom no source of bleeding has been identified despite evaluation with EGD and colonoscopy (28). Patient preparation consists of a 10-hour fast, followed by ingestion of the capsule with a glass of water. Data interpretation occurs after 8 hours of transit time, after which 2–3 hours are needed to download the data to a workstation (29). Capsule retention by intestinal stricture is the most serious complication (30). Because of the prolonged imaging time and the need for pre-procedural fasting, there is presently no defined role for WCE in the evaluation of acute gastrointestinal bleeding.
Table 3 shows the cost, advantages, and disadvantages of endoscopy for gastrointestinal bleeding.
CT Angiography
Recent advances in CT technology allowing thinner collimation, faster scanning times, greater anatomic coverage, and better multiplanar reformatted (MPR) images have greatly expanded the diagnostic role of CT angiography for various pathologic processes. In porcine models, helical CT has depicted active colonic hemorrhage with bleeding rates as low as 0.3 mL/min (31), which is below the reported threshold for selective catheter angiography. Recently, Tew et al (32) described the use of four–detector row CT in the evaluation of acute lower gastrointestinal bleeding in 13 consecutive patients and reported no false-positive or false-negative results. Yoon et al (33) conducted a four–detector row CT angiographic study of 26 consecutive patients with significant gastrointestinal bleeding that resulted in either systemic hypotension (systolic blood pressure < 90 mm Hg) or a transfusion requirement of at least four units of packed red cells in a 24-hour period. Their study demonstrated an overall location-based sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for CT angiography in the detection and localization of gastrointestinal bleeding of 90.9%, 99%, 97.6%, 95%, and 98%, respectively (33).
The CT angiographic diagnosis of active gastrointestinal bleeding is made when hyperattenuating extravasated contrast material is seen within the bowel lumen (Fig 1). The extravasated contrast material may demonstrate linear, jetlike, swirled, ellipsoid, or pooled configurations (Figs 2, 3) or may fill the entire bowel lumen, resulting in a hyperattenuating loop. Whereas other authors have applied attenuation thresholds as criteria for the diagnosis of acute bleeding with CT angiography (32,33), we prefer to compare sequentially acquired unenhanced CT scans and CT angiograms without rigid adherence to attenuation analysis. Although it is probably true that most cases of acutely extravasated contrast material into the bowel lumen will exceed the 90 HU threshold applied by Yoon et al (33), it is conceivable that small amounts of bleeding or thin contrast material "jets " may not reach this threshold due to volume averaging within either the section itself or the user-defined region of interest. In addition, comparison with unenhanced images allows differentiation of active hemorrhage from other high-attenuation material that may be present within the gastrointestinal tract at the time of CT angiographic evaluation, thereby preventing false-positive interpretation (Figs 4–6). Therefore, high-attenuation material detected within the bowel lumen at CT angiography that was not present at unenhanced CT performed immediately prior to the CT angiography is, in our experience, diagnostic for acute gastrointestinal hemorrhage. Care must be taken to distinguish intraluminal contrast material extravasation from mucosal enhancement, which can have a similar appearance, especially when the bowel loop is somewhat collapsed (Fig 7).
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Figure 1a. Active sigmoid bleeding in a 94-year-old woman who presented with bright red blood from the rectum. (a, b) Axial (a) and coronal (b) CT angiograms demonstrate active contrast material extravasation into the sigmoid colon (arrow). Note the multiple colonic diverticuli in this region and the contrast material–filled diverticulum that is optimally demonstrated on the coronal image, presumably representing the site of hemorrhage. (c) Findings on an IMA angiogram confirm the presence of active sigmoid bleeding (arrowheads). The patient was treated successfully with coil embolization.
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Figure 1b. Active sigmoid bleeding in a 94-year-old woman who presented with bright red blood from the rectum. (a, b) Axial (a) and coronal (b) CT angiograms demonstrate active contrast material extravasation into the sigmoid colon (arrow). Note the multiple colonic diverticuli in this region and the contrast material–filled diverticulum that is optimally demonstrated on the coronal image, presumably representing the site of hemorrhage. (c) Findings on an IMA angiogram confirm the presence of active sigmoid bleeding (arrowheads). The patient was treated successfully with coil embolization.
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Figure 1c. Active sigmoid bleeding in a 94-year-old woman who presented with bright red blood from the rectum. (a, b) Axial (a) and coronal (b) CT angiograms demonstrate active contrast material extravasation into the sigmoid colon (arrow). Note the multiple colonic diverticuli in this region and the contrast material–filled diverticulum that is optimally demonstrated on the coronal image, presumably representing the site of hemorrhage. (c) Findings on an IMA angiogram confirm the presence of active sigmoid bleeding (arrowheads). The patient was treated successfully with coil embolization.
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Figure 2a. Active gastrointestinal bleeding in a hemodynamically unstable 71-year-old man who presented with massive hematemesis that obscured endoscopic findings. (a) Coronal CT angiogram through the gastric body and antrum shows a large amount of clotted blood within the distended stomach (*) and pooling of extravasated contrast material (arrow). These findings allowed direction of the catheter toward the left gastric artery. (b) Angiogram obtained after injection of the left gastric artery shows a bleeding gastric branch (arrow). The patient was treated successfully with microcoil embolization.
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Figure 2b. Active gastrointestinal bleeding in a hemodynamically unstable 71-year-old man who presented with massive hematemesis that obscured endoscopic findings. (a) Coronal CT angiogram through the gastric body and antrum shows a large amount of clotted blood within the distended stomach (*) and pooling of extravasated contrast material (arrow). These findings allowed direction of the catheter toward the left gastric artery. (b) Angiogram obtained after injection of the left gastric artery shows a bleeding gastric branch (arrow). The patient was treated successfully with microcoil embolization.
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Figure 3a. Active ileal bleeding in a 75-year-old woman. (a) Unenhanced CT scan shows no hyperattenuating material within the terminal ileum (arrow). (b) CT angiogram obtained immediately after a demonstrates pooling of contrast material within the terminal ileum (arrow). (c) Coronal oblique CT angiogram shows a prominent ileocolic branch coursing toward the bleeding terminal ileum (arrow). (d) Catheter angiogram shows active bleeding from an ileocolic branch of the SMA and pooling of contrast material within the terminal ileum (arrow), thereby helping confirm the CT angiographic findings. The patient was treated successfully with coil embolization.
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Figure 3b. Active ileal bleeding in a 75-year-old woman. (a) Unenhanced CT scan shows no hyperattenuating material within the terminal ileum (arrow). (b) CT angiogram obtained immediately after a demonstrates pooling of contrast material within the terminal ileum (arrow). (c) Coronal oblique CT angiogram shows a prominent ileocolic branch coursing toward the bleeding terminal ileum (arrow). (d) Catheter angiogram shows active bleeding from an ileocolic branch of the SMA and pooling of contrast material within the terminal ileum (arrow), thereby helping confirm the CT angiographic findings. The patient was treated successfully with coil embolization.
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Figure 3c. Active ileal bleeding in a 75-year-old woman. (a) Unenhanced CT scan shows no hyperattenuating material within the terminal ileum (arrow). (b) CT angiogram obtained immediately after a demonstrates pooling of contrast material within the terminal ileum (arrow). (c) Coronal oblique CT angiogram shows a prominent ileocolic branch coursing toward the bleeding terminal ileum (arrow). (d) Catheter angiogram shows active bleeding from an ileocolic branch of the SMA and pooling of contrast material within the terminal ileum (arrow), thereby helping confirm the CT angiographic findings. The patient was treated successfully with coil embolization.
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Figure 3d. Active ileal bleeding in a 75-year-old woman. (a) Unenhanced CT scan shows no hyperattenuating material within the terminal ileum (arrow). (b) CT angiogram obtained immediately after a demonstrates pooling of contrast material within the terminal ileum (arrow). (c) Coronal oblique CT angiogram shows a prominent ileocolic branch coursing toward the bleeding terminal ileum (arrow). (d) Catheter angiogram shows active bleeding from an ileocolic branch of the SMA and pooling of contrast material within the terminal ileum (arrow), thereby helping confirm the CT angiographic findings. The patient was treated successfully with coil embolization.
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Figure 4a. Hyperattenuating bowel loop mimicking active hemorrhage. (a, b) Axial (a) and coronal (b) unenhanced CT scans demonstrate hyperattenuating material completely filling a small bowel loop within the right lower quadrant (arrow). (c, d) Axial (c) and coronal (d) CT angiograms obtained immediately after a and b demonstrate a hyperattenuating loop in the right lower quadrant (arrow) that mimics active hemorrhage. Unfortunately, the CT angiograms were not compared with the unenhanced scans, resulting in incorrect interpretation of this hyperattenuating loop as active hemorrhage. The patient was immediately transferred to the angiography suite for transcatheter embolization. Angiography failed to help detect active hemorrhage.
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Figure 4b. Hyperattenuating bowel loop mimicking active hemorrhage. (a, b) Axial (a) and coronal (b) unenhanced CT scans demonstrate hyperattenuating material completely filling a small bowel loop within the right lower quadrant (arrow). (c, d) Axial (c) and coronal (d) CT angiograms obtained immediately after a and b demonstrate a hyperattenuating loop in the right lower quadrant (arrow) that mimics active hemorrhage. Unfortunately, the CT angiograms were not compared with the unenhanced scans, resulting in incorrect interpretation of this hyperattenuating loop as active hemorrhage. The patient was immediately transferred to the angiography suite for transcatheter embolization. Angiography failed to help detect active hemorrhage.
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Figure 4c. Hyperattenuating bowel loop mimicking active hemorrhage. (a, b) Axial (a) and coronal (b) unenhanced CT scans demonstrate hyperattenuating material completely filling a small bowel loop within the right lower quadrant (arrow). (c, d) Axial (c) and coronal (d) CT angiograms obtained immediately after a and b demonstrate a hyperattenuating loop in the right lower quadrant (arrow) that mimics active hemorrhage. Unfortunately, the CT angiograms were not compared with the unenhanced scans, resulting in incorrect interpretation of this hyperattenuating loop as active hemorrhage. The patient was immediately transferred to the angiography suite for transcatheter embolization. Angiography failed to help detect active hemorrhage.
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Figure 4d. Hyperattenuating bowel loop mimicking active hemorrhage. (a, b) Axial (a) and coronal (b) unenhanced CT scans demonstrate hyperattenuating material completely filling a small bowel loop within the right lower quadrant (arrow). (c, d) Axial (c) and coronal (d) CT angiograms obtained immediately after a and b demonstrate a hyperattenuating loop in the right lower quadrant (arrow) that mimics active hemorrhage. Unfortunately, the CT angiograms were not compared with the unenhanced scans, resulting in incorrect interpretation of this hyperattenuating loop as active hemorrhage. The patient was immediately transferred to the angiography suite for transcatheter embolization. Angiography failed to help detect active hemorrhage.
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Figure 5a. Active left colonic diverticular hemorrhage. (a, b) Axial (a) and coronal (b) 3-mm maximum-intensity-projection (MIP) CT angiographic images demonstrate a swirling jet of extravasated contrast material within the lumen of the descending colon (arrow). Multiple colonic diverticuli were also seen, and diverticular bleeding was suspected. (c) Angiogram obtained during microcoil embolization of bleeding left colic artery branches shows puddling of contrast material within the left colon (arrow), a finding that represents hemorrhage. Subsequent colonoscopy performed after bowel preparation revealed multiple large diverticuli within the descending colon, several of which contained blood. No active hemorrhage was seen at colonoscopy.
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Figure 5b. Active left colonic diverticular hemorrhage. (a, b) Axial (a) and coronal (b) 3-mm maximum-intensity-projection (MIP) CT angiographic images demonstrate a swirling jet of extravasated contrast material within the lumen of the descending colon (arrow). Multiple colonic diverticuli were also seen, and diverticular bleeding was suspected. (c) Angiogram obtained during microcoil embolization of bleeding left colic artery branches shows puddling of contrast material within the left colon (arrow), a finding that represents hemorrhage. Subsequent colonoscopy performed after bowel preparation revealed multiple large diverticuli within the descending colon, several of which contained blood. No active hemorrhage was seen at colonoscopy.
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Figure 5c. Active left colonic diverticular hemorrhage. (a, b) Axial (a) and coronal (b) 3-mm maximum-intensity-projection (MIP) CT angiographic images demonstrate a swirling jet of extravasated contrast material within the lumen of the descending colon (arrow). Multiple colonic diverticuli were also seen, and diverticular bleeding was suspected. (c) Angiogram obtained during microcoil embolization of bleeding left colic artery branches shows puddling of contrast material within the left colon (arrow), a finding that represents hemorrhage. Subsequent colonoscopy performed after bowel preparation revealed multiple large diverticuli within the descending colon, several of which contained blood. No active hemorrhage was seen at colonoscopy.
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Figure 6a. Retained barium mimicking active bleeding in a hemodynamically stable 77-year-old man who presented with bright red blood from the rectum. Transverse (a) and sagittal (b) CT angiograms show retained colonic barium from a prior examination (arrow). No contrast material jet is seen, and the barium is hyperattenuating relative to extravasated contrast material. Results from subsequent catheter angiography were also negative. Retained contrast material can mimic active bleeding or limit the CT angiographic evaluation of lower gastrointestinal bleeding.
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Figure 6b. Retained barium mimicking active bleeding in a hemodynamically stable 77-year-old man who presented with bright red blood from the rectum. Transverse (a) and sagittal (b) CT angiograms show retained colonic barium from a prior examination (arrow). No contrast material jet is seen, and the barium is hyperattenuating relative to extravasated contrast material. Results from subsequent catheter angiography were also negative. Retained contrast material can mimic active bleeding or limit the CT angiographic evaluation of lower gastrointestinal bleeding.
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Figure 7a. Mucosal enhancement. (a) Coronal unenhanced CT scan shows multiple colonic diverticuli without any hyperattenuating material within the bowel. (b) CT angiogram demonstrates diffuse mucosal enhancement throughout the descending colon (arrowheads), within the stomach (large arrow), and in portions of the small bowel. Such a finding can mimic acute hemorrhage, but the contracted appearance of the bowel, the striated peripheral enhancement pattern (small arrows), and the diffuse multifocal appearance support the correct diagnosis of mucosal enhancement. (c, d) Unenhanced CT scan (c) and CT angiogram (d) demonstrate the typical striated appearance of mucosal enhancement within the stomach.
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Figure 7b. Mucosal enhancement. (a) Coronal unenhanced CT scan shows multiple colonic diverticuli without any hyperattenuating material within the bowel. (b) CT angiogram demonstrates diffuse mucosal enhancement throughout the descending colon (arrowheads), within the stomach (large arrow), and in portions of the small bowel. Such a finding can mimic acute hemorrhage, but the contracted appearance of the bowel, the striated peripheral enhancement pattern (small arrows), and the diffuse multifocal appearance support the correct diagnosis of mucosal enhancement. (c, d) Unenhanced CT scan (c) and CT angiogram (d) demonstrate the typical striated appearance of mucosal enhancement within the stomach.
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Figure 7c. Mucosal enhancement. (a) Coronal unenhanced CT scan shows multiple colonic diverticuli without any hyperattenuating material within the bowel. (b) CT angiogram demonstrates diffuse mucosal enhancement throughout the descending colon (arrowheads), within the stomach (large arrow), and in portions of the small bowel. Such a finding can mimic acute hemorrhage, but the contracted appearance of the bowel, the striated peripheral enhancement pattern (small arrows), and the diffuse multifocal appearance support the correct diagnosis of mucosal enhancement. (c, d) Unenhanced CT scan (c) and CT angiogram (d) demonstrate the typical striated appearance of mucosal enhancement within the stomach.
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Figure 7d. Mucosal enhancement. (a) Coronal unenhanced CT scan shows multiple colonic diverticuli without any hyperattenuating material within the bowel. (b) CT angiogram demonstrates diffuse mucosal enhancement throughout the descending colon (arrowheads), within the stomach (large arrow), and in portions of the small bowel. Such a finding can mimic acute hemorrhage, but the contracted appearance of the bowel, the striated peripheral enhancement pattern (small arrows), and the diffuse multifocal appearance support the correct diagnosis of mucosal enhancement. (c, d) Unenhanced CT scan (c) and CT angiogram (d) demonstrate the typical striated appearance of mucosal enhancement within the stomach.
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The available early data as well as our own clinical experience (unpublished) has led to the use of CT angiography at our institution as a screening modality in all patients without a definitively diagnosed source of active gastrointestinal bleeding who are referred for angiography. Angiography is deferred when active bleeding is not depicted on the CT examination, except in cases when the patient is unstable from massive hemorrhage.
In addition to helping detect active gastrointestinal hemorrhage, CT angiography allows concurrent evaluation of the gastrointestinal and proximal femoral vasculature. Because significant anatomic variation of the gastrointestinal vasculature exists, preoperative knowledge of the active gastrointestinal bleeding site and its vascular supply is extremely useful for preinterventional planning (Fig 8). In our experience, this preoperative knowledge has resulted in a decreased number of digital subtraction angiographic exposures, faster catheterization of bleeding vessels, decreased contrast material use during angiography, and shorter procedure times. It has also reduced patient (and operator) radiation exposure within the angiography suite.
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Figure 8a. Bleeding pancreaticoduodenal branch in a 90-year-old man with a history of duodenal ulcers who presented with a 2-day history of melena. Initial work-up included endoscopy, CT angiography, and conventional angiography; results from all studies were negative. Gastrointestinal bleeding recurred the next morning, and repeat CT angiography was performed. (a) Coronal CT angiogram demonstrates active extravasation of contrast material into the second portion of the duodenum (arrow). (b) CT angiogram shows the extravasated contrast material with a swirled appearance (arrow). The hepatic artery was replaced from the SMA; note the two parallel vessels anterior to the aorta (arrowheads). (c) Angiogram obtained during hepatic artery injection shows a bleeding pancreaticoduodenal branch (arrow) arising from the gastroduodenal artery and a small amount of contrast material that has refluxed into the SMA (arrowheads). (d) Angiogram shows successful microcoil embolization of the bleeding vessel (arrow). Preprocedural knowledge of the vascular variant in this case resulted in less delay in finding and embolizing the bleeding vessel.
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Figure 8b. Bleeding pancreaticoduodenal branch in a 90-year-old man with a history of duodenal ulcers who presented with a 2-day history of melena. Initial work-up included endoscopy, CT angiography, and conventional angiography; results from all studies were negative. Gastrointestinal bleeding recurred the next morning, and repeat CT angiography was performed. (a) Coronal CT angiogram demonstrates active extravasation of contrast material into the second portion of the duodenum (arrow). (b) CT angiogram shows the extravasated contrast material with a swirled appearance (arrow). The hepatic artery was replaced from the SMA; note the two parallel vessels anterior to the aorta (arrowheads). (c) Angiogram obtained during hepatic artery injection shows a bleeding pancreaticoduodenal branch (arrow) arising from the gastroduodenal artery and a small amount of contrast material that has refluxed into the SMA (arrowheads). (d) Angiogram shows successful microcoil embolization of the bleeding vessel (arrow). Preprocedural knowledge of the vascular variant in this case resulted in less delay in finding and embolizing the bleeding vessel.
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Figure 8c. Bleeding pancreaticoduodenal branch in a 90-year-old man with a history of duodenal ulcers who presented with a 2-day history of melena. Initial work-up included endoscopy, CT angiography, and conventional angiography; results from all studies were negative. Gastrointestinal bleeding recurred the next morning, and repeat CT angiography was performed. (a) Coronal CT angiogram demonstrates active extravasation of contrast material into the second portion of the duodenum (arrow). (b) CT angiogram shows the extravasated contrast material with a swirled appearance (arrow). The hepatic artery was replaced from the SMA; note the two parallel vessels anterior to the aorta (arrowheads). (c) Angiogram obtained during hepatic artery injection shows a bleeding pancreaticoduodenal branch (arrow) arising from the gastroduodenal artery and a small amount of contrast material that has refluxed into the SMA (arrowheads). (d) Angiogram shows successful microcoil embolization of the bleeding vessel (arrow). Preprocedural knowledge of the vascular variant in this case resulted in less delay in finding and embolizing the bleeding vessel.
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Figure 8d. Bleeding pancreaticoduodenal branch in a 90-year-old man with a history of duodenal ulcers who presented with a 2-day history of melena. Initial work-up included endoscopy, CT angiography, and conventional angiography; results from all studies were negative. Gastrointestinal bleeding recurred the next morning, and repeat CT angiography was performed. (a) Coronal CT angiogram demonstrates active extravasation of contrast material into the second portion of the duodenum (arrow). (b) CT angiogram shows the extravasated contrast material with a swirled appearance (arrow). The hepatic artery was replaced from the SMA; note the two parallel vessels anterior to the aorta (arrowheads). (c) Angiogram obtained during hepatic artery injection shows a bleeding pancreaticoduodenal branch (arrow) arising from the gastroduodenal artery and a small amount of contrast material that has refluxed into the SMA (arrowheads). (d) Angiogram shows successful microcoil embolization of the bleeding vessel (arrow). Preprocedural knowledge of the vascular variant in this case resulted in less delay in finding and embolizing the bleeding vessel.
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Evaluation of gastrointestinal bleeding with CT angiography may also provide etiologic information in many cases, especially with lower gastrointestinal bleeding. CT angiography can easily help diagnose colonic diverticuli, the most common cause of lower gastrointestinal bleeding in the United States. In a study of 26 patients, Junquera et al (34) reported a sensitivity, specificity, and positive predictive value of 70%, 100%, and 100%, respectively, for two–detector row helical CT angiography in the detection of colonic angiodysplasia. Angiodysplasia may account for up to 40% of cases of lower gastrointestinal bleeding in patients over 60 years of age (33) and is the second most common cause of such bleeding. Distinguishing diverticular from angiodysplastic bleeding (when possible) is important because of the prognostic differences between these two lesions. Although bleeding will cease spontaneously in 80% or more of cases of angiodysplastic bleeding (1) and in 75% of cases of diverticular bleeding (5), recurrent bleeding will develop in up to 85% of cases of untreated angiodysplastic bleeding (35) as opposed to only 25% of cases of untreated diverticular bleeding (36). CT angiography can also help accurately diagnose neoplasms and colitis, the third and fourth most common causes of lower gastrointestinal bleeding, respectively.
Concurrent localization of active hemorrhage and diagnosis of the underlying cause can also have important treatment and management implications. CT angiographic localization of bleeding can assist in determining the endoscopic approach, especially when clinical localization of bleeding to the upper or lower gastrointestinal tract is difficult or unreliable. Conversely, localization of bleeding within the small bowel may prevent unnecessary endoscopic examinations while expediting endovascular or surgical interventions (Fig 9). A surgical approach may be preferred when anorectal or neoplastic bleeding is encountered (Fig 10), whereas more conservative medical therapy may be considered in the setting of diverticular bleeding, given its propensity for spontaneous cessation.
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Figure 9a. Gastrointestinal bleeding in a 37-year-old woman in whom steroid treatment for severe lupus was complicated by spontaneous jejunal perforation secondary to ulcer disease. The perforated ulcers were oversewn at laparotomy, and the patient subsequently developed severe gastrointestinal bleeding. (a, b) Axial (a) and sagittal (b) CT angiograms help localize the bleeding to a proximal anterior jejunal loop, where pooling of contrast material is seen (arrows). Embolization therapy failed, and the patient developed recurrent gastrointestinal bleeding the next morning. Small bowel resection was subsequently performed. (c) Clinical photograph demonstrates multiple jejunal ulcers (bottom arrowheads), as well as the gastropexy clip (top arrowheads) that was used during CT-guided percutaneous localization of the bleeding loop.
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Figure 9b. Gastrointestinal bleeding in a 37-year-old woman in whom steroid treatment for severe lupus was complicated by spontaneous jejunal perforation secondary to ulcer disease. The perforated ulcers were oversewn at laparotomy, and the patient subsequently developed severe gastrointestinal bleeding. (a, b) Axial (a) and sagittal (b) CT angiograms help localize the bleeding to a proximal anterior jejunal loop, where pooling of contrast material is seen (arrows). Embolization therapy failed, and the patient developed recurrent gastrointestinal bleeding the next morning. Small bowel resection was subsequently performed. (c) Clinical photograph demonstrates multiple jejunal ulcers (bottom arrowheads), as well as the gastropexy clip (top arrowheads) that was used during CT-guided percutaneous localization of the bleeding loop.
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Figure 9c. Gastrointestinal bleeding in a 37-year-old woman in whom steroid treatment for severe lupus was complicated by spontaneous jejunal perforation secondary to ulcer disease. The perforated ulcers were oversewn at laparotomy, and the patient subsequently developed severe gastrointestinal bleeding. (a, b) Axial (a) and sagittal (b) CT angiograms help localize the bleeding to a proximal anterior jejunal loop, where pooling of contrast material is seen (arrows). Embolization therapy failed, and the patient developed recurrent gastrointestinal bleeding the next morning. Small bowel resection was subsequently performed. (c) Clinical photograph demonstrates multiple jejunal ulcers (bottom arrowheads), as well as the gastropexy clip (top arrowheads) that was used during CT-guided percutaneous localization of the bleeding loop.
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Figure 10a. Massive rectal bleeding in a 47-year-old man. (a) On an unenhanced CT scan, the rectum (arrow) appears normal. (b) Coronal CT scan demonstrates swirling and pooling of contrast material within the rectum (arrow), a finding that was not seen on the unenhanced scan. (c) CT angiogram shows a large amount of clotted blood that has refluxed into the sigmoid and distal descending colon (arrowheads). The patient underwent surgery, which showed large bleeding hemorrhoids and a bleeding anal condyloma.
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Figure 10b. Massive rectal bleeding in a 47-year-old man. (a) On an unenhanced CT scan, the rectum (arrow) appears normal. (b) Coronal CT scan demonstrates swirling and pooling of contrast material within the rectum (arrow), a finding that was not seen on the unenhanced scan. (c) CT angiogram shows a large amount of clotted blood that has refluxed into the sigmoid and distal descending colon (arrowheads). The patient underwent surgery, which showed large bleeding hemorrhoids and a bleeding anal condyloma.
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Figure 10c. Massive rectal bleeding in a 47-year-old man. (a) On an unenhanced CT scan, the rectum (arrow) appears normal. (b) Coronal CT scan demonstrates swirling and pooling of contrast material within the rectum (arrow), a finding that was not seen on the unenhanced scan. (c) CT angiogram shows a large amount of clotted blood that has refluxed into the sigmoid and distal descending colon (arrowheads). The patient underwent surgery, which showed large bleeding hemorrhoids and a bleeding anal condyloma.
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CT Angiographic Protocol for Detection of Gastrointestinal Bleeding.—
Images are acquired with the following parameters: detector configuration, 64 x 0.625 mm; section thickness, 0.9 mm; section increment, 0.45 mm; 120 kV; 405 mA; pitch, 0.923; and rotation time, 0.75 seconds. (We used a 64–detector row scanner [Brilliance 64; Phillips Medical Systems, Cleveland, Ohio].) One hundred milliliters of intravenous contrast material (Optiray 300; Mallinkrodt, St Louis, Mo) is delivered via a mechanical injector at a rate of 4 mL/sec, typically via an antecubital vein. Automatic bolus-triggering software with use of a circular region of interest is placed on the abdominal aorta at the level of the diaphragm with a trigger threshold of 150 HU. Data acquisition commences 25 seconds after the bolus-trigger threshold is reached, and scanning is performed from the xyphoid process through the ischial tuberosities. The acquired data are then reconstructed into 2-mm-thick axial sections with a section increment of 1 mm for workstation review (Extended Brilliance Workspace; Phillips Medical Systems, Best, the Netherlands) and contiguous 3-mm axial sections for picture archiving and communication system (PACS) review (Centricity; GE Healthcare, Waukesha, Wis). Contiguous 3-mm coronal and sagittal MIP reformatted images are also routinely generated and transferred to the PACS.
An unenhanced CT scan is obtained immediately prior to CT angiography to identify any pre-existing hyperattenuating areas within the bowel lumen that could be confused with hemorrhage at CT angiography. The technical parameters used to acquire the unenhanced data are as follows: detector configuration, 64 x 0.625 mm; section thickness, 3 mm; section increment, 3 mm; 120 kV; 150 mA; pitch, 0.891; and rotation time, 0.5 seconds. Contiguous 3-mm axial sections are then reconstructed and transferred to the PACS with the CT angiographic data for review.
Study Interpretation.—
We interpret the study primarily with use of the contiguous 3-mm axial unenhanced CT and CT angiographic images transferred to a PACS workstation. We first evaluate the axial CT angiographic data, and the diagnosis of active gastrointestinal bleeding is made when hyperattenuating extravasated contrast material is seen within the bowel lumen. We then compare the unenhanced CT findings to confirm the diagnosis. When active hemorrhage is detected, it is usually readily apparent on the axial CT angiograms. Coronal MIP reformatted images are useful for localizing the bleeding segment of bowel within the abdomen and are also used in conjunction with the axial images to evaluate the proximal femoral vasculature when transcatheter intervention is anticipated (Fig 11). Sagittal MIP reformatted images are useful for evaluating the rectum as well as the aorta and the origins of the celiac artery, SMA, and IMA. Detailed mapping of the small mesenteric vessels is performed as needed using a workstation that is capable of generating real-time MIP and MPR images. Various degrees of obliquity or curved MPR images may be required to delineate the entire course of the small mesenteric vessels. Rapid study interpretation and communication of results is essential for optimal case management.
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Figure 11a. Occlusion of the right common iliac artery. Axial (a) and coronal (b) CT angiograms show occlusion of a short segment of the right common iliac artery at its origin (arrow). The occlusion necessitated a left femoral approach to access the mesenteric vasculature for transcatheter intervention.
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Figure 11b. Occlusion of the right common iliac artery. Axial (a) and coronal (b) CT angiograms show occlusion of a short segment of the right common iliac artery at its origin (arrow). The occlusion necessitated a left femoral approach to access the mesenteric vasculature for transcatheter intervention.
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Protocol Design Considerations.—
Because of the intermittent nature of gastrointestinal bleeding, it is imperative that the CT angiographic examination begin as soon as possible after the clinical detection of active gastrointestinal hemorrhage to maximize detection capabilities. Given the time-sensitive nature of this study, we do not require our patients to be nothing per orum (NPO) (ie, to have ingested nothing orally), nor do we administer oral contrast agents. In fact, positive oral contrast agents would obscure active hemorrhage. In addition, retained positive contrast agents within the bowel lumen may be erroneously interpreted as active hemorrhage if an unenhanced CT scan is not concurrently acquired.
A delay of 25 seconds from the 150-HU bolus-trigger threshold to the commencement of scanning was chosen to obtain CT angiographic data during the late capillary phase of bowel enhancement. We believe that scanning during this phase of enhancement offers several advantages. Most important, scanning during the late capillary phase allows ample time for the injected contrast material to pass through the small vasculature of the gastrointestinal tract, reach the bleeding lesion, and pool in the bowel lumen. Delineation of small mesenteric vessels is superb when MIP images are used and enhancement of the major arterial structures remains diagnostic, despite the 25-second delay from the bolus-trigger threshold. Theoretically, the additional time delay provided by scanning during the late capillary phase may also increase the sensitivity of CT angiography, allowing detection of slower bleeding rates that may not be evident at arterial phase scanning. One must also consider that acquisition times for CT angiography are considerably shorter with newer multidetector scanners than with the two–and four–detector row scanners that were first used to detect gastrointestinal hemorrhage (31–33). For example, the mean duration of data acquisition was 22 seconds in the Yoon (four–detector row) study (33), whereas our typical acquisition time on a 64–detector row scanner is approximately 6–8 seconds. Longer acquisition times inherently provide more circulatory time for extravasated contrast material to accumulate within the bowel lumen. Thus, scanners with less than 64 detectors may require a shorter delay time between trigger threshold and the start of data acquisition for late capillary phase imaging. Ultimately, further clinical trials are needed to optimize scanning protocols and should focus on maximizing the capacity of CT angiography to help detect active hemorrhage while concurrently characterizing the underlying bleeding lesion.
Table 3 shows the cost, advantages, and disadvantages of CT angiography for gastrointestinal bleeding.
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Conclusions
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Initial experience with multidetector CT angiography for acute gastrointestinal bleeding shows it to be a promising first-line modality for sensitive and accurate diagnosis in this setting, while p
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Abstract
Introduction
