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Gastrointestinal Imaging |
1 From the Department of Radiology, Chonnam National University Hospital, Chonnam National University Medical School, 8 Hak-dong, Dong-gu, Gwangju 501-757, Republic of Korea. Received February 3, 2005; revision requested April 4; revision received April 18; accepted June 3; final version accepted June 20. Address correspondence to W.Y. (e-mail: radyoon{at}chonnam.ac.kr).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Materials and Methods: Institutional review board approved this study; written informed consent was obtained from each patient or patient's family after procedures, including radiation dose, were explained. Twenty-six consecutive patients (17 men, nine women; age range, 18–89 years) had acute massive GI bleeding (defined as requirement of transfusion of at least 4 units of blood during 24 hours in the hospital or as hypotension with systolic blood pressure <90 mm Hg) and underwent arterial phase multi–detector row CT before angiography. Scans were obtained during arterial phase to identify extravasation of contrast material with attenuation greater than 90 HU within bowel lumen; this finding was considered diagnostic for active GI bleeding. Presence of contrast medium extravasation in each anatomic location was recorded. Sensitivity, specificity, positive and negative predictive values, and accuracy of multi–detector row CT for detection of acute GI bleeding were assessed. Accuracy for localization of acute GI bleeding was assessed by comparing locations of active bleeding at both multi–detector row CT and angiography in each patient who had active bleeding.
Results: Arterial phase multi–detector row CT depicted extravasation of contrast material in 21 of 26 patients. Overall location-based sensitivity, specificity, accuracy, and positive and negative predictive values of multi–detector row CT for detection of GI bleeding were 90.9% (20 of 22), 99% (107 of 108), 97.6% (127 of 130), 95% (20 of 21), and 98% (107 of 109), respectively. Overall patient-based accuracy of multi–detector row CT for detection of acute GI bleeding was 88.5% (23 of 26). The location of contrast material extravasation on multi–detector row CT scans corresponded exactly to that of active bleeding on angiograms in all patients with contrast medium extravasation at both multi–detector row CT and angiography.
Conclusion: Arterial phase multi–detector row CT is accurate for detection and localization of bleeding sites in patients with acute massive GI bleeding.
© RSNA, 2006
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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There is considerable controversy in regard to the best modality for initial diagnosis of acute lower GI tract bleeding. Diagnostic procedures for lower GI tract bleeding include colonoscopy, technetium 99m (99mTc)–red blood cell scintigraphy, mesenteric angiography, and combinations of these. Although colonoscopy is becoming the most frequently used examination for patients with lower GI tract bleeding, its usefulness for the diagnosis of acute massive bleeding is still controversial. It is generally believed that colonoscopy is usually appropriate when bleeding has stopped spontaneously and bowel preparation is possible (7). Although nuclear scintigraphy is simple to perform, noninvasive, and sensitive, it is time consuming and has limited ability for localization of sites of bleeding. Its high rates of false localization have led most clinicians to perform other diagnostic tests for confirmation of the site of bleeding (7). Some authors believe that mesenteric angiography is the most accurate modality for the diagnosis of acute lower GI tract bleeding (8). Rates of detection of bleeding sites with angiography have been reported to be 58%–86% (9). The major drawback of angiography is that its rate of detection is influenced by several factors, including the rate of bleeding at the time of angiography and the timing of angiography. Sites of bleeding cannot be demonstrated with angiography even in patients with massive GI bleeding because of its intermittent nature (10).
The use of contrast material–enhanced CT in the diagnosis of acute GI bleeding has received little attention. The capability of contrast-enhanced CT to depict acute GI bleeding has been documented only in case reports and a few retrospective series (11–14). Recently, multi–detector row helical CT has increasingly been used in the diagnostic evaluation of most vascular diseases (15). Compared with single–detector row helical CT, multi–detector row CT features strikingly increased image resolution and markedly decreased scanning time. These attributes enable acquisition of accurate arterial phase images and, thus, identification of extravasation of contrast material into the intestinal lumen, a finding diagnostic of acute GI bleeding, before the contrast material is diluted. We hypothesized that active extravasation of contrast material would be identifiable on arterial phase contrast-enhanced multi–detector row CT scans in patients with acute massive GI bleeding and that such identification would enable precise localization of sites of bleeding. Thus, the purpose of our study was to prospectively evaluate the accuracy of arterial phase multi–detector row CT for the depiction and localization of acute massive GI bleeding, with angiography as the reference standard.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Bleeding was considered upper or lower GI tract bleeding if its origin was located proximal or distal to the ligament of Treitz, respectively. Acute GI bleeding was defined as hematemesis, melena, or hematochezia that occurred within 24 hours before CT. Massive bleeding was considered to have occurred if either of the following two criteria was met: The patients required transfusion of at least 4 units of blood during a 24-hour period in the hospital, or they had hemodynamic instability (hypotension with systolic blood pressure <90 mm Hg). The causes of upper GI tract bleeding (n = 7) were duodenal ulcer (n = 4), gastric ulcer (n = 1), coagulopathy (n = 1), and duodenal diverticulitis (n = 1). The causes of lower GI tract bleeding (n = 19) were stress ulceration (n = 7), coagulopathy (n = 2), angiodysplasia (n = 1), stromal tumor of the GI tract (n = 1), Crohn disease (n = 1), colon cancer (n = 1), nonspecific colitis (n = 1), and unknown (n = 5). Coagulopathy was defined as the presence of thrombocytopenia (platelet count, <50 000 mm3 [50 x 109/L]) or an international normalized ratio of greater than 1.5. Our institutional review board approved this prospective study, and written informed consent was obtained from each patient or patient's family after the procedures for this study, including radiation dose, were explained.
CT Examination and Interpretation of Results
All patients were hydrated with intravenous infusion of 500–1000 mL of saline, which was commenced 1 hour before CT and was continued for 12 hours after CT. Multi–detector row CT was performed with a four-detector row CT scanner (Lightspeed QX/i; GE Medical Systems, Milwaukee, Wis) with a gantry rotation speed of 0.8 second per rotation. Contrast material or water was not orally administered in any patient. Preliminary unenhanced CT scans were obtained to depict any preexisting hyperattenuating material in the bowel lumen. These unenhanced scans were obtained with a section thickness of 10 mm and a scan range from the hepatic dome to the inferior pubic ramus.
Multi–detector row scans were obtained during the arterial phase to help identify active extravasation of contrast material within the bowel lumen. Imaging parameters for arterial phase multi–detector row CT scans were nominal section thickness of 2.5 mm, beam pitch of 1.5, table speed of 15 mm per rotation, reconstruction interval of 2 mm, tube voltage of 120 kV, and tube current of 200 mA. All patients received 140 mL of contrast agent with 350 mg of iodine per milliliter (iohexol, Omnipaque 350; Nycomed-Amersham, Princeton, NJ), which was administered intravenously by means of an automated injector (LF CT 9000; Liebel-Flarsheim, Cincinnati, Ohio) at an injection rate of 3.5 mL/sec. We used an antecubital vein as the access route and 18-gauge intravenous needles. The scan delay was determined by using automatic bolus-triggering software (SmartPrep; GE Healthcare, Milwaukee, Wis) program with a circular region of interest positioned at the level of the abdominal aorta and a predefined 100-HU enhancement threshold level for triggering data acquisition. The mean duration of data acquisition was 22 seconds. The scan range for arterial phase CT was identical to that for unenhanced CT. Delayed scans were not obtained in this study. Arterial phase multi–detector row CT was successfully performed in all 26 patients.
With arterial phase multi–detector row CT, the following two features were considered diagnostic of acute GI bleeding: (a) the presence of extravasation of contrast material in the bowel lumen and (b) extravasated contrast material with attenuation level of greater than 90 HU. For the evaluation of the diagnostic accuracy of multi–detector row CT in depiction of acute GI bleeding, the GI tract was classified according to five anatomic locations: stomach, duodenum, small bowel, colon, and rectum. The presence or absence of CT features diagnostic of acute GI bleeding was recorded for each anatomic location in each patient. Two radiologists (Y.Y.J. and S.S.S.) with 7 and 2 years of experience, respectively, with abdominal CT analyzed the CT images. Final decisions in regard to the CT findings were determined in consensus. In 23 patients, both observers independently established the same interpretation. In the remaining three patients, a decision was reached with consensus. Transferred transverse CT images were reviewed as digital images on a picture archiving and communication system monitor (MFGD; Barco, Kortrijk, Belgium). Three-dimensional reconstruction of data sets was not performed in this study.
Angiography and Interpretation
Patients were hydrated with intravenous infusion of saline, which was commenced 6 hours before angiography and was continued for 12 hours after angiography. Angiography and subsequent embolization were performed in all 26 patients by an interventional radiologist (W.Y.) with 4 years of experience in angiography and embolization. Angiography was used as the standard of reference for diagnosis of acute GI bleeding. In all patients, angiography was performed with a digital subtraction technique (Angiostar, Siemens Medical Systems, Erlangen, Germany; or Advantx LCN+, GE Medical Systems). Celiac arteriograms, superior mesenteric arteriograms, and inferior mesenteric arteriograms were obtained in all patients. Angiography was performed by inserting a catheter via the femoral artery. Various types of angiographic catheters were used for selective injection in different arteries. The following angiographic findings were considered indicative of acute GI bleeding: (a) active extravasation of contrast material within the bowel lumen or (b) pseudoaneurysm. Superselective embolization of bleeding vessels was performed in patients in whom diagnostic angiography depicted a focus of bleeding.
Two interventional radiologists (W.Y. and J.K.K., with 12 years of experience with angiography) reviewed all angiograms and noted whether angiographic findings positive for GI tract bleeding were present or absent in each anatomic location in each patient. Conclusions were reached in consensus. In all 26 patients, both observers independently established the same interpretation. All patients were followed up at 30 days after angiography.
The accuracy for localization of acute GI bleeding was assessed by comparing the locations of active bleeding in each patient who had active bleeding at both multi–detector row CT and angiography. For this assessment, the location of GI bleeding was recorded for the following anatomic locations: stomach, duodenum, jejunum, ileum, ascending colon, transverse colon, descending colon, and rectum. The locations of active bleeding were individually recorded by two authors (Y.Y.J., for multi–detector row CT, and W.Y., for angiography). Then, the locations noted at multi–detector row CT were compared with those detected at angiography for each patient.
Analysis of Clinical Data
Time from onset of symptoms to CT, interval between CT and angiography, and hemodynamic status at the time of both examinations were prospectively recorded for each patient. Before CT, each patient's baseline renal function was assessed with measurements of serum creatinine concentration. Preexisting renal insufficiency was defined as a baseline serum creatinine concentration of greater than 1.5 mg/dL (133 µmol/L). To assess induction of nephrotoxicity from iodinated contrast agents injected during CT and angiography, serum creatinine concentration was determined at 48 hours after each study. Contrast material–induced nephrotoxicity was defined as an increase in serum creatinine concentration of more than 0.5 mg/dL (44 ìmol/L) at 48 hours after any of the imaging studies (16). For each patient, the following variables were also recorded: age, sex, underlying medical conditions, coagulation status, transfusion requirements, and endoscopic or scintigraphic findings, if available. Clinical follow-up data were collected and reviewed by one of the authors (W.Y.).
Statistical Analysis
Calculation of sensitivity, specificity, accuracy, and positive and negative predictive values for detection of acute GI bleeding with multi–detector row CT was performed on the basis of a per-location analysis in relation to results at angiography. For the purposes of statistical analysis, a true-positive finding was defined as depiction at multi–detector row CT of the presence of contrast material extravasation when the results of angiography were positive for active bleeding. A false-positive finding was defined as depiction at multi–detector row CT of the presence of active bleeding that was not detected at angiography. A true-negative finding was defined as the lack of identification of a bleeding focus on multi–detector row CT images when the results of angiography were negative for active bleeding. A false-negative finding was defined as depiction at multi–detector row CT of the absence of active bleeding despite detection of active bleeding at angiography.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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In two patients, angiography revealed acute duodenal bleeding that was not detected at multi–detector row CT (false-negative multi–detector row CT findings). Of these two patients, one, who had massive hematemesis 5 days after undergoing splenectomy, had acute stress ulceration in the second portion of the duodenum at endoscopy of the upper GI tract. Endoscopic hemoclip (HX-600, HX-610; Olympus Medical Systems, Tokyo, Japan) placement was performed but did not stop the bleeding. In this patient, the second portion of the duodenum could not be clearly evaluated at multi–detector row CT because of metallic artifact from hemoclips in the duodenal mucosa. Angiography revealed a small pseudoaneurysm arising from a branch of the gastroduodenal artery. In the other patient, arterial phase multi–detector row CT failed to reveal active bleeding in the duodenum that was, however, detected at selective gastroduodenal arteriography. Thus, overall patient-based accuracy of multi–detector row CT in the detection of acute GI bleeding was 88.5% (23 of 26). In 21 patients in whom multi–detector row CT depicted extravasation of contrast material, the mean attenuation level was 245 HU (attenuation range, 137–330 HU).
We evaluated 130 anatomic locations in 26 patients for the presence or absence of acute GI bleeding (Table). The overall location-based sensitivity, specificity, accuracy, and positive and negative predictive values for the detection of GI bleeding at multi–detector row CT were 90.9% (20 of 22), 99% (107 of 108), 97.6% (127 of 130), 95% (20 of 21), and 98% (107 of 109), respectively. Of the 130 locations evaluated, 20 had evidence of acute GI bleeding at both multi–detector row CT and angiography (true-positive CT findings) (Figs 1–4). A false-positive CT finding was obtained in one case. In two cases without evidence of acute GI bleeding at multi–detector row CT, findings were positive at angiography (false-negative findings). As previously stated, all these false-positive and false-negative findings occurred in the duodenum.
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Analysis of Clinical Data
The time to performance of CT after onset of symptoms was less than 24 hours for 19 patients (mean time, 11.7 hours; range, 1–22 hours) and between 1 day and 1 week for six patients (mean time, 2.9 days; range, 1.7–4.2 days). The time to performance of CT for the remaining patient was 8 days. The interval between performance of CT and that of angiography was no more than 1 hour for 12 patients (mean interval, 42.5 minutes; range, 30–60 minutes) and between 1 hour and 24 hours for 13 patients (mean interval, 8.3 hours; range, 1.5–22 hours). The interval for the remaining patient was 26 hours. Thus, most patients underwent angiography within 1 day after CT. At the time of CT, 23 patients were hemodynamically stable and three patients were hemodynamically unstable (systolic blood pressure < 90 mm Hg). At the time of angiography, 24 patients were stable and two patients were unstable. Thus, most patients were hemodynamically stable when imaging studies were performed.
Prior to CT, three patients had preexisting renal insufficiency due to diabetic nephropathy, with baseline serum creatinine levels of 2.0, 6.4, and 6.2 mg/dL (177, 566, and 548 ìmol/L, respectively). Contrast material–induced nephrotoxicity occurred in two patients. For these two patients, the intervals between CT and angiography were 2 and 26 hours. Both of these patients underwent hemodialysis after angiography. None of the 23 patients who had normal baseline renal function experienced contrast material–induced nephrotoxicity after imaging studies.
In the seven patients with acute upper GI tract bleeding, endoscopy of the upper GI tract was performed prior to CT in six. In these six patients, endoscopy of the upper GI tract revealed a definite focus of bleeding in only four. Endoscopy of the upper GI tract revealed only a large hematoma in the stomach and duodenum; no foci of bleeding were detected in the remaining two patients. One patient with acute upper GI tract bleeding refused endoscopic examination. In the 19 patients with acute lower GI tract bleeding, both endoscopy of the upper GI tract and colonoscopy were performed prior to CT in 10. The results of endoscopy of the upper GI tract were negative for bleeding in these 10 patients. In these 10 patients, colonoscopy revealed findings positive for bleeding in only two: angiodysplasia of the ascending colon in one patient and sigmoid colon cancer in the other. Colonoscopic findings were not diagnostic in the remaining eight patients. In patients with acute lower GI tract bleeding, 99mTc–red blood cell scintigraphy was performed in three patients prior to CT. Two of these three patients had a finding positive for bleeding at scintigraphy.
Transarterial Embolization and Follow-up
Thirty-day follow-up after CT and angiography was performed in all patients. Of 26 patients, 21 underwent transarterial embolization after diagnostic angiography. Of these patients, 20 had a focus of bleeding that was identified at angiography. The remaining patient, who had a false-positive CT finding in the duodenum, underwent blind embolization (defined as embolization without angiographic proof of extravasation of contrast material [17]) of the gastroduodenal artery, and bleeding ceased after embolization.
Two patients with active foci of bleeding depicted at angiography did not undergo embolization. One of these patients had a small-bowel tumor with active bleeding identified at multi–detector row CT and underwent emergency surgery. Pathologic examination confirmed a GI stromal tumor arising from the jejunum. The other patient had congestive heart failure, valvular heart disease, coagulopathy due to oral anticoagulant therapy with warfarin, and acute gastric bleeding identified at both CT and angiography. This patient died of sudden cardiac arrest during angiography.
Of three patients with no definite focus of bleeding at either CT or angiography, two were treated conservatively and had cessation of bleeding, without recurrence of bleeding during the follow-up period. The remaining patient had continued bleeding and underwent right hemicolectomy on the basis of CT findings of edematous wall thickening in the hepatic flexure of the colon. Pathologic examination revealed chronic nonspecific colitis.
Of the 26 patients, four underwent intestinal surgery after angiography. Of these four patients, two had a focus of bleeding identified at both CT and angiography and underwent surgery because of continued bleeding after transarterial embolization. In these four patients, surgical and pathologic findings confirmed small-bowel ulceration in two patients, a jejunal GI stromal tumor in one patient, and nonspecific colitis in one patient.
Overall, angiography revealed a focus of bleeding in 22 of 26 patients. Thus, the rate of detection of acute GI bleeding for angiography was 84.6% (22 of 26) in this study. Of 21 patients who underwent transarterial embolization, 18 recovered uneventfully. Two patients underwent surgery after embolization, and one patient, who had sigmoid colon cancer that was confirmed with findings at colonoscopy, had continued bleeding. Thus, the rate of success of transarterial embolization was 85.7% (18 of 21). The 30-day mortality rate in this patient group was 3.8% (one of 26 patients).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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The use of helical CT angiography for the diagnosis of lower GI tract bleeding has been infrequently reported in the literature, and previous studies were retrospective with small numbers of patients or anecdotal case reports. In 1997, Ettorre et al (11) published an article that included a series of 18 consecutive patients with acute GI bleeding who underwent catheterization of the abdominal aorta followed by single–detector row helical CT angiography after intraarterial injections of a contrast medium through an angiographic catheter positioned near the origin of the celiac trunk. In their series of patients, helical CT angiography revealed the site of contrast material extravasation in 72% (13 of 18). The site of bleeding was revealed at angiography in two of five patients who had negative results at helical CT angiography. One of the limitations of their study was the complexity and invasiveness of the methods used for diagnosis, and those methods included arterial catheterization.
Recently, Ernst et al (13) reported that single–detector row helical CT after intravenous injection of contrast material helped locate sites of bleeding in 79% (15 of 19) of patients with acute lower GI tract bleeding. In their study, minor or inconclusive CT findings, such as high-attenuating peribowel fat, intestinal wall thickening, polyp, tumor, and vascular dilatation, as well as contrast material extravasation, were also used as diagnostic criteria for acute GI bleeding. Extravasation of contrast medium was found in only three of 15 patients, although they used a larger volume of contrast materials (160 mL) and a faster injection rate (4 mL/sec) than we used in our study, and this finding suggests that single–detector row helical CT has only a limited role in clinical diagnosis of active GI bleeding. More recently, Tew et al (14) performed a retrospective review of 13 patients with acute lower GI tract bleeding who underwent multi–detector row CT angiography with a four–detector row multi–detector row CT scanner prior to angiography. They reported that multi–detector row CT angiography depicted a site of bleeding in 54% (seven of 13) of patients, with all such sites confirmed at angiography. In their study, the six patients with negative multi–detector row CT findings experienced resolution of bleeding without further intervention. They thus obtained no false-positive or false-negative findings with multi–detector row CT.
The results of our study indicated that arterial phase multi–detector row CT is highly accurate for both detection and localization of acute massive GI bleeding. For the detection of acute GI bleeding, multi–detector row CT had a sensitivity of 90.9% and a specificity of 99% in this study. There were two false-negative diagnoses and one false-positive diagnosis with CT, and all of these were for bleeding in the duodenum. One false-negative finding was caused by a metallic artifact from hemoclips located in the vicinity of a focus of bleeding. One drawback of CT for the diagnosis of acute GI bleeding is that CT artifacts can obscure contrast material extravasation in the bowel lumen. In the patient with a false-positive diagnosis, multi–detector row CT clearly revealed active extravasation of contrast material from the lateral wall of the second portion of the duodenum, but angiography failed to reveal active bleeding. Although we classified this case as a false-positive diagnosis in accordance with our diagnostic criteria, this case might not, in fact, have been false-positive. It is known that acute GI bleeding can be intermittent in nature even in cases of massive bleeding; therefore, this failure to detect active bleeding at angiography may not prove the absence of active foci of bleeding.
In the present study, arterial phase multi–detector row CT had an accuracy of 100% for localization of acute GI bleeding. The site of contrast material extravasation on multi–detector row CT scans corresponded to the site of bleeding identified on angiograms in all patients with acute GI bleeding. This correspondence is of particular importance in the performance of angiography and subsequent embolization procedures in critically ill patients with acute massive GI bleeding. Interventional radiologists can use the location of contrast material extravasation on multi–detector row CT scans to direct the performance of more selective investigations of arteries that are most likely to be bleeding, and this adjunctive use may improve the rate of angiographic detection of acute GI bleeding. In addition, interventional radiologists can confidently perform delayed follow-up examinations of arteries that supply specific areas when the first angiographic examination fails to depict a site of bleeding despite the presence of contrast material extravasation on multi–detector row CT scans. This delayed follow-up examination might reveal foci of bleeding that were not demonstrated at the first examination and, thus, also might increase the rate of detection of acute GI bleeding at angiography.
Our study had several limitations. First, patients with nonmassive or minute GI bleeding were not included in this study. Thus, we were unable to determine whether multi–detector row CT has the same capability for diagnosis of nonmassive or chronic GI bleeding. A second limitation of this study was that there was a selection bias in the study population. Of the patients who had acute upper GI tract bleeding during the study period, those in whom endoscopic examination or hemostasis failed were selected for this study. A third limitation was that delayed phase scanning was not performed in this study. Additional portal venous phase scans may be useful in the determination of the cause of acute GI bleeding, especially in cases of intestinal tumor. The objective of this study, however, was not to determine whether multi–detector row CT can be used for the diagnosis of the cause of acute GI bleeding. Another limitation of the study was that the numbers of patients in the study group were relatively small.
In conclusion, our findings suggest that arterial phase multi–detector row CT is accurate for the depiction and localization of sites of bleeding in patients with acute massive GI bleeding.
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FOOTNOTES |
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Abbreviations: GI = gastrointestinal
Authors stated no financial relationship to disclose.
Author contributions: Guarantor of integrity of entire study, W.Y.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, W.Y; clinical studies, all authors; statistical analysis, W.Y.; and manuscript editing, W.Y., H.K.K.
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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