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Everything you need to know about Computed Tomography (CT) & CT Scanning

Imaging Pearls ❯ Colon ❯ GI Bleeding

  
  • Purpose To compare CT angiography (CTA) and tagged red blood cell (RBC) scan as a function of time from these initial imaging studies to subsequent conventional angiography and catheter-directed embolization in patients with gastrointestinal (GI) bleeding.
    Conclusions In patients requiring conventional angiography for GI bleeding, CT angiography results in a faster time to angi- ography than tagged RBC scan, which appears to be due to the longer duration required to complete the tagged RBC scan. Decreasing time to angiography is vital, as GI bleeding can be fatal and earlier diagnosis and intervention has the potential to reduce morbidity and mortality, while also increasing sensitivity of angiography. These findings may assist ordering clinicians in deciding on the appropriate diagnostic study.
    Time to conventional angiography in gastrointestinal bleeding: CT angiography compared to tagged RBC scan
    Hsu MJ et al.
    Abdominal Radiol (in press ) 2019
  • “The mean time from diagnostic study order to study completion was 3 h and 4 min for the CTA group and 5 h and 1 min for the tagged RBC scan group (p value = 0.0001). There was no statistically significant difference between the time to angiography after completion of the preceding diagnostic study. The total mean time from diagnostic study order to inter- vention was 6 h and 8 min for the CTA group and 9 h and 29 min for the tagged RBC scan group, a statistically significant difference (p value = 0.028).”
    Time to conventional angiography in gastrointestinal bleeding: CT angiography compared to tagged RBC scan
    Hsu MJ et al.
    Abdominal Radiol (in press ) 2019
  • ”The results show that in the clinical setting of a patient presenting with GI bleeding requiring catheter-directed embolization, CTA reduces the time to angiography as compared to tagged RBC scanning. Furthermore, the overall time from the decision to order a radiologic study to catheter angiography is faster with CTA. Given the time from diagnostic study completion to angiography was not statistically significant between the two groups, it can be inferred that the limiting step was with diagnosis.”
    Time to conventional angiography in gastrointestinal bleeding: CT angiography compared to tagged RBC scan
    Hsu MJ et al.
    Abdominal Radiol (in press ) 2019
  • Purpose To compare CT angiography (CTA) and tagged red blood cell (RBC) scan as a function of time from these initial imaging studies to subsequent conventional angiography and catheter-directed embolization in patients with gastrointestinal (GI) bleeding.
    Conclusions In patients requiring conventional angiography for GI bleeding, CT angiography results in a faster time to angi- ography than tagged RBC scan, which appears to be due to the longer duration required to complete the tagged RBC scan. Decreasing time to angiography is vital, as GI bleeding can be fatal and earlier diagnosis and intervention has the potential to reduce morbidity and mortality, while also increasing sensitivity of angiography. These findings may assist ordering clinicians in deciding on the appropriate diagnostic study.
    Time to conventional angiography in gastrointestinal bleeding: CT angiography compared to tagged RBC scan
    Hsu MJ et al.
    Abdominal Radiol (in press ) 2019
  • “The mean time from diagnostic study order to study completion was 3 h and 4 min for the CTA group and 5 h and 1 min for the tagged RBC scan group (p value = 0.0001). There was no statistically significant difference between the time to angiography after completion of the preceding diagnostic study. The total mean time from diagnostic study order to inter- vention was 6 h and 8 min for the CTA group and 9 h and 29 min for the tagged RBC scan group, a statistically significant difference (p value = 0.028).”
    Time to conventional angiography in gastrointestinal bleeding: CT angiography compared to tagged RBC scan
    Hsu MJ et al.
    Abdominal Radiol (in press ) 2019
  • ”The results show that in the clinical setting of a patient presenting with GI bleeding requiring catheter-directed embolization, CTA reduces the time to angiography as compared to tagged RBC scanning. Furthermore, the overall time from the decision to order a radiologic study to catheter angiography is faster with CTA. Given the time from diagnostic study completion to angiography was not statistically significant between the two groups, it can be inferred that the limiting step was with diagnosis.”
    Time to conventional angiography in gastrointestinal bleeding: CT angiography compared to tagged RBC scan
    Hsu MJ et al.
    Abdominal Radiol (in press ) 2019
  • “Both CTA and RBC scintigraphy can be used to identify active bleeding in 38% of cases. However, the site of bleeding is localized with CTA in a significantly higher proportion of studies.” 


    Localizing Acute Lower Gastrointestinal Hemorrhage: CT Angiography Versus Tagged RBC Scintigraphy 
Feuerstein JD et al.
AJR 2016; 207:578–584
  • “In total, 45 CTA and 90 RBC scintigraphic examinations were performed during the study period. Seventeen (38%) CTA scans showed active gastrointestinal bleeding compared with 34 (38%) RBC scintigraphic scans (p = 1.000). However, the site of bleeding was accurately localized on 24 (53%) CTA scans. This proportion was significantly greater than the proportion localized on RBC scintigraphic scans (27 [30%]) (p = 0.008). There were no significant differences between the two groups in average hospital length of stay, blood transfusion requirement, incidence of acute kidney injury, or in-hospital mortality.”

    
Localizing Acute Lower Gastrointestinal Hemorrhage: CT Angiography Versus Tagged RBC Scintigraphy 
Feuerstein JD et al.
AJR 2016; 207:578–584
  • “The average time to complete an RBC scin- tigraphic examination was 3 hours 9 minutes after the order was placed. CTA examinations were completed an average of 1 hour 41 minutes after the initial order (p < 0.001). In the CTA group, 32 of 45 (71%) examinations were completed within 2 hours of initial order, com- pared with 31 of 90 (34%) RBC scintigraphic examinations (p < 0.001).” 


    Localizing Acute Lower Gastrointestinal Hemorrhage: CT Angiography Versus Tagged RBC Scintigraphy 
Feuerstein JD et al.
AJR 2016; 207:578–584
  • “Gastrointestinal (GI) bleeding is a common medical problem, with high associated morbidity and mortality. The clinical presentation of gastrointestinal hemorrhage varies with the location of the bleeding source, the intensity of the bleed, and the presence of comorbidities that affect the ability to tolerate blood loss.”
Gastrointestinal hemorrhage: evaluation with MDCT.


    Soto JA et al.
Abdom Imaging. 2015 Jun;40(5):993-1009
  • “Conventional endoscopic examinations are usually the initial diagnostic tests in patients presenting with overt gastrointestinal hemorrhage. However, implementation of upper tract endoscopy and colonoscopy in the emergency setting can be challenging due to inconsistent availability of the service and difficulties in achieving adequate colonic cleansing in emergent situations. Thus, imaging tests are often relied upon to establish the location and the cause of bleeding, either for initial diagnosis or after non-revealing upper and lower tract endoscopies ("obscure" bleeding). This article discusses the imaging evaluation of patients with gastrointestinal bleeding and reviews the imaging appearance of the most common causes, taking into account the two most relevant clinical presentations: overt bleeding and obscure bleeding.
“

    Gastrointestinal hemorrhage: evaluation with MDCT.
Soto JA et al.
Abdom Imaging. 2015 Jun;40(5):993-1009
  • “The anatomic landmark traditionally used to classify the source of GI bleeding is the ligament of Treitz, with upper GI bleeding originating proximal to the ligament and lower GI bleeding distal to it.”

    Gastrointestinal hemorrhage: evaluation with MDCT.
Soto JA et al.
Abdom Imaging. 2015 Jun;40(5):993-1009
  • “The most common causes of upper tract bleeds are esophageal or gastric varices, gastritis or duodenitis, gastric cancer, and peptic ulcer disease. Causes of acute lower gastrointestinal tract hemorrhage include colonic diverticula, angioectasia, colonic or small bowel neoplasms, Meckel’s diverticulum, rectal ulcers, and hemorrhoids.”


    Gastrointestinal hemorrhage: evaluation with MDCT.
Soto JA et al.
Abdom Imaging. 2015 Jun;40(5):993-1009
  • “A careful evaluation is necessary to differentiate clot from non-hemorrhagic hyperattenuating contents, such as retained enteric contrast material, foreign bodies, and suture material. The attenuation coefficient of extraluminal blood typically is higher than usual intestinal contents: 30–45 Hounsfield units (HU) for unclotted blood and 40–70 HU for clotted blood.”


    Gastrointestinal hemorrhage: evaluation with MDCT.
Soto JA et al.
Abdom Imaging. 2015 Jun;40(5):993-1009
  • “In addition, low intensity bleeds may be difficult to detect when extravasated contrast material dilutes with pre-existent intraluminal fluid or clot. Hyperenhancement of the bowel and hypervascular masses can simulate or mask true extravasated contrast material. Ingested or retained hyperattenuating foci in the bowel lumen can easily be characterized as such by comparing the unenhanced with the two enhanced series.”

    Gastrointestinal hemorrhage: evaluation with MDCT.
Soto JA et al.
Abdom Imaging. 2015 Jun;40(5):993-1009
  • “Angioectasia is the most common vascular abnormality and consists of thin tortuous veins usually 2–10 mm in size with an arborizing pattern. Angioectasias are common in the general population. They are frequently multiple and most do not bleed. Therefore, the detection of angioectasia does not necessarily indicate that this is the source of bleeding.”

    Gastrointestinal hemorrhage: evaluation with MDCT.
Soto JA et al.
Abdom Imaging. 2015 Jun;40(5):993-1009
  • “Based on the clinical presentation, GI bleeding can be ‘‘overt’’ (visible evidence of bleeding such as hematemesis or melena) or ‘‘occult’’ (iron deficiency anemia and positive fecal blood test). Bleeding is ‘‘obscure’’ when evaluation with conventional upper and lower tract endoscopy does not reveal the source.”
Gastrointestinal hemorrhage: evaluation with MDCT.
Soto JA et al.
Abdom Imaging. 2015 Jun;40(5):993-1009
  • BACKGROUND: Active lower gastrointestinal (GI) bleeding is a potentially dangerous situation because patients with this condition may fall into shock. Colonoscopy, angiography, and scintigraphy have been used widely to localize the source of bleeding, but time is needed to perform these examinations. The purpose of this study was to illustrate how vividly enhanced computed tomography (CT) may show active lower GI bleeding in a short time.
    CONCLUSION: Enhanced helical CT was useful for the detection of an active lower GI bleeding source. The procedure was brief, less invasive, and less demanding. Enhanced CT may be the first step for diagnosing lower GI tract bleeding.

    Enhanced CT for initial localization of active lower gastrointestinal bleeding.
    Yamaguchi T,Yoshikawa K.
    Abdom Imaging. 2003 Sep-Oct;28(5):634-6
  • BACKGROUND: Active lower gastrointestinal (GI) bleeding is a potentially dangerous situation because patients with this condition may fall into shock. Colonoscopy, angiography, and scintigraphy have been used widely to localize the source of bleeding, but time is needed to perform these examinations.
    CONCLUSION: Enhanced helical CT was useful for the detection of an active lower GI bleeding source. The procedure was brief, less invasive, and less demanding. Enhanced CT may be the first step for diagnosing lower GI tract bleeding.

    Enhanced CT for initial localization of active lower gastrointestinal bleeding.
    Yamaguchi T,Yoshikawa K
    Abdom Imaging. 2003 Sep-Oct;28(5):634-6
  • PURPOSE: To prospectively evaluate accuracy of arterial phase multi-detector row helical computed tomography (CT) for detection and localization of acute massive gastrointestinal (GI) bleeding, with angiography as reference standard.
    CONCLUSION: Arterial phase multi-detector row CT is accurate for detection and localization of bleeding sites in patients with acute massive GI bleeding.

    Acute massive gastrointestinal bleeding: detection and localization with arterial phase multi-detector row helical CT.
    Yoon W  et al.
    Radiology. 2006 Apr;239(1):160-7
  • “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.”

    Acute massive gastrointestinal bleeding: detection and localization with arterial phase multi-detector row helical CT.
    Yoon W  et al.
    Radiology. 2006 Apr;239(1):160-7
  • “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).”

    Acute massive gastrointestinal bleeding: detection and localization with arterial phase multi-detector row helical CT.
    Yoon W  et al.
    Radiology. 2006 Apr;239(1):160-7
  • “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. 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.”

    Acute Gastrointestinal Bleeding: Emerging Role of Multidetector CT Angiography and Review of Current Imaging Techniques
    Laing CJ et al.
    Radiographics. 2007 Jul-Aug;27(4):1055-70
  • “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 .”

    Acute Gastrointestinal Bleeding: Emerging Role of Multidetector CT Angiography and Review of Current Imaging Techniques
    Laing CJ et al.
    Radiographics. 2007 Jul-Aug;27(4):1055-70
  • “The overall sensitivity for detecting bleeding was 0.44 for an arterial acquisition alone, 0.68 for a portal venous acquisition, 0.68 for the combination unenhanced/arterial, 0.72 for unenhanced/portal venous and 0.80 for arterial/portal. Bleeding velocities of above 0.25 ml/min were detected with a sensitivity of 0.59 for arterial, 0.88 for portal venous, 0.85 for unenhanced/arterial, 0.94 for unenhanced/portal venous and 0.97 for arterial/portal venous contrast phase protocols, respectively MDCT provides the highest sensitivity and specificity in the detection of intestinal bleeding using arterial and portal venous acquisition in comparison to mono-phase protocols.

    Detection of intestinal bleeding with multi-detector row CT in an experimental setup. How many acquisitions are necessary?
    Dobritz M et al.
    Eur Radiol. 2009 Dec;19(12):2862-9
  • “Bleeding velocities of above 0.25 ml/min were detected with a sensitivity of 0.59 for arterial, 0.88 for portal venous, 0.85 for unenhanced/arterial, 0.94 for unenhanced/portal venous and 0.97 for arterial/portal venous contrast phase protocols, respectively MDCT provides the highest sensitivity and specificity in the detection of intestinal bleeding using arterial and portal venous acquisition in comparison to mono-phase protocols.”

    Detection of intestinal bleeding with multi-detector row CT in an experimental setup. How many acquisitions are necessary?
    Dobritz M et al.
    Eur Radiol. 2009 Dec;19(12):2862-9
  • “Most investigators agree that it is useful to obtain a precontrast study prior to the injection of IV contrast. This will help the differentiation of potential extravasated IV contrast from other high-density materials in the bowel, such as pills, sutures, or old oral contrast, etc.”

    Acute gastrointestinal bleeding: the potential role of 64 MDCT and 3D imaging in the diagnosis
    Horton KM, Jeffrey RB Jr.,Federle MP, Fishman EK
    Emerg Radiol (2009) 16:349–356 
  • “This is a relatively new application for CT, which cannot only detect the site of hemorrhage but can also map out the relevant vascular anatomy, which is crucial for either interventional emboli- zation or surgical resection. It is possible that CT will also be able to help triage patient to either observation or supportive care vs. urgent intervention, as many patients with acute bleeding will stop spontaneously.”

    Acute gastrointestinal bleeding: the potential role of 64 MDCT and 3D imaging in the diagnosis
    Horton KM, Jeffrey RB Jr.,Federle MP, Fishman EK
    Emerg Radiol (2009) 16:349–356 
  • “There were no cases in which CT angiography was negative and subsequent angiography within 24 hours was positive. The overall sensitivity, specificity, accuracy, and positive and negative predictive value of CT angiography in the detection of active GI hemorrhage within this study population were 79%, 95%, 91%, 86%, and 92%, respectively.”

    Detection of active gastrointestinal hemorrhage with CT angiography: a 4(1/2)-year retrospective review.
    Kennedy DW et al.
    J Vasc Interv Radiol. 2010 Jun;21(6):848-55
  • “CT angiography provides valuable information that can be used to determine the appropriateness of catheter angiography and guide mesenteric catheterization if a bleeding source is localized. The authors' experience with this study cohort supports its use before angiography in those patients with acute GI bleeding of an unknown source who are being considered for catheter-directed intervention.”

    Detection of active gastrointestinal hemorrhage with CT angiography: a 4(1/2)-year retrospective review.
    Kennedy DW et al.
    J Vasc Interv Radiol. 2010 Jun;21(6):848-55
  • OBJECTIVES: To compare the respective capabilities of the arterial, the portal, and the combined set in the detection and localization of acute gastrointestinal (GI) bleeding with 64-section computed tomography (CT).
    CONCLUSIONS: Using 64-section CT, the diagnostic performance was not different among the arterial, the portal, and the combined set for the detection and localization of acute GI bleeding.

    Diagnosis of acute gastrointestinal bleeding: comparison of the arterial, the portal, and the combined set using 64-section computed tomography.
    Kim JW et al
    J Comput Assist Tomogr. 2011 Mar-Apr;35(2):206-11
  • “Both observers correctly detected the bleeding site in 81.3% and 84.4% on the arterial set, in 81.3% and 84.4% on the portal set, and in 84.4% and 84.4% on the combined set, respectively.”

    Diagnosis of acute gastrointestinal bleeding: comparison of the arterial, the portal, and the combined set using 64-section computed tomography.
    Kim JW et al
    J Comput Assist Tomogr. 2011 Mar-Apr;35(2):206-11
  • CTA Protocol for Suspected GI Bleed
    - Oral contrast
    - IV contrast
    - Phases of data acquisition
    - Display of the data in MPR and 3D views with realtime rendering
  • CTA Protocol for Suspected GI Bleed
    - Oral contrast (1000 cc water over 15 minutes)
    - IV contrast (100-120 cc injected at 5cc/sec)
    - Phases of data acquisition (arterial and venous at 30 and 70 sec)
    - Display of the data in MPR and 3D views with realtime rendering (MPR Coronal and Sagital Images and real-time 3D VRT)
  • OBJECTIVE: We evaluated the diagnostic performance of computed tomography (CT) as an initial radiologic test for assessing the optimal timing of colonoscopy in patients with acute lower gastrointestinal bleeding (LGIB) and investigated the effectiveness of contrast-enhanced (CE) CT for detecting colonic diverticular bleeding
    CONCLUSION: Urgent CT is useful for determining the optimal timing of colonoscopy in cases of acute LGIB. CE-CT may be used to depict the presence and location of active hemorrhage and provides useful information for subsequent colonoscopy, especially in patients with diverticular bleeding.

    Urgent computed tomography for determining the optimal timing of colonoscopy in patients with acute lower gastrointestinal bleeding.
    Nakatsu S et al.
    Intern Med. 2015;54(6):553-8
  • “Urgent CT is useful for determining the optimal timing of colonoscopy in cases of acute LGIB. CE-CT may be used to depict the presence and location of active hemorrhage and provides useful information for subsequent colonoscopy, especially in patients with diverticular bleeding.”

    Urgent computed tomography for determining the optimal timing of colonoscopy in patients with acute lower gastrointestinal bleeding.
    Nakatsu S et al.
    Intern Med. 2015;54(6):553-8
  • “If the 638 patients who underwent CE-CT, diverticula were observed in 346 cases, including 104 cases of extravasation indicating ongoing diverticular bleeding. Among these 104 patients, the site of bleeding was identified in 71 subjects (68%) during colonoscopy. The rate of detection of the bleeding source on colonoscopy was significantly higher in the patients with extravasation on CE-CT than in those without extravasation on CE-CT (68% vs. 20%, respectively; p<0.001).”

    Urgent computed tomography for determining the optimal timing of colonoscopy in patients with acute lower gastrointestinal bleeding.
    Nakatsu S et al.
    Intern Med. 2015;54(6):553-8
  • “The rate of detection of the bleeding source on colonoscopy was significantly higher in the patients with extravasation on CE-CT than in those without extravasation on CE-CT (68% vs. 20%, respectively; p<0.001).”

    Urgent computed tomography for determining the optimal timing of colonoscopy in patients with acute lower gastrointestinal bleeding.
    Nakatsu S et al.
    Intern Med. 2015;54(6):553-8
  • GI Bleeding: Background Facts
    - Acute gastrointestinal bleeding is a common medical emergency
    - 1-2% of all medical admissions
    - 20-27 cases /100,000 for lower GI bleeding
    - 40-150 cases /100,000 for upper GI bleeding
    - Mortality as high as 40% in patients with hemodynamic instability
    - 75% of cases cease spontaneously, but bleeding recurs in 25%
  • GI Bleeding: Background Facts
    - Upper GI bleeding occurs proximal to ligament of Trietz
    - Hematemesis, coffee ground vomiting, or melena
    - Lower GI bleeding occurs distal to ligament of Trietz
    - Melena, hematochezia, positive fecal occult blood test (hemoccult) or rectal bleeding
  • Diverticulosis
    - Incidence of diverticulosis increases substantially with age
    - Most common cause of hematochezia in the elderly
    - Diverticular bleeding is usually arterial, and can be massive and severe
    - Even if active bleeding is not visualized, the presence of many colonic diverticula should be suggestive of cause of bleeding
  • Stercoral Colitis
    - Primarily seen in elderly patients
    - Overdistension of rectal lumen from impacted stool
    - Increased luminal pressure results in rectal wall ischemia (disrupts blood supply)
    - Ulcers of rectal wall result in bleeding and perforation
    - Affects up to 6% of elderly patients in long-term care
    - Active extravasation almost never visualized
    - Slow, intermittent bleeding
    - MDCT shows distended rectum with wall thickening and perirectal stranding
  • “Although colonoscopy remains the first-line modality for the diagnosis of lower gastrointestinal tract bleeding, colonoscopy may not be possible for unstable patients, and moreover, even for patients who undergo colonoscopy, the examination may still fail to diagnose a cause for bleeding. MDCT with CT angiography and 3D mapping now offers a valuable option for diagnosis, not only for patients whose colonoscopy findings were negative, but also as a first-line screening modality for patients with active bleeding and hemodynamic instability. This article reviews the valuable role of MDCT in the diagnosis of multiple different causes of rectal bleeding, including rectal vascular malformations, rectal varices, ischemic colitis, stercoral colitis, inflammatory bowel disease, radiation proctopathy, infectious colitis, and rectal cancer.”
    MDCT and CT Angiography Evaluation of Rectal Bleeding: The Role of Volume Visualization
    Raman SP, Horton KM, Fishman EK
    AJR 2013 Sep;201(3):589-97
  • “Although colonoscopy remains the first-line modality for the diagnosis of lower gastrointestinal tract bleeding, colonoscopy may not be possible for unstable patients, and moreover, even for patients who undergo colonoscopy, the examination may still fail to diagnose a cause for bleeding. MDCT with CT angiography and 3D mapping now offers a valuable option for diagnosis, not only for patients whose colonoscopy findings were negative, but also as a first-line screening modality for patients with active bleeding and hemodynamic instability.”
    MDCT and CT Angiography Evaluation of Rectal Bleeding: The Role of Volume Visualization
    Raman SP, Horton KM, Fishman EK
    AJR 2013 Sep;201(3):589-97
  • Radionuclide scintigraphy, most often performed using technetium-99m labeled red blood cells, allows the detection of bleeding as slow as 0.2 cc/min, and can detect bleeding from either arterial or venous sources.  However, even though these studies can detect intermittent bleeding as a result of long acquisition times, identification of an exact site of bleeding can be inordinately difficult, partially as a result of poor spatial resolution, but also in cases where there is significant bowel peristalsis.  Moreover, the need for prolonged imaging over time, as well as the practical difficulties in administering radiotracers at night or in the acute emergency department setting, have largely precluded the widespread use of radionuclide imaging in the setting of acute bleeding.
  • Catheter angiography can detect bleeding as slow as 1.0 cc/min, and at its best, can identify an exact source of bleeding.  However, angiography is time-consuming, invasive, has difficulty in identifying venous sources of bleeding, suffers from poor contrast resolution, and can easily miss sources of bleeding due to variant anatomy.
  • “MDCT has increasingly taken on a larger role in the diagnosis of acute gastrointestinal hemorrhage, as it can not only identify luminal sources of bleeding (both arterial and venous) and precisely localize the site of hemorrhage, but it can also identify a wide range of extraluminal sources of bleeding (vascular malformations, bowel wall tumors, etc.) which may not be readily apparent on colonoscopy, nuclear medicine studies, or angiography.”
    MDCT/CTA Evaluation of Rectal Bleeding: The Role of Volume Visualization
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • “We have found MIP imaging to be extraordinarily helpful in identifying subtle active extravasation in the bowel that can be easily overlooked on the source axial images.  Moreover, MIP images also can nicely delineate a suspected vascular malformation or angiodysplasia, which can often be difficult to recognize in the axial plane.  The VR images, on the other hand, have proven very useful in illustrating abnormalities in the bowel wall itself, including mucosal hyperemia, submucosal edema and wall thickening, or subtle engorgement of the adjacent vasa recta.”
    MDCT/CTA Evaluation of Rectal Bleeding: The Role of Volume Visualization
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • “For the vast majority of patients with lower gastrointestinal hemorrhage, including hemorrhage originating from the rectum, colonoscopy remains the appropriate first-choice modality for diagnostic evaluation.  Nevertheless, as the examples in this review illustrate, MDCT has an important role to play in the evaluation of these patients:  Not only can CT be valuable in those patients for whom colonoscopy is not feasible or impractical, but it can also identify a variety of extraluminal findings which may not be visible to the endoscopist. Moreover, CT can provide a wealth of valuable information beyond the presence or absence of active contrast extravasation/bleeding, such as bowel wall inflammation, perirectal inflammation, or the presence of an underlying vascular anomaly.”
    MDCT/CTA Evaluation of Rectal Bleeding: The Role of Volume Visualization
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • “For the vast majority of patients with lower gastrointestinal hemorrhage, including hemorrhage originating from the rectum, colonoscopy remains the appropriate first-choice modality for diagnostic evaluation.  Nevertheless, as the examples in this review illustrate, MDCT has an important role to play in the evaluation of these patients:  Not only can CT be valuable in those patients for whom colonoscopy is not feasible or impractical, but it can also identify a variety of extraluminal findings which may not be visible to the endoscopist. Moreover, CT can provide a wealth of valuable information beyond the presence or absence of active contrast extravasation/bleeding, such as bowel wall inflammation, perirectal inflammation, or the presence of an underlying vascular anomaly.”
    MDCT/CTA Evaluation of Rectal Bleeding: The Role of Volume Visualization
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • Rectal Bleeding: Causes As Diagnosed by CT
    - Angiodysplasia
    - Rectal AVM
    - Rectal varices
    - Diverticulosis
    - Stercoral colitis
    - Rectal cancer
    - Chronic radiation proctitis
    - Ischemic colitis
    - Infectious colitis
  • Angiodysplasia of the Colon:Facts
    - Angiodysplasia, also known as vascular ectasia, represents an abnormal proliferation of venules and capillaries within the submucosal layer of the bowel wall.  The incidence of angiodysplasia is thought to increase with age, and may also be associated with chronic renal failure.  Because bleeding from angiodysplasia is venous in nature, bleeding tends to be episodic and self-limited, and for the most part, not particularly severe. Angiodysplasia can occur anywhere in the GI tract, but is most common in the colon, particularly in the cecum and ascending colon. While the CT imaging features of angiodysplasia have not been often described in the literature, findings may include nodular, hypertrophied vessels within the bowel wall on the arterial phase images, often with an early draining vein.
  • Rectal Arteriovenous Malformations (AVM):
    Facts
    - 5% of all patients with lower gastrointestinal hemorrhage never have a source of bleeding identified, and it is thought that up to 40% of these patients may have an undiagnosed AVM .  True AVM’s are distinct from angiodysplasia:  Unlike angiodysplasia, which represents a proliferation of normal sized vessels within the submucosal layer of the bowel in elderly patients, AVM’s extend through the mucosa and submucosa into the muscular layer of the bowel, and are more common in young patients.  While the most common location for gastrointestinal AVM’s is in the small bowel (typically the jejunum), they can occur anywhere in the GI tract, including the colon and rectum.  As with AVM’s elsewhere in the body, CT can demonstrate an abnormal communication of small arteries and veins within the bowel wall, a distinct vascular nidus, and early filling of veins on arterial phase images. 
  • Rectal Varices: Facts
    - Rectal varices are most commonly seen in the setting of cirrhosis and portal hypertension, with a prevalence ranging between 40 – 77% of all patients with portal hypertension.  Nevertheless, the clinical incidence of bleeding in patients with rectal varices is still relatively low, perhaps less than 5%.  From an imaging standpoint, rectal varices appear no different from hemorrhoids, although rectal varices typically occur more proximally in the rectum (proximal to the dentate line), rather than at the level of the anus.  As with hemorrhoids, large serpiginous veins can be seen both surrounding the rectum (pararectal varices) and within the rectal wall itself (rectal varices) on portal venous phase images.  Notably, unlike a rectal AVM, these serpiginous vessels do not enhance on the arterial phase images, and no early draining vein should be present.  Given that bleeding from rectal varices is venous in nature, active extravasation is almost never visualized.  Although they can appear quite similar on imaging, rectal varices should not be confused with hemorrhoids: Hemorrhoids occur in the anus, rather than the rectum, have no communication with the portal circulation, are not associated with portal hypertension, and merely represent vascular cushions .
  • Diverticulosis: Facts
    - Given that the incidence of diverticulosis increases substantially with age, the most common cause of hematochezia in the elderly is diverticulosis.  Usually occurring in patients without diverticulitis, diverticular bleeding is arterial in nature, and as a result, can be massive and severe.  Even if active extravasation or bleeding is not visualized on the arterial phase images, the presence of substantial diverticulosis can be a potential clue as to the etiology of a patient’s bleeding .
  • Stercoral Colitis: Facts
    -  A disorder primarily seen in the elderly, stercoral colitis results from overdistension of the rectal lumen secondary to severe fecal impaction, with a resultant increase in luminal pressure, decrease in blood supply to the bowel wall, and rectal ischemia.  In those cases that are not treated with aggressive disimpaction, patients are at risk for developing ulcers of the rectal wall (with associated bleeding) or even perforation.  While the exact incidence is unknown, autopsy studies suggest that stercoral colitis may affect up to 6% of elderly patient in long-term care facilities. In most cases, frank active extravasation is not likely to be visualized, as bleeding in these cases is usually slow, intermittent, and chronic.  However, the presence of a severely distended rectum as a result of fecal impaction, focal thickening of the rectal wall, and perirectal fat stranding are all highly suggestive imaging features.
  • “For the vast majority of patients with lower gastrointestinal hemorrhage, including hemorrhage originating from the rectum, colonoscopy remains the appropriate first-choice modality for diagnostic evaluation.  Nevertheless, as the examples in this review illustrate, MDCT has an important role to play in the evaluation of these patients:  Not only can CT be valuable in those patients for whom colonoscopy is not feasible or impractical, but it can also identify a variety of extraluminal findings which may not be visible to the endoscopist. Moreover, CT can provide a wealth of valuable information beyond the presence or absence of active contrast extravasation/bleeding, such as bowel wall inflammation, perirectal inflammation, or the presence of an underlying vascular anomaly.”
    MDCT/CTA Evaluation of Rectal Bleeding: The Role of Volume Visualization
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • “ Not only can CT be valuable in those patients for whom colonoscopy is not feasible or impractical, but it can also identify a variety of extraluminal findings which may not be visible to the endoscopist. Moreover, CT can provide a wealth of valuable information beyond the presence or absence of active contrast extravasation/bleeding, such as bowel wall inflammation, perirectal inflammation, or the presence of an underlying vascular anomaly.”
    MDCT/CTA Evaluation of Rectal Bleeding: The Role of Volume Visualization
    Raman SP, Horton KM, Fishman EK
    AJR 2013 (in press)

 

  • “We have found MIP imaging to be extraordinarily helpful in identifying subtle active extravasation in the bowel that can be easily overlooked on the source axial images.  Moreover, MIP images also can nicely delineate a suspected vascular malformation or angiodysplasia, which can often be difficult to recognize in the axial plane.  The VR images, on the other hand, have proven very useful in illustrating abnormalities in the bowel wall itself, including mucosal hyperemia, submucosal edema and wall thickening, or subtle engorgement of the adjacent vasa recta.”
    CT Evaluationof Rectal Bleeding
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • “5% of all patients with lower gastrointestinal hemorrhage never have a source of bleeding identified, and it is thought that up to 40% of these patients may have an undiagnosed AVM.  True AVM’s are distinct from angiodysplasia:  Unlike angiodysplasia, which represents a proliferation of normal sized vessels within the submucosal layer of the bowel in elderly patients, AVM’s extend through the mucosa and submucosa into the muscular layer of the bowel, and are more common in young patients.  While the most common location for gastrointestinal AVM’s is in the small bowel (typically the jejunum), they can occur anywhere in the GI tract, including the colon and rectum.  As with AVM’s elsewhere in the body, CT can demonstrate an abnormal communication of small arteries and veins within the bowel wall, a distinct vascular nidus, and early filling of veins on arterial phase images.”
    CT Evaluation of Rectal Bleeding
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • “Rectal varices are most commonly seen in the setting of cirrhosis and portal hypertension, with a prevalence ranging between 40 – 77% of all patients with portal hypertension.  Nevertheless, the clinical incidence of bleeding in patients with rectal varices is still relatively low, perhaps less than 5% .  From an imaging standpoint, rectal varices appear no different from hemorrhoids, although rectal varices typically occur more proximally in the rectum (proximal to the dentate line), rather than at the level of the anus.  As with hemorrhoids, large serpiginous veins can be seen both surrounding the rectum (pararectal varices) and within the rectal wall itself (rectal varices) on portal venous phase images.  Notably, unlike a rectal AVM, these serpiginous vessels do not enhance on the arterial phase images, and no early draining vein should be present. .”
    CT Evaluation of Rectal Bleeding
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • “For the vast majority of patients with lower gastrointestinal hemorrhage, including hemorrhage originating from the rectum, colonoscopy remains the appropriate first-choice modality for diagnostic evaluation.  Nevertheless, as the examples in this review illustrate, MDCT has an important role to play in the evaluation of these patients:  Not only can CT be valuable in those patients for whom colonoscopy is not feasible or impractical, but it can also identify a variety of extraluminal findings which may not be visible to the endoscopist. Moreover, CT can provide a wealth of valuable information beyond the presence or absence of active contrast extravasation/bleeding, such as bowel wall inflammation, perirectal inflammation, or the presence of an underlying vascular anomaly.”
    CT Evaluation of Rectal Bleeding
    Raman SP, Horton KM, Fishman EK
    AJR (in press)
  • GI Bleeding: Classification
    - Upper GI Bleed: proximal to the ligament of Trietz and accounts for 70% of bleeds. Mortality rate up to 10%
    - Lower GI Bleed: distal to the ligament of Trietz and accounts for 30% of cases of GI bleed. Mortality rate up to 3.6%
  • Imaging Techniques
    - Small bowel series and conventional enteroclysis
    - Computed tomography including CT enteroclysis
    - CT angiography
    - Tagged RBC study
    - Catheter directed angiography
    - Capsule endoscopy
  • Obscure GI Bleeding: Causes
    Lower GI lesions
    - Angiectasia
    - Neoplasms
  • Obscure GI Bleeding: Causes
    Middle GI lesions (over age 40)
    - Angiectasia
    - NSAID enteropathy
    - Celiac disease
  • Obscure GI Bleeding: Causes
    Middle GI lesions (under age 40)
    - Tumors
    - Meckel diverticulum
    - Crohn disease
    - Celiac disease
  • Obscure GI Bleeding: Causes
    Upper GI lesions
    - Varices
    - Peptic ulcer
    - Angiectasia
    - Gastric antral vascular ectasia
  • "Obscure GI bleeding (OGIB) is defined as loss of blood with no source identified after upper endoscopy and colonoscopy."

    Gastroenterologic and Radiologic Approach to Obscure Gastrointestinal Bleeding: How, Why and When?
    Graca BM et al.
    RadioGraphics 2010; 30:235-252

  • "Obscure GI bleeding (OGIB) refers to bleeding from the GI tract that persists or recurs without an obvious cause after esophagogastroduodenoscopy and colonoscopy."

    Gastroenterologic and Radiologic Approach to Obscure Gastrointestinal Bleeding: How, Why and When?
    Graca BM et al.
    RadioGraphics 2010; 30: 235-252

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