You are in: eMedicine Specialties > Radiology > VASCULAR/INTERVENTIONAL Gastrointestinal Bleeding, LowerArticle Last Updated: Jun 18, 2004AUTHOR AND EDITOR INFORMATIONSection 1 of 6
  Author: Atif Rana, MBBS, Assistant Professor, Department of Radiology, Section of Interventional Radiology, University of Alabama at Birmingham Atif Rana is a member of the following medical societies: Radiological Society of North America and Society of Cardiovascular and Interventional Radiology Editors: Anthony Watkinson, MD, Professor of Interventional Radiology, The Peninsula Medical School; Consultant and Senior Lecturer, Department of Radiology, The Royal Devon and Exeter Hospital, UK; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Douglas M Coldwell, MD, PhD, Professor of Interventional Radiology, Department of Radiology, University of Texas Southwestern Medical Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Kyung J Cho, MD, FACR, William Martel Professor of Radiology, Fellowship Program Director, Department of Radiology, Division of Interventional Radiology, University of Michigan Medical School Author and Editor Disclosure Synonyms and related keywords: lower gastrointestinal bleeding, GI bleeding, lower GI bleeding, gastrointestinal hemorrhage, GI hemorrhage INTRODUCTIONSection 2 of 6
  BackgroundLower gastrointestinal (GI) hemorrhage is defined as bleeding from the bowel distal to the ligament of Treitz. Acute lower GI bleeding is of recent onset and results in hemodynamic instability and decreasing hemoglobin levels, which need to be treated with transfusions. During recent years, colonoscopy has emerged as the procedure of choice, but angiography still remains the best option in a patient in unstable condition. In cases in which colonoscopy is unsuccessful, scanning during episodes of bleeding and arteriography are considered to be next imaging tests to determine the cause of the bleeding. Arteriography also provides therapeutic options. This article reviews the current recommendations for work-up and management of acute lower GI bleeds. For excellent patient education resources, visit eMedicine's Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education articles, Gastrointestinal Bleeding and Rectal Bleeding. PathophysiologyThe causes of acute lower GI bleeding include diverticulosis, angiodysplasia, colon cancer, colitis (including infectious, ischemic, or radiation-induced forms), inflammatory bowel disease, polyps, Meckel diverticulum, and aortoenteric fistula. Hemorrhoids are probably the most common cause of lower GI bleeding, but they usually do not pose difficulties in the diagnosis and they rarely cause massive bleeding. Similarly, anorectal fissures can bleed, but again, these are easily diagnosed on the basis of the history and the clinical findings. Lower GI bleeding appears as the passage of bright red blood per rectum. In about 10-15% of cases, the cause may be proximal to the ligament of Treitz. In these cases, nasogastric tube placement is frequently needed to confirm that the upper GI tract is the source of the bleeding. The most common cause of lower GI bleeding involves the colonic diverticula. In 1976, Myeres et al reported on the pathogenesis of bleeding diverticula. They showed asymmetric rupture of the vasa recta at the dome of the diverticulum, with intimal eccentric thickening and medial thinning at or near the bleeding point. Comparing this with control diverticula, they suggested that traumatic injury may play a role in predisposing the diverticula to bleeding and rupture. Diverticulosis has been implicated as the source of bleeding in as many as 60% of cases of lower GI bleeding. The diverticula are more prevalent in the left or sigmoid colon, but positive arteriographic findings for bleeding localizes the bleeding to the right colon in 60% of cases. Angiodysplasia has an incidence of 1-2%; this involves ectatic vessels in the mucosa and submucosa of the GI tract. At endoscopy, they appear as red, flat lesions, and a feeding vessel is sometimes shown. These vessels are reported to be responsible for 3-12% of cases of acute lower GI bleeding. The majority are present in the right colon. An association with various systemic diseases has been described; these diseases include aortic stenosis, von Willebrand disease, chronic obstructive pulmonary disease (COPD), cirrhosis, chronic renal disease, and collagen vascular disease. Other causes of lower GI bleeding include neoplasia, such as a polyp or carcinoma. Significant bleeding can also occur in about 2-4% of cases after endoscopic removal of polyps from the colon, though other studies have shown lower rates. Inflammatory bowel disease and other types of colitis account for as many as 30% of cases of acute lower intestinal bleeding. Less frequent causes of acute colorectal bleeding include solitary rectal ulcer, portal colopathy, Dieulafoy lesions of the colon, endometriosis, and colonic varices. RADIOGRAPHSection 3 of 6
FindingsAfter resuscitation of the patient, diagnostic and therapeutic steps are taken. Colonoscopy is the procedure of choice, according to guidelines published by American Society for Gastrointestinal Endoscopy in 2001. According to these guidelines, angiography should be performed in cases of massive bleeding. Scintigraphy and/or angiography also play important role in diagnosis and embolization when colonoscopy reveals negative findings or when it is not feasible. Colonoscopy Colonoscopy after rapid oral purging is recommended for the evaluation of acute lower GI bleeding. This procedure has a yield of 69-80%. As mentioned earlier, bleeding diverticula and angiodysplasia are the most common causes. However, about 10% of cases are ultimately found to involve an upper GI source of bleeding. For this reason, some also advocate an upper GI endoscopy after colonoscopy yields negative results. Colonoscopy also provides a mean for therapy in cases of lower GI bleeding. This procedure involves the use of thermal contact modalities or epinephrine injections in cases of diverticula and vascular ectasia. Similarly, other causes of lower GI bleeding can be effectively treated during colonoscopy. Radiology The 2 widely used diagnostic tests for lower GI bleeding are nuclear scanning during episodes of bleeding or arteriography. Scintigraphy Since late 1970s, technetium-99m sulfur colloid and 99mTc-labeled RBCs have been used in the evaluation of GI bleeding. In 1977, Alavi et al described use of 99mTc sulfur colloid tests for diagnosis of bleeding induced in the small bowel and colon of dogs. Bleeding rates as low as 0.05-0.1 mL/min can be detected. The disadvantage of sulfur colloid scanning is the potential masking of bleeding in the upper abdomen by activity in the liver and spleen. 99mTc-labeled RBC scanning does not have this problem, and an animal study by Thorne et al in 1987 showed bleeding detection rates as low as 0.04 mL/min, which are comparable to those of sulfur colloid scanning. Bunker et al compared the 2 techniques and found that 99mTc RBC scanning was superior to sulfur colloid scanning. The former demonstrated a sensitivity of 93%, a specificity of 95%, and an overall accuracy of 94% in detecting and localizing GI hemorrhage. Initial studies showed acceptable sensitivities for GI bleeding, but a few studies in late 1980s raised doubts about the accuracy of scintigraphic studies. One group reported inaccurate localization leading to a surgical error rate of 42%. Some claim that most available reports in literature base their conclusions on results obtained with older techniques. The newer techniques involve more dynamic imaging (more frequent acquisition of data), extra large field-of-view gamma cameras, and cine scintigraphy or movie-mode displays. Recent studies have shown that RBC scans have an accuracy of nearly 90% in the localization of the bleeding site. Scintigraphy is reported to increase the diagnostic yield of angiography. Gunderman et al showed that, without scintigraphic screening, angiograms depicted bleeding at a rate of 22%. After the implementation of scintigraphic screening, 53% of the arteriograms depicted bleeding. In another study, Ng et al showed that, when 99mTc RBC scans showed immediate blush, patients required urgent angiography. In contrast, patients whose scans showed delayed blush have low angiographic yields. They recommended that, when scans show delayed blush or negative results, patients may be observed and evaluated with colonoscopy. The advantages of "bleeding" scanning are that it is noninvasive and that it requires no special patient preparation. Bleeding is diagnosed when an abnormal focus of activity is seen. This activity increases over time and changes in position due to peristalsis. An advantage of 99mTc RBC scanning is that repeat imaging can be performed after an interval of as long as 24 hours. Angiography The earliest description of the angiographic demonstration of GI bleeding was in 1963. Since that time, angiography has been used in evaluation of GI bleeding, though with varying frequency over time and with the advent of colonoscopy and scintigraphy. Screen-film arteriography can demonstrate bleeding at rates as low as 0.5 mL/min in dogs, although some authors claim that the actual detectable rate of bleeding in clinical conditions may be in the range of 1.0-1.5 mL/min. Digital subtraction angiography (DSA) has been reported to be more sensitive than conventional screen-film angiography. In 1988, Rees et al showed that DSA tended to be more sensitive than conventional angiography in depicted simulated extravasation in vitro; however, in the clinical study, DSA was severely limited in evaluation of the lower GI tract because of misregistration artifact caused by bowel motion. In another study, Kruger et al showed similar findings. They reported that DSA was superior to conventional angiography, provided that it is performed with adequate parasympathicolysis and suspended respiration. On angiograms, hemorrhage is identified as the extravasation of contrast material into the lumen of the bowel. The contrast material extravasation can be free or pooling, and it persists during or even after the injection. The angiodysplasia has been described to have characteristic appearance. It appears as a vascular tuft, along with an early and persistent draining vein. The clinical sensitivity of angiography has been reported variably in different studies. The typical values are around 60%. Attempts to identify predictors for positive angiographic findings have shown mixed results. In a retrospective study, Pennoyer et al did not identify any single useful predictor to increase the likelihood of obtaining a positive angiographic result. Evaluated factors included a history of prior GI bleeding, transfusions, orthostatic hypotension, and tachycardia. However, Nicholson et al found a perfect correlation between a systolic blood pressure of less than 100 mm Hg and a positive arteriographic result. Therefore, some clinicians advocate immediate arteriography rather than nuclear medicine imaging in hemodynamically unstable patients. Pharmacologic techniques have been used to increase the diagnostic yield of arteriography. These include the use of heparin, vasodilators, and thrombolytics. The reported studies show a 33-65% increase in the yield of angiography. These small studies have not shown any significant complications, although larger studies are needed to prove safety of this method. New advances are being made with computed tomographic angiography (CTA) and magnetic resonance angiography (MRA). Junquera et al recently used CTA to evaluate suspected colonic angiodysplasia. The sensitivity, specificity, and positive predictive values of CTA in the detection of colonic angiodysplasia were 70%, 100%, and 100%, respectively, compared with findings of angiography or colonoscopy. In an animal study, Hilfiker et al evaluated use of 3-dimensional (3D) MRI. They compared 99mTc RBC scintigraphy with 3D MRI after the intravascular administration of contrast agent. MRI had 100% sensitivity and specificity, compared with 78% sensitivity and 72% specificity for scintigraphy. INTERVENTIONSection 4 of 6
Transcatheter therapy for GI bleeding Two transcatheter methods for the treatment of GI bleeding include vasopressin infusion and embolization. Superselective embolization has become more accepted in recent years. Vasopressin infusion Vasopressin infusion causes vasoconstriction of the small arteries, arterioles, and capillaries, and it has been used for both upper and lower GI bleeds. The rate of successful control of bleeding has been reported to be 70-90%. The repeat bleeding rate is reported to be 17-27%. The infusion is started with the catheter in the main trunk of the mesenteric artery that is cause of bleeding. The initial rate is 0.2 U/min. A follow-up angiogram is obtained after about 30 minutes. In cases of active hemorrhage, the rate is increased to 0.4 U/min. Higher rates are not recommended because the potential complications from vasoconstriction can exceed the benefits. The infusion is tapered at 6- to 12-hour intervals and then stopped if no further bleeding ensues. Complications of vasopressin infusion include myocardial ischemia, arrhythmia, hypertension, bowel ischemia, peripheral vascular ischemia, and antidiuretic effects. Because of significant rebleeding, variable success, the need for ICU monitoring, and the aforementioned adverse effects of the infusion, renewed interest in embolization therapy has developed over the last few years. In fact, embolization has now become the preferred transcatheter therapy. Embolization also achieves immediate control of the bleeding, and ICU monitoring to the degree required with vasopressin infusion is avoided. Embolization The aim of embolization is to decrease the arterial inflow so that the pressure at the bleeding site is decreased and hemostasis occurs. The important issue is to avoid devascularization of the tissues, which leads to ischemia and infarction. Although upper GI bleeds have been managed with embolization for years, enthusiasm for the use of this technique with lower GI bleeds was limited. The lack of rich collaterals in the colon and small bowel, unlike the stomach and duodenum, was thought to jeopardize the integrity of bowel after embolization. Because of the previously mentioned issues related to vasopressin use, interest in this technique was renewed, and embolization has now become the preferred transcatheter therapy. In 1974, Bookstein first described transcatheter embolization by using an autologous clot. Since that time, various investigators have described small series of transcatheter embolization for lower GI bleeds, with varying success. The potential complication of bowel ischemia and infarction initially limited use of this technique. Earlier groups had described postembolization bowel infarction rates ranging from 0% to 23%. However, some authors claim that the high rate of significant ischemia may have been related to proximal embolization sites in relation to the marginal artery, as lack of large vascular collaterals in large bowel may jeopardize significant areas of colon. With this issue in mind, further studies with superselective catheterization techniques and embolization were performed. Polyvinyl alcohol (PVA, Contour, Medi-tech Inc. Natick, Mass) particles and Gelfoam (Upjohn, Kalamazoo, Mich) have been used, although most of the studies have used microcoils (platinum coils), either alone or in conjunction with Gelfoam or PVA. In 2000, Evangelista et al described superselective embolization in 17 patients. They used coils (n = 12), coils with PVA (n = 4), PVA alone (n = 2), and Gelfoam with coils (n = 1). They reported an 88% success rate. Two patients developed transient signs of bowel ischemia, but none developed infarction, perforation, or stricture. These authors argue against the use of PVA as sole embolization agent. The reasoning is that the small particles may reach intramural circulation and thus occlude the submucosal plexus beyond the level of collateralization, leading to significant bowel ischemia. Another advantage of coils is that they are visible and, therefore, more controllable. A more recent retrospective study involved the use of PVA. Bandi et al reported their experience with 39 procedures in 35 patients. They performed embolization in only those patients in whom they could successfully catheterize the arteria recta leading to the bleeding point. They used only PVA (150-500 µm) in 28 of these procedures. Twenty-five patients underwent objective follow-up with colonoscopy (n = 12), surgery (n = 9), or both (n = 4). Mucosal ischemia was demonstrated in 6 (24%) of these patients, but they remained asymptomatic without clinical sequela. No clinically significant bowel ischemia was seen. An advantage of angiography over coloscopy or scintigraphy is that no special preparation is needed. Arterial access is obtained in a standard fashion from the right side of the groin, and a sheath is placed. A 5F diagnostic catheter can then be advanced through this site. Glucagon (0.5-1.0 mg) is intravenously administered to decrease the bowel peristalsis. The superior mesenteric artery (SMA) is usually selected first, because about 60% of angiographically detected lower GI bleeds are reported to be from the right side of the colon. The inferior mesenteric artery (IMA) is then evaluated. Both these territories may require multiple injections for complete coverage. Because a middle colic artery origin from the celiac axis or splenic artery and other rare anomalous vascular patterns have been described, celiac arteriography is performed if no source is found with injections in the SMA and the IMA. This technique also aids in excluding the upper GI tract as a possible source of bleeding. Embolization is performed by a 3F microcatheter coaxially placed through the diagnostic 5F catheter. This catheter is usually advanced over a 0.018-in guidewire. The microcatheter should be advanced as far as possible, to the level of arteria recta, so that large areas of colon are not at risk for ischemia from embolization. As mentioned earlier, microcoils are the most commonly used agents, although PVA and Gelfoam, alone or with coils, are also used. PVA sizes reported in literature range from 150-500 µm. PVA particles are suspended in contrast material and delivered through the microcatheter under fluoroscopic guidance. Summary Most patients with a lower GI hemorrhage stop bleeding with conservative management. Colonoscopy after a rapid purge is now considered the procedure of choice for the evaluation of acute lower GI bleeds. In the case of a hemodynamically unstable patient, angiography may be the best option because it can be performed in a relatively short period and because it also provides a means for immediate treatment. Patients in stable condition can undergo scintigraphy to guide and increase the yield of angiography. MULTIMEDIASection 5 of 6
REFERENCESSection 6 of 6
Gastrointestinal Bleeding, Lower excerpt Article Last Updated: Jun 18, 2004 | ||||||||||||||||||||||||||||||||||||||||||
