Lower gastrointestinal bleeding other imaging findings

Lower gastrointestinal bleeding Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Lower gastrointestinal bleeding from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
Diagnostic Study of Choice
History and Symptoms
Physical Examination
Laboratory Findings
Electrocardiogram
X-ray
Echocardiography and Ultrasound
CT scan
MRI
Other Imaging Findings
Other Diagnostic Studies
Treatment
Management Initial resuscitation Pharmacotherapy
Surgery Surgical Management Endoscopic Intervention
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Guidelines for Management
Case Studies
Case #1
Lower gastrointestinal bleeding other imaging findings On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Lower gastrointestinal bleeding other imaging findings All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Lower gastrointestinal bleeding other imaging findings
CDC on Lower gastrointestinal bleeding other imaging findings
Lower gastrointestinal bleeding other imaging findings in the news
Blogs on Lower gastrointestinal bleeding other imaging findings
Directions to Hospitals Treating Psoriasis
Risk calculators and risk factors for Lower gastrointestinal bleeding other imaging findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Other Imaging Findings

Angiography

• Mainly indicated in patients with active bleeding who are relatively hemodynamically stable or have been resuscitated.
• A minimum bleeding rate of between 1 to 1.5 mL/min is required for angiographic detection, although this can be operator dependent.
• Access into the arterial system is normally via a common femoral artery approach. If this is not possible, the brachial artery can be used, although this carries a small risk of stroke.
• A wide range of catheters can be used to access the mesenteric arteries (majority of bleeds due to diverticula or angiodysplasia receive their blood supply from the superior mesenteric artery).
• In practice, the inferior mesenteric artery is selectively catheterized before the superior mesenteric artery to avoid a bladder full of contrast obscuring the inferior mesenteric branches.
• If no bleeding source is identified from these two vessels (SMA, IMA) the celiac axis is catheterized and assessed, as bleeding points may be discovered from the gastroduodenal artery (eg, in patients with a brisk hemorrhage from a peptic ulcer).
• The main advantage of angiography is that it does not require bowel preparation.
• It also allows accurate anatomic localization in approximately half of all patients and permits therapeutic intervention in some patients via the catheter.

Radionuclide imaging

• Radionuclide imaging is more sensitive than angiography in detecting the source of bleeding; however, it is less specific than either a positive endoscopic or angiographic examination.
• Rates of bleeding as little as 0.1 to 0.5 mL/min can be detected.
• Radionuclide imaging is indicated prior to angiography in patients in whom the bleeding is intermittent or has a low rate, or in whom bleeding points were not identified using CTA, angiography, or colonoscopy.
• Accuracy rates have varied across reports, and range from 24% to 91%.

Procedure

• Erythrocytes are initially labeled by intravenously injecting 2 mL of a stannous agent.
• Twenty minutes later, 400 MBq of technetium pertechnetate are injected.
• Scans are then performed every 5 minutes for up to an hour.
• Single static images are taken several hours later

Nuclear scanning agents

• Two different types of nuclear scanning agents are commonly used: technetium (99mTc) sulphur colloid, which has a short half-life, and 99mTc pertechnetate, which has a longer half-life.
• With 99mTc pertechnetate, patients can be scanned several times over a 24-hour period. Therefore the latter agent has become the favored radiotracer to use

Advantages

• Advantages common to both techniques are that they are noninvasive and have a higher sensitivity than does angiography.

Disadvantages

• The main disadvantages are that radionuclide scanning can only localize bleeding to an area of the abdomen, and the resolution does not allow the identification of a specific site in the colon.
• Anaphylactic reaction to the radioisotope

Contraindications

• Radionuclide imaging is not recommended in pregnant or breastfeeding women.