الفهرس | Only 14 pages are availabe for public view |
Abstract Although there have been advances in diagnosis and therapy, acute gastrointestinal bleeding remains an emergency situation with mortality rates. Depending on the site of bleeding (localized proximal or distal to the ligament of Treitz) GI hemorrhage can be divided into bleeding of the upper or lower GI tract. Annual incidences for GI bleeding range between 20 and 150 cases per 100,000 persons, with a higher incidence of upper GI hemorrhage. Mortality rates range from 3.6% to 19%, with a slightly lower mortality rate for upper GI bleeding. For sufficient hemostatic therapy, fast detection and localization of the bleeding site is essential. 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 examination for patients with lower GI tract bleeding, its usefulness for the diagnosis for acute massive bleeding is still controversial. It is usually appropriate when bleeding has stopped spontaneously and bowel preparation is possible. Although nuclear scintigraphy is simple to perform, non-invasive and sensitive, it is time consuming and has limited ability for localization of the site of bleeding. It has high rates of false localization. Some authors believe that mesenteric angiography is the most accurate modality for the diagnosis of acute GI bleeding with rates of detection of bleeding sites 58-86%. The major drawback is the rate of bleeding at the time of angiography and the timing of angiography. The introduction of MDCT has increased scanning speed allowing shorter acquisition times, greater volume coverage and decreased contrast requirement while diminishing respiratory motion artifacts. Thin-slice collimation protocols are used which generate isotropic 3D voxels that improve image quality. Optimization of contrast enhancement is beneficial and offers separation between arterial and venous phases. MDCT offers a (one scan-many views) option useful in imaging vascular diseases. |