الفهرس 
Vascular and Gastrointestinal Tract AnatomyOnly 14 pages are availabe for public view
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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.