الفهرس 
MSCT ANATOMY OF MESENTRIC VESSELSOnly 14 pages are availabe for public view
 |  | from | 163 |  |  |
| | | from | 163 | | |
Abstract
Mesenteric ischemia is an emergency disorder. Arterial embolism accounts for approximately one third of acute cases of AMI. Emboli to the mesenteric arteries are usually from a dislodged cardiac thrombus. The SMA is most commonly affected with the IMA rarely affected due to its small caliber. Arterial thrombosis accounts for approximately one third of acute cases of AMI. It is usually due to acute worsening of ischemia in patients who have preexisting atherosclerosis of the mesenteric arteries.
MDCT scan of the abdomen is the diagnostic test of choice if suspicion for mesenteric venous thrombosis is high; sensitivities are greater than 90%. Findings of AMI included mesenteric arterial or venous thrombus, mesenteric venous gas, pneumatosis intestinalis, bowel-wall thickening, increased or decreased enhancement of the bowel wall, bowel dilatation, mesenteric or perienteric fat stranding, ascites, pneumoperitoneum, and solid organ infarction are easily detected by MSCT.
Non occlusive etiology accounts for approximately one third of acute cases of AMI. The primary mechanism is severe and prolonged intestinal vasoconstriction. The most common setting is severe systemic illness with systemic shock usually secondary to reduced cardiac output.
Chronic mesenteric ischemia usually results from long-standing atherosclerotic disease of 2 or more mesenteric vessels. Symptoms are caused by the gradual reduction in blood flow to the intestine that occurs during eating since total blood flow to the intestine can increase by 15% during meals.
Recent improvements in multi–detector row CT technology represent an important step toward rabid and correct diagnosis of patients with mesenteric ischemia. The excellent delineation of the intestinal vasculature beside detection of the intestinal changes secondary to intestinal ischemia makes this technique a primary tool for the evaluation of patients with suspected steno-occlusive diseases of the abdominal vessels.
MSCT and 3-dimensional imaging provide a detailed examination of small bowel and the mesenteric vessels and is a valuable tool for the evaluation of mesenteric ischemia. Multiple studies have shown a sensitivity ranging from 96-100% and specificity ranging from 89-94%.
Mesenteric MSCT angiography is a non-invasive tool for visualizing normal vascular anatomy, its variants and vascular pathology. It has an important role in diagnosis of suspected cases of acute and chronic mesenteric ischemia.
MSCT technology with the faster scanning speed increases volume coverage during a single breath-hold and improves the exploitation of contrast medium. Moreover, with the better spatial resolution, allows reconstruction of high-resolution three-dimensional images. Postprossing and reconstruction techniques such as VR, MIP, SSD is capable of displaying the visceral vasculature from any external point. MSCTA not only delineates vessels but also depicts the anatomical relationship to adjacent structures. MSCTA also has become an emerging tool for the pre- and post interventional assessment of vascular anatomy.
Faster scanning ability of MSCT is a beneficial advantage in imaging the mesenteric vasculature in patients with suspected mesenteric ischemia over traditional spiral CT. MSCT also allows creation of superior 3D volume sets and improves visualization of distal branches of the mesenteric arteries and veins.
Longer scanning time of MRA (25 minutes) is considered a disadvantage in comparison to shorter scanning time with MSCT (approximately 25 seconds). As well as easy 3D reformatted images data sets with MSCT gives information about all mesenteric arterial branches especially the distal ones.
MSCT is a safe, fast and easy procedure that does not have the complications of catheterization of conventional angiography with its associated morbidity and mortality. MSCTA can routinely performed as an outpatient non-invasive procedure at a lower cost with no need for patient hospitalization that is necessary after conventional angiography. MSCT is also more helpful than DSA in ruling out extrinsic causes of vessel obstruction e.g., vessel encasement or compression by lesions.