Mesenteric Venous Thrombosis Part 1

Mesenteric Venous Thrombosis

Mesenteric ischemia encompasses a broad spectrum of diseases

   1.     acute arterial occlusive disease,

   2.     nonobstructive mesenteric arterial insufficiency,

   3.     mesenteric venous occlusion, and

   4.     chronic mesenteric ischemia

Venous occlusions account for a relatively small percentage of such cases, about 15%–20%.

Mesenteric venous thrombosis can be classified on the basis of its cause as primary or secondary.

Spontaneous, idiopathic thrombosis of the splanchnic veins not associated with any predisposing conditions has been termed primary mesenteric venous thrombosis.

Patients with known medical conditions or factors associated with portal or mesenteric venous thrombosis, such as pancreatitis, hypercoagulability states, cirrhosis, or surgery, are said to have secondary mesenteric venous thrombosis.

Cases may also be classified into acute and chronic presentations for management purposes. Acute mesenteric venous thrombosis is defined as the process that exists in those patients with presenting symptoms of less than 4 weeks duration.

 Typical signs and symptoms of acute bowel ischemia were found to include pain out of proportion to the physical findings.

The differential diagnosis for acute mesenteric ischemia is extensive, comprising both 

intravascular and extravascular causes.

-         Arterial causes include embolic or atheromatous disease, dissecting aortic aneurysm, arteritis, fibromuscular dysplasia, endotoxin shock, hypoperfusion (shock, hypovolemia), direct trauma, and disseminated intravascular coagulation. Arterial causes can be further subdivided into occlusive mesenteric infarction (embolus lodging distal to the middle colic artery or thrombosis of the superior mesenteric artery) and nonocclusive mesenteric ischemia (pre-existing atherosclerosis with a systemic low-flow state).

-         Venous causes make up a much smaller percentage of cases and are generally seen in younger patients, typically in the setting of abdominal surgery.

-         Extravascular causes include incarcerated hernia, volvulus, intussusception, and constricting adhesive bands.

Chronic mesenteric ischemia

-    

      Most patients with chronic disease are asymptomatic until late complications occur, such as variceal bleeding due to portal hypertension. Weight loss, food avoidance, vague postprandial abdominal pain, or distention may also be demonstrated. The pain usually occurs within the first hour after eating, diminishing over the next 1–2 hours.

Radiologic Findings of MVT

-         Radiographic findings of bowel ischemia or infarction demonstrated on plain radiograph or barium studies are usually nonspecific;

o   most often, these studies demonstrate a nonspecific ileus pattern with dilated, fluid-filled loops of bowel.

o    Thumbprinting (focal mural thickening secondary to submucosal hemorrhage), separation of bowel loops due to mesenteric thickening, intramural pneumatosis, and mesenteric or portal venous gas may occasionally be seen but usually indicate late-stage disease.

     Doppler Ultrasonography

Venous flow anomalies or thrombus, a thickened bowel wall, free intraperitoneal fluid, and biliary disease can also be demonstrated.