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.
