Mesenteric venous thrombosis (MVT) is a vascular emergency characterized by thrombus formation in the superior mesenteric vein (SMV) or inferior mesenteric vein (IMV) and/or their branches. It accounts for 5-15% of all mesenteric ischemia cases. Virchow's triad (stasis, endothelial injury, hypercoagulability) plays a role in pathogenesis; portal hypertension, cirrhosis, myeloproliferative diseases, thrombophilias, oral contraceptives, and intra-abdominal inflammation (pancreatitis, appendicitis, diverticulitis) are predisposing factors. Thrombus disrupts mesenteric venous drainage leading to bowel wall congestion, edema, hemorrhage, and ultimately transmural ischemia/necrosis. On CT angiography, filling defect in SMV/IMV, bowel wall thickening, mesenteric edema, and ascites are diagnostic findings. Treatment is based on anticoagulation; surgical exploration is required in the presence of peritonitis.
Age Range
30-75
Peak Age
55
Gender
Equal
Prevalence
Uncommon
In MVT, thrombus formation disrupts mesenteric venous drainage and increases venous pressure. Venous hypertension elevates capillary pressure in the bowel wall causing transcapillary fluid leakage → bowel wall edema and thickening. Progressive venous stasis leads to erythrocyte extravasation → submucosal hemorrhage and hemorrhagic bowel wall thickening (hyperdense wall on CT). When venous drainage is completely obstructed, arterial inflow is also compromised → transmural ischemia and necrosis develop. Fluid leakage from the necrotic bowel segment into the peritoneal cavity creates ascites; peritonitis develops in case of perforation. On CT, venous filling defect is a direct indicator of thrombus; bowel wall thickening reflects venous congestion, mesenteric haziness reflects perivenous edema, and ascites reflects severity. Portal vein involvement may add hepatic perfusion abnormalities.
Non-enhancing filling defect in the superior mesenteric vein lumen on portal venous phase — direct indicator of acute mesenteric venous thrombosis.
Non-enhancing filling defect in the SMV lumen on portal venous phase. In acute thrombosis, thrombus is hypodense and homogeneous; in subacute stage, peripheral enhancement (vein wall inflammation) may be seen. In chronic thrombosis, vein caliber is decreased, collateral vessels have developed, and thrombus may be calcified. The extent of filling defect (SMV trunk, branches, portal vein) predicts the extent of ischemic bowel segment.
Report Sentence
Filling defect in the superior mesenteric vein is observed, consistent with acute mesenteric venous thrombosis.
Diffuse wall thickening (>3 mm) and submucosal edema in the affected bowel segment. Bowel wall may be hemorrhagic due to venous congestion — hyperdense wall on non-contrast CT. On contrast-enhanced CT, 'target sign' may be seen: enhancing mucosa, hypodense submucosal edema, and enhancing serosa. Wall thickening is diffuse and symmetric, different from segmental thickening in arterial occlusion.
Report Sentence
Diffuse wall thickening and submucosal edema in the affected bowel segment are observed, consistent with mesenteric venous congestion.
Diffuse haziness, vascular engorgement and perivenous edema in the mesentery. Mesenteric veins appear dilated and engorged. Perivenous fat tissue has increased density due to edema (misty mesentery-like but in the setting of vascular pathology). This finding reflects the impact of venous drainage disruption on the mesentery and is proportional to thrombus severity.
Report Sentence
Diffuse haziness, vascular engorgement and perivenous edema in the mesentery are observed, consistent with venous congestion due to mesenteric venous thrombosis.
Hyperdense thrombus within the SMV lumen on non-contrast CT (50-70 HU). Acute thrombus is denser than surrounding blood and soft tissue due to high hemoglobin concentration of fresh clot. This finding is a direct indicator of thrombus on non-contrast studies and has diagnostic value especially in patients with contrast allergy. In chronic thrombosis, thrombus density decreases and organizes.
Report Sentence
Hyperdense thrombus in the superior mesenteric vein lumen on non-contrast CT is observed, consistent with acute mesenteric venous thrombosis.
Reduced or heterogeneous wall enhancement in the affected bowel segment on arterial phase. When venous congestion also impairs arterial inflow, the bowel wall cannot show adequate enhancement. Loss of enhancement is an indicator of transmural ischemia and suggests need for surgical intervention. Comparative evaluation with normally enhancing adjacent bowel segments is important.
Report Sentence
Reduced wall enhancement in the affected bowel segment on arterial phase is observed, suggesting careful evaluation regarding transmural ischemia risk.
Free fluid in the peritoneal cavity (ascites). Transudative ascites due to venous thrombosis initially has simple fluid density (0-15 HU). When ischemic bowel necrosis develops, ascites may become hemorrhagic (>20 HU). Ascites volume reflects thrombus severity and extent of bowel ischemia. Massive and hemorrhagic ascites are indicators of poor prognosis.
Report Sentence
Free fluid in the peritoneal cavity is observed, evaluated as a complication of mesenteric venous thrombosis.
Criteria
Symptom duration <4 weeks; fresh hypodense thrombus in SMV; bowel wall thickening and edema
Distinct Features
Sudden onset abdominal pain, vomiting, bloody stool; filling defect in dilated SMV and bowel wall edema on CT
Criteria
Symptom duration 4-6 weeks; thrombus beginning to organize; early collateral development
Distinct Features
Chronifying abdominal pain; organized thrombus, beginning peripheral recanalization and early collateral veins on CT
Criteria
Symptom duration >6 weeks; cavernous transformation and prominent collateral network; portal hypertension findings
Distinct Features
Portal hypertension, splenomegaly, gastric varices; cavernous transformation of SMV and periportal/peripancreatic collateral venous network on CT
Distinguishing Feature
Omental infarction is usually a focal fat-density inflammatory area without mesenteric vein thrombosis; MVT shows venous filling defect and diffuse bowel involvement
Distinguishing Feature
Mesenteric panniculitis has fat ring sign and pseudocapsule; MVT features venous filling defect, bowel wall thickening and hemorrhagic findings
Distinguishing Feature
Bacterial peritonitis shows dominant diffuse peritoneal thickening and enhancement; venous filling defect is differentiating in MVT
Distinguishing Feature
Retroperitoneal hematoma is a hyperdense collection limited to the retroperitoneal space without mesenteric vein thrombosis findings
Urgency
emergentManagement
medicalBiopsy
Not NeededFollow-up
specialist-referralMVT is a vascular emergency requiring urgent anticoagulation. Heparin infusion should be started immediately upon diagnosis. Emergent surgical exploration is required in the presence of peritonitis or suspected transmural ischemia/necrosis. Thrombolysis or mechanical thrombectomy may be applied in selected cases. Underlying thrombophilia screening should be performed.
MVT is an emergency that can result in bowel ischemia/necrosis. Early diagnosis and anticoagulation therapy are critical. Underlying causes (malignancy, thrombophilia, cirrhosis) should be investigated. Surgical intervention is required if bowel necrosis findings are present.