Mesenteric hematoma is blood collection between mesenteric leaves resulting from trauma, anticoagulant therapy, vasculitis, pancreatitis, surgical complications, or spontaneous bleeding. Unlike retroperitoneal hematoma, it is located in the intraperitoneal compartment. CT shows acute high-density (50-70 HU) collection, subacute heterogeneous density, and chronic low density with encapsulation. Sentinel clot sign identifies bleeding source. Displaces bowel loops and creates claw sign by enveloping mesenteric vascular structures. Treatment may be conservative or surgical/embolization based on hemodynamic stability. Large hematomas carry risk of bowel ischemia — mesenteric vessel compression may reduce bowel perfusion requiring urgent intervention. Anticoagulant-related cases are the most common clinical scenario; traumatic cases are detected on emergency trauma CT protocol.
Age Range
30-80
Peak Age
55
Gender
Equal
Prevalence
Uncommon
Mesenteric hematoma results from bleeding of vascular structures between mesenteric leaves (mesenteric artery/vein branches, vasa recta) or from adjacent organs (pancreas, small bowel). In traumatic mechanism, blunt abdominal trauma lacerates mesenteric vascular structures; deceleration injuries cause avulsion-type injuries at fixed mesenteric points (ligament of Treitz, ileocecal junction). Anticoagulant-related spontaneous bleeding results from inability to control normally self-limiting minor vascular leaks due to coagulation cascade disruption. Vasculitis (such as polyarteritis nodosa) causes mycotic aneurysm and wall necrosis in mesenteric artery branches leading to bleeding. In pancreatitis-related hematoma, pancreatic enzymes (especially elastase) erode peripancreatic vascular structures causing pseudoaneurysm formation and rupture. Imaging correlation: acute hematoma shows high CT density (50-70 HU) and MRI T1 isointensity/T2 hypointensity; subacute methemoglobin causes T1 hyperintensity; chronic hemosiderin causes T2 hypointensity. Bowel ischemia risk from mesenteric hematoma relates to compression of mesenteric artery branches reducing bowel wall perfusion — this may lead to ischemia-reperfusion injury and bowel necrosis.
Principle that the highest density clot (60-80 HU) within mesenteric hematoma on non-contrast CT is nearest to the bleeding source. Localizes bleeding point from mesenteric artery branch, vasa recta, or pseudoaneurysm. Blood dilutes with serum away from bleeding point with gradual density decrease. Critical guide for both bleeding source localization and embolization planning.
Non-contrast CT shows high-density (50-70 HU) collection between mesenteric leaves. Acute hematoma characteristically shows homogeneous high density; erythrocyte and hemoglobin concentration determine density. Sentinel clot sign — highest density clot (60-80 HU) nearest to bleeding source. Mesenteric location confirmed by bowel loop displacement and mesenteric vessel stretching around the collection (claw sign). Subacute hematoma (2-14 days) shows heterogeneous density — peripheral high density (organized clot) and central low density (serous fluid). Chronic hematoma (<25 HU) may show encapsulation and calcification.
Report Sentence
High-density (average [X] HU) collection between mesenteric leaves displacing bowel loops consistent with acute mesenteric hematoma.
Arterial phase contrast-enhanced CT detects active bleeding focus as contrast extravasation within hematoma. Extravasation area appears as bright contrast focus (>90 HU) markedly higher than surrounding hematoma (50-70 HU). Extravasation focus enlarges in portal venous phase. Bleeding source: mesenteric artery branch, vasa recta, or pseudoaneurysm (pancreatitis-related). CT angiography provides detailed mesenteric vascular anatomy assessment and embolization target identification.
Report Sentence
Contrast extravasation within mesenteric hematoma in arterial phase consistent with active bleeding; urgent intervention required.
MRI T1 signal of mesenteric hematoma varies with stage. Acute hemorrhage (0-48 hours): T1 isointense or mildly hyperintense. Subacute hemorrhage (2-14 days): marked T1 hyperintensity from methemoglobin — most reliable MR finding for hemorrhage diagnosis. Chronic hemorrhage (>14 days): mild T1 hypointensity from hemosiderin with peripheral capsule. T1 hyperintensity is preserved on fat-suppressed sequences (differentiating from fat — signal loss indicates fat, signal persistence indicates hemorrhage).
Report Sentence
T1-hyperintense collection within the mesentery consistent with subacute hemorrhage (methemoglobin).
Portal venous phase shows bowel wall changes accompanying mesenteric hematoma indicating complications. Bowel wall thickening (>3 mm) and decreased enhancement suggest bowel ischemia from hematoma pressure. In advanced ischemia, loss of bowel wall enhancement (paper-thin wall), pneumatosis intestinalis (intramural gas), and portal venous gas may be seen — indicating transmural necrosis and perforation risk. Compression or occlusion of mesenteric vascular structures by hematoma is the ischemia mechanism. Free intraperitoneal fluid and peritoneal enhancement suggest peritonitis complication.
Report Sentence
Bowel wall thickening and decreased enhancement in bowel segment adjacent to mesenteric hematoma suggesting bowel ischemia; urgent surgical evaluation recommended.
B-mode ultrasonography shows echogenic or heterogeneous collection within the mesentery. Acute hematoma appears hyperechoic in first 24 hours (clotting blood); progressively becomes hypoechoic over time. Bowel loop displacement and collection position between mesenteric structures confirms mesenteric location. Doppler shows no vascularity within collection (avascular); compression of surrounding mesenteric vessels should be assessed. US plays primary role in FAST protocol for peritoneal free fluid screening but CT is needed for detailed mesenteric hematoma evaluation.
Report Sentence
Echogenic collection within the mesentery on ultrasonography; CT confirmation and etiological investigation recommended.
T2-weighted images show variable signal of mesenteric hematoma depending on stage. Acute (0-48 hours): marked T2 hypointensity from deoxyhemoglobin — 'dark clot'. Early subacute (2-7 days): intracellular methemoglobin maintains T2 hypointensity. Late subacute (7-14 days): extracellular methemoglobin after erythrocyte lysis creates T2 hyperintensity — 'bright blood'. Chronic (>14 days): hemosiderin deposition creates T2 hypointense peripheral rim — pathognomonic finding of chronic organized hematoma. Hemosiderin blooming artifact is more prominent on GRE/SWI sequences.
Report Sentence
Collection with variable T2 signal within the mesentery consistent with [acute/subacute/chronic] stage hemorrhage.
Criteria
Develops after blunt abdominal trauma. Deceleration injury causes avulsion at fixed mesenteric points (Treitz, ileocecal junction). Associated organ injuries should be sought. AAST mesenteric injury grade I-IV.
Distinct Features
Trauma history is definitive diagnostic clue. Grade III-IV injuries (vascular avulsion, bowel transection) require emergency surgery. Active extravasation, peritoneal free fluid, bowel wall thickening, and bowel discontinuity should be carefully evaluated on CT. Mesenteric injury may be missed on initial CT — repeat CT recommended with clinical deterioration.
Criteria
Develops without trauma under anticoagulant use. INR >3 (warfarin), renal insufficiency (NOAC), platelet dysfunction are risk factors. Clinical triad: acute abdominal pain + hemoglobin drop + anticoagulant history.
Distinct Features
No trauma history. Anticoagulation cessation/reversal is essential. Conservative treatment sufficient in most cases; embolization for active extravasation. Bowel ischemia findings require emergency surgery.
Criteria
Complication of acute or chronic pancreatitis. Pancreatic enzymes (elastase) erode peripancreatic vascular structures forming pseudoaneurysms; pseudoaneurysm rupture causes massive mesenteric hemorrhage. Most commonly affected vessels: gastroduodenal artery, splenic artery, SMA branches.
Distinct Features
Pancreatitis history and peripancreatic inflammatory changes guide diagnosis. Pseudoaneurysm detected on CTA as contrast-filled sac in arterial phase — detection and embolization before rupture is life-saving. Ruptured pseudoaneurysm may cause massive bleeding with mortality exceeding 40%. Embolization (coils, liquid embolic agents) is primary treatment.
Distinguishing Feature
Retroperitoneal hematoma is bounded by fascial planes in retroperitoneal compartment; mesenteric hematoma is intraperitoneal. Retroperitoneal hematoma is localized around kidneys, adrenals, or psoas; mesenteric hematoma between bowel loops. Both show high CT density consistent with acute hemorrhage.
Distinguishing Feature
Mesenteric ischemia is caused by primary vascular occlusion (embolic, thrombotic) leading to bowel ischemia; mesenteric hematoma causes secondary ischemia through vascular compression from bleeding. In ischemia, CTA shows vascular occlusion (filling defect in SMA); in hematoma, extraluminal blood collection and compression without occlusion. Bowel wall changes are earlier and more extensive in ischemia; in hematoma, bowel changes depend on hematoma size and compression degree.
Distinguishing Feature
Mesenteric cyst appears as thin-walled cystic mass at water density (0-20 HU); mesenteric hematoma shows high density (50-70 HU). Hemorrhagic mesenteric cyst may have similar density to acute hematoma; however cyst wall is thin and smooth while hematoma has irregular borders. Clinical history (trauma, anticoagulant vs asymptomatic incidental) guides differential.
Distinguishing Feature
Omental torsion is characterized by inflammation and edema in omental fat — CT shows omental fat stranding and whirl pattern. In mesenteric hematoma, high-density collection is present; omental torsion has no collection but shows fat tissue density increase and inflammatory changes. Torsion pain has sudden onset and may localize to right lower quadrant (mimicking appendicitis); hemoglobin drop expected in hematoma.
Urgency
emergentManagement
interventionalBiopsy
Not NeededFollow-up
3-monthMesenteric hematoma is potentially life-threatening requiring urgent evaluation due to massive bleeding and bowel ischemia risks. Management: (1) Hemodynamically stable without active extravasation — conservative: anticoagulation cessation, transfusion, serial hemoglobin, CT at 6-12 hours. (2) Active extravasation — selective mesenteric embolization. (3) Bowel ischemia signs — emergency surgical exploration with necrotic bowel resection. (4) Pseudoaneurysm — pre-rupture embolization is life-saving. Post-treatment follow-up: hemoglobin stabilization and hematoma resolution on CT.
Mesenteric hematoma is associated with trauma, anticoagulant therapy, or spontaneous hemorrhage. Small hematomas can be managed conservatively. Active bleeding may require angiography or surgical intervention. Adjustment of anticoagulant medications is important.