What is peritoneal vascular thrombosis?

Peritoneal Vascular Thrombosis: Overview

Definition and Scope

Peritoneal vascular thrombosis refers to thrombotic occlusion of the venous vessels within the splanchnic (abdominal) circulation, most commonly affecting the mesenteric, portal, splenic, and hepatic veins. This condition represents a subset of splanchnic vein thrombosis (SPVT), which encompasses the entire venous network supplying the abdominal viscera 1.

Anatomical Distribution

• Mesenteric venous thrombosis (MVT) accounts for less than 10% of all mesenteric ischemia cases but carries significant mortality risk 1
• Portal vein thrombosis (PVT) represents 34-40% of isolated splanchnic vein thrombosis cases 1
• Multiple segment involvement occurs in 38-50% of SPVT cases, conferring worse prognosis with 10-year survival of 48% versus 68% for single-segment disease 1

Pathophysiology

The development of peritoneal vascular thrombosis follows Virchow's triad—stagnated blood flow, hypercoagulability, and vascular inflammation—though approximately 20% of cases remain idiopathic 1.

Key Mechanisms

• Venous occlusion leads to bowel edema and increased vascular resistance, which paradoxically reduces arterial inflow and precipitates intestinal ischemia 1
• Progressive thrombosis can extend from mesenteric veins into the portal system, creating life-threatening intestinal infarction in 30-45% of patients at diagnosis 1
• Cavernous transformation develops when chronic obstruction persists beyond 6 months, representing collateral vessel formation around the occluded vein 1

Risk Factors

Inherited Thrombophilias

• Factor V Leiden mutation 1
• Prothrombin gene mutation 1
• Protein C, protein S, and antithrombin deficiency 1
• Antiphospholipid syndrome 1
• JAK2V617F mutation (detected in 20-40% of SPVT patients without overt myeloproliferative disorders) 1

Acquired Conditions

• Malignancies, particularly abdominal tumors and myeloproliferative disorders 1
• Portal hypertension and cirrhosis 1
• Recent abdominal surgery, especially splenectomy 1
• Pancreatitis and inflammatory bowel disease 1
• Oral contraceptives and exogenous estrogen therapy 1
• Paroxysmal nocturnal hemoglobinuria (PNH), which carries high propensity for splanchnic thrombosis 1

Clinical Presentation

Acute Presentation

Severe abdominal pain out of proportion to physical examination findings is the hallmark of acute mesenteric venous thrombosis and should be assumed to represent mesenteric ischemia until proven otherwise 1, 2.

• Abdominal pain occurs in 86-95% of acute cases, typically mid-abdominal and colicky in nature 1, 2
• Associated symptoms include nausea (44%), vomiting (35%), diarrhea (35%), and gastrointestinal bleeding (10-16%) 1
• Peritoneal signs (rebound tenderness, guarding, fever) indicate progression to bowel infarction and mandate immediate surgical exploration 1

Chronic Presentation

• Asymptomatic in 50-70% of chronic cases due to collateral formation 1, 2
• Post-prandial abdominal pain when symptomatic 2
• Portal hypertension manifestations including splenomegaly, ascites, and variceal bleeding 1

Diagnostic Approach

Imaging Modalities

Contrast-enhanced CT scan in the portal venous phase is the diagnostic gold standard, demonstrating absent portal vein lumen, thrombus extension, and signs of bowel ischemia 2.

• Doppler ultrasound should be the initial screening study, showing absent portal vein flow 2
• Avoid late arterial phase imaging as delayed contrast arrival creates false-positive diagnoses 2
• Key CT findings include filling defects in mesenteric/portal veins, bowel wall thickening, mesenteric edema, and ascites 1, 2

Laboratory Evaluation

• Complete blood count with differential 1
• PT/aPTT and basic metabolic profile 1
• Serum lactate (elevated levels suggest bowel infarction) 1
• Thrombophilia screening including JAK2V617F mutation testing 1

Prognostic Considerations

Mortality Risk

• 30-day mortality for mesenteric venous thrombosis ranges from 20% 1
• Intestinal infarction occurs in 30-45% at diagnosis, with 19% mortality rate 1
• Multiple segment involvement significantly worsens prognosis compared to isolated thrombosis 1

High-Risk Features

• Diabetes mellitus (independently associated with need for bowel resection) 2
• Extensive clot burden involving multiple venous segments 3
• Organ failure, shock, metabolic acidosis 2
• Massive ascites and rectal bleeding 2

Critical Clinical Pitfalls

• Do not dismiss mild or non-specific abdominal symptoms, as significant thrombosis can present subtly and progress to cavernomatous transformation if diagnosis is delayed 2
• Never delay anticoagulation while awaiting complete thrombophilia workup if clinical suspicion is high 4, 3
• Recognize that physical examination may be unrevealing in early disease despite severe underlying ischemia 1
• Heightened vigilance required in diabetic patients presenting with abdominal pain and suspected peritoneal vascular thrombosis 2