What are the symptoms of Superior Mesenteric Vein (SMV) thrombosis?

Symptoms of Superior Mesenteric Vein Thrombosis

The most common symptom of superior mesenteric vein thrombosis (SMVT) is abdominal pain that is often out of proportion to physical examination findings. 1

Clinical Presentation

Cardinal Symptoms

• Abdominal pain:
  • Usually diffuse and progressive over days to weeks
  • Often described as colicky or cramping
  • May be out of proportion to physical examination findings
  • Typically worsens over 2-14 days (subacute presentation)

Associated Symptoms

• Nausea (44% of patients) 1
• Vomiting (35% of patients) 1
• Diarrhea (35% of patients) 1
• Blood per rectum (16% of patients) 1
• Approximately one-third of patients present with the triad of abdominal pain, fever, and hemocult-positive stools 1

Physical Examination Findings

• Initially, physical examination may be unremarkable despite significant pain
• As the condition progresses, patients may develop:
  • Abdominal distension
  • Bowel sounds changes
  • Mild to moderate tenderness
  • Peritoneal signs (if bowel infarction has occurred)

Advanced/Late Symptoms

• Signs of intestinal infarction:
  • Persistent severe abdominal pain despite anticoagulation
  • Organ failure (shock, renal failure, metabolic acidosis)
  • Elevated arterial lactates
  • Massive ascites
  • Rectal bleeding 1

Risk Factors to Consider

SMVT is associated with several risk factors that should prompt increased suspicion:

• Hypercoagulable states:

  • Factor V Leiden
  • Prothrombin mutation
  • Protein S deficiency
  • Protein C deficiency
  • Antithrombin deficiency
  • Antiphospholipid syndrome 1

• Local factors:

  • Portal hypertension
  • Pancreatitis
  • Inflammatory bowel disease
  • Recent abdominal surgery 1

• Other factors:

  • Oral contraceptive use
  • Malignancies
  • Hematologic disorders 1

Diagnostic Considerations

When SMVT is suspected based on symptoms:

1. First-line imaging: Doppler ultrasound (may be limited by bowel gas) 2
2. Definitive imaging: Contrast-enhanced CT scan during portal phase showing:
   • Absence of flow in the superior mesenteric vein
   • Filling defect in the vein lumen
   • Bowel wall thickening
   • Mesenteric stranding 1

Clinical Pitfalls to Avoid

• Delayed diagnosis: The nonspecific nature of symptoms often leads to delayed diagnosis. Maintain high suspicion in patients with risk factors and persistent abdominal pain 3
• Misdiagnosis: SMVT may be mistaken for other causes of abdominal pain
• Inadequate imaging: Images must be acquired during portal phase, not arterial phase, to avoid false positives 2
• Overlooking intestinal infarction: This is the most concerning complication with mortality up to 60% if not promptly identified and treated 1

Management Approach

When SMVT is diagnosed:

1. Immediate systemic anticoagulation (if no contraindications) 1
2. Monitor closely for signs of intestinal infarction
3. Consider surgical intervention if peritoneal signs develop

Early diagnosis and prompt anticoagulation are critical to prevent progression to intestinal infarction and improve outcomes.