What are the symptoms of acute Superior Mesenteric Artery (SMA) disease?

Symptoms of Acute Superior Mesenteric Artery (SMA) Disease

The hallmark presentation of acute SMA occlusion is severe abdominal pain that is disproportionate to minimal physical examination findings, often accompanied by bowel emptying (vomiting and diarrhea) and a cardiac source of embolus such as atrial fibrillation. 1

Classic Clinical Triad (Acute Embolic SMA Occlusion)

In almost 80% of acute embolic SMA occlusions, patients present with the following triad: 1

• Severe abdominal pain with minimal findings on examination - the classic "pain out of proportion to exam" 1, 2
• Bowel emptying - both vomiting and diarrhea occurring together 1
• Presence of an embolic source - most commonly atrial fibrillation, which is present in nearly 50% of cases 1, 2

Primary Symptoms by Frequency

The most common presenting symptoms in acute mesenteric ischemia include: 1, 2

• Abdominal pain - present in 95% of patients, typically severe and acute in onset 1, 2
• Nausea - occurs in 44% of patients 1, 2
• Vomiting - occurs in 35% of patients, often bilious 1, 2
• Diarrhea - occurs in 35% of patients 1, 2
• Blood per rectum - occurs in 16% of patients 1

Approximately one-third of patients present with the triad of abdominal pain, fever, and hemocult-positive stools. 1, 2

Distinguishing Features by Etiology

Acute Embolic Occlusion

• Sudden onset of strong abdominal pain and vomiting 1
• Associated cardiac risk factors: atrial fibrillation, recent MI, cardiac thrombi, mitral valve disease, left ventricular aneurysm, endocarditis, or previous embolic disease 1
• May have concurrent emboli to other arterial beds (spleen, kidney) which helps orient the diagnosis 1

Acute Thrombotic Occlusion

• Progressive or sudden abdominal pain with vomiting, diarrhea, and/or melena 1
• Often preceded by chronic mesenteric ischemia symptoms: postprandial pain ("intestinal angina"), weight loss, or "food fear" 1
• Associated with diffuse atherosclerotic disease, smoking history, and other atherosclerotic manifestations 1
• May have history of dehydration, low cardiac output, or hypercoagulability 1

Late/Advanced Presentation

When diagnosis is delayed, patients may present with: 1, 2

• Signs of peritonitis - indicating irreversible intestinal ischemia with bowel necrosis 1, 2
• Septic shock - patients presenting in extremis 1
• Abdominal distension and worsening general condition 1

Critical Laboratory Findings

While no laboratory test is diagnostic, the following abnormalities support the diagnosis: 1, 2

• Leukocytosis - present in more than 90% of patients 1, 2
• Metabolic acidosis with elevated lactate - occurs in 88% of cases 1, 2
• Lactate > 2 mmol/L - associated with irreversible intestinal ischemia (hazard ratio 4.1) 1, 2
• Elevated D-dimer - highly sensitive (96%) but not specific (40%); D-dimer > 0.9 mg/L has 82% specificity and 60% sensitivity 1
• Elevated amylase - present in roughly half of patients, which can lead to misdiagnosis as acute pancreatitis 1

Critical Clinical Pitfalls

A common and dangerous pitfall is being falsely reassured by minimal physical examination findings despite severe pain - this is the classic presentation and should heighten, not diminish, suspicion for acute mesenteric ischemia. 2

Lactate elevation is a late finding - it is metabolized effectively by the liver and only becomes elevated after bowel gangrene has developed, so normal lactate does not exclude early ischemia. 1

The presence of lactic acidosis combined with abdominal pain in a patient who may not otherwise appear clinically ill should prompt immediate consideration of CTA. 1

Diagnostic Urgency

Every 6 hours of delay in diagnosis doubles mortality, which ranges from 30-70% despite modern knowledge of this entity. 1 The outcome is extremely time-sensitive and dependent on early clinical suspicion. 1

High-resolution CTA should be performed urgently without delay in any patient with suspected acute mesenteric ischemia, even in the presence of elevated creatinine. 1