What is the most likely diagnosis in a 69-year-old woman presenting with acute onset abdominal pain, a single episode of vomiting, and hematochezia?

Most Likely Diagnosis: Acute Mesenteric Ischemia

In a 69-year-old woman presenting with acute onset abdominal pain, vomiting, and hematochezia, acute mesenteric ischemia (AMI) is the most likely diagnosis and must be assumed until proven otherwise. This triad of symptoms in an elderly patient represents a surgical emergency with mortality approaching 60% if diagnosis and treatment are delayed 1, 2.

Why Acute Mesenteric Ischemia is the Primary Concern

The clinical presentation fits the classic pattern described in current guidelines:

• Acute severe abdominal pain is the hallmark of AMI 1
• Blood in stool (hematochezia) occurs in approximately 10% of AMI cases and is highly suggestive when combined with abdominal pain 1
• Age 69 years places her in the highest risk category—AMI incidence increases exponentially with age, and in patients ≥75 years, AMI is more prevalent than appendicitis as a cause of acute abdomen 1
• Single episode of vomiting is consistent with the nausea and vomiting commonly seen in mesenteric ischemia 1

Specific AMI Subtypes to Consider

The four main types of AMI have distinct clinical patterns 1:

1. Mesenteric Arterial Embolism (Most Common)

• Accounts for approximately 25-40% of AMI cases
• Look for: atrial fibrillation, recent MI, valvular heart disease, or prior embolic events
• Presents with sudden, severe pain
• This is the most likely subtype if she has cardiac risk factors 2

2. Mesenteric Arterial Thrombosis (Increasingly Common)

• Now accounts for up to 40% of cases (increasing trend)
• Look for: history of chronic postprandial pain, weight loss, or previous vascular procedures
• Atherosclerotic disease is the underlying cause 1

3. Mesenteric Venous Thrombosis

• Presents with nausea, vomiting, diarrhea, and abdominal cramping
• Hematochezia occurs in 10% of cases
• Look for: hypercoagulable states, malignancy, inflammatory bowel disease, recent abdominal surgery 1

4. Non-Occlusive Mesenteric Ischemia (NOMI)

• Less likely in this case unless she is critically ill
• Typically seen in ICU patients on vasopressors with multiorgan dysfunction
• Right-sided pain with passage of maroon or bright red blood is highly suggestive 1

Critical Pitfalls to Avoid

The physical examination may be deceptively benign even with catastrophic conditions like mesenteric ischemia 3. In older patients:

• Initial diagnosis is correct only 50% of the time
• Presentation differs from younger patients
• Physical findings are often misleadingly reassuring despite life-threatening pathology 3

Immediate Diagnostic Approach

CT angiography (CTA) of the abdomen and pelvis with triple-phase imaging (non-contrast, arterial, and portal venous phases) is the diagnostic test of choice 2. This will:

• Identify arterial occlusion (embolus or thrombus in SMA)
• Detect venous thrombosis (target sign in SMV)
• Reveal bowel ischemia findings: wall thickening, pneumatosis, free fluid
• Exclude other causes of acute abdomen 1

Plain radiographs are not recommended—they have limited diagnostic value 1.

Alternative Diagnoses to Consider (But Less Likely)

While AMI is the primary concern, other diagnoses in this age group include:

• Diverticulitis with bleeding (common in elderly but typically left lower quadrant pain)
• Ischemic colitis (usually less severe, self-limited)
• Acute cholecystitis (most common surgical indication in elderly, but typically right upper quadrant pain) 3

However, given the combination of acute pain, vomiting, and hematochezia in a 69-year-old, you must rule out AMI first due to its high mortality and need for urgent intervention 1.

Immediate Management While Awaiting Imaging

Even before imaging confirmation 1:

• Aggressive fluid resuscitation with crystalloids to enhance visceral perfusion
• Correct electrolyte abnormalities (watch for hyperkalemia and metabolic acidosis)
• Nasogastric decompression
• Empiric broad-spectrum antibiotics
• Anticoagulation if no contraindications
• Urgent surgical consultation
• Avoid vasopressors if possible; if needed, use dobutamine or low-dose dopamine over norepinephrine 1

Time is bowel—delays in diagnosis and revascularization directly correlate with bowel infarction, need for resection, and mortality.