A 67-year-old man presents to the emergency room reporting sudden-onset abdominal and back pain that began 3 hours ago. He was eating dinner when he started feeling severe pain in his abdomen that made him lose his appetite. He denies any diarrhea or hematochezia and says the pain is not affected by movement. He has a history of hypertension, hyperlipidemia, and depression. He currently takes amlodipine and atorvastatin and is compliant with his medications. He has a 45-pack-year smoking history, but he does not drink alcohol or use any illicit drugs. His temperature is 98.6°F (37°C), his blood pressure is 110/64 mmHg, pulse is 97/min, and respirations are 15/min. Physical exam is notable for diffuse abdominal tenderness without rigidity or guarding. During evaluation, the patient becomes diaphoretic and pale and reports that he feels fatigued. Repeat blood pressure is 87/50 and pulse is 127. Intravenous fluid boluses are administered. Which of the following is the most likely diagnosis?
Ischemic colitis
Ruptured abdominal aortic aneurysm
Aortic dissection
Acute pancreatitis
Ruptured abdominal aortic aneurysm
This patient who presents with sudden-onset abdominal pain, hemodynamic instability (symptomatic hypotension with tachycardia), and significant history of hypertension and smoking most likely has a ruptured abdominal aortic aneurysm (AAA).

Abdominal aortic aneurysms are dilations in the vessel wall that can predispose to rupture. Risk factors for AAA include advanced age (> 60 years), smoking history, male sex, and history of atherosclerosis. AAA can be asymptomatic or mildly symptomatic until it markedly expands or ruptures, leading to abdominal pain, back pain, or flank pain. The evaluation of suspected AAA depends on the hemodynamic stability of the patient and prior knowledge (or lack thereof) of the existence of an AAA. A hemodynamically unstable patient with a known history of AAA should be assumed to have a ruptured AAA and undergo surgical intervention without further workup (though bedside ultrasound can support the diagnosis). In an unstable patient without a known history, a bedside ultrasound to confirm the diagnosis should precede surgical intervention. In a hemodynamically stable patient with or without a known AAA history, an abdominal CTA is appropriate.

Sakalihasan et al. present a review of the presentation and treatment of abdominal aortic aneurysms. They discuss how patients are often asymptomatic until catastrophic rupture occurs. They recommend immediate surgical repair of the aneurysm during ruptures to prevent death.

Incorrect Answers
Answer A: Acute pancreatitis also presents with abdominal pain and can present with hemodynamic instability in severe cases of hemorrhagic conversion of pancreatitis. This is a rare entity and is less likely in this patient. Treatment is immediate transcatheter arterial embolization for unstable patients with hemorrhagic pancreatitis.

Answer B: Aortic dissection has similar risk factors to AAA (history of hypertension, advanced age) and also presents with acute onset back pain. Dissection normally occurs in the setting of hypertension. This diagnosis is possible but less likely in this man with a history of smoking.

Answer C: Ischemic colitis can also present with abdominal pain in a patient with risk factors for atherosclerotic disease. It is associated with hematochezia and diarrhea and is unlikely to cause the level of hypotension in this patient. Treatment is with restoration of blood flow to the ischemic bowel segment or resection if this is not possible. Management is usually centered on medical optimization.

Answer D: Perforated viscus is a surgical emergency that can also present acutely with hemodynamic instability and severe abdominal pain. However, signs of peritoneal irritation are usually present (guarding, rigidity). Treatment is with immediate surgical exploration and repair or resection.

Bullet Summary:
Patients with new-onset back and abdominal pain and a positive smoking history that progresses to hemodynamic instability should be suspected of having a ruptured abdominal aortic aneurysm.