A 65-year-old woman with a history of hyperlipidemia was brought to an ambulance after an episode of syncope. She had been experiencing abdominal pain for two hours prior to this.
She had undergone a colonoscopy 14 days before her visit and emergency medical services reported that she had subjective fevers, for which she was started on metronidazole as an outpatient.
The patient told EMS that the pain started suddenly in her lower abdomen two hours before the syncopal episode, and was sharp and constant and associated with nausea and intermittent diarrhea. She was alert and oriented but tachycardic and hypotensive on arrival. No head trauma, chest pain, shortness of breath, vomiting or diarrhea were reported.
The patient was alert, awake and moderately distressed in the emergency department. Her blood pressure was 105/72 mm Hg, her heart rate was 135 bpm and her temperature was 37.2°C, and she had a normal respiratory rate and a pulse oxygenation of 99% on room air. His blood sugar was 85 mg/dL. Examination revealed dry mucous membranes and clammy, diaphoretic skin, tachycardia with a steady rhythm, clear breath sounds, and distension and tenderness in the lower abdomen.
The patient was placed in the Trendelenburg position, IV access was obtained, and a sepsis alert was activated. An ECG demonstrated sinus tachycardia with no evidence of arrhythmia, and baseline lactate returned to 4.8 mmol/L. A portable STAT chest x-ray was obtained (image), which did not show free air below the diaphragm, an enlarged cardiac silhouette, or an enlarged mediastinum.
A point-of-care ultrasound to assess abdominal aortic aneurysm was performed immediately upon arrival. (Image.) A CT scan of the abdomen/pelvis was ordered, blood cultures were obtained and broad-spectrum antibiotics were started. What is the diagnosis of this patient?
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Diagnosis: Superior mesenteric artery aneurysm
Superior mesenteric artery aneurysm (SMA) is a rare diagnosis that is part of a larger group of conditions known as visceral artery aneurysms (VAA). These are aneurysms of the splenic, hepatic, superior mesenteric, celiac, gastroduodenal, pancreaticoduodenal and inferior mesenteric arteries. (Mount Sinai J Med. 2010;77:296.)
An SMA aneurysm is the third most common AAV and usually involves the proximal 5 cm of the SMA. The etiologies of these include infections, atherosclerosis and vascular collagen disorders as well as polyarteritis nodosa. (J. Vasc Surg. 2002;36:234; https://bit.ly/3O37VcI.) Data are sparse due to the rarity of this disease, but a case series has demonstrated that the average size of an unruptured SMA is 2.2 cm and most patients remain asymptomatic. Indications for intervention include a size of 2 cm or more, the presence of symptoms, and demonstrated growth of the aneurysm.
The discovery of an aneurysm or a dissection of the SMA can be fortuitous on imaging, especially if the patient is asymptomatic. Management is based on surgeon preference, which may vary from conservative management (outpatient observation or medical treatment) or surgical intervention (endovascular or open surgery). (J. Vasc Surg. 2018;68:1228; https://bit.ly/3b7930n.)
Patients with AAV may present with vague symptoms that are difficult to identify, but may include discomfort after eating, symptoms of intermittent bowel ischemia, hemobilia, or bilious vomiting. (Operation. 1996;120:627.) Treatment options for symptomatic patients include coil embolization using interventional radiology and open surgical fixation. Side effects of these procedures may include abdominal ischemia requiring testing for loss of bowel viability.
Case reports have demonstrated poor outcomes in patients with ruptures. Nearly 22% of AVA present as acute emergencies and 8.5% lead to death. (J. Vasc Surg 1986;3:836.) Only four of eight patients survived after presenting with a ruptured SMA aneurysm in one case series. (J. Vasc Surg. 2002;36:234; https://bit.ly/3O37VcI.) These patients should be treated with adequate colloidal and crystalloid resuscitation, immediate surgical consultation, and interventional radiology rather than open surgery, like any other patient with hemorrhagic shock.
Doctors were called to the emergency CT room for our patient’s altered mentality, hypotension and tachycardia. Immediate CT examination showed large volume hemoperitoneum with retroperitoneal bleeding. (Image.) The massive transfusion protocol was activated and the patient was transported to the surgical ICU with surgical planning for open surgery rather than interventional radiation embolization.
She was intubated, transfused, resuscitated and rushed following interventional radiology, where an angiogram demonstrated active extravasation of the first branch of the SMA. The embolization was successful. She had an extended course in hospital and was discharged after multiple surgeries on day 61 with home health care.
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Dr. Smalleyis Director of Emergency Ultrasound and Associate Professor of Emergency Medicine at the Cleveland Clinic Institute of Emergency Services. Follow her on Twitter@SmallsSono.