Case Presentation
A 101-year-old man with history of hypertension is brought to the Emergency Department (ED) by ambulance after family members found him down at his home. Paramedics obtained an initial blood pressure of 63/39, which improved to 114/68 after a 1-liter bolus of intravenous fluids. Upon arrival in the ED, he is confused and unable to provide a reliable history. Physical examination reveals a pale and diaphoretic elderly man with no obvious signs of trauma. No palpable masses on abdominal examination. He complains only of back pain while the physical examination is being performed.
Vitals
| BP | 89/68 mmHg |
| P | 86 bpm |
| RR | 20 respirations/min |
| O2 | 98% room air |
| T | 37.2 C |
Differential Diagnosis
- Abdominal aortic aneurysm
- Acute coronary syndrome
- Aortic dissection
- Infection
- Metabolic abnormality
- Stroke
- Syncope
- Toxidrome/overdose
- Traumatic injury
Initial Workup
Given the broad differential diagnosis of an altered and hypotensive elderly patient with no reliable history, blood work was drawn and the emergency physician performed a point-of-care ultrasound given his hemodynamic instability and complaint of back pain.
Point-of-care Ultrasound
Figure 1. Abdominal ultrasound reveals a large 8-9 cm abdominal aortic aneurysm (AAA).
Figure 2. FAST exam reveals subtle positive free fluid in Morrison’s Pouch.
Figure 3. Free fluid (blue arrow) in Morrison’s Pouch.
The bedside ultrasound shows a large AAA (Fig. 1), defined as a diameter greater than 3.0 cm, with positive free fluid in Morrison’s Pouch (Fig. 2, 3). Together with the clinical findings, is highly suspicious for ruptured AAA. Of note, a FAST may still be negative in the setting of a ruptured AAA with a retroperitoneal hemorrhage.
Ultrasound Image Quality Assurance (QA)
Point-of-care ultrasonography of the aorta is one of the essential and critical skills that every Emergency Physician must have. It has the utility of being able to provide a quick and potentially life-saving diagnosis, especially in the patient who is too unstable for computed tomography (CT) scan.
The exam involves using the curvilinear probe, whose low frequency is often necessary to visualize the aorta, especially in obese patients. The abdominal aorta sits anterior to the spine, which provides a convenient sonographic landmark that aids in identification of the aorta. In a transverse orientation, the spine appears as a hyperechoic “horseshoe sign” with posterior shadowing (Fig. 4).
Figure 4. Large abdominal aortic aneurysm (AAA) measured at 7.5 cm, sits just anterior to the spine, the “horseshoe sign” (blue arrow) with posterior shadowing.
A full examination of the abdominal aorta involves scanning through in a transverse plane starting proximally from the subxiphoid area at the level of the superior mesenteric artery (SMA), and though to the bifurcation at the iliac arteries. A measurement of greater than 3.0 cm, made from the outer wall to outer wall, is considered aneurysmal. Ideally, 3 measurements (proximal, mid, and distal) should be made along the abdominal aorta, including a longitudinal (sagittal) view.
Common pitfalls include the inability to adequately visualize the aorta due to overlying bowel gas, and incorrect measurement. Bowel gas can be gently pushed out of the way by applying firm, steady pressure with the ultrasound probe. Measurement of the abdominal aorta, as mentioned previously, should be measured “outer wall-to-outer wall”, to avoid potentially measuring a false lumen of a large AAA with an intramural thrombus (Fig. 5).
Figure 5. Potential pitfall: Measuring a false pseudo-lumen (#1 – incorrect measurement) of a large abdominal aortic aneurysm with an intramural clot (#2 – correct measurement).
Disposition and Case Conclusion
Given the findings on the point-of-care ultrasound (a large AAA with free fluid in Morrison’s pouch) in the right clinical setting, the patient had a ruptured AAA until proven otherwise. The massive transfusion protocol was activated, and vascular surgery was emergently consulted.
The decision was made to obtain a stat computed tomography (CT) scan to confirm the diagnosis, as he was momentarily hemodynamically stable with aggressive resuscitation. The CT confirmed the findings of a large ruptured AAA, seen below (Fig. 6):
Figure 6. CT reveals a large abdominal aortic aneurysm measuring up to 8.5 cm with evidence of high density intraperitoneal fluid consistent with rupture of abdominal aortic aneurysm.
The vascular surgery and emergency medicine teams had a collaborative discussion with the patient’s family regarding his poor prognosis and unlikelihood that he would survive surgery. The patient’s family ultimately decided to make him comfort care only.
The point-of-care ultrasound in this case was able to quickly identify the patient’s diagnosis of a ruptured abdominal aortic aneurysm (AAA) and vascular surgery was emergently consulted. Unfortunately, due to the high mortality associated with a ruptured AAA and the patient’s advanced age, he did not survive. However this doesn’t diminish the critical role of bedside ultrasonography in patients at risk for AAA.
An estimated 5% of the population over the age of 50 are estimated to have a AAA, and the incidence of this potentially life-threatening disease in the United States has been increasing over the past few decades.1 However despite this, more than 80% of patients are unaware of their aneurysmal disease.2 This makes the diagnosis of a ruptured AAA challenging. Additionally, the presenting symptoms of a ruptured AAA are often non-specific, and patients will often not have hemodynamic instability until there has been significant disease progression and blood loss. The most common misdiagnoses include renal colic, acute diverticulitis, and gastrointestinal bleed.
The physical examination in patients with aortic aneurysms has been studied and found to be unreliable; the ability to palpate a pulsatile mass on physical examination has been shown to detect only 39% of all AAAs.3 Furthermore, the ‘classic triad’ of ruptured AAA that is often taught consisting of abdominal or flank pain, palpable abdominal mass, and hypotension has also been proven to be unreliable, and is present in only 30-50% of cases of ruptured AAA.2
The mortality rate of a ruptured AAA is high at an estimated 90%, with greater than 10,000 deaths annually in the United States.1,4 The utility of a real-time point-of-care imaging modality like ultrasound is vital to the prompt diagnosis, and has been shown to decrease mortality from 75% to 35%.5
While CT is considered the gold-standard for diagnosis of AAA, ultrasonography of the aorta by emergency physicians has been shown to have a general agreement compared with radiology-read CT imaging. There have been several studies proving that ultrasonography is accurate, approaching 100% sensitivity and specificity [Table 1].
When performed early in the workup of a patient suspected of having a ruptured AAA, as was done in this case, bedside ultrasound can expedite surgical consultation and definitive care.
| Sample Size | % Sensitivity (95% CI) | % Specificity (95% CI) | |
| Lanoix et al. 2000 | 21 | 100 | 94.1 |
| Kuhn et al. 2000 | 68 | 100 | 95.2 |
| Rowland et al. 2001 | 33 | 100 | 100 |
| Jones et al. 2003 | 66 | 97.5 | 100 |
| Tayal et al. 2003 | 125 | 100 | 98 |
| Knaut et al. 2005 | 104 | 100 | 97 |
| Costantino et al. 2005 | 238 | 94 | 100 |
| Table 1. Summary of Sensitivity and Specificity of Ultrasound to Detect AAA. Adapted from Rubano et al. 2013.6 | |||
Take Home Points
- There is an increasing prevalence of abdominal aortic aneurysms (AAA) in the United States in patients who are unaware of their aneurysmal disease, and a ruptured AAA can be a difficult and elusive diagnosis that is associated with high mortality rate.
- Point-of-care ultrasonography is the imaging modality of choice in unstable patients with suspicion for AAA, and can expedite surgical consultation and definitive management.
- Emergency physicians can correctly identify AAA (defined as >3 cm) on bedside ultrasonography with 94% sensitivity and 100% specificity.7
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