Small ruptured abdominal aneurysm diagnosed by emergency physician ultrasound

Small RupturedAbdominalAneurysm Diagnosed by EmergencyPhysicianUltrasound JEFF MILLER, MD,* JULIE MILLER, MDt Ruptured abdominal aortic aneurysms currently have a high rate of both mortality and misdiagnosis. Aneurysms smaller than 4 cm are not commonly considered for surgical repair. This report describes the case of a ruptured abdominal aneurysm measuring less than 4 cm diagnosed by the emergency physician utilizing bedside ultrasound. Within 30 minutes of arrival at the emergency department the patient's abdominal pain resolved spontaneously after defecation. If the bedside ultrasound had not been performed it is possible the patient would have been discharged from the hospital without surgical intervention. Bedside ultrasound by emergency physicians may improve the diagnosis of ruptured aortic aneurysms, particularly if the presentation is atypical. (Am J Emerg Med 1999;17:174-175. Copyright © 1999 by W.B. Saunders Company) An elderly patient presented with abdominal pain that resolved spontaneously after defecation. In this clinical setting, a reasonable assumption would have been that the pain was benign and self-limiting. However, a bedside ultrasound, performed by the emergency physician as part of the initial evaluation, revealed a small abdominal aneurysm. Computed tomography (CT) subsequently demonstrated a posterior leak. This case reiterates the fact that ruptured aneurysms may or may not present with severe, constant pain, unaffected by position. Aneurysms smaller than 4 cm occasionally rupture. Finally, given the high rate of misdiagnosis in ruptured abdominal aneurysms, bedside ultrasound should be considered as a potential tool to improve the sensitivity of the emergency physician's initial evaluation.

CASE REPORT Paramedics transferred an 85-year-old Filipino man to the emergency department (ED) from church after an acute episode of weakness, dizziness, and abdominal pain. In the field the patient was noted to be hypotensive. Initial vital signs in the ED department were: blood pressure, 120/72 mm Hg; pulse, 67 beats/rain; respirations, 18 breaths/min; and temperature, 36.4°C. The patient's physical exam was significant for diffuse abdominal tenderness and guarding. Bowel sounds were normal and no mass was appreciated. Rectal findings were guiac-negative. As part of the initial evaluation a bedside ultrasound was performed by the emergency physician with a preliminary impression of an abdominal aneurysm measuring 3.3 cm and an intraluminal clot (Figure 1). Baseline laboratory values were normal, including a white blood cell count of 11,100/pL and hematocrit of 40. From *Emergency Medicine, Bellflower Kaiser, Bellflower, CA, and tMiller Radiology, Rolling Hills Estates, CA. Manuscript received August 19, 1997, returned September 9, 1997; revision received September 20, 1997, accepted October 1, 1997. Reprint requests to Dr Jeff Miller, Chief of Emergency Medicine, Bellflower Kaiser, 9400 E Rosecrans Ave, Bellflower, CA 90706. Key Words: Ultrasound, emergency medicine, ruptured aortic abdominal aneurysm. Copyright © 1999 by W.B. Saunders Company 0735-6757/99/1702-0017510.00/0 174

Shortly after arrival in the ED, the patient's abdominal pain resolved after a bowel movement. The patient requested discharge but was persuaded to undergo formal ultrasound in the radiology department, which corroborated the aneurysm (Figure 2). Contrast CT confirmed the aneurysm as measuring 3.8 cm (Figure 3). Additionally, a small leak was noted in the posterior wall of the aorta. Ectasia of both common iliac arteries was seen with intraluminal clot. The patient was taken to the operating room and had resection of the leaking abdominal aortic aneurysm with placement of a tube graft. He also had bilateral femoral thromboembolectomy. Postoperative complications included acute renal failure and T10-12 areflexia of the knees and ankles, with minimum use of hip flexors and leg extensors. His renal function gradually normalized and he was discharged to a rehabilitation facility for physical therapy after 2 weeks of inpatient hospital care.

DISCUSSION Ruptured abdominal aortic aneurysms account for at least 15,000 deaths per year in the US and are the tenth leading cause of death among men older than 55 years of age. ~ Rupture is frequently the first manifestation of an aortic aneurysm. Up to two thirds of abdominal aortic aneurysms are unrecognized before rupture. 2 The classic triad of abdominal pain, hypotension, and pulsatile mass is present in only half of patients, but abdominal pain is noted in more than 80% of patients. When the correct diagnosis is established initially, the mortality of ruptured abdominal aortic aneurysms is 35%. However, the mortality rate is increased to 75% when a raptured abdominal aortic aneurysm is not recognized initially. 3 Marston et al 4 reviewed 152 patients with ruptured abdominal aortic aneurysm and noted a 30% prevalence of misdiagnosis as defined by a delay of 6 hours on initial diagnosis. Almost half of these patients were misdiagnosed as renal colic. Another one third was misdiagnosed as diverticulitis or gastrointestinal bleed. 4 Risk of rupture and long-term survival of patients without operation has been found to be directly related to the size of the aneurysm. The 5-year rate for rupture of aneurysms exceeds 75% in those measuring 7.0 cm or more. For aneurysms measuring 6 cm the 5-year rupture rate is approximately 35%. Aneurysms measuring 5.0 to 5.9 cm ruptured approximately 25% of time. Approximately 10% of all aneurysms less than 4 cm rupture and cause death. 4-7 Currently, elective surgery is recommended for all patients with aneurysms larger than 6 cm and a selective approach is used for aneurysms larger than 5 cm. Because of the high mortality associated with a ruptured aorta, the diagnosis should be considered in elderly patients who present with abdominal or back pain and in elderly patients with transitory episodes of hypotension. 4 Injudicious delay incurred by performing unnecessary tests in hypotensive patients before taking them to the operating room further

MILLER AND MILLER • ULTRASOUND DIAGNOSIS OF ABDOMINAL ANEURYSM

FIGURE 1. Ultrasound performed by emergency physician. Longitudinal image of the infrarenal abdominal aorta shows an aorta dilated to 3.3 cm. The walls are irregular and clot is shown along the posterior wall (arrow). increases excessive mortality. Plain X-rays are of limited utility in the evaluation of abdominal aortic aneurysms. Clinical studies confirm that ultrasound in the radiology department is efficacious in confirming the presence or absence of aneurysms in 95% to 98% of patients. 8,9 However, ultrasound does not detect the presence or absence of rupture. If the patient is hemodynamically stable, contrast CT should be performed. High-resolution CT correctly identifies the proximal and distal extent of aortic aneurysms, as well as iliac aneurysms, in the vast majority of cases. CT is 77% sensitive and 100% specific for retroperitoneal blood.l° Magnetic resonance imaging is an excellent tool for the preoperative evaluation of aortic aneurysms. However, cost and availability favor CT in most emergency patients. Emergency physician performance of bedside ultrasound is controversial in the medical community. Emergency physicians have utilized bedside ultrasound to diagnose gallstones, abdominal aneurysms, intrauterine pregnancies, pericardial fluid, and intraperitoneal fluid, and as an aid in vein catheterization. 11-13 Issues related to the competency credentials for emergency physician-performed ultrasound

FIGURE 2. Ultrasound performed in the radiology department confirms an infrarenal aortic aneurysm dilated to 3.8 cm. Posterior wall clot is again demonstrated (arrow).

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FIGURE 3. Axial contrast CT shows a dilated infrarenal abdominal aorta. Significant mural thrombus and calcification are seen circumferentially. A posterior rupture is identified (arrow) and was subsequently confirmed operatively. have not been resolved. L4Given the high incidence of mortality and misdiagnosis of ruptured aortic abdominal aneurysms, however, there is a compelling argument for any tool that improves the sensitivity of the emergency physician's evaluation.

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