腹主動脈瘤破裂 : 在香港一急症室的 7 年回顧性觀察研究

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1 Hong Kong Journal of Emergency Medicine Ruptured abdominal aortic aneurysm: a 7-year retrospective observational study in an emergency department of Hong Kong 腹主動脈瘤破裂 : 在香港一急症室的 7 年回顧性觀察研究 NH Chu 朱雁鴻 Objectives: To review the clinical presentations and outcomes of patients with ruptured abdominal aortic aneurysm (AAA) in a regional hospital and its evaluation in the accident and emergency department (AED). Methods: This is a retrospective observational study of patients admitted through the AED with the discharge or post-mortem diagnosis of ruptured AAA from 1st January 2002 to 31st December 2008 in a regional pubic hospital of Hong Kong. Their demographic and clinical data were recorded and analysed. The sensitivity of the AED in detecting ruptured AAA or symptomatic AAA was evaluated. Results: Twenty-six patients were found to have ruptured AAA and included in the study. All were Chinese. Seventeen patients had repair surgery done by open surgical method. Eighteen (69%) patients were diagnosed to have ruptured AAA or found to have symptomatic AAA in the AED. Three (12%) ruptured AAAs were diagnosed at postmortem. The most common presenting symptoms were abdominal pain (73%) and loss of consciousness (46%). Only five (19%) patients had the classical triad of abdominal pain, haemorrhagic shock and a pulsatile abdominal mass. Ultrasound of aorta was performed in 74% of cases in the group with ruptured AAA or symptomatic AAA diagnosed in the AED but none in the delayed diagnosis group (p=0.001). The former group were 3.7 times more likely to proceed to repair surgery (p=0.188) and had surgical repair operation 40.8 hours earlier than the latter group (p=0.006). Systolic blood pressure less than 90 mmhg at any time point before operation was found to correlate significantly with mortality (p=0.029). Conclusion: A high index of suspicion and prompt recognition of ruptured AAA is of paramount importance. Emergency physicians should familiarise themselves with the clinical presentation and management of patients with ruptured AAA. Emergency ultrasound performed in the AED helps in the early detection of AAA. (Hong Kong j.emerg.med. 2010;17: ) 目的 : 審查一區域性醫院腹主動脈瘤破裂病人的臨床徵狀和結果, 及在急症室內的評估 方法 : 這是一個回顧性觀察研究, 對象為 2001 年 1 月 1 日至 2008 年 12 月 31 日由急室收進香港一區域性公立醫院, 而出院或驗屍的診斷為腹主動脈瘤破裂的病人 ; 記錄及分析他們的人口統計及臨床數據 ; 評估急症室查出腹主動脈瘤徵狀或破裂的敏感度 結果 : 本研究找出及包括 26 名腹主動脈瘤破裂的病人 全部是華裔 17 名病人以開放式手術方法修補 18 名病人 (69%) 在急症室發現腹主動脈瘤徵狀或破裂 ; 3 人 (12%) 在驗屍時診斷為腹主動脈瘤破裂 最常呈現的症狀為腹痛 (73%) 及神志不清 (46%) 只有 5 名病人 (19%) 有典型的三聯徵 : 腹痛 出血性休克及腹部搏動的團塊 在急症室診斷為腹主動脈瘤徵狀或破裂的組別中,74% 的個案進行了主動脈超聲波檢查, 但在延遲診斷的組別中則沒有人進行過 (p=0.001) 前組進行修補手術多出 3.7 倍 (p=0.188) 及比後組的修補手術早 40.8 小時 (p=0.006) Correspondence to: Chu Ngan Hung, MBChB, MRCP(UK) Kwong Wah Hospital, Accident and Emergency Department, 25 Waterloo Road, Yau Ma Tei, Kowloon, Hong Kong chunh4@gmail.com

2 Chu/Ruptured abdominal aortic aneurysm 119 發覺在手術前任何時間的收縮血壓低於 90 mmhg 與死亡率有顯著的關聯 (p=0.029) 總結 : 高度懷疑及迅速認出腹主動脈瘤破裂是極重要的 急症科醫生應熟悉腹主動脈瘤破裂的臨床徵狀及病人的處理 在急症室內進行超聲波檢查有助及早診斷腹主動脈瘤 Keywords: Aortic rupture, hospital emergency service, hospital mortality, ruptured aneurysm 關鍵詞 : 主動脈破裂 醫院緊急服務 醫院死亡率 動脈瘤破裂 Introduction Ruptured abdominal aortic aneurysm (AAA) is a surgical emergency with high mortality. The overall mortality for ruptured AAA including out-of-hospital deaths exceeds 80%. 1,2 Those who survive to hospital and undergo emergency repair surgery have mortality as high as 50%. 1 On the other hand, the mortality rate for elective abdominal aortic aneurysm repair is less than 5%. A previous study showed that 12.5% of patients would die within two hours of emergency department arrival among those not undergoing emergent surgical repair. 3 Therefore, ruptured AAA is a lethal event that mandates early identification in the accident and emergency department (AED). One retrospective study in the United States showed that 30% of ruptured AAA were initially misdiagnosed. 4 There were only a few studies on the role of emergency physicians in the management of ruptured AAA. 5-7 This is a retrospective study in a regional hospital in Hong Kong to describe the clinical pattern of ruptured AAA in Hong Kong and to assess the role of emergency physicians in the diagnosis and management of this condition. Materials and methods It was a retrospective observational study in Kwong Wah Hospital (KWH) which is an acute hospital in the urban area of Hong Kong. The AED has an annual attendance of approximately 140,000. Patients requiring emergency repair of ruptured AAA would be admitted through the AED under the care of the Surgical Unit, which delivers comprehensive services including vascular surgery. Those with unstable haemodynamic status might be directly admitted to the Intensive Care Unit or transferred directly to the operating theatre after assessment by surgical specialists. All patients admitted through KWH AED with the discharge or post-mortem diagnosis of ruptured AAA during a study period of 7 years from 1st January 2002 to 31st December 2008 were included. The eligible cases were retrieved from the Clinical Data Analysis and Reporting System, which is a computerised data retrieval system in the Hospital Authority of Hong Kong. Patients with ICD-9 code (abdominal aneurysm, ruptured) or (aortic aneurysm of unspecified site, ruptured) were retrieved and the case records were reviewed by the author. Patients who had post-mortem examination performed and ruptured AAA diagnosed by the Pathology Department of KWH were also included in the study. Data were collected from AED notes and hospitalisation records after being reviewed by the author. The author excluded clinical elective admission cases, patients with rupture developed during elective repair of the abdominal aortic aneurysm and ruptured AAA secondary to trauma. All ruptured AAA patients were divided into two groups: ruptured AAA or symptomatic AAA diagnosed in the AED (early detection group) versus those diagnosed elsewhere (delayed diagnosis group). Subgroup analysis was performed in those who had repair surgery done. Comparison of clinical parameters between the two groups was performed by using Fisher's exact test for categorical variables and Mann- Whitney U test for continuous variables. Statistical significance was taken at p value less than Data analysis was performed using SPSS (Statistical Package for the Social Sciences) version 15.0.

3 120 Hong Kong j. emerg. med. Vol. 17(2) Apr 2010 Results There were 26 patients with ruptured AAA (mean age 73.4 years, range from 42 to 92) who were alive on arrival at the AED during the 7-year study period. There were 20 men and 6 women, with a ratio of about 3:1. All patients in the study happened to be Chinese. Their clinical characteristics are summarised in Table 1. Table 2 summarises the clinical features and outcomes of patients with ruptured AAA. The most common presenting symptoms were abdominal pain (73%) and loss of consciousness (46%). More than half of the patients (15/26, 58%) had systolic blood pressure equal to or greater than 90 mmhg on arrival. Only 5 (19%) patients had the classical triad of abdominal pain, haemorrhagic shock and pulsatile abdominal mass. Five patients (19%) required cardiopulmonary resuscitation in the AED. Of the 26 patients with ruptured AAA, 17 patients had repair surgery done by open surgical method. None had endovascular repair performed. Seventeen patients died within 30 days of the AED attendance. The overall hospital mortality rate for ruptured AAA was 65%. Table 3 summarises the initial identifier of the ruptured AAAs or symptomatic AAAs. One patient (4%) had symptomatic AAA suspected by the referring physician before arrival at the AED. Eighteen cases (69%, 12 cases as ruptured AAAs and 6 cases as symptomatic AAAs) were detected in the AED; 4 ruptured AAAs ( 15%) were diagnosed in the ward or during laparotomy exploration, and 3 ruptured AAAs (12%) were diagnosed at post-mortem. By excluding the only case with AAA diagnosed before the AED arrival, the Table 2. Clinical features and outcomes of patients with ruptured abdominal aortic aneurysm in Kwong Wah Hospital ( , N=26) Clinical feature No./N (%) Presenting symptom Abdominal pain 19/26 (73%) Syncope or loss of consciousness 12/26 (46%) Back pain 7/26 (27%) Dizziness 5/26 (19%) Nausea or vomiting 3/26 (12%) Groin or scrotal pain 2/26 (8%) Initial systolic blood pressure >140 mmhg 5/26 (19%) mmhg 10/26 (38%) <90 mmhg 11/26 (42%) Pulsatile abdominal mass 14/26 (54%) Table 1. Clinical characteristics of patients with ruptured abdominal aortic aneurysm (AAA) in Kwong Wah Hospital ( , N=26) Characteristic No./N (%) Age in years (mean; SD) 73.4; 12.4 Age 70 years 18/26 (69%) Male 20/26 (77%) Smoking status Chronic or ex-smoker 18/26 (69%) Non-smoker 3/26 (12%) Unknown 5/26 (19%) Pre-existing medical problem Hypertension 20/26 (77%) Hyperlipidaemia 7/26 (27%) Coronary artery disease 7/26 (27%) Old cerebrovascular accident 5/26 (19%) Known history of underlying AAA 5/26 (19%) Diabetes mellitus 4/26 (15%) Chronic obstructive airway disease 2/26 (8%) Classical triad 5/26 (19%) Hypotension, abdominal pain and pulsatile abdominal mass Ultrasound aorta done in AED 14/26 (54%) Computed tomography abdomen done 6/26 (23%) Cardiopulmonary resuscitation in AED 5/26 (19%) Repair surgery performed 17/26 (65%) 30-day mortality 17/26 (65%) AED=accident and emergency department Table 3. Initial identifier of ruptured or symptomatic abdominal aortic aneurysm Diagnosis site No./N (%) By referring physician 1/26 (4%) Accident and emergency department 18/26 (69%) After admission or intra-operative finding 4/26 (15%) Post-mortem 3/26 (12%)

4 Chu/Ruptured abdominal aortic aneurysm 121 sensitivity of KWH AED in detecting ruptured AAA or symptomatic AAA was 18/25 (72%). The presumptive diagn osis on admiss ion was summarised in Figure 1. Among the delayed diagnoses, two were abdominal pain for further investigation; the remaining five cases were renal colic, appendicitis, syncope, aortic dissection and intestinal obstruction respectively. The clinical characteristics of the patients with ruptured AAA/symptomatic AAA diagnosed in the AED or before AED arrival (early detection group Group A) were compared with those with ruptured AAA diagnosed elsewhere (delayed diagnosis group Group B). The results are shown in Table 4. A pulsatile abdominal mass was found in only 14% of Group B patients versus 68% of Group A patients (p=0.026). Ultrasound aorta was done in 74% of cases in group A but none in group B (p=0.001). Sonographic findings of the 14 cases with ultrasound aorta performed included the presence of AAA (n=13), presence of mural thrombus (n=1), and heterogeneous abdominal mass (n=1). None of the cases were reported to have retroperitoneal haematoma or haemoperitoneum in bedside ultrasonography. Group B had 71% mortality rate, which was not significantly different from Group A (63%, p=1.000). The odds of ruptured AAAs in Group A and Group B to have repair surgery were 2.8 and 0.75 respectively. Therefore, ruptured AAAs in Group A were 3.7 times more likely to proceed to repair surgery than those of Group B (p=0.188). As shown in Table 5, patients in the early detection group had mean transfer time to operating theatre 40.8 hours earlier than those with ruptured AAA diagnosed elsewhere (3.3 versus 44.1 hours). The difference was found to be statistically significant (p=0.006). Subgroup analysis was performed in the 17 patients wh o had repair s urg er y don e. The clinic al characteristics of those who survived or died were compared in Table 6. Nine patients survived and 8 patients died after repair surgery. The overall operative mortality for ruptured AAA was 47%. The non-survival group was found to have a mean initial haemoglobin level significantly lower than that of the survival group (8.4 g/dl versus 11.4 g/dl, p=0.021). The occurrence of systolic blood pressure less than 90 mmhg at any time point before operation was the only factor found to correlate significantly with mortality (p=0.029). Figure 1. Presumptive diagnosis in the accident and emergency department (AED) for patients with ruptured abdominal aortic aneurysm (AAA).

5 122 Hong Kong j. emerg. med. Vol. 17(2) Apr 2010 Table 4. Early detection group (Group A) versus delayed diagnosis group (Group B) Group A Group B p-value* n=19 n=7 (2-tailed) Age (mean) Age 70 13/19 (68%) 5/7 (71%) Male 15/19 (79%) 5/7 (71%) Smoking status Chronic or ex-smoker 13/19 (68%) 5/7 (71%) Non-smoker 3/19 (16%) 0/7 (0%) Unknown 3/19 (16%) 2/7 (29%) Known history of AAA 4/19 (21%) 1/7 (14%) Pre-existing medial problem Hypertension 14/19 (74%) 6/7 (86%) Hyperlipidaemia 5/19 (26%) 2/7 (29%) Coronary artery disease 5/19 (26%) 2/7 (29%) Old cerebrovascular accident 5/19 (26%) 0/7 (0%) Diabetes mellitus 3/19 (16%) 1/7 (14%) Chronic obstructive airway disease 2/19 (11%) 0/7 (0%) Presenting symptom Abdominal pain 13/19 (68%) 6/7 (86%) Syncope 10/19 (53%) 2/7 (29%) Back pain 5/19 (26%) 2/7 (29%) Nausea or vomiting 2/19 (11%) 1/7 (14%) Groin or scrotal pain 1/19 (5%) 1/7 (14%) Initial systolic BP in mmhg (mean) Initial diastolic BP in mmhg (mean) Initial systolic BP <90 mmhg 9/19 (47%) 2/7 (29%) Pulse per minute (mean) Pulsatile abdominal mass 13/19 (68%) 1/7 (14%) Initial haemoglobin level g/dl Ultrasound done in AED 14/19 (74%) 0/7 (0%) day mortality 12/19 (63%) 5/7 (71%) Repair surgery done 14/19 (74%) 3/7 (43%) *Comparison of categorical variables between two groups was performed by using Fisher's exact test, unless specified otherwise; Mann-Whitney U test AAA=abdominal aortic aneurysm, AED=accident and emergency department, BP=blood pressure Table 5. Comparison of transfer time to operating theatre (OT) in hours between patients in the early detection group versus those with delayed diagnosis Early detection Delayed diagnosis Mean/median p-value* group group difference (2-tailed) Transfer time to OT in hours Mean Median *Mann-Whitney U test

6 Chu/Ruptured abdominal aortic aneurysm 123 Table 6. Subgroup analysis for the patients with repair surgery performed: clinical characteristics of survivors versus those who died within 30 days after admission Survived group, n=9 Death group, n=8 p-value*(2-tailed) Age (mean) Age 70 5/9 (56%) 6/8 (75%) Male 8/9 (89%) 6/8 (75%) Smoking status Chronic or ex-smoker 5/9 (56%) 6/8 (75%) Non-smoker 2/9 (22%) 1/8 (13%) Unknown 2/9 (22%) 1/8 (13%) Correct diagnosis of ruptured AAA in AED 7/9 (78%) 7/8 (88%) Pre-existing medial problem Hypertension 6/9 (67%) 5/8 (63%) Coronary artery disease 2/9 (22%) 3/8 (38%) Old cerebrovascular accident 1/9 (11%) 1/8 (13%) Diabetes mellitus 2/9 (22%) 1/8 (13%) Hyperlipidaemia 1/9 (11%) 2/8 (25%) Chronic obstructive airway disease 0/9 (0%) 1/8 (13%) History of syncope 5/9 (56%) 3/8 (38%) Initial systolic BP in mmhg (mean) Initial diastolic BP in mmhg (mean) Pulse per minute (mean) Haemoglobin level g/dl Diameter of AAA (cm) Transfer time to operating theatre in hours Mean Median Peri-operative transfusion (PRBC unit) Systolic BP <90 mmhg at any time point before operation *Comparison of categorical variables between two groups was performed by using Fisher's exact test, unless specified otherwise; Mann-Whitney U test AAA=abdominal aortic aneurysm, AED=accident and emergency department, BP=blood pressure, PRBC=packed red blood cell Discussion Ruptured AAA is a major vascular catastrophe and diagnosis of the condition remains a challenge for all emergency physicians. In one study done in the United States, the incidence of AAA and the size of AAA at the time of diagnosis were found to have increased over the last three decades. 8 One local study showed that the annual incidence of AAA in Hong Kong was 13.7 per 100,000 population and 105 per 100,000 for those aged 65 and above. About 10% of AAA first presented with rupture and the overall mortality rate for ruptured AAA was 78%. 9 The diagnosis of ruptured AAA is frequently delayed unt il th e patients decompensa te and develop hypovolaemic shock. A high index of suspicion is required for the condition to be recognised in the initial presentation. In our study, the classical triad of ruptured AAA (abdominal pain, hypotension and pulsatile abdominal mass) was found in less than one fifth of the cases (19%). More than half of our patients had initial systolic blood pressure equal to or greater than 90 mmhg because the ruptured aneurysm might be temporarily contained by the retroperitoneum. It is important for emergency physicians to recognise the subtle signs of shock in the early phase. Obesity could

7 124 Hong Kong j. emerg. med. Vol. 17(2) Apr 2010 compromise the accuracy in detecting the pulsatile abdominal mass. The absence of a palpable aortic aneurysm should never be used to rule out ruptured AAA in patients at risk. Failure to recognise some atypical symptoms associated with ruptured AAA such as groin pain may delay the diagnosis. The sensitivity of our AED in detecting ruptured AAA or symptomatic AAA was 72%, which was comparable to the series reported by Marston et al in the US. 4 Only 12% of ruptured AAA patients were diagnosed at autopsy, which might be an underestimate because not all deaths in KWH had post-mortem examination. Traditional Chinese custom goes against autopsy. The family of the deceased person might request waiving the autopsy unless it was legally enforced by coroner's order. In this study, the operative mortality (30 days) was 47%. The result was slightly lower than another series in Hong Kong (54%) reported by Cheng et al 9 but was comparable to the 48% in the meta-analysis of 50 years of ruptured AAA repair reported by Bown et al. 10 In this study, ultrasound of the aorta was done in 74% of the cases in the early detection group but none in the delayed diagnosis group. Ultrasound of the aorta by emergency physicians is a fast and accurate bedside imaging test which only takes a few minutes' time. Tayal et al reported a study of 125 ultrasound scans performed by emergency physicians. There were 100% sensitivity and 98% specificity for AAA after confirmation by formal ultrasonography, CT scan, abdominal MRI or laparotomy. 11 The sonographic feature of r uptured AAA was the presence of retroperitoneal haematoma which appeared as a retroperitoneal fluid collection especially in the periaortic location. In this case series, ultrasound examinations done in the emergency room could provide accurate, useful information about the presence of aneurysm but the sensitivity for detecting peri-aortic haemorrhage was poor. In another series reported by Shuman et al, 60 patients with suspected ruptured AAAs had real-time rapid ultrasound examination in the emergency room. The result showed that the use of ultrasonography could identify 97% of AAAs but the detection rate for peri-aortic haemorrhage was 4% only. 12 Therefore, ultrasound abdomen is a good tool to detect AAA but not a good tool to confirm its rupture. On the other hand, in the proper clinical setting (a patient with abdominal pain or hypotension), detection of an aortic aneur ysm on bedside ultrasonography has a high correlation with rupture. In the delayed diagnosis group, two elderly patients (72 and 81 years old respectively) were admitted with the presumptive diagnosis of abdominal pain for further investigation. Diagnostic difficulties in elderly patients with abdominal pain include atypical presentations and physical findings, and confounding underlying medical conditions. 13 Managing elderly patients with abdominal pain in the emergency department requires considerable skill and judgment. The correct diagnosis was often difficult to establish at initial presentation. Another case was a 60 years old man who was admitted to the surgical unit with a presumptive diagnosis of left renal colic. This case illustrates the danger of diagnosing renal colic in elderly patients before ruptured AAA has been excluded. Performing bedside ultrasonography in elderly patients presenting with abdominal pain or loin pain may help emergency physicians to identify severe intraabdominal pathologies and accelerate the disposition of patients to the operating room. The effect of early diagnosis failed to show improvement in mortality rate (30 days) in our study. This was somewhat in contrary to expectation. The lack of difference in mortality rates might be due to (1) the small sample size in our study which limited the reliability of the conclusion; and (2) relatively more patients in the delayed diagnosis group who arrived in the stage of compensation and were stable enough to withstand the delay in diagnosis and surgical repair. There were some limitations in our study. Firstly, the retrospective nature of this study resulted in potential bias during data collection. Secondly, it was an observational study to include only those alive on arrival at AED over a 7 year period. Not all ruptured AAA cases might have been identified. Some patients who died in the emergency room before ruptured AAA was diagnosed might have no autopsy done. Thirdly,

8 Chu/Ruptured abdominal aortic aneurysm 125 our study included only a small number of ruptured AAA case recruiting from patients living in the West Kowloon and Wong Tai Sin areas of Hong Kong. Selection bias might have occurred. Conclusion Emergency physicians should familiarise themselves with the clinical presentations and management of ruptured AAA. A high index of suspicion and prompt recognition of the condition is of paramount importance. Emergency ultrasound performed in the AED helps in the early detection of AAA. For ruptured AAA or symptomatic AAA patients diagnosed in the AED, the mean transfer time to operating theatre was 40.8 hours earlier than the delayed diagnosis group. Patients in the former group were 3.7 times more likely to proceed to repair surgery. Beneficial effect of early diagnosis was demonstrated in this small observational study. Larger scale research would be useful to study the role of emergency physicians in the management of ruptured AAA. Acknowledgement The author would like to thank Dr. Tung Wai Kit (Chiefof-service, Accident and Emergency Department, Kwong Wah Hospital); Dr. Lo Chor Man (Consultant, Accident and Emergency Department, Kwong Wah Hospital); Dr. Hui Pak Kwan (Consultant-in-charge, Department of Pathology, Kwong Wah Hospital) and Dr. Alice Chan Htain Ngot (Associate consultant, Department of Pathology, Kwong Wah Hospital) for their invaluable advice and support in conducting the study. The author would also like to thank Mr. Chan Ming Fat, mortuary officer of Kwong Wah Hospital for assisting in data collection. References 1. Thomas PR, Steward RD. Abdominal aortic aneurysm. Br J Surg 1988;75(8): Budd JS, Finch DR, Carter PG. A study of the mortality from ruptured abdominal aortic aneurysms in a district community. Eur J Vasc Surg 1989;3(4): Lloyd GM, Bown MJ, Norwood MG, Deb R, Fishwick G, Bell PR, et al. Feasibility of preoperative computer tomography in patients with ruptured abdominal aortic aneurysm: a time-to-death study in patients without operation. J Vasc Surg 2004;39(4): Marston WA, Ahlquist R, Johnson G, Meyer AA. Misdiagnosis of ruptured abdominal aortic aneurysms. J Vasc Surg 1992;16(1): Dent B, Kendall RJ, Boyle AA, Atkinson PR. Emergency ultrasound of the abdominal aorta by UK emergency physicians: a prospective cohort study. Emerg Med J 2007;24(8): Khan N, Razzak JA, Sharif H, Qazi SH. Non-traumatic aortic emergencies--experience from a tertiary care centre in Karachi, Pakistan. J Pak Med Assoc 2005;55 (1): Vaidyanathan S, Wadhawan H, Welch P, El-Salamani M. Ruptured abdominal aortic aneurysm masquerading as isolated hip pain: an unusual presentation. CJEM 2008;10(3): Bickerstaff LK, Hollier LH, Van Peenen HJ, Melton LJ 3rd, Pairolero PC, Cherry KJ. Abdominal aortic aneurysms: the changing natural history. J Vasc Surg 1984;1(1): Cheng SW, Ting AC, Tsang SH. Epidemiology and outcome of aortic aneurysms in Hong Kong. World J Surg 2003;27(2): Bown MJ, Sutton AJ, Bell PR, Sayers RD. A metaanalysis of 50 years of ruptured abdominal aortic aneurysm repair. Br J Surg 2002;89(6): Tayal VS, Graf CD, Gibbs MA. Prospective study of accuracy and outcome of emergency ultrasound for abdominal aortic aneurysm over two years. Acad Emerg Med 2003;10(8): Shuman WP, Hastrup W Jr, Kohler TR, Nyberg DA, Wang KY, Vincent LM, et al. Suspected leaking abdominal aortic aneurysm: use of sonography in the emergency room. Radiology 1988;168(1): Kamin RA, Nowicki TA, Courtney DS, Powers RD. Pearls and pitfalls in the emergency department evaluation of abdominal pain. Emerg Med Clin North Am 2003;21(1):61-72, vi.