Pediatr Surg Int DOI 10.1007/s00383-015-3669-0
ORIGINAL ARTICLE
Diagnostic imaging for acute appendicitis: interfacility differences in practice patterns Maria Michailidou • Maria G. Sacco Casamassima Omar Karim • Colin Gause • Jose H. Salazar • Seth D. Goldstein • Fizan Abdullah
•
Accepted: 20 January 2015 Ó Springer-Verlag Berlin Heidelberg 2015
Abstract Purpose To evaluate trends and factors associated with interfacility differences in imaging modality selection in the diagnosis and management of children with suspected acute appendicitis. Methods We conducted a retrospective review of diagnostic imaging selection and outcomes in patients\20 years of age who underwent appendectomy at a single Children’s Hospital from June 2008 to June 2013. These results were then compared with those of referring hospitals. Results A total of 232 children underwent appendectomy during the study period. Imaging results contributed to diagnostic and management decisions in 95.3 % of cases. CT scan was utilized as first-line imaging in 50 % of cases. CTs were preferentially performed at referring institutions (78 vs. 46 %, p \ 0.001). Children were five times more likely to undergo CT at referring institutions (OR = 5.5, CI 3.0–10.2). Adjusting for demographics and Alvarado score, diagnostic imaging choice was independent of patient’s clinical status. Conclusion This study demonstrates that initial presentation to a referring hospital independently predicts the use of CT scan for suspected acute appendicitis. Further efforts should be undertaken to develop a clinical pathway that minimizes radiation exposure in the diagnosis of acute
M. Michailidou M. G. Sacco Casamassima O. Karim C. Gause J. H. Salazar S. D. Goldstein F. Abdullah Division of Pediatric Surgery, Center for Pediatric Surgical Clinical Trials and Outcomes Research, Johns Hopkins University School of Medicine, Baltimore, MD, USA F. Abdullah (&) Bloomberg Children’s Center, Johns Hopkins University School of Medicine, # 7351, Baltimore, MD 21287, USA e-mail: [email protected]
appendicitis, with focus on access to pediatric abdominal ultrasound. Keywords Appendicitis Ultrasonography Computed tomography Imaging choice Pediatric
Introduction Acute appendicitis is the most common surgical emergency in children, affecting over 70,000 children in the United States annually, one-third of which are under 18 years of age [1, 2]. The signs and symptoms of acute appendicitis are similar to those of other causes of acute abdominal pain, posing a diagnostic challenge for physicians. Accordingly, missed appendicitis is one of the most common reasons for formal practice claims against emergency physicians [3]. Given this challenge, in the last two decades there has been an increasing trend toward utilization of advanced diagnostic imaging [4–6]. Computed tomography (CT), due to its high sensitivity and specificity, has become the preferred imaging modality for pediatric patients who present with acute abdominal pain in the emergency department (ED) [7, 8]. However, given the increasing concerns regarding the long-term consequences of radiation exposure in children [9–11], protocols have been developed by pediatric centers that focus on limiting the use of CT scan, and instead encourage the use of ultrasound (US) as an alternative imaging modality in patients with suspicion of acute appendicitis [12–15]. Although there is an increasing awareness of the risks related to radiation exposure in children, there remains considerable variability in imaging utilization in the diagnosis of this common condition. CT scan remains the most common imaging modality employed in the diagnosis of
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acute appendicitis, particularly in non-pediatric community hospitals, where a large proportion of children are cared for [5, 6, 16]. We sought to compare the diagnostic imaging utilization for suspected acute appendicitis in our Children’s Center with that of referring institutions.
analysis to adjust for the severity of clinical presentation. In patients who presented from an outside hospital, the calculation was based on findings at the time of their initial evaluation at the referring hospital. A p value less than 0.05 was considered statistically significant. All calculations were performed using STATA version 12.1 (Stata Corp LP, TX, USA).
Materials and methods After institutional review board approval, a retrospective review was conducted on all patients under the age of 20 years who underwent appendectomy from June 2008 to June 2013 in the Johns Hopkins Children’s Center (JHCC). Children who underwent incidental appendectomy were excluded from the analysis. Demographics, clinical symptoms, imaging upon initial presentation, pathology results, and hospital length of stay were retrieved from electronic chart review. Patients were grouped according to hospital type of initial presentation (JHCC or RHs), and clinical evaluation for suspected acute appendicitis. Imaging modality utilization was compared between our tertiary children center (JHCC) and non-pediatric RHs. Choice of imaging modality was typically at the discretion of the emergency physicians both in our emergency department (ED) and the RH. Patients who initially underwent an US read as indeterminate for appendicitis either underwent CT scan of the abdomen and pelvis with oral and intravenous contrast or were admitted to the General Pediatric Surgery service for serial abdominal exams. Based upon the terminology used within the US or CT reports, imaging results were coded as ‘‘appendicitis’’ (appendix seen and abnormal), ‘‘inconclusive’’ (finding worrisome for, but not definitely diagnostic for appendicitis), ‘‘appendix not visualized’’ (no secondary findings, but appendix not seen), or ‘‘normal’’ (normal appendix seen). For measurement of the performance of a binary classification test, these four categories were collapsed in two in accordance with prior studies [15, 17–20]. Thus, imaging studies with indeterminate imaging results or those in which the appendix was not visualized were considered to have a negative study for appendicitis. Sensitivities and specificities of the imaging studies were calculated based on final pathology results. Univariate analysis, utilizing t test and Chi squared goodness of fit was performed to compare demographics and imaging utilization between JHCC and RHs. Multivariate logistic regression was performed to calculate the odds ratio (OR) of undergoing each particular imaging study based on the location of initial presentation. The Alvarado score is an established clinical scoring system for acute appendicitis which has been validated in pediatric population [21–23]. This score was retrospectively calculated from electronic charts and used in multivariate
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Results A total of 245 children with suspected acute appendicitis were evaluated by pediatric surgeons at the Johns Hopkins ED and underwent appendectomy during the study period. Thirteen patients (5.3 %) were excluded due to incomplete records. The remaining 232 patients met inclusion criteria and were included in the analysis. The majority of children presented from a RH (n = 133, 57.3 %). Patients from a RH were younger than patients directly evaluated at our institution (mean age 9.01 ± 3.7 vs. 10.6 ± 4.4 vs. p = 0.004). There were no significant differences in gender or severity of clinical presentation. The Alvarado score was C7 in 74.8 % in patients evaluated at JHCC and 76.7 % of patients transferred from RH (p = 0.73) (Table 1). The diagnosis of acute appendicitis was based only on physical examination and laboratory tests in eleven cases, (4.7 %), while diagnostic imaging was performed in the majority of cases (n = 221, 95.3 %). A total of 151 CT scans and 105 US were performed to confirm or rule out acute appendicitis. CT scan alone was performed in 50 % (n = 116) of cases of suspected appendicitis, US alone was utilized in 30.2 % (n = 70) of cases, and both imaging modalities were used in 15.1 % (n = 35) (Fig. 1). The majority of CT scans confirmed acute appendicitis (n = 138, 91.4 %), with nine indeterminate scans (6 %) and four scans showing a normal appendix (2.6 %). Similarly, the majority of ultrasound evaluations, (n = 65, 61.9 %) confirmed acute appendicitis, while 32.4 % (n = 34) were unable to identify the appendix and the remainder showed a normal appendix (n = 6, 5.7 %). CT scan was the first-line imaging study for the majority of referred patients (n = 91, 68.4 %). At JHCC, however, the use of US was favored as the initial imaging modality (n = 64, 64.7 %). After controlling for age, gender and Alvarado score, children who initially presented at a RH had significantly higher chances of getting a CT scan compared to those evaluated at our home institution (OR 5.5, 95 % CI 2.96–10.23; P \ 0.001) and less chances of getting an US (OR = 0.23, 95 % CI 0.14–0.40; P \ 0.01) (Table 2). Following surgical evaluation, 217 patients underwent immediate appendectomy. The remaining 15 patients, all of whom had confirmed perforated appendicitis, were placed
Pediatr Surg Int Table 1 Patient characteristics, imaging utilization and outcomes for direct versus outside admissions
Variable
Children’s Center (n = 99)
Referring hospitals (n = 133)
2–4
8 (8.1)
15 (11.3)
5–9
34 (35.3)
64 (48.1)
Age category (years), n (%)
0.04
10–18
57 (57.6)
54 (40.6)
Female, n (%)
40 (40.4)
65 (48.9)
0.2
Alvarado score C7, n (%)
74 (74.8)
102 (76.7)
0.73
25 (25.3)
91 (68.4)
\0.001
Imaging CT scan, n (%)
SD standard deviation, OR odds ratio, CI confidence interval
US, n (%)
44 (44.4)
26 (19.6)
CT and US, n (%)
20 (20.2)
15 (11.3)
No imaging, n (%) Perforated appendicitis, n (%)
10 (10.1) 34 (34.4)
1 (0.7) 56 (42.1)
0.23
Negative appendectomy, n (%)
3 (3.0)
3 (2.3)
0.71
Hospital length of stay, days, mean ± SD
3.1 ± 3.8
3.1 ± 3.7
0.95
negative appendectomy rate was 2.5 % (n = 6), all of whom had received a preoperative CT scan. After comparing imaging results to pathology reports, the sensitivity and specificity of the CT scan and the US, when used as first modality imaging, were 98.2 and 80 % for CT and 62.5 and 100 % for US. When CT scan was ordered for an equivocal US finding, the sensitivity and specificity was 85.3 and 100 %, respectively. Overall, there was a downward trend in CT utilization during the study period. The percentage of patients who underwent CT scan was 11 % in 2008 and 50 % in 2013. This change in the diagnostic imaging utilization was more consistent at our institution where the percentage of CT as a first-line imaging modality decreased from 50 % in 2008 to 0 % in 2013 (Fig. 2a, b).
Fig. 1 Imaging type for acute appendicitis for direct versus outside admissions for the period 2008–2013. RH Referring Hospital, JHCC Johns Hopkins Children’s Center
on antibiotics and underwent interval appendectomy during a subsequent admission. Two of these patients underwent drainage of pelvic abscesses by interventional radiology at the time of presentation. Appendicitis was pathologically confirmed in 97.0 % (n = 225) of cases. Perforated appendicitis was found in 38.8 % (n = 90) of cases. One case revealed a carcinoid tumor of the appendix. The overall Table 2 Multivariate logistic regression analysis for the use of CT scan or US for the diagnosis of acute appendicitis
P value
Imaging upon presentation
Discussion This study describes the differences in diagnostic imaging utilization between a tertiary Children’s Center (JHCC) CT OR
US 95 % CI
P value
OR
95 % CI
P value
0.32–2.84 0.38–3.3
0.94 0.83
1.31 1.10
0.49–3.56 0.41–2.99
0.59 0.84
Age category 2–4
Ref.
5–9 10–18
0.96 1.13
Female gender
1.79
0.97–3.32
0.06
1.02
0.56–1.71
0.94
Alvarado score
0.76
0.63–0.93
0.006
1.12
0.94–1.33
0.19
\0.001
0.23
0.14–0.40
\0.001
Hospital type OR odds ratio, CI confidence interval
Children’s
Ref.
Referring
5.5
2.96–10.23
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Pediatr Surg Int Fig. 2 a Trends of imaging type for acute appendicitis at JHCC. b Trends of imaging type for acute appendicitis at RH. RH referring Hospital, JHCC Johns Hopkins Children’s Center
and associated referring hospitals. We found a decreased use of CT scan in the diagnosis of acute appendicitis when compared to referring institutions, where CT imaging predominates. Traditionally, a false-negative rate of up to 15 % has been accepted in surgical practice as an appropriate benchmark, owing to the difficulty in diagnosis of appendicitis and the consequences associated with a missed or delayed diagnosis [24, 25]. The actual false-negative rate has since decreased in modern practice owing to an associated increase in diagnostic imaging [26, 27]. CT scan contributes to the majority of this change, the use of which has decreased the rate of negative appendectomy to under 3 % in pediatric patients [26, 27]. In this study we find a similar inverse association between diagnostic imaging utilization and lower negative appendectomy rate. This advantage, however, should be balanced with the potential risk of radiation exposure [28]. This study confirms that advanced diagnostic imaging is routinely used in the ED for the diagnosis of acute appendicitis. In this series, the decision to proceed with appendectomy was based on clinical findings alone in only 4.7 % of cases. This indicates that preoperative imaging was ordered in many cases, regardless of whether the clinical presentation was typical or equivocal. Although we were not able to fully elucidate the reason for this finding, one possible explanation is that in selected cases of perforated appendicitis, an alternative therapeutic strategy was used rather than immediate appendectomy. Percutaneous abscess drainage and antibiotic therapy, followed by interval appendectomy, has been proven to be a valid
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alternative therapeutic approach [29], and was successfully adopted in 6.5 % of cases in this series. As an academic Children’s Center, transfers are often accepted from RHs for patients with suspected acute appendicitis. These patients typically arrive to JHCC with a diagnosis confirmed by imaging. Over half of the patients in this series underwent initial evaluation at a RH, and the majority underwent CT scan prior to transfer. Factors associated with choice of imaging modality have been previously investigated [16, 30]. Higher BMI, older age, female gender, white race, weekend admission, and initial evaluation in a non-pediatric community hospital have been identified as significant factors associated with an increased use of CT in the evaluation of suspected acute appendicitis in pediatric population [1, 16, 30]. In contrast with these studies, the factor most associated with CT scan usage in our cohort of patients was the presenting center at which the initial evaluation took place. Several factors may explain differences in patterns of imaging utilization between our institution and RHs. At our institution, a distinct effort has been made to improve communication between emergency physicians, pediatric radiologists, and pediatric surgeons, as well as providing 24 hour access to ultrasonography. This interdisciplinary approach favors the use of US as first-line imaging. Numerous factors likely contribute to the use of CT scan at RHs, including a lack of shared protocols between pediatric tertiary centers and non-pediatric facilities, resource disparity, the need for an established diagnosis to justify transfer, and the low diagnostic performance of the US.
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It is known that patient-related factors, such as age, body habitus, presence of abundant bowel gas and an anomalous appendiceal location can affect the sensitivity of the US. Additionally, diagnosis can be difficult in early appendicitis, when sonographic signs are blurred, and in late appendicitis, when perforation has occurred and the appendix is decompressed or obliterated. Finally, the likelihood of achieving a correct diagnosis varies considerably with both the skill and diligence of the sonographer and the supervising radiologist [19]. During the transition phase to the use of US as first-line imaging, the sensitivity of US at JHCC was somewhat lower (62.5 %) than those reported by other studies [8]. Despite this, however, timely involvement of the pediatric surgeon in the decision-making process reduced the number of unnecessary CT orders without affecting outcomes. The imaging pathway of US followed by CT in equivocal cases has been proven to be the most cost-effective strategy to reduce misdiagnosis [31]. With the use of this pathway at our institution, the rate of negative appendectomy was 2.6 %.Some authors argue that this imaging pathway may lead to unnecessary delay in definitive management of acute appendicitis [32, 33], as a delay from triage to operation in patients who are shunted into this pathway may theoretically result in an increased risk of perforation. The rate of perforation in our series was 38.8 %. Though we do not have data regarding the interval between ED visit and appendectomy, we did not find differences in perforation rate between non-imaged patients and imaged patients. Although the risk of perforation progressively increases with each additional interval day between admission and appendectomy [34], it is understood that appendectomy is an urgent rather than an emergent procedure. Thus, it is unlikely that a delay of a few hours in the definitive management to arrive at a proper diagnosis makes a meaningful difference in outcomes. As an alternative to imaging, several clinical scoring systems, including the Alvarado and the Pediatric appendicitis score (PAS), have been proposed to assist physicians in the diagnosis of acute appendicitis [35, 36]. However, the accuracy of these systems has not been shown to be superior to clinical judgment alone [21, 37–39], and prospective validation studies have failed to reproduce the accuracy shown in the derivation setting [37, 39]. Neither score was sufficient as a stand-alone to establish a diagnosis of appendicitis; however, the accuracy of risk stratification increases when included in a clinical pathway combining a clinical grading score and selective use of US [38]. Recent investigations have demonstrated that MRI has higher sensitivity and specificity compared to CT in the diagnosis of acute appendicitis [40, 41]. MRI is currently the imaging modality of choice for the evaluation of pregnant patients [42]. Higher cost, limited availability,
increased acquisition time, and the need for sedation to reduce motion artifacts have been major deterrents to its use in pediatric patients with acute abdominal pain. Technological developments have made ultrafast sequences possible, permitting the use of MRI in an emergent setting. In the setting in which this ultrafast-MRI is available, an algorithm including US followed by MRI is feasible, with comparable accuracy to that of US followed by CT scan [41]. The ultrafast-MRI may be performed without sedation and is easily tolerated by children as young as 4 years of age [41, 43]. An algorithm of US followed by MRI might thus be the best imaging means of reducing misdiagnosis and radiation exposure in children. The lack of availability of MRI represents the main limitation of the applicability of this protocol. Therefore, the risk-benefit curve may be markedly different if the US performed in a RH is inconclusive and MRI is unavailable. In these cases, it would be reasonable to transfer patients with inconclusive laboratory tests and US findings to a pediatric center for further evaluation. Limitations of this study include the retrospective nature of the data extraction and the sole inclusion of patients who underwent appendectomy. By including patients with suspicion of appendicitis who did not undergo appendectomy, we would be better able to report overall CT scan and US use. However, because this is a retrospective study, including all patients evaluated in ED for the chief complaint of abdominal pain could introduce other potential bias as patients with missed appendicitis or those who sought care elsewhere after discharge could not be tracked. In addition, we provide the results of a single institution analysis, which responds to a particular geographical and hospital referral pattern. Therefore, the generalizability of the results is limited, as other regions may have different practice patterns. The study design presents a theoretical potential limitation in that the referred patients may be considered a distinct subset not equivalent to the patients initially evaluated at JHCC. As data regarding the total number of patients screened at RH were not available, whether community physicians routinely or selectively obtain imaging before inter facility transfer for operative care cannot be determined from this study. Although we are unable to identify the specific reasons for which patients were transferred to our institution, we do not believe that this group of patients represents a selected subgroup of patients. Patients included in this series were only those who underwent appendectomy, and there were no differences between those directly admitted at our ED and those transferred from RH in terms of severity of disease. Therefore, we believe it is unlikely that patients who underwent operation at RH were only cases which required less extensive diagnostic work-up or were less complicated
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cases. We thus believe that the inclusion criteria correct for potential confounding biases. This study describes differences in diagnostic imaging utilization, and in particular, decreased use of CT scans in the diagnosis of acute appendicitis between a tertiary Children’s Center when compared to referring institutions. In non-pediatric dedicated facilities, CT remains the most common imaging study in the diagnosis of acute appendicitis, likely due to technician or radiologic availability and inexperience, and low confidence in US as a diagnostic modality. Improvements in the diagnosis of children with suspected acute appendicitis should include the development of cost-effective diagnostic pathways which limit unnecessary radiation exposure and ensure safe and high quality care. A collaborative multidisciplinary effort of all physicians involved in pediatric care is necessary to ensure that imaging is appropriately ordered, in accordance with the ALARA principle.US as first-line imaging is a valuable tool; however, further efforts should be made to improve its accuracy and avoid a high rate of inconclusive diagnoses. The pathway of US and potential subsequent MRI seems a promising and cost-effective strategy. Conflict of interest The authors declare that they have no conflicts of interest.
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10. Brenner DJ, Hall EJ (2007) Computed tomography–an increasing source of radiation exposure. N Engl J Med 357:2277–2284 11. Pearce MS, Salotti JA, Little MP et al (2012) Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. Lancet 380:499–505 12. Pena BM, Taylor GA, Fishman SJ et al (2002) Effect of an imaging protocol on clinical outcomes among pediatric patients with appendicitis. Pediatrics 110:1088–1093 13. Rezak A, Abbas HM, Ajemian MS et al (2011) Decreased use of computed tomography with a modified clinical scoring system in diagnosis of pediatric acute appendicitis. Arch Surg 146:64–67 14. Adibe OO, Amin SR, Hansen EN et al (2011) An evidence-based clinical protocol for diagnosis of acute appendicitis decreased the use of computed tomography in children. J Pediatr Surg 46:192–196 15. Thirumoorthi AS, Fefferman NR, Ginsburg HB et al (2012) Managing radiation exposure in children–reexamining the role of ultrasound in the diagnosis of appendicitis. J Pediatr Surg 47:2268–2272 16. Raval MV, Deans KJ, Rangel SJ et al (2012) Factors associated with imaging modality choice in children with appendicitis. J Surg Res 177:131–136 17. Ang A (2001) Chong NK, Daneman A: pediatric appendicitis in ‘‘real-time’’: the value of sonography in diagnosis and treatment. Pediatr Emerg Care 17:334–340 18. Jaremko JL, Crockett A, Rucker D et al (2011) Incidence and significance of inconclusive results in ultrasound for appendicitis in children and teenagers. Can Assoc Radiol J 62:197–202 19. Strouse PJ (2010) Pediatric appendicitis: an argument for US. Radiology 255:8–13 20. Wiersma F, Toorenvliet BR, Bloem JL et al (2009) US examination of the appendix in children with suspected appendicitis: the additional value of secondary signs. Eur Radiol 19:455–461 21. Escriba A, Gamell AM, Fernandez Y et al (2011) Prospective validation of two systems of classification for the diagnosis of acute appendicitis. Pediatr Emerg Care 27:165–169 22. Macklin CP, Radcliffe GS, Merei JM et al (1997) A prospective evaluation of the modified Alvarado score for acute appendicitis in children. Ann R Coll Surg Engl 79:203–205 23. Kulik DM, Uleryk EM, Maguire JL (2013) Does this child have appendicitis? A systematic review of clinical prediction rules for children with acute abdominal pain. J Clin Epidemiol 66:95–104 24. Acheson J (2010) Blindness in neurological disease: a short overview of new therapies from translational research. Curr Opin Neurol 23:1–3 25. Kaiser S, Jorulf H, Soderman E et al (2004) Impact of radiologic imaging on the surgical decision-making process in suspected appendicitis in children. Acad Radiol 11:971–979 26. Newman K, Ponsky T, Kittle K et al (2003) Appendicitis 2000: variability in practice, outcomes, and resource utilization at thirty pediatric hospitals. J Pediatr Surg 38:372–379 (discussion 372–379) 27. Applegate KE, Sivit CJ, Salvator AE et al (2001) Effect of crosssectional imaging on negative appendectomy and perforation rates in children. Radiology 220:103–107 28. Hall EJ, Brenner DJ (2008) Cancer risks from diagnostic radiology. Br J Radiol 81:362–378 29. Knott EM, Thomas P, Sharp NE et al (2013) Reduced use of computed tomography in patients treated with interval appendectomy after implementing a protocol from a prospective, randomized trial. Pediatr Surg Int 29:1293–1296 30. Saito JM, Yan Y, Evashwick TW et al (2013) Use and accuracy of diagnostic imaging by hospital type in pediatric appendicitis. Pediatrics 131:e37–e44
Pediatr Surg Int 31. Krishnamoorthi R, Ramarajan N, Wang NE et al (2011) Effectiveness of a staged US and CT protocol for the diagnosis of pediatric appendicitis: reducing radiation exposure in the age of ALARA. Radiology 259:231–239 32. York D, Smith A, Phillips JD et al (2005) The influence of advanced radiographic imaging on the treatment of pediatric appendicitis. J Pediatr Surg 40:1908–1911 33. Poonai N, Gregory J, Thompson G et al (2014) Is pelvic ultrasound associated with an increased time to appendectomy in pediatric appendicitis? J Emerg Med 47:51–58 34. Papandria D, Goldstein SD, Rhee D et al (2013) Risk of perforation increases with delay in recognition and surgery for acute appendicitis. J Surg Res 184:723–729 35. Alvarado A (1986) A practical score for the early diagnosis of acute appendicitis. Ann Emerg Med 15:557–564 36. Samuel M (2002) Pediatric appendicitis score. J Pediatr Surg 37:877–881 37. Schneider C, Kharbanda A, Bachur R (2007) Evaluating appendicitis scoring systems using a prospective pediatric cohort. Ann Emerg Med 49:778–784, 784.e1
38. Saucier A, Huang EY, Emeremni CA et al (2014) Prospective evaluation of a clinical pathway for suspected appendicitis. Pediatrics 133:e88–e95 39. Bhatt M, Joseph L, Ducharme FM et al (2009) Prospective validation of the pediatric appendicitis score in a Canadian pediatric emergency department. Acad Emerg Med 16:591–596 40. Aspelund G, Fingeret A, Gross E et al (2014) Ultrasonography/MRI versus CT for diagnosing appendicitis. Pediatrics 133:586–593 41. Moore MM, Gustas CN, Choudhary AK et al (2012) MRI for clinically suspected pediatric appendicitis: an implemented program. Pediatr Radiol 42:1056–1063 42. Tkacz JN, Anderson SA, Soto J (2009) MR imaging in gastrointestinal emergencies. Radiographics 29:1767–1780 43. Johnson AK, Filippi CG, Andrews T et al (2012) Ultrafast 3-T MRI in the evaluation of children with acute lower abdominal pain for the detection of appendicitis. Am J Roentgenol 198:1424–1430
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ORIGINAL ARTICLE
Diagnostic imaging for acute appendicitis: interfacility differences in practice patterns Maria Michailidou • Maria G. Sacco Casamassima Omar Karim • Colin Gause • Jose H. Salazar • Seth D. Goldstein • Fizan Abdullah
•
Accepted: 20 January 2015 Ó Springer-Verlag Berlin Heidelberg 2015
Abstract Purpose To evaluate trends and factors associated with interfacility differences in imaging modality selection in the diagnosis and management of children with suspected acute appendicitis. Methods We conducted a retrospective review of diagnostic imaging selection and outcomes in patients\20 years of age who underwent appendectomy at a single Children’s Hospital from June 2008 to June 2013. These results were then compared with those of referring hospitals. Results A total of 232 children underwent appendectomy during the study period. Imaging results contributed to diagnostic and management decisions in 95.3 % of cases. CT scan was utilized as first-line imaging in 50 % of cases. CTs were preferentially performed at referring institutions (78 vs. 46 %, p \ 0.001). Children were five times more likely to undergo CT at referring institutions (OR = 5.5, CI 3.0–10.2). Adjusting for demographics and Alvarado score, diagnostic imaging choice was independent of patient’s clinical status. Conclusion This study demonstrates that initial presentation to a referring hospital independently predicts the use of CT scan for suspected acute appendicitis. Further efforts should be undertaken to develop a clinical pathway that minimizes radiation exposure in the diagnosis of acute
M. Michailidou M. G. Sacco Casamassima O. Karim C. Gause J. H. Salazar S. D. Goldstein F. Abdullah Division of Pediatric Surgery, Center for Pediatric Surgical Clinical Trials and Outcomes Research, Johns Hopkins University School of Medicine, Baltimore, MD, USA F. Abdullah (&) Bloomberg Children’s Center, Johns Hopkins University School of Medicine, # 7351, Baltimore, MD 21287, USA e-mail: [email protected]
appendicitis, with focus on access to pediatric abdominal ultrasound. Keywords Appendicitis Ultrasonography Computed tomography Imaging choice Pediatric
Introduction Acute appendicitis is the most common surgical emergency in children, affecting over 70,000 children in the United States annually, one-third of which are under 18 years of age [1, 2]. The signs and symptoms of acute appendicitis are similar to those of other causes of acute abdominal pain, posing a diagnostic challenge for physicians. Accordingly, missed appendicitis is one of the most common reasons for formal practice claims against emergency physicians [3]. Given this challenge, in the last two decades there has been an increasing trend toward utilization of advanced diagnostic imaging [4–6]. Computed tomography (CT), due to its high sensitivity and specificity, has become the preferred imaging modality for pediatric patients who present with acute abdominal pain in the emergency department (ED) [7, 8]. However, given the increasing concerns regarding the long-term consequences of radiation exposure in children [9–11], protocols have been developed by pediatric centers that focus on limiting the use of CT scan, and instead encourage the use of ultrasound (US) as an alternative imaging modality in patients with suspicion of acute appendicitis [12–15]. Although there is an increasing awareness of the risks related to radiation exposure in children, there remains considerable variability in imaging utilization in the diagnosis of this common condition. CT scan remains the most common imaging modality employed in the diagnosis of
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acute appendicitis, particularly in non-pediatric community hospitals, where a large proportion of children are cared for [5, 6, 16]. We sought to compare the diagnostic imaging utilization for suspected acute appendicitis in our Children’s Center with that of referring institutions.
analysis to adjust for the severity of clinical presentation. In patients who presented from an outside hospital, the calculation was based on findings at the time of their initial evaluation at the referring hospital. A p value less than 0.05 was considered statistically significant. All calculations were performed using STATA version 12.1 (Stata Corp LP, TX, USA).
Materials and methods After institutional review board approval, a retrospective review was conducted on all patients under the age of 20 years who underwent appendectomy from June 2008 to June 2013 in the Johns Hopkins Children’s Center (JHCC). Children who underwent incidental appendectomy were excluded from the analysis. Demographics, clinical symptoms, imaging upon initial presentation, pathology results, and hospital length of stay were retrieved from electronic chart review. Patients were grouped according to hospital type of initial presentation (JHCC or RHs), and clinical evaluation for suspected acute appendicitis. Imaging modality utilization was compared between our tertiary children center (JHCC) and non-pediatric RHs. Choice of imaging modality was typically at the discretion of the emergency physicians both in our emergency department (ED) and the RH. Patients who initially underwent an US read as indeterminate for appendicitis either underwent CT scan of the abdomen and pelvis with oral and intravenous contrast or were admitted to the General Pediatric Surgery service for serial abdominal exams. Based upon the terminology used within the US or CT reports, imaging results were coded as ‘‘appendicitis’’ (appendix seen and abnormal), ‘‘inconclusive’’ (finding worrisome for, but not definitely diagnostic for appendicitis), ‘‘appendix not visualized’’ (no secondary findings, but appendix not seen), or ‘‘normal’’ (normal appendix seen). For measurement of the performance of a binary classification test, these four categories were collapsed in two in accordance with prior studies [15, 17–20]. Thus, imaging studies with indeterminate imaging results or those in which the appendix was not visualized were considered to have a negative study for appendicitis. Sensitivities and specificities of the imaging studies were calculated based on final pathology results. Univariate analysis, utilizing t test and Chi squared goodness of fit was performed to compare demographics and imaging utilization between JHCC and RHs. Multivariate logistic regression was performed to calculate the odds ratio (OR) of undergoing each particular imaging study based on the location of initial presentation. The Alvarado score is an established clinical scoring system for acute appendicitis which has been validated in pediatric population [21–23]. This score was retrospectively calculated from electronic charts and used in multivariate
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Results A total of 245 children with suspected acute appendicitis were evaluated by pediatric surgeons at the Johns Hopkins ED and underwent appendectomy during the study period. Thirteen patients (5.3 %) were excluded due to incomplete records. The remaining 232 patients met inclusion criteria and were included in the analysis. The majority of children presented from a RH (n = 133, 57.3 %). Patients from a RH were younger than patients directly evaluated at our institution (mean age 9.01 ± 3.7 vs. 10.6 ± 4.4 vs. p = 0.004). There were no significant differences in gender or severity of clinical presentation. The Alvarado score was C7 in 74.8 % in patients evaluated at JHCC and 76.7 % of patients transferred from RH (p = 0.73) (Table 1). The diagnosis of acute appendicitis was based only on physical examination and laboratory tests in eleven cases, (4.7 %), while diagnostic imaging was performed in the majority of cases (n = 221, 95.3 %). A total of 151 CT scans and 105 US were performed to confirm or rule out acute appendicitis. CT scan alone was performed in 50 % (n = 116) of cases of suspected appendicitis, US alone was utilized in 30.2 % (n = 70) of cases, and both imaging modalities were used in 15.1 % (n = 35) (Fig. 1). The majority of CT scans confirmed acute appendicitis (n = 138, 91.4 %), with nine indeterminate scans (6 %) and four scans showing a normal appendix (2.6 %). Similarly, the majority of ultrasound evaluations, (n = 65, 61.9 %) confirmed acute appendicitis, while 32.4 % (n = 34) were unable to identify the appendix and the remainder showed a normal appendix (n = 6, 5.7 %). CT scan was the first-line imaging study for the majority of referred patients (n = 91, 68.4 %). At JHCC, however, the use of US was favored as the initial imaging modality (n = 64, 64.7 %). After controlling for age, gender and Alvarado score, children who initially presented at a RH had significantly higher chances of getting a CT scan compared to those evaluated at our home institution (OR 5.5, 95 % CI 2.96–10.23; P \ 0.001) and less chances of getting an US (OR = 0.23, 95 % CI 0.14–0.40; P \ 0.01) (Table 2). Following surgical evaluation, 217 patients underwent immediate appendectomy. The remaining 15 patients, all of whom had confirmed perforated appendicitis, were placed
Pediatr Surg Int Table 1 Patient characteristics, imaging utilization and outcomes for direct versus outside admissions
Variable
Children’s Center (n = 99)
Referring hospitals (n = 133)
2–4
8 (8.1)
15 (11.3)
5–9
34 (35.3)
64 (48.1)
Age category (years), n (%)
0.04
10–18
57 (57.6)
54 (40.6)
Female, n (%)
40 (40.4)
65 (48.9)
0.2
Alvarado score C7, n (%)
74 (74.8)
102 (76.7)
0.73
25 (25.3)
91 (68.4)
\0.001
Imaging CT scan, n (%)
SD standard deviation, OR odds ratio, CI confidence interval
US, n (%)
44 (44.4)
26 (19.6)
CT and US, n (%)
20 (20.2)
15 (11.3)
No imaging, n (%) Perforated appendicitis, n (%)
10 (10.1) 34 (34.4)
1 (0.7) 56 (42.1)
0.23
Negative appendectomy, n (%)
3 (3.0)
3 (2.3)
0.71
Hospital length of stay, days, mean ± SD
3.1 ± 3.8
3.1 ± 3.7
0.95
negative appendectomy rate was 2.5 % (n = 6), all of whom had received a preoperative CT scan. After comparing imaging results to pathology reports, the sensitivity and specificity of the CT scan and the US, when used as first modality imaging, were 98.2 and 80 % for CT and 62.5 and 100 % for US. When CT scan was ordered for an equivocal US finding, the sensitivity and specificity was 85.3 and 100 %, respectively. Overall, there was a downward trend in CT utilization during the study period. The percentage of patients who underwent CT scan was 11 % in 2008 and 50 % in 2013. This change in the diagnostic imaging utilization was more consistent at our institution where the percentage of CT as a first-line imaging modality decreased from 50 % in 2008 to 0 % in 2013 (Fig. 2a, b).
Fig. 1 Imaging type for acute appendicitis for direct versus outside admissions for the period 2008–2013. RH Referring Hospital, JHCC Johns Hopkins Children’s Center
on antibiotics and underwent interval appendectomy during a subsequent admission. Two of these patients underwent drainage of pelvic abscesses by interventional radiology at the time of presentation. Appendicitis was pathologically confirmed in 97.0 % (n = 225) of cases. Perforated appendicitis was found in 38.8 % (n = 90) of cases. One case revealed a carcinoid tumor of the appendix. The overall Table 2 Multivariate logistic regression analysis for the use of CT scan or US for the diagnosis of acute appendicitis
P value
Imaging upon presentation
Discussion This study describes the differences in diagnostic imaging utilization between a tertiary Children’s Center (JHCC) CT OR
US 95 % CI
P value
OR
95 % CI
P value
0.32–2.84 0.38–3.3
0.94 0.83
1.31 1.10
0.49–3.56 0.41–2.99
0.59 0.84
Age category 2–4
Ref.
5–9 10–18
0.96 1.13
Female gender
1.79
0.97–3.32
0.06
1.02
0.56–1.71
0.94
Alvarado score
0.76
0.63–0.93
0.006
1.12
0.94–1.33
0.19
\0.001
0.23
0.14–0.40
\0.001
Hospital type OR odds ratio, CI confidence interval
Children’s
Ref.
Referring
5.5
2.96–10.23
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Pediatr Surg Int Fig. 2 a Trends of imaging type for acute appendicitis at JHCC. b Trends of imaging type for acute appendicitis at RH. RH referring Hospital, JHCC Johns Hopkins Children’s Center
and associated referring hospitals. We found a decreased use of CT scan in the diagnosis of acute appendicitis when compared to referring institutions, where CT imaging predominates. Traditionally, a false-negative rate of up to 15 % has been accepted in surgical practice as an appropriate benchmark, owing to the difficulty in diagnosis of appendicitis and the consequences associated with a missed or delayed diagnosis [24, 25]. The actual false-negative rate has since decreased in modern practice owing to an associated increase in diagnostic imaging [26, 27]. CT scan contributes to the majority of this change, the use of which has decreased the rate of negative appendectomy to under 3 % in pediatric patients [26, 27]. In this study we find a similar inverse association between diagnostic imaging utilization and lower negative appendectomy rate. This advantage, however, should be balanced with the potential risk of radiation exposure [28]. This study confirms that advanced diagnostic imaging is routinely used in the ED for the diagnosis of acute appendicitis. In this series, the decision to proceed with appendectomy was based on clinical findings alone in only 4.7 % of cases. This indicates that preoperative imaging was ordered in many cases, regardless of whether the clinical presentation was typical or equivocal. Although we were not able to fully elucidate the reason for this finding, one possible explanation is that in selected cases of perforated appendicitis, an alternative therapeutic strategy was used rather than immediate appendectomy. Percutaneous abscess drainage and antibiotic therapy, followed by interval appendectomy, has been proven to be a valid
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alternative therapeutic approach [29], and was successfully adopted in 6.5 % of cases in this series. As an academic Children’s Center, transfers are often accepted from RHs for patients with suspected acute appendicitis. These patients typically arrive to JHCC with a diagnosis confirmed by imaging. Over half of the patients in this series underwent initial evaluation at a RH, and the majority underwent CT scan prior to transfer. Factors associated with choice of imaging modality have been previously investigated [16, 30]. Higher BMI, older age, female gender, white race, weekend admission, and initial evaluation in a non-pediatric community hospital have been identified as significant factors associated with an increased use of CT in the evaluation of suspected acute appendicitis in pediatric population [1, 16, 30]. In contrast with these studies, the factor most associated with CT scan usage in our cohort of patients was the presenting center at which the initial evaluation took place. Several factors may explain differences in patterns of imaging utilization between our institution and RHs. At our institution, a distinct effort has been made to improve communication between emergency physicians, pediatric radiologists, and pediatric surgeons, as well as providing 24 hour access to ultrasonography. This interdisciplinary approach favors the use of US as first-line imaging. Numerous factors likely contribute to the use of CT scan at RHs, including a lack of shared protocols between pediatric tertiary centers and non-pediatric facilities, resource disparity, the need for an established diagnosis to justify transfer, and the low diagnostic performance of the US.
Pediatr Surg Int
It is known that patient-related factors, such as age, body habitus, presence of abundant bowel gas and an anomalous appendiceal location can affect the sensitivity of the US. Additionally, diagnosis can be difficult in early appendicitis, when sonographic signs are blurred, and in late appendicitis, when perforation has occurred and the appendix is decompressed or obliterated. Finally, the likelihood of achieving a correct diagnosis varies considerably with both the skill and diligence of the sonographer and the supervising radiologist [19]. During the transition phase to the use of US as first-line imaging, the sensitivity of US at JHCC was somewhat lower (62.5 %) than those reported by other studies [8]. Despite this, however, timely involvement of the pediatric surgeon in the decision-making process reduced the number of unnecessary CT orders without affecting outcomes. The imaging pathway of US followed by CT in equivocal cases has been proven to be the most cost-effective strategy to reduce misdiagnosis [31]. With the use of this pathway at our institution, the rate of negative appendectomy was 2.6 %.Some authors argue that this imaging pathway may lead to unnecessary delay in definitive management of acute appendicitis [32, 33], as a delay from triage to operation in patients who are shunted into this pathway may theoretically result in an increased risk of perforation. The rate of perforation in our series was 38.8 %. Though we do not have data regarding the interval between ED visit and appendectomy, we did not find differences in perforation rate between non-imaged patients and imaged patients. Although the risk of perforation progressively increases with each additional interval day between admission and appendectomy [34], it is understood that appendectomy is an urgent rather than an emergent procedure. Thus, it is unlikely that a delay of a few hours in the definitive management to arrive at a proper diagnosis makes a meaningful difference in outcomes. As an alternative to imaging, several clinical scoring systems, including the Alvarado and the Pediatric appendicitis score (PAS), have been proposed to assist physicians in the diagnosis of acute appendicitis [35, 36]. However, the accuracy of these systems has not been shown to be superior to clinical judgment alone [21, 37–39], and prospective validation studies have failed to reproduce the accuracy shown in the derivation setting [37, 39]. Neither score was sufficient as a stand-alone to establish a diagnosis of appendicitis; however, the accuracy of risk stratification increases when included in a clinical pathway combining a clinical grading score and selective use of US [38]. Recent investigations have demonstrated that MRI has higher sensitivity and specificity compared to CT in the diagnosis of acute appendicitis [40, 41]. MRI is currently the imaging modality of choice for the evaluation of pregnant patients [42]. Higher cost, limited availability,
increased acquisition time, and the need for sedation to reduce motion artifacts have been major deterrents to its use in pediatric patients with acute abdominal pain. Technological developments have made ultrafast sequences possible, permitting the use of MRI in an emergent setting. In the setting in which this ultrafast-MRI is available, an algorithm including US followed by MRI is feasible, with comparable accuracy to that of US followed by CT scan [41]. The ultrafast-MRI may be performed without sedation and is easily tolerated by children as young as 4 years of age [41, 43]. An algorithm of US followed by MRI might thus be the best imaging means of reducing misdiagnosis and radiation exposure in children. The lack of availability of MRI represents the main limitation of the applicability of this protocol. Therefore, the risk-benefit curve may be markedly different if the US performed in a RH is inconclusive and MRI is unavailable. In these cases, it would be reasonable to transfer patients with inconclusive laboratory tests and US findings to a pediatric center for further evaluation. Limitations of this study include the retrospective nature of the data extraction and the sole inclusion of patients who underwent appendectomy. By including patients with suspicion of appendicitis who did not undergo appendectomy, we would be better able to report overall CT scan and US use. However, because this is a retrospective study, including all patients evaluated in ED for the chief complaint of abdominal pain could introduce other potential bias as patients with missed appendicitis or those who sought care elsewhere after discharge could not be tracked. In addition, we provide the results of a single institution analysis, which responds to a particular geographical and hospital referral pattern. Therefore, the generalizability of the results is limited, as other regions may have different practice patterns. The study design presents a theoretical potential limitation in that the referred patients may be considered a distinct subset not equivalent to the patients initially evaluated at JHCC. As data regarding the total number of patients screened at RH were not available, whether community physicians routinely or selectively obtain imaging before inter facility transfer for operative care cannot be determined from this study. Although we are unable to identify the specific reasons for which patients were transferred to our institution, we do not believe that this group of patients represents a selected subgroup of patients. Patients included in this series were only those who underwent appendectomy, and there were no differences between those directly admitted at our ED and those transferred from RH in terms of severity of disease. Therefore, we believe it is unlikely that patients who underwent operation at RH were only cases which required less extensive diagnostic work-up or were less complicated
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Pediatr Surg Int
cases. We thus believe that the inclusion criteria correct for potential confounding biases. This study describes differences in diagnostic imaging utilization, and in particular, decreased use of CT scans in the diagnosis of acute appendicitis between a tertiary Children’s Center when compared to referring institutions. In non-pediatric dedicated facilities, CT remains the most common imaging study in the diagnosis of acute appendicitis, likely due to technician or radiologic availability and inexperience, and low confidence in US as a diagnostic modality. Improvements in the diagnosis of children with suspected acute appendicitis should include the development of cost-effective diagnostic pathways which limit unnecessary radiation exposure and ensure safe and high quality care. A collaborative multidisciplinary effort of all physicians involved in pediatric care is necessary to ensure that imaging is appropriately ordered, in accordance with the ALARA principle.US as first-line imaging is a valuable tool; however, further efforts should be made to improve its accuracy and avoid a high rate of inconclusive diagnoses. The pathway of US and potential subsequent MRI seems a promising and cost-effective strategy. Conflict of interest The authors declare that they have no conflicts of interest.
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