International Journal of Surgery 13 (2015) 165e169
Contents lists available at ScienceDirect
International Journal of Surgery journal homepage: www.journal-surgery.net
Original research
The value of ultrasonography in the diagnosis of appendicitis N. D'Souza a, *, C. D'Souza b, D. Grant c, E. Royston a, M. Farouk d a
Wessex Deanery, Southern House, Otterbourne, Winchester, Hampshire, UK Royal Hampshire County Hospital, Winchester, UK c Oxford Deanery, UK d Department of General Surgery, Bucks NHS Healthcare Trust, Buckinghamshire, UK b
h i g h l i g h t s The diagnostic accuracy of ultrasonography is overestimated in the literature. The appendix was only visualised in 45% of 573 ultrasound scans across three sites. The sensitivity dropped from 81.7% to 51.8% when inconclusive scans were included.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 May 2014 Received in revised form 4 November 2014 Accepted 8 November 2014 Available online 8 December 2014
Introduction: Ultrasonography is a commonly used investigation in the UK for patients with right iliac fossa pain where the diagnosis of appendicitis is unclear. The published sensitivity and specificity of ultrasonography is higher than the results observed by clinicians in every day practice. The aim of this study was to elucidate the real-world value of ultrasonography in the diagnosis of appendicitis, and its impact on negative appendicectomy rates (NAR). Methods: A retrospective multicentre audit was conducted at three UK hospitals over a twelve month period in 2012. Results: 573 patients underwent ultrasonography prior to appendicectomy. The appendix was not visualised in 45% of scans. The sensitivity and specificity of ultrasonography for the diagnosis of appendicitis was 51.8% and 81.4%. The mean NAR was 26.7%, or 18.3% after a positive ultrasound scan. Conclusion: In clinical practice at UK centres, ultrasonography commonly does not visualise the appendix, and has a low sensitivity for appendicitis. To reduce the NAR, management options include a return to observation and serial examination, increased use of CT or a commitment to improving the performance of ultrasonography. © 2014 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
Keywords: Appendicitis Ultrasonography Sensitivity and specificity
1. Introduction Despite advances in blood tests and imaging studies, the negative appendicectomy still remains a possible outcome in patients presenting with right iliac fossa pain. Ultrasonography, computer tomography (CT) and magnetic resonance imaging (MRI) are noninvasive imaging studies, while laparoscopy can be classified as an invasive diagnostic modality. A commonly utilised imaging test for appendicitis in the UK is ultrasonography, with high sensitivity and specificity quoted in previous published studies. Amongst other ultrasound criteria, a blind ending, aperistaltic incompressible tubular structure in the right iliac fossa (RIF) with a thickened
* Corresponding author. Queen Alexandra Hospital, Southwick Hill Rd, Portsmouth, Hampshire PO6 3LY, UK. E-mail address: [email protected] (N. D'Souza). http://dx.doi.org/10.1016/j.ijsu.2014.11.039 1743-9191/© 2014 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
wall and widened diameter would suggest a diagnosis of appendicitis. Yet the growing number of scans reported as “appendix not visualized”, has led to a dissonance between the published and real-world diagnostic accuracy of ultrasonography in appendicitis. The aim of this study was to elucidate the value of ultrasonography in the diagnosis of appendicitis, and its impact on negative appendicectomy rates. This was carried out by investigation of 3 variables: a. Negative appendicectomy rate (NAR) b. Percentage of ultrasound scans where appendix is not visualized c. Sensitivity and specificity of ultrasonography for appendicitis
166
N. D'Souza et al. / International Journal of Surgery 13 (2015) 165e169
Table 1 Patient demographics.
Centre 1 Centre 2 Centre 3 TOTAL
Appendicectomies
Mean age (years)
Number of females
760 455 629 (453 adults, 176 children) 1844
29.0 25.6 29.5
371 (48.8%) 236 (51.9%) 307 (48.8%)
28.0
914 (49.6%)
2. Material and methods A retrospective multi-centre study across three UK hospitals over a twelve month period was performed in 2012. Centres 1 þ 2 are district general hospitals providing adult general surgical services with emergency paediatric surgery cover (age > 5). Centre 3 is a tertiary hospital with adult and specialist paediatric (age < 16 years) surgical services. The study population was derived from all patients that underwent emergency appendicectomy for suspected acute appendicitis during the study period. The results of ultrasound scans performed prior to appendicectomy and the histology reports of excised appendix specimens were analysed. The time interval between scanning and surgery was not recorded. Ultrasound scans were performed by the radiologists (medically trained) and radiographers (radiography technicians) of each hospital's radiology department. Radiologists were either registrars or
consultants, and radiographers also were of varying experience. All sonographers received the patient's clinical details on the ultrasound request form. In our analysis, an ultrasound report that visualized the appendix and confirmed that it was inflamed recorded as a positive result. Ultrasound reports that visualized the appendix and reported it as normal were recorded as a negative result. Ultrasound scans that did not visualize the appendix, auxiliary signs of appendicitis (e.g. inflammation in the RIF) or comment on it in the report were uninterpretable as the key diagnostic feature of the test was missing. These results were classified as “appendix not seen”. The histology of appendix specimens was reported by consultant histopathologists of each respective hospital. Any degree of inflammation leading to a histological diagnosis of appendicitis was coded as an inflamed appendix. Ethics approval was not sought as retrospective data was collected and analysed as part of audits conducted and presented on each site by the local auditors (Charlotte D'Souza, David Grant, Elizabeth Royston). The raw data was rechecked by the primary investigator (Nigel D'Souza) for quality assurance. Results were tabulated on Microsoft Excel, which was also used to calculate the sensitivity and specificity analyses, and confidence intervals.
3. Results During the study period, 1844 patients underwent appendicectomy (see Table 1 for demographics and Fig. 1 for the STARD flow
Fig. 1. STARD flow diagram.
N. D'Souza et al. / International Journal of Surgery 13 (2015) 165e169 Table 2 Rates of appendix visualisation with ultrasound.
Centre 1 Centre 2 Centre 3 TOTAL
Appendix seen
Appendix not seen
% Seen
146 25 142 313
109 93 58 260
57 21 71 55
Table 3 (Centre 1): sensitivity and specificity of ultrasound for appendicitis. ‘x’ denotes merged “appendix not visualized” and “non-inflamed appendix” results. Appendicitis
Not appendicitis
US þve for appendicitis
105
15
US ve for appendicitis
14
12
US ve or appendix not seen 77 Sens ¼ 88.2% CI 80.7e93.1% xSens 57.7% CI 50.1e64.9%
58 Spec ¼ 44.4% CI 26.0e64.4% xSpec ¼ 79.5% CI 68.1e87.7%
PPV 87.5% CI 80.0e92.6% NPV 46.2% CI 27.1e66.3% xPPV 87.5% CI 80.0e92.6% xNPV 43.0% CI 34.6e51.8%
Table 4 (Centre 2): sensitivity and specificity of ultrasound for appendicitis. ‘x’ denotes merged “appendix not visualized” and “non-inflamed appendix” results. Appendicitis
Not appendicitis
US þve for appendicitis
18
5
US ve for appendicitis
0
2
US ve or appendix not seen 31 Sens ¼ 100% CI 78.1e100% xSens 36.7% CI 23.8e51.7%
64 Spec ¼ 28.6% CI 5.10e69.7% xSpec ¼ 92.8% CI 83.2e97.3%
PPV 78.3% CI 55.8e91.7% NPV 100% CI 19.8e100% xPPV 78.3% CI 55.8e91.7% xNPV 67.4% 56.9e76.4%
Table 5 (Centre 3): sensitivity and specificity of ultrasound for appendicitis. ‘x’ denotes merged “appendix not visualized” and “non-inflamed appendix” results. Appendicitis
Not appendicitis
US þve for appendicitis
60
21
US ve for appendicitis
27
34
US ve or appendix not seen 62 Sens ¼ 69.0% CI 58.0e78.2% xSens 49.2% CI 40.1e58.3%
57 Spec ¼ 61.8% CI 47.7e74.3% xSpec ¼ 73.1% CI 61.6e82.2%
PPV 74.1% CI 62.9e82.9% NPV 55.7% CI 42.5e68.2% xPPV 74.1% CI 62.9e82.9% xNPV 47.9% CI 17.1e37.1%
Table 6 Results from all trusts. Appendicitis
Not appendicitis
US þve for appendicitis
183
41
US ve for appendicitis
41
48
US ve or appendix not seen 170 Sens ¼ 81.7% CI 75.9e86.4% xSens 51.8% CI 46.5e57.1%
179 Spec ¼ 53.9% CI 43.1e64.4% xSpec ¼ 81.4% CI 75.4e86.2%
PPV 81.7% CI 75.9e86.4% NPV 53.9% CI 43.1e64 4% xPPV 81.7% CI 75.9e86.4% xNPV 51.3% CI 45.9e56.6%
167
diagram). 573 (31.3%) patients underwent ultrasonography across all three centres. The mean rate of appendix visualization was 55% (range 21e71, see Table 2). Across all centres, the overall sensitivity and specificity of ultrasound scans that visualized the appendix was 81.7% and 53.9% (see Tables 3e6). When ultrasound scans that did not identify the appendix were merged with the negative scan results (i.e. noninflamed appendix), the mean sensitivity dropped to 51.8% and specificity increased to 81.4% (Fig. 1). The NAR at all three centres ranged between 16.8% and 31.9%, with a mean NAR of 26.7% (see Table 7). The mean NAR was 38.4% in all patients undergoing ultrasonography, falling to 18.3% in patients with a positive ultrasound scan identifying an inflamed appendix. 4. Discussion The results of this UK multi-centre study confirmed our experience of ultrasonography; that it commonly does not visualize the appendix and is frequently non-contributory to the management of patients with suspected appendicitis. American, Italian and French surgeons were asked in a recent survey [1] which investigation would be requested to assess a young patient presenting with acute right iliac fossa pain and normal blood tests and urinalysis. The American surgeons in the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) leant heavily towards CT, while the European surgeons favoured laparoscopy above CT, especially in female patients. Neither group looked to ultrasonography to provide a diagnosis, and MRI was not discussed as an imaging modality. The published figures for the accuracy of ultrasonography in appendicitis make it on paper an attractive option to reduce the NAR. In two systematic reviews [2,3], ultrasonography has a composite sensitivity between 78 and 86% and specificity between 81 and 83% for appendicitis. In our clinical practice, ultrasonography's overall sensitivity of 51.8% is inferior to published results, although the specificity remained high at 81.4%. Published studies of ultrasonography often do not mention whether the appendix is visualized; in our study, only 55% of scans identified the appendix. When a positive ultrasound scan confirmed appendicitis, the NAR decreased, but remained worryingly high at 18.3%. Various explanations may account for the divergence in sonographic diagnostic accuracy between trials and clinical practice. In the UK radiography technicians routinely perform diagnostic ultrasonography, but do not have the expertise of a consultant gastrointestinal radiologist to evaluate for bowel pathology such as appendicitis. In our study, centres 1 þ 3 had high appendix visualisation rates, due to a strong radiological expertise in this modality in these hospitals. The variability of appendix visualisation rates in different centres in this study would confirm the generally held belief that this modality of investigation is highly operator dependent. In cases of uncertainty, there may be a reluctance to report an appendix as normal or inflamed on ultrasonography, which could influence the decision to operate. Ultrasound scans for suspected appendicitis are often added urgently onto busy scanning lists with time pressure to perform and report scans. A Hawthorne Effect may contribute to the high sensitivity of ultrasound in the published; when a participant in a prospective trial is being observed, they may act differently e.g. not stop looking for the appendix until it is found. We believe that a lack of expertise, medico-legal concerns, a Hawthorne effect, and publication bias are the most likely explanations for the discrepancy of “real-world” results. Unfortunately this study did not obtain potentially useful data on other variables that could affect ultrasound scan accuracy. This could include the scanning technique (e.g. graded compression
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N. D'Souza et al. / International Journal of Surgery 13 (2015) 165e169
Table 7 NAR at all 3 centres. Centre 1
Total number operations No Imaging Ultrasound (any outcome) Positive ultrasound
Centre 2
Centre 3
Total
No. patients
NAR (%)
No. patients
NAR (%)
No. patients
NAR (%)
No. patients
NAR (%)
760 435 255 120
16.8 14.3 28.6 12.5
455 315 118 23
31.6 28.6 58.5 21.7
629 310 200 81
35.0 30.3 39.0 25.9
1844 1060 573 224
26.7% 23.2% 38.4% 18.3%
with or without posterior manual compression or lateral decubitus position), the ultrasound equipment used (grayscale alone versus colour doppler), or the role and seniority of the sonographer (radiology consultant, registrar, or technician). Nor did this study capture other factors such as obesity, retrocaecal appendix position, fasting status of patients or other potential limitations to appendix visualisation. As the population was derived retrospectively from patients undergoing surgery, we are unable to tell when ultrasonography prevented unnecessary surgery by identifying a normal appendix, or a gynaecological condition that did not require operative intervention. As poor rates of appendix visualization frequently lead to inconclusive ultrasound reports, surgeons instead use ultrasonography to exclude gynaecological causes of RIF pain, or to possibly rule in appendicitis in slim patients or children (particularly if a GI radiologist is requested to perform the scan). However, if ultrasound fails to identify any other pathology or visualize the appendix, these patients frequently progress to surgery. CT scanning would seem to be a more useful imaging modality to directly evaluate the appendix. The sensitivity and specificity of CT for appendicitis has been estimated at 94% and 95% respectively in a systematic review of twelve studies [2], and is more frequently available than MRI. While the NAR only decreases to 18.3% in our results after a positive ultrasound scan, a meta-analysis of 28 studies [4] found a reduction in the NAR from 16.7% to 8.7% after CT scanning versus clinical evaluation alone. The SCOAP study with nearly 20 000 appendicectomies performed has achieved a NAR of 4.1% with routine CT scanning [5]. Routine CT for all patients with right iliac fossa pain can incur considerable costs, as well as the consequences of irradiation. While CT scans of the abdomen with IV and oral contrast have an estimated cancer risk of 1 in 250 for young women in some studies [6], new low-dose protocols have been developed [7] to evaluate the appendix with equivalent efficacy with less radiation exposure. Costs of routine scanning have also been less than the costs of unnecessary surgery and inpatient stay in an emergency service with a high NAR [8]. The costs to the economy resulting from employed patients without appendicitis taking time off work to recover from surgery also exist, but are more difficult to quantify. Most importantly, a negative appendicectomy is a potentially unnecessary, preventable operation that could result in harm to a patient from complications. The NAR of 26.7% in the hospitals in this study appears very high, but lies between the rates of other studies conducted in the UK [9e11]. A comprehensive investigation into the reasons for the high NAR in the UK is beyond the remit of this study. In the contemporary NHS, pressure to increase bed turnover and discharge early may lower the threshold for surgery to avoid discharging patients with possible appendicitis, who may represent later with peritonitis and its attendant complications, including reduced fertility in women. The traditional preference for ultrasound over CT scanning in the UK due to radiation exposure and cost restraints may increase the NAR. Finally, while laparoscopy has been used as a diagnostic test for patients with right iliac fossa pain,
the operation frequently commits the patient to an appendicectomy. When surgeons find no other significant pathology inside the abdomen, a macroscopically normal appendix is commonly removed due to the possibility of non-macroscopic appendicitis, or to prevent future appendicitis. In the UK, two studies [10,11] have shown a rise in the negative appendicectomy rate since the introduction of laparoscopic appendicectomy. However, UK NAR remains higher than other countries such as the USA in the era of laparoscopy, where a national audit has shown a decreasing NAR (8.4% in 2007 [12]). As surgeons, we need to manage our patients with abdominal pain of uncertain aetiology to the highest possible standards whilst maintaining patient safety. In the UK we have used ultrasonography to assess patients with right iliac fossa pain. However, our results from multiple centres show that the appendix is not even visualized in 45% of cases, and that the sensitivity and specificity of ultrasound is lower than published results. Improved performance in this modality should be demanded if it is to remain the most common imaging modality. Laparoscopy has lowered the threshold for operating in cases of suspected appendicitis, and can provide useful diagnostic information. However, it has its own costs, morbidity, and may result in an appendicectomy in cases of uncertainty. If pressure for an early, definitive management plan prohibits a period of observation, in cases of uncertainty it may be necessary to ask our patients if they would rather have a CT scan instead of a “diagnostic” laparoscopy.
5. Conclusion Ultrasonography is only useful to diagnose appendicitis if sufficient radiological expertise is available. The appendix was not visualized in 45% of the 573 scans performed across three UK hospitals in this study. After including inconclusive ultrasound scans, sensitivity of ultrasound for diagnosing appendicitis was 51.8%, and the specificity was 81.4%. The mean NAR was 26.7%, or 18.3% after a positive ultrasound scan. To reduce the NAR, management options include a return to observation and serial examination, increased use of CT or a commitment to improving the performance of ultrasonography.
Studies carried out Department of General Surgery, Bucks Healthcare NHS Trust. Department of Paediatric Surgery, Oxford University Hospitals Trust. Department of General Surgery, Poole Hospital Foundation Trust.
Ethical approval Data collected as part of audits registered at each local hospital.
N. D'Souza et al. / International Journal of Surgery 13 (2015) 165e169
Funding None. Author contribution Nigel D'Souza: study design, data analysis, writing. Charlotte Lobban: data collection, data analysis, writing. David Grant: data collection, data analysis, writing. Elizabeth Royston: data collection, data analysis. Marwan Farouk: writing. Kirsty Steele: data collection at local centre.
[3]
[4]
[5]
[6]
[7] [8]
Conflicts of interest None. References [1] S.S. Jaunoo, et al., An international survey of opinion regarding investigation of possible appendicitis and laparoscopic management of a macroscopically normal appendix, Ann. R. Coll. Surg. Engl. 94 (7) (2012) 476e480. [2] T. Terasawa, et al., Systematic review: computed tomography and
[9]
[10] [11] [12]
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ultrasonography to detect acute appendicitis in adults and adolescents, Ann. Intern. Med. 141 (7) (2004) 537e546. A. van Randen, et al., Acute appendicitis: meta-analysis of diagnostic performance of CT and graded compression US related to prevalence of disease1, Radiology 249 (1) (2008) 97e106. S. Krajewski, et al., Impact of computed tomography of the abdomen on clinical outcomes in patients with acute right lower quadrant pain: a metaanalysis, Can. J. Surg. 54 (1) (2011) 43e53. F.T. Drake, et al., Progress in the diagnosis of appendicitis: a report from Washington State's Surgical Care and Outcomes Assessment Program, Ann. Surg. 256 (4) (2012) 586e594. R. Smith-Bindman, et al., Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer, Arch. Intern. Med. 169 (22) (2009) 2078e2086. K. Kim, et al., Low-dose abdominal CT for evaluating suspected appendicitis, N. Engl. J. Med. 366 (17) (2012) 1596e1605. P.M. Rao, et al., Effect of computed tomography of the appendix on treatment of patients and use of hospital resources, N. Engl. J. Med. 338 (3) (1998) 141e146. Multicentre observational study of performance variation in provision and outcome of emergency appendicectomy, Br. J. Surg. 100 (9) (2013) 1240e1252. F. Akbar, et al., Changing management of suspected appendicitis in the laparoscopic era, Ann. R. Coll. Surg. Engl. 92 (1) (2010) 65e68. G.E. Jones, et al., Increased use of laparoscopy in acute right iliac fossa pain e is it good for patients? Colorectal Dis. 14 (2) (2012) 237e242. S.A. Seetahal, et al., Negative appendectomy: a 10-year review of a nationally representative sample, Am. J. Surg. 201 (4) (2011) 433e437.
Contents lists available at ScienceDirect
International Journal of Surgery journal homepage: www.journal-surgery.net
Original research
The value of ultrasonography in the diagnosis of appendicitis N. D'Souza a, *, C. D'Souza b, D. Grant c, E. Royston a, M. Farouk d a
Wessex Deanery, Southern House, Otterbourne, Winchester, Hampshire, UK Royal Hampshire County Hospital, Winchester, UK c Oxford Deanery, UK d Department of General Surgery, Bucks NHS Healthcare Trust, Buckinghamshire, UK b
h i g h l i g h t s The diagnostic accuracy of ultrasonography is overestimated in the literature. The appendix was only visualised in 45% of 573 ultrasound scans across three sites. The sensitivity dropped from 81.7% to 51.8% when inconclusive scans were included.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 May 2014 Received in revised form 4 November 2014 Accepted 8 November 2014 Available online 8 December 2014
Introduction: Ultrasonography is a commonly used investigation in the UK for patients with right iliac fossa pain where the diagnosis of appendicitis is unclear. The published sensitivity and specificity of ultrasonography is higher than the results observed by clinicians in every day practice. The aim of this study was to elucidate the real-world value of ultrasonography in the diagnosis of appendicitis, and its impact on negative appendicectomy rates (NAR). Methods: A retrospective multicentre audit was conducted at three UK hospitals over a twelve month period in 2012. Results: 573 patients underwent ultrasonography prior to appendicectomy. The appendix was not visualised in 45% of scans. The sensitivity and specificity of ultrasonography for the diagnosis of appendicitis was 51.8% and 81.4%. The mean NAR was 26.7%, or 18.3% after a positive ultrasound scan. Conclusion: In clinical practice at UK centres, ultrasonography commonly does not visualise the appendix, and has a low sensitivity for appendicitis. To reduce the NAR, management options include a return to observation and serial examination, increased use of CT or a commitment to improving the performance of ultrasonography. © 2014 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
Keywords: Appendicitis Ultrasonography Sensitivity and specificity
1. Introduction Despite advances in blood tests and imaging studies, the negative appendicectomy still remains a possible outcome in patients presenting with right iliac fossa pain. Ultrasonography, computer tomography (CT) and magnetic resonance imaging (MRI) are noninvasive imaging studies, while laparoscopy can be classified as an invasive diagnostic modality. A commonly utilised imaging test for appendicitis in the UK is ultrasonography, with high sensitivity and specificity quoted in previous published studies. Amongst other ultrasound criteria, a blind ending, aperistaltic incompressible tubular structure in the right iliac fossa (RIF) with a thickened
* Corresponding author. Queen Alexandra Hospital, Southwick Hill Rd, Portsmouth, Hampshire PO6 3LY, UK. E-mail address: [email protected] (N. D'Souza). http://dx.doi.org/10.1016/j.ijsu.2014.11.039 1743-9191/© 2014 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
wall and widened diameter would suggest a diagnosis of appendicitis. Yet the growing number of scans reported as “appendix not visualized”, has led to a dissonance between the published and real-world diagnostic accuracy of ultrasonography in appendicitis. The aim of this study was to elucidate the value of ultrasonography in the diagnosis of appendicitis, and its impact on negative appendicectomy rates. This was carried out by investigation of 3 variables: a. Negative appendicectomy rate (NAR) b. Percentage of ultrasound scans where appendix is not visualized c. Sensitivity and specificity of ultrasonography for appendicitis
166
N. D'Souza et al. / International Journal of Surgery 13 (2015) 165e169
Table 1 Patient demographics.
Centre 1 Centre 2 Centre 3 TOTAL
Appendicectomies
Mean age (years)
Number of females
760 455 629 (453 adults, 176 children) 1844
29.0 25.6 29.5
371 (48.8%) 236 (51.9%) 307 (48.8%)
28.0
914 (49.6%)
2. Material and methods A retrospective multi-centre study across three UK hospitals over a twelve month period was performed in 2012. Centres 1 þ 2 are district general hospitals providing adult general surgical services with emergency paediatric surgery cover (age > 5). Centre 3 is a tertiary hospital with adult and specialist paediatric (age < 16 years) surgical services. The study population was derived from all patients that underwent emergency appendicectomy for suspected acute appendicitis during the study period. The results of ultrasound scans performed prior to appendicectomy and the histology reports of excised appendix specimens were analysed. The time interval between scanning and surgery was not recorded. Ultrasound scans were performed by the radiologists (medically trained) and radiographers (radiography technicians) of each hospital's radiology department. Radiologists were either registrars or
consultants, and radiographers also were of varying experience. All sonographers received the patient's clinical details on the ultrasound request form. In our analysis, an ultrasound report that visualized the appendix and confirmed that it was inflamed recorded as a positive result. Ultrasound reports that visualized the appendix and reported it as normal were recorded as a negative result. Ultrasound scans that did not visualize the appendix, auxiliary signs of appendicitis (e.g. inflammation in the RIF) or comment on it in the report were uninterpretable as the key diagnostic feature of the test was missing. These results were classified as “appendix not seen”. The histology of appendix specimens was reported by consultant histopathologists of each respective hospital. Any degree of inflammation leading to a histological diagnosis of appendicitis was coded as an inflamed appendix. Ethics approval was not sought as retrospective data was collected and analysed as part of audits conducted and presented on each site by the local auditors (Charlotte D'Souza, David Grant, Elizabeth Royston). The raw data was rechecked by the primary investigator (Nigel D'Souza) for quality assurance. Results were tabulated on Microsoft Excel, which was also used to calculate the sensitivity and specificity analyses, and confidence intervals.
3. Results During the study period, 1844 patients underwent appendicectomy (see Table 1 for demographics and Fig. 1 for the STARD flow
Fig. 1. STARD flow diagram.
N. D'Souza et al. / International Journal of Surgery 13 (2015) 165e169 Table 2 Rates of appendix visualisation with ultrasound.
Centre 1 Centre 2 Centre 3 TOTAL
Appendix seen
Appendix not seen
% Seen
146 25 142 313
109 93 58 260
57 21 71 55
Table 3 (Centre 1): sensitivity and specificity of ultrasound for appendicitis. ‘x’ denotes merged “appendix not visualized” and “non-inflamed appendix” results. Appendicitis
Not appendicitis
US þve for appendicitis
105
15
US ve for appendicitis
14
12
US ve or appendix not seen 77 Sens ¼ 88.2% CI 80.7e93.1% xSens 57.7% CI 50.1e64.9%
58 Spec ¼ 44.4% CI 26.0e64.4% xSpec ¼ 79.5% CI 68.1e87.7%
PPV 87.5% CI 80.0e92.6% NPV 46.2% CI 27.1e66.3% xPPV 87.5% CI 80.0e92.6% xNPV 43.0% CI 34.6e51.8%
Table 4 (Centre 2): sensitivity and specificity of ultrasound for appendicitis. ‘x’ denotes merged “appendix not visualized” and “non-inflamed appendix” results. Appendicitis
Not appendicitis
US þve for appendicitis
18
5
US ve for appendicitis
0
2
US ve or appendix not seen 31 Sens ¼ 100% CI 78.1e100% xSens 36.7% CI 23.8e51.7%
64 Spec ¼ 28.6% CI 5.10e69.7% xSpec ¼ 92.8% CI 83.2e97.3%
PPV 78.3% CI 55.8e91.7% NPV 100% CI 19.8e100% xPPV 78.3% CI 55.8e91.7% xNPV 67.4% 56.9e76.4%
Table 5 (Centre 3): sensitivity and specificity of ultrasound for appendicitis. ‘x’ denotes merged “appendix not visualized” and “non-inflamed appendix” results. Appendicitis
Not appendicitis
US þve for appendicitis
60
21
US ve for appendicitis
27
34
US ve or appendix not seen 62 Sens ¼ 69.0% CI 58.0e78.2% xSens 49.2% CI 40.1e58.3%
57 Spec ¼ 61.8% CI 47.7e74.3% xSpec ¼ 73.1% CI 61.6e82.2%
PPV 74.1% CI 62.9e82.9% NPV 55.7% CI 42.5e68.2% xPPV 74.1% CI 62.9e82.9% xNPV 47.9% CI 17.1e37.1%
Table 6 Results from all trusts. Appendicitis
Not appendicitis
US þve for appendicitis
183
41
US ve for appendicitis
41
48
US ve or appendix not seen 170 Sens ¼ 81.7% CI 75.9e86.4% xSens 51.8% CI 46.5e57.1%
179 Spec ¼ 53.9% CI 43.1e64.4% xSpec ¼ 81.4% CI 75.4e86.2%
PPV 81.7% CI 75.9e86.4% NPV 53.9% CI 43.1e64 4% xPPV 81.7% CI 75.9e86.4% xNPV 51.3% CI 45.9e56.6%
167
diagram). 573 (31.3%) patients underwent ultrasonography across all three centres. The mean rate of appendix visualization was 55% (range 21e71, see Table 2). Across all centres, the overall sensitivity and specificity of ultrasound scans that visualized the appendix was 81.7% and 53.9% (see Tables 3e6). When ultrasound scans that did not identify the appendix were merged with the negative scan results (i.e. noninflamed appendix), the mean sensitivity dropped to 51.8% and specificity increased to 81.4% (Fig. 1). The NAR at all three centres ranged between 16.8% and 31.9%, with a mean NAR of 26.7% (see Table 7). The mean NAR was 38.4% in all patients undergoing ultrasonography, falling to 18.3% in patients with a positive ultrasound scan identifying an inflamed appendix. 4. Discussion The results of this UK multi-centre study confirmed our experience of ultrasonography; that it commonly does not visualize the appendix and is frequently non-contributory to the management of patients with suspected appendicitis. American, Italian and French surgeons were asked in a recent survey [1] which investigation would be requested to assess a young patient presenting with acute right iliac fossa pain and normal blood tests and urinalysis. The American surgeons in the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) leant heavily towards CT, while the European surgeons favoured laparoscopy above CT, especially in female patients. Neither group looked to ultrasonography to provide a diagnosis, and MRI was not discussed as an imaging modality. The published figures for the accuracy of ultrasonography in appendicitis make it on paper an attractive option to reduce the NAR. In two systematic reviews [2,3], ultrasonography has a composite sensitivity between 78 and 86% and specificity between 81 and 83% for appendicitis. In our clinical practice, ultrasonography's overall sensitivity of 51.8% is inferior to published results, although the specificity remained high at 81.4%. Published studies of ultrasonography often do not mention whether the appendix is visualized; in our study, only 55% of scans identified the appendix. When a positive ultrasound scan confirmed appendicitis, the NAR decreased, but remained worryingly high at 18.3%. Various explanations may account for the divergence in sonographic diagnostic accuracy between trials and clinical practice. In the UK radiography technicians routinely perform diagnostic ultrasonography, but do not have the expertise of a consultant gastrointestinal radiologist to evaluate for bowel pathology such as appendicitis. In our study, centres 1 þ 3 had high appendix visualisation rates, due to a strong radiological expertise in this modality in these hospitals. The variability of appendix visualisation rates in different centres in this study would confirm the generally held belief that this modality of investigation is highly operator dependent. In cases of uncertainty, there may be a reluctance to report an appendix as normal or inflamed on ultrasonography, which could influence the decision to operate. Ultrasound scans for suspected appendicitis are often added urgently onto busy scanning lists with time pressure to perform and report scans. A Hawthorne Effect may contribute to the high sensitivity of ultrasound in the published; when a participant in a prospective trial is being observed, they may act differently e.g. not stop looking for the appendix until it is found. We believe that a lack of expertise, medico-legal concerns, a Hawthorne effect, and publication bias are the most likely explanations for the discrepancy of “real-world” results. Unfortunately this study did not obtain potentially useful data on other variables that could affect ultrasound scan accuracy. This could include the scanning technique (e.g. graded compression
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Table 7 NAR at all 3 centres. Centre 1
Total number operations No Imaging Ultrasound (any outcome) Positive ultrasound
Centre 2
Centre 3
Total
No. patients
NAR (%)
No. patients
NAR (%)
No. patients
NAR (%)
No. patients
NAR (%)
760 435 255 120
16.8 14.3 28.6 12.5
455 315 118 23
31.6 28.6 58.5 21.7
629 310 200 81
35.0 30.3 39.0 25.9
1844 1060 573 224
26.7% 23.2% 38.4% 18.3%
with or without posterior manual compression or lateral decubitus position), the ultrasound equipment used (grayscale alone versus colour doppler), or the role and seniority of the sonographer (radiology consultant, registrar, or technician). Nor did this study capture other factors such as obesity, retrocaecal appendix position, fasting status of patients or other potential limitations to appendix visualisation. As the population was derived retrospectively from patients undergoing surgery, we are unable to tell when ultrasonography prevented unnecessary surgery by identifying a normal appendix, or a gynaecological condition that did not require operative intervention. As poor rates of appendix visualization frequently lead to inconclusive ultrasound reports, surgeons instead use ultrasonography to exclude gynaecological causes of RIF pain, or to possibly rule in appendicitis in slim patients or children (particularly if a GI radiologist is requested to perform the scan). However, if ultrasound fails to identify any other pathology or visualize the appendix, these patients frequently progress to surgery. CT scanning would seem to be a more useful imaging modality to directly evaluate the appendix. The sensitivity and specificity of CT for appendicitis has been estimated at 94% and 95% respectively in a systematic review of twelve studies [2], and is more frequently available than MRI. While the NAR only decreases to 18.3% in our results after a positive ultrasound scan, a meta-analysis of 28 studies [4] found a reduction in the NAR from 16.7% to 8.7% after CT scanning versus clinical evaluation alone. The SCOAP study with nearly 20 000 appendicectomies performed has achieved a NAR of 4.1% with routine CT scanning [5]. Routine CT for all patients with right iliac fossa pain can incur considerable costs, as well as the consequences of irradiation. While CT scans of the abdomen with IV and oral contrast have an estimated cancer risk of 1 in 250 for young women in some studies [6], new low-dose protocols have been developed [7] to evaluate the appendix with equivalent efficacy with less radiation exposure. Costs of routine scanning have also been less than the costs of unnecessary surgery and inpatient stay in an emergency service with a high NAR [8]. The costs to the economy resulting from employed patients without appendicitis taking time off work to recover from surgery also exist, but are more difficult to quantify. Most importantly, a negative appendicectomy is a potentially unnecessary, preventable operation that could result in harm to a patient from complications. The NAR of 26.7% in the hospitals in this study appears very high, but lies between the rates of other studies conducted in the UK [9e11]. A comprehensive investigation into the reasons for the high NAR in the UK is beyond the remit of this study. In the contemporary NHS, pressure to increase bed turnover and discharge early may lower the threshold for surgery to avoid discharging patients with possible appendicitis, who may represent later with peritonitis and its attendant complications, including reduced fertility in women. The traditional preference for ultrasound over CT scanning in the UK due to radiation exposure and cost restraints may increase the NAR. Finally, while laparoscopy has been used as a diagnostic test for patients with right iliac fossa pain,
the operation frequently commits the patient to an appendicectomy. When surgeons find no other significant pathology inside the abdomen, a macroscopically normal appendix is commonly removed due to the possibility of non-macroscopic appendicitis, or to prevent future appendicitis. In the UK, two studies [10,11] have shown a rise in the negative appendicectomy rate since the introduction of laparoscopic appendicectomy. However, UK NAR remains higher than other countries such as the USA in the era of laparoscopy, where a national audit has shown a decreasing NAR (8.4% in 2007 [12]). As surgeons, we need to manage our patients with abdominal pain of uncertain aetiology to the highest possible standards whilst maintaining patient safety. In the UK we have used ultrasonography to assess patients with right iliac fossa pain. However, our results from multiple centres show that the appendix is not even visualized in 45% of cases, and that the sensitivity and specificity of ultrasound is lower than published results. Improved performance in this modality should be demanded if it is to remain the most common imaging modality. Laparoscopy has lowered the threshold for operating in cases of suspected appendicitis, and can provide useful diagnostic information. However, it has its own costs, morbidity, and may result in an appendicectomy in cases of uncertainty. If pressure for an early, definitive management plan prohibits a period of observation, in cases of uncertainty it may be necessary to ask our patients if they would rather have a CT scan instead of a “diagnostic” laparoscopy.
5. Conclusion Ultrasonography is only useful to diagnose appendicitis if sufficient radiological expertise is available. The appendix was not visualized in 45% of the 573 scans performed across three UK hospitals in this study. After including inconclusive ultrasound scans, sensitivity of ultrasound for diagnosing appendicitis was 51.8%, and the specificity was 81.4%. The mean NAR was 26.7%, or 18.3% after a positive ultrasound scan. To reduce the NAR, management options include a return to observation and serial examination, increased use of CT or a commitment to improving the performance of ultrasonography.
Studies carried out Department of General Surgery, Bucks Healthcare NHS Trust. Department of Paediatric Surgery, Oxford University Hospitals Trust. Department of General Surgery, Poole Hospital Foundation Trust.
Ethical approval Data collected as part of audits registered at each local hospital.
N. D'Souza et al. / International Journal of Surgery 13 (2015) 165e169
Funding None. Author contribution Nigel D'Souza: study design, data analysis, writing. Charlotte Lobban: data collection, data analysis, writing. David Grant: data collection, data analysis, writing. Elizabeth Royston: data collection, data analysis. Marwan Farouk: writing. Kirsty Steele: data collection at local centre.
[3]
[4]
[5]
[6]
[7] [8]
Conflicts of interest None. References [1] S.S. Jaunoo, et al., An international survey of opinion regarding investigation of possible appendicitis and laparoscopic management of a macroscopically normal appendix, Ann. R. Coll. Surg. Engl. 94 (7) (2012) 476e480. [2] T. Terasawa, et al., Systematic review: computed tomography and
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