Ultrasound First in Suspected Appendicitis

Why are we are still subjecting patients–particularly children–to dangerous doses of CT radiation when imaging for appendicitis?

Why are we are still subjecting patients–particularly children–to dangerous doses of CT radiation when imaging for appendicitis?

One of the major frustrations in medicine is dealing with the gap between what is “known” and what is “practiced.” Often the literature will clearly defend a certain treatment and yet it will take years for the treatment to become common practice. In the interim, patients do not get the benefit of the new treatment or technology.

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Probably one of the best examples of this was the 10-year gap in getting thrombolytic therapy for myocardial infarctions into the main stream. Dr. Sol Sherry, of my alma mater, Temple University, effectively demonstrated the efficacy of urokinase as a clot buster and subsequently, streptokinase. But incorporation into routine practice was very slow. Think of all of the patients who could have benefited had the use of this therapy been accelerated.

But there is a saying in medicine – “never be the first to adopt a new treatment – or the last.” There is a natural reluctance to change, and frequently the literature that is initially positive turns out to be negative in subsequent trails. Sometimes this admonition is appropriate, but many times it is an excuse for excessive delays.

One practice that should have changed in the U.S. long ago is the persistent use of CTs in patients with suspected appendicitis. Currently the vast majority of patients are exposed to substantial radiation when CTs are used as the first-line imaging choice. It has been noted that in adults a CT is the equivalent to 500 chest X-rays with regard to radiation and it is anticipated that one in 4,000 patients getting a CT of the chest or abdomen will die of the cancer that it causes. It has been estimated that up to 2% of all future cancers will be due to the radiation from CTs.

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In children the risks are substantial worse since the mutagenic effects of the radiation received will have decades to result in the development of cancer. Two studies have noted that children are ten times more sensitive to radiation than middle age adults and that girls are more sensitive than boys. So there is, at least in some circles, active attempts to decrease not only the frequency of pediatric CTs (some say 25-35% are unnecessary – this sounds very, very conservative) but also the radiation dose received by children when subjected to a CT (the ALARA concept – As Low as Reasonably Achievable).

Unfortunately, it is clear that radiologists, family physicians and emergency physicians are inadequately aware of the radiation issues and, as a result, children are the fastest growing subset of the population to receive CTs – because CTs are faster now and take less time to perform and therefore don’t require pediatric sedation as they once did – an unintended consequence of progress.

The literature is unequivocal when it comes to imaging for appendicitis – especially in children. If any imaging is to be done, all should have an ultrasound as the first examination. Unfortunately, ultrasound techs are much more difficult to find that CT techs and many hospitals have only limited ultrasound capabilities during the nights and weekends. In addition, unlike CTs, obtaining a good ultrasound is an operator-dependent skill – so there are issues related to the quality of ultrasound studies. Finally many U.S radiologists have little experience reading ultrasound studies focusing on the appendix and use this as an excuse for supporting CT studies over the use of ultrasound. Bottom line, there are lots of potential excuses why ultrasound is not the preferred study in the United States.

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But we must change. The use of CTs in children has become rampant, yet in Europe the trend is just the opposite – relatively speaking CTs are being less frequently performed than ultrasounds.

There is a large amount of literature supporting the “ultrasound first” approach – this is not a flash in the pan or something that will be found to be incorrect with time. The problem is two fold. First and foremost, treating physicians need to order ultrasounds first. The radiologists can bitch and moan, but the only way some will learn to get good at reading these studies is to practice – and ordering physicians should give them the opportunity to practice. Will they give equivocal readings at first? Probably. But how else are we going to make progress and do the right thing?

The second thing that needs to be done is that, like any specialty in medicine, practitioners need to update their skills. There have to be courses on the internet that radiologists can take or seminars in Cancun that will help them advance their skill-set in this area. The status quo is just not acceptable from both the standpoint of ordering physicians and radiologists – both groups must change.

Finally there is the issue of the sensitivity and specificity of the two tests. Are they equal? No. Are they close? Yes. The sensitivity of ultrasound tends to be around 91% and specificity is high at about 97-98%. For CT scans the sensitivity tends to be around 95% and specificity similar to ultrasound. Is the difference worth the cost and radiation – most would say “no” if there was the option to perform a CT in equivocal ultrasound cases.

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Here are just four papers that make the “ultrasound first” case. They are, by no means, the only ones – the literature on this topic is robust and compelling.

1 The first paper is very impressive – the ratio of ultrasound studies to CT scans was 6:1 overall and a whopping 24:1 in children.

ROUTINE ULTRASOUND AND LIMITED COMPUTED TOMOGRAPHY FOR THE DIAGNOSIS OF ACUTE APPENDICITIS
Toorenvliet, B.R., et al, World J Surg 34(10):2278, October 2010

METHODS: This prospective Dutch study examined an approach to the diagnosis of acute appendicitis that included clinical evaluation by surgical residents and/or attending surgeons, followed if imaging was believed to be necessary by performance of ultrasonography by a radiologist, and CT scanning if the ultrasound was equivocal. Patients who were not immediately admitted were reevaluated after 24 hours.

RESULTS: Appendicitis was suspected based on the clinical evaluation in 164 of 802 patients with acute abdominal pain. The final diagnosis was appendicitis in 119 of the 802 patients (14.8%, including 104 patients in whom it was clinically suspected and 15 in whom it was not initially suspected). The sensitivity and specificity of the clinical evaluation were 87% and 91%, respectively (positive and negative predictive values 63% and 98%). Among the patients with suspected appendicitis, imaging was performed in 116 (97.5%), including 118 ultrasound studies and 19 CT studies (ratio of ultrasound to CT, about 6:1 overall and 24:1 in children). Sensitivity and specificity were 91% and 98% for ultrasonography and 100% each for CT scanning. Overall, imaging provided an accurate diagnosis in 98% of the patients in whom it was performed, and resulted in a change in management for 20 patients. The negative appendectomy rate was 3.3%. The overall perforation rate was 23.5%, but the rate of missed perforated appendicitis was 3.4%.

CONCLUSIONS: Clinical examination does not appear to be sufficiently reliable to identify or exclude acute appendicitis. The authors feel that their findings support routine imaging when appendicitis is suspected, with ultrasonography as the initial modality followed if equivocal by CT scanning. 43 references (br.toorenvliet@tiscali.nl – no reprints)
Copyright 2011 by Emergency Medical Abstracts – All Rights Reserved 2/11 – #14

2 The second paper teaches us a number of lessons. First, the radiologist was the one to perform the ultrasound study. Second, imaging increased over
time when compared to clinical examination alone. But, catch this, ultrasound was the only study performed in 43% of the children, 9% had an ultrasound and CT and 5% had a CT only. The use of ultrasound increased over time from 36% in 2002-2003 to 64% in 2006-2007. And notice that the sensitivity and specificity were the same as in the first abstract.

MANAGEMENT OF ACUTE APPENDICITIS: AN IMAGING STRATEGY IN CHILDREN
Neufeld, D., et al, Ped Surg Internat 26(2):167, February 2010

METHODS: These Israeli authors reviewed their experience with the management of 2,218 children aged 2-17 years presenting from 2002 through 2007 with suspected appendicitis. Evaluation included an initial clinical assessment, ultrasonography (US) performed by an experienced radiologist when the clinical diagnosis and brief observation were uncertain, and selective use of CT scanning in patients with an inconclusive US exam. During the final two years, US was performed in the ED, permitting prompt discharge of those with negative findings.

RESULTS: Among the entire study population, 43% of the children were managed on the basis of clinical findings, US alone was performed in 43%, both US and CT scanning were performed in 9%, and 5% had CT scanning alone. During the six years of study, there was a progressive increase in the percentage of patients managed nonoperatively, which the authors attributed to the diagnostic guidance provided by imaging. In 2006 and 2007, when US was performed in the ED, there was a decrease in the number of children who were admitted and treated nonoperatively. The use of US prior to surgery increased from 36.5% in 2002-2003 to 63.7% in 2006-2007, and performance of surgery based on clinical findings alone decreased from 55% to 19%. The false-positive appendectomy rate in patients undergoing imaging studies decreased from 11.4% in 2002-2003 to 2.4% in 2006-2007. The diagnosis of acute appendicitis with US had a sensitivity and specificity of 91.3% and 97.7%, respectively.

CONCLUSIONS: These authors advocate initial ultrasonography for clinically equivocal cases of suspected pediatric appendicitis, with CT scanning reserved for cases in which clinical evaluation and ultrasonography are indeterminate. 10 references (neufeldd@clalit.org.il – no reprints)
Copyright 2010 by Emergency Medical Abstracts – All Rights Reserved 6/10 – #17

3 The third paper is one of the less common U.S. studies. The title is a disaster – it is a paragraph long in itself and it doesn’t tell us the results of the study – you actually have to read the paper. But, their “ultrasound first” pathway (if negative, no surgery; if positive, surgery; if equivocal, CT) decreased CTs by 49% if all who had imaging had only a CT.

AN INTERDISCIPLINARY INITIATIVE TO REDUCE RADIATION EXPOSURE: EVALUATION OF APPENDICITIS IN A PEDIATRIC EMERGENCY DEPARTMENT WITH CLINICAL ASSESSMENT SUPPORTED BY A STAGED ULTRASOUND AND COMPUTED TOMOGRAPHY PATHWAY
Ramarajan, N., et al, Acad Emerg Med 16(11):1258, November 2009

BACKGROUND: The principles of an as-low-as-reasonably-achievable (ALARA) approach to radiation exposure in children suggest that alternative strategies for the evaluation of possible pediatric appendicitis should be explored.

METHODS: The authors report on a pathway for the evaluation of possible pediatric appendicitis developed by the departments of surgery, radiology and emergency medicine at the Stanford/Lucile Packard Children’s Hospital. The pathway called for ultrasonography (US) as the primary imaging modality with further management by pediatric surgeons if the US was read as positive for appendicitis by an attending radiologist, management by emergency physicians if the US was clearly negative, and performance of CT scanning if the US was equivocal. Findings were retrospectively assessed in 680 children evaluated for appendicitis over a six-year period. All imaging was at the discretion of managing physicians.

RESULTS: The pathway was followed for 407 children (59.8%). The sensitivity and specificity of this approach for appendicitis were 99% and 91%, respectively, and the positive and negative predictive values were 85% and 99%, respectively. There was one case of missed appendicitis and the negative appendectomy rate was 7%. If it is assumed that all children would have undergone CT scanning prior to implementation of the pathway, 49% of CT scans would have been avoided with this strategy.

CONCLUSIONS: Implementation of an ultrasound-first imaging strategy for suspected pediatric appendicitis is suggested as a means of reducing radiation exposure without decreasing safety and efficacy. 18 references (ewen@stanford.edu for reprints)
Copyright 2010 by Emergency Medical Abstracts – All Rights Reserved 4/10 – #16

4 Finally, a 57-study meta-analysis that was published in 2006 — so the data is probably at least six years old and more recent studies are probably even more positive. Look at the remarkable conclusion. Assuming a 15% prevalence of appendicitis, the number of cases missed by using US instead of CT would be 10 per 1,000 children and 18 per 1,000 adults (48/1,000 children and 83/1,000 adults assuming a maximum prevalence of 75%)

US OR CT FOR DIAGNOSIS OF APPENDICITIS IN CHILDREN AND ADULTS? A META-ANALYSIS
Doria, A.S., et al, Radiology 241(1):83, October 2006

BACKGROUND: Both ultrasonography (US) and CT scanning have been advocated for the imaging of patients with suspected appendicitis. Both imaging modalities have advantages as well as disadvantages.

METHODS: The authors, from the University of Toronto, performed a meta-analysis of 57 studies of the diagnostic performance of US and CT scanning (most often third-generation helical CT) in patients with suspected appendicitis. Of the 57 studies, 26 involved 9,356 children (mean age, 7-12) and 31 involved 4,341 adults (mean age, 20- 49).

RESULTS: The median methodologic quality score was 34.4% for the pediatric studies and 42.2% for the adult studies. After exclusion of outliers the pooled sensitivity of US and CT were 88% vs. 94%, respectively, in the pediatric population and 83% vs. 94%, respectively, in adults. Pooled specificities were 94% for US and 95% for CT in the pediatric studies, and 93% vs. 94%, respectively, in adults. Assuming a 15% minimum prevalence of appendicitis, the number of cases missed by using US rather than CT for diagnostic imaging would be 10 per 1000 in children and 18 per 1000 in adults. Assuming a 75% maximum prevalence of appendicitis, the number of cases missed through use of US rather than CT imaging would be 48 per 1000 in children and 83 per 1000 in adults.

CONCLUSIONS: CT scanning appears to be more sensitive than ultrasonography for the imaging of patients with suspected appendicitis. When making a decision about imaging in such patients, radiation exposure associated with CT scanning should be considered, particularly for pediatric patients. 106 references (andrea.doria@sickkids.ca)
Copyright 2007 by Emergency Medical Abstracts – All Rights Reserved 2/07 – #22

Bottom line – we have an obligation to our patients to take into consideration both the risks and benefits of our assessment and treatment decisions. In the case of CTs for possible appendicitis, especially in children, there is a clear choice about what is the best strategy for our patients – ultrasound first. We need the courage to push for the transition from current practice of doing CTs almost universally in suspected appendicitis cases to using much more ultrasonography.

W. Richard Bukata, MD, is the medical editor of Emergency Medical Abstracts