Clinical Ultrasound Is Safe and Highly Specific for Acute Appendicitis in Moderate to High Pre-test Probability Patients

Integrating Pre-test Probability and Point-of-Care Ultrasound (POCUS) in the Emergency Department (ED) Diagnosis of Small Bowel Obstruction (SBO)

Introduction A computed tomography (CT) scan and point-of-care ultrasound (POCUS) are commonly employed for diagnosing small bowel obstructions (SBOs). Prior studies demonstrated that POCUS has 90-95% sensitivity and specificity compared with CT scanning, which is the gold standard. Unlike other imaging modalities (in which the ordering and performing clinician are not the same), POCUS-performing/interpreting sonologists must recognize the risk of confirmation bias in the POCUS application. Per Bayesian analysis, the likelihood of a diagnosis being true following a diagnostic test is based on the ordering clinician's pre-test probability and the test characteristics (sensitivity and specificity, from which positive and negative likelihood ratios can be calculated). Consequently, establishing pre-test probability is important in informing downstream diagnostic or therapeutic interventions, as pre-test probability influences post-test odds. Little research has been done on the role of POCUS sonologist's pre-test probability and actual POCUS results regarding SBO. This study assessed the role of POCUS, integrating pre-test probability and POCUS results to determine post-test odds. Methods One hundred six patients were recruited on a convenience basis and underwent POCUS and CT between April 2017 and December 2022. All sonographers were credentialed in POCUS. POCUS sonologists' pre-test probabilities and POCUS and CT results were captured, which were compared. Sensitivity, specificity, LR+, and LR- were calculated, and correlations were made between pre-test probability and POCUS and CT results.  Results POCUS exhibited a sensitivity of 92% and specificity of 90%, with a corresponding positive likelihood ratio (LR+) of 9.3 and a negative likelihood ratio (LR-) of 0.09 for diagnosing SBO. Among patients with a high pre-test probability of SBO, a negative ultrasound yielded post-test odds of 0.4%, whereas a positive POCUS yielded post-test odds of 39.6%. Among patients with a low pre-test probability, a negative POCUS resulted in post-test odds of 0%, while a positive POCUS led to post-test odds of 2.1%, yielding a number needed to scan (NNS) of ~50 to identify a patient with an SBO on CT. Conclusion This study confirmed POCUS's sensitivity and specificity of ~90-95% and a corresponding LR+ of 9.2 and LR- of 0.9. Pre-test probability substantially affected post-test odds. Patients with a high pre-test probability and a positive POCUS had post-test odds of 39.6 and should have a confirmatory CT, while those with a negative POCUS have very low post-test odds and very likely will not benefit from CT. Patients with low pre-test probability and a positive POCUS have post-test odds of 2.1%, similar to the Wells Score and HEART score; such patients may not benefit from a CT, though clinicians should use their judgment/discretion. Patients with a low pre-test probability and a negative POCUS have post-test odds of 0% and should not have a CT. Among low pre-test probability patients, the NNS was ~50 to identify patients with an SBO on CT.

Diagnosis and treatment of appendicitis: systematic review and meta-analysis

BACKGROUND

The optimal diagnosis and treatment of appendicitis remains controversial. This systematic review details the evidence and current best practices for the evaluation and management of uncomplicated and complicated appendicitis in adults and children.

METHODS

Eight questions regarding the diagnosis and management of appendicitis were formulated. PubMed, Embase, CINAHL, Cochrane and clinicaltrials.gov/NLM were queried for articles published from 2010 to 2022 with key words related to at least one question. Randomized and non-randomized studies were included. Two reviewers screened each publication for eligibility and then extracted data from eligible studies. Random effects meta-analyses were performed on all quantitative data. The quality of randomized and non-randomized studies was assessed using the Cochrane Risk of Bias 2.0 or Newcastle Ottawa Scale, respectively.

RESULTS

2792 studies were screened and 261 were included. Most had a high risk of bias. Computerized tomography scan yielded the highest sensitivity (> 80%) and specificity (> 93%) in the adult population, although high variability existed. In adults with uncomplicated appendicitis, non-operative management resulted in higher odds of readmission (OR 6.10) and need for operation (OR 20.09), but less time to return to work/school (SMD - 1.78). In pediatric patients with uncomplicated appendicitis, non-operative management also resulted in higher odds of need for operation (OR 38.31). In adult patients with complicated appendicitis, there were higher odds of need for operation following antibiotic treatment only (OR 29.00), while pediatric patients had higher odds of abscess formation (OR 2.23). In pediatric patients undergoing appendectomy for complicated appendicitis, higher risk of reoperation at any time point was observed in patients who had drains placed at the time of operation (RR 2.04).

CONCLUSIONS

This review demonstrates the diagnosis and treatment of appendicitis remains nuanced. A personalized approach and appropriate patient selection remain key to treatment success. Further research on controversies in treatment would be useful for optimal management.

The Effect of Preoperative Imaging on the Negative Appendicectomy Rate

Background Appendicitis is one of the most common causes of acute abdominal pain and appendicectomy is one of the most frequently performed surgical procedures. The proliferation of radiological imaging has reduced the number of patients who have a normal appendix removed, i.e., a negative appendicectomy. We aimed to assess the effect of preoperative imaging on the negative appendicectomy rate (NAR). Methodology All emergency appendicectomies performed at a district general hospital in the United Kingdom over two separate one-year periods were retrospectively analysed using emergency theatre log books. The timeframes were chosen based on the introduction of a diagnostic pathway to reduce the number of appendicectomies performed on patients later found not to have appendicitis or alternative abnormality, i.e., a negative appendicectomy. This pathway involved a greater emphasis placed on preoperative imaging (CT or ultrasound) for patients with suspected appendicitis. The study excluded any patients who were found to have an alternative pathology during surgery. Information technology databases were used to collect data on patient demographics, date of surgery, histology, and any preoperative imaging that was performed. All histological findings showing acutely inflamed appendices and those positive for malignancy were categorised as positive, whereas all other findings were categorised as negative. Results During our initial data collection period (April 2018 to April 2019), we collected data on 207 patients who underwent an appendicectomy. The NAR was 17%. During our subsequent data collection period (August 2020 to August 2021), we collected data on 184 patients. The NAR was 16%. In our adult population, the NAR decreased from 13% to 9%. Discussion At first glance, the NAR does not seem to have improved. On closer look, all patients over the age of 21 years in our re-audit underwent pr-operative CT, and there was a reduction in the NAR in these patients. The issue arises with younger patients, in whom justifying the radiation associated with a CT scan may be difficult. Although ultrasound does not carry the same radiation risk, previous audits at our trust have that shown its sensitivity and specificity for appendicitis is approximately 60%. We may have to explore alternative imaging modalities such as MRI in the paediatric population or accept the higher NAR.

Diagnostic accuracy of a pragmatic, ultrasound-based approach to adult patients with suspected acute appendicitis in the ED

BACKGROUND

Systematic imaging reduces the rate of missed appendicitis and negative appendectomies in patients with suspected acute appendicitis (AA). Little is known about the utility of ultrasound as a first diagnostic measure in patients with suspected AA. The aim of this retrospective study is to determine whether ultrasound, performed by emergency physicians or radiologists, can be used as first diagnostic measure in suspected cases to rule out AA and to avoid unnecessary CT.

METHODS

We performed a retrospective analysis at the ED of the University Hospital Bern, Switzerland, from 2012 to 2014. Our standard protocol is that all adult patients suspected of appendicitis receive an ultrasound as their first imaging test, either by an emergency physician or a radiologist. The test characteristics of conclusive and inconclusive ultrasound exams were compared with a pragmatic gold standard.

RESULTS

The study included 508 patients with suspected AA. 308 patients (60.4%) had a conclusive ultrasound. Among these, sensitivity for appendicitis was 89.6% (95% CI 82.1% to 94.3%), specificity 93.8% (89.1% to 96.6%), the positive predictive value was 87.98 (80.84 to 92.71) and the negative predictive value was 94.65 (91.18 to 96.80). The remaining 200 (39.4%) patients had an inconclusive ultrasound exam. 29% (59/200) of these patients ultimately had appendicitis. Less experienced emergency physician sonographers came to a definitive conclusion in 48.1% (95% CI 36.9% to 59.5%), experienced emergency physician sonographers in 76.0% (68.4% to 82.5%) and radiologists in 52.4% (44.5% to 60.2%).

CONCLUSION

A conclusive ultrasound of the appendix performed by either emergency physicians or radiologists is a sensitive and specific exam to diagnose or exclude AA in patients with suspected AA. Because of 6% false negative exams, clinical follow-up is mandatory for patients with negative ultrasound. An inconclusive ultrasound warrants further imaging or a follow-up visit, since 29% of patients with inconclusive ultrasound had an AA.

A prospective, multicenter evaluation of point-of-care ultrasound for appendicitis in the emergency department

OBJECTIVE

The main objective of this study was to evaluate the accuracy of point-of-care ultrasound (POCUS) for the diagnosis of appendicitis in a general emergency department (ED) population as performed by emergency physicians with variable ultrasound experience.

METHODS

We performed a prospective, multicenter, observational study examining a convenience sample of adult patients with potential appendicitis presenting to the ED between July 2014 and February 2020. Each emergency physician-performed POCUS was interpreted at the bedside and retrospectively by an expert reviewer. Test characteristics were calculated for POCUS and blinded expert interpretation compared to surgical pathology in patients undergoing appendectomy and advanced imaging in patients managed nonoperatively.

RESULTS

A total of 256 subjects were included in the primary analysis with an overall appendicitis prevalence of 28.1%. For the diagnosis of appendicitis, POCUS demonstrated an overall sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 0.85 (95% confidence interval [CI] = 0.74 to 0.92), 0.63 (95% CI = 0.56 to 0.70), 2.29 (95% CI = 1.85 to 2.84), and 0.24 (95% CI = 0.14 to 0.42), respectively. Expert review yielded a lower sensitivity (0.74 [95% CI = 0.62 to 0.83]) with a similar specificity (0.63 [95% CI = 0.56 to 0.70]).

CONCLUSION

POCUS is moderately accurate for acute appendicitis as performed by emergency physicians with a wide range of ultrasound expertise, but lacks adequate sensitivity and specificity to function as a definitive test in an undifferentiated ED population. Further study is warranted to elucidate the optimal role of integrated POCUS in the general approach to suspected appendicitis.

Identifying Retrocecal Appendicitis on Point-of-Care Ultrasound (POCUS)

BACKGROUND

Retrocecal appendicitis may be challenging to find. We present the first case series in which retrocecal appendicitis was found on point-of-care ultrasound (POCUS).

CASE REPORTS

In each of the five cases, appendicitis was found by a pediatric emergency physician in the right periumbilical region or right upper quadrant. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The POCUS practitioner should scan both the right upper and right lower quadrant of the abdomen in search of appendicitis, as well as in search of signs of perforation.

Point-of-care ultrasound in primary care: a systematic review of generalist performed point-of-care ultrasound in unselected populations

BACKGROUND

Both the interest and actual extent of use of point-of-care ultrasound, PoCUS, among general practitioners or family physicians are increasing and training is also increasingly implemented in residency programs. However, the amount of research within the field is still rather limited compared to what is seen within other specialties in which it has become more established, such as in the specialty of emergency medicine. An assumption is made that what is relevant for emergency medicine physicians and their populations is also relevant to the general practitioner, as both groups are generalists working in unselected populations. This systematic review aims to examine the extent of use and to identify clinical studies on the use of PoCUS by either general practitioners or emergency physicians on indications that are relevant for the former, both in their daily practice and in out-of-hours services.

METHODS

Systematic searches were done in PubMed/MEDLINE using terms related to general practice, emergency medicine, and ultrasound.

RESULTS

On the extent of use, we identified 19 articles, as well as 26 meta-analyses and 168 primary studies on the clinical use of PoCUS. We found variable, but generally low, use among general practitioners, while it seems to be thoroughly established in emergency medicine in North America, and increasingly also in the rest of the world. In terms of clinical studies, most were on diagnostic accuracy, and most organ systems were studied; the heart, lungs/thorax, vessels, abdominal and pelvic organs, obstetric ultrasound, the eye, soft tissue, and the musculoskeletal system. The studies found in general either high sensitivity or high specificity for the particular test studied, and in some cases high total accuracy and superiority to other established diagnostic imaging modalities. PoCUS also showed faster time to diagnosis and change in management in some studies.

CONCLUSION

Our review shows that generalists can, given a certain level of pre-test probability, safely use PoCUS in a wide range of clinical settings to aid diagnosis and better the care of their patients.