Paediatric Point of care ultrasound: Big Kids playing with toys or the future of Paediatric emergency medicine? Part I

‘That it will ever come into general use, notwithstanding its value, is extremely doubtful; because its beneficial application requires much time and gives a good bit of trouble both to the patient and the practitioner; because its hue and character are foreign and opposed to all our habits and associations.’

You could be forgiven for thinking that this famous quote has been taken from a review of the latest handheld ultrasound device from Butterfly or Clarius but you’d be wrong! No, instead this quote was taken from an 1821 review of the stethoscope, grandly titled “A Treatise on the Diseases of the Chest, in which they are described according to their Anatomical Characters, and their Diagnosis established on a new Principle using Acoustick Instruments” by an eminent English doctor Sir John Forbes (more on him at the end). The symbol of doctors worldwide- the stethoscope had recently been invented by the French physician René-Théophile-Hyacinthe Laënnec in 1819. Despite being over two hundred years old the content of the review could also be applied by some critics to Point-of-care ultrasonography (POCUS) and especially to the discipline of paediatric POCUS. I for one certainly don’t think this is true of POCUS (although it does take time and effort to learn the skills) but whenever something new comes along in medicine be that a new test, treatment or clinical decision rule as clinicians we owe it to ourselves and patients to weigh up the evidence and make an informed decision to change or continue the way we practice. POCUS in adults is well-established in most emergency departments but less so in paediatric emergency medicine. I believe that the weight of evidence supports its use in paediatric emergency medicine in many conditions as a quick, accurate and radiation-free extension of the clinical examination.

Point-of-care ultrasonography (POCUS) is defined as ultrasonography brought to the patient and performed by the clinician in real-time. POCUS by emergency physicians is designed to ask rapid binary yes or no questions at the patient’s bedside that will immediately alter the clinical course e.g. does this patient have a pneumothorax or testicular torsion? (Friedman et al 2019). Its practice has become an ‘essential tool’ in adult emergency medicine (Leidi, A., et al. 2020) but is used less in paediatric emergency medicine despite its clear suitability. Its biggest advantage in young children is the reduction of radiation exposure where the hazards of radiation causing malignancies are becoming better understood. Data now shows that one solid organ malignancy occurs in one out of every 300 to 390 girls and one out of every 670 to 690 boys undergoing abdominal CT with the risks highest in younger children (Miglioretti et al 2013). Other benefits include the use of repeated scanning of the same patient to assess the impact of an intervention, its low cost and improved patient safety during invasive procedures. Lastly, it promotes time at the bedside of the critically ill child, which has direct benefits of prompt recognition of deterioration and potentially indirect benefits of increasing parental satisfaction (Potter and Griksaitis 2019).

Reasons, why POCUS is used less in paediatric patients, include poor access to training, perceived lack of evidence and difficulties with image acquisition (Le Coz, et al. 2018). Other concerns regard the risk of litigation from a wrong diagnosis but whilst anxiety about being involved in a lawsuit is genuine the evidence doesn’t support this. A retrospective study of American medical lawsuits found that between 2008-2012 only five cases of malpractice against emergency physicians involving POCUS and the complaint was that POCUS wasn’t used when it should have been. (Stolz et al 2015).

Despite the benefits of POCUS, the evidence base isn’t as well established as in adults so the purpose of this blog post is to review the current role and evidence for POCUS in the practice and management of common paediatric presentations.

The Lungs

Anatomically speaking children are well suited to lung ultrasound. Their relative absence of adipose tissue compared to adults, the fact that the chest wall is only partially ossified and the larger thymus acting as an acoustic window all allow good access to the lungs with POCUS (Musolino, A., et al. 2022). So useful is lung POCUS that Chaoyang District Maternal and Child Healthcare Hospital in Beijing, China have abolished chest X-rays and rely solely on lung ultrasound!

Pneumothorax

One of the most useful applications of POCUS is in the diagnosis of pneumothorax. A pneumothorax is a potentially life-threatening condition where the visceral and parietal pleura of the lung separate due to air entrapment in the pleural space. Many clinicians will be familiar with using the linear probe between two rib spaces in adults where the pleura is clearly seen as a sliding white line. In a pneumothorax this characteristic lung sliding appearance of the pleura is absent and the normal ‘waves and beach’ appearance on M-mode is also lost and replaced by the ‘Barcode or Stratosphere’ sign.

Other useful signs to rule out a pneumothorax are the presence of B-lines, using pulsed wave doppler at the pleura to confirm lung sliding (especially in conditions with less lung sliding such as apnoea or pleuritis) and the presence of the ‘lung pulse’ which is produced by the transmission of cardiac pulsation through the touching visceral and parietal pleura (Potter and Griksaitis, 2019). The ‘Lung point’ is a sign that is thought to have 100% specificity for diagnosing a pneumothorax. This is the junction where the visceral pleura begins to separate from the parietal resulting in partial lung sliding at the pleura and mixed normal and barcode appearance on M-mode. (Lichtenstein, D. and Malbrain, M.L., 2015). A good summary with images and scanning tips can be found here.

In a systematic review and meta-analysis the pooled specificity and sensitivity of lung ultrasound in the diagnosis of neonatal pneumothorax was 98% and 99% respectively (Fei, Q., Lin, Y. and Yuan, T.M., 2021). This successful diagnostic process has also been shown to lead to faster bedside interventions (Deng, B.Y et al. 2020).

Pneumonia

Across the world pneumonia is the highest infectious cause of mortality in children under five years of age. Guidelines suggest the diagnosis should be made clinically (Harris et al., 2011) but this can be challenging due to non-specific signs, cross-over with viral illness and the risk of inappropriate antibiotic use. Chest radiography is commonly used to aid diagnosis but lacks sensitivity and has no clear definition of what a positive x-ray is (Lissaman et al., 2019). Chest auscultation has also been shown to have a limited value in childhood pneumonia especially when the area of consolidated lung is small as shown on lung ultrasound (Lovrenski et al., 2016). Pneumonia has characteristic appearances on lung ultrasound that help clinicians make a diagnosis. Pleural line abnormalities, consolidated lung, dynamic air bronchograms, B-lines and pleural effusion can all be visualised on lung ultrasound.

A meta-analysis of lung ultrasound for pneumonia has shown lung ultrasound to have a much higher diagnostic accuracy compared to chest radiography in the diagnosis of paediatric pneumonia with a pooled sensitivity of 96% and specificity of 93% (Pereda et al., 2015).

A further area of promising research is in POCUS ability to differentiate between bacterial and viral causes of pneumonia (Guitart et al., 2021) If this is proven in future research this could lead to better diagnoses and reduced inappropriate antibiotic use.

As in adults, lung ultrasound has been used in the diagnosis of children with suspected Covid-19 infections. Common findings include B-lines, sub-pleural consolidations and pleural irregularities.

Lung ultrasound is also useful in the evaluation of other lung diseases such as bronchiolitis and atelectasis. Studies have demonstrated that clinicians can differentiate pneumonia from bronchiolitis and atelectasis with >85% sensitivity and specificity. Lung ultrasound can also predict the severity, requirement for oxygen and prognosis in emergency department patients with bronchiolitis (Burton, Bhargava and Kong, 2021).

Musculoskeletal

Limping child

The limping child is a common presentation to emergency departments worldwide with a reported annual incidence of 1.5–3.6 per 1000 (Adamson and Waterfield, 2020). The differential is wide from benign transient synovitis to more serious causes such as a septic hip, fractures and malignancies.

Whilst hip and pelvis X-rays form the majority of the diagnostic work-up, the role of POCUS is becoming more established. The hip is best imaged with a linear probe with the marker pointed toward the umbilicus. The key area of interest to look for is an effusion in the synovial space anterior to the femoral neck. The opposite hip should also be imaged for comparison. A positive scan is defined as a measured effusion is >0.5 cm between the anterior surface of the femoral neck and the posterior surface of the iliopsoas muscle, an effusion with >0.2 cm difference compared to the opposite hip or asymmetrical views of the anterior synovial space compared o the other hip. Good summaries can be found here and here.

The best evidence for POCUS in suspected hip effusion comes from a retrospective study by Cruz et al in 2018. They looked at the notes of 516 patients (926 hip POCUS exams) to assess the utility of hip POCUS exams. The results of hip POCUS had a sensitivity of 85% and a specificity of 98%. The overall accuracy of the PEM-physician performed hip POCUS was 93%.

https://www.thepocusatlas.com/pediatrics

Fractures

Forearm fractures account for one-third of paediatric fractures, usually as a result of a fall onto an outstretched arm. In 2016 a systematic review and meta-analysis looking at the accuracy of POCUS in diagnosing paediatric forearm fractures compared to plain X-rays. It looked at 16 studies with 1,204 patients and showed an excellent pooled sensitivity of 97% (93–99% 95% CI), specificity of 95% (89–98% 95% CI), positive likelihood ratio (LR) 20.0 (8.5–47.2) and negative LR 0.03 (0.01–0.08). One caution with this review is that adults were also included but 11 of the papers involved only children. Unfortunately, there was no review of the paediatric papers solely (Hamer et al., 2016).

In two more recent papers looking at the accuracy of POCUS for distal forearm fractures solely in children found sensitivities of 94.7% and 91.5% respectively and specificities of 93.5% and 87.6%. In addition, despite having the probe placed over a fracture site POCUS was found to be no more painful than having an X-ray, was quicker to perform than an X-ray and was preferred to X-rays by both the child and their caregivers. (Poonai et al., 2017 and Rowlands et al., 2017). POCUS can also assist with fracture reductions.

More recently this paper in the New England Journal of Medicine by Dr Peter Snelling demonstrated that POCUS as the initial diagnostic imaging method was non-inferior to radiography about the outcome of physical function of the arm at 4 weeks. The technique is relatively easy to learn with another study, also by Dr Snelling showing 90% accuracy of scanners after only 15 scans.

There is less evidence for POCUS in lower limb fractures but it has been used in the diagnosis of toddler’s fractures of the tibia. The evidence is limited but POCUS appears to be useful, especially in cases when the X-rays are initially negative (Hulme and Naguib, 2022)

Gastrointestinal

Acute Appendicitis

Abdominal pain is a very common presentation to paediatric emergency departments and acute appendicitis, the leading cause of emergency paediatric surgery is one of the chief differential diagnoses. Appendicitis is caused when the appendiceal lumen is obstructed by stones, faecoliths or other inflammatory processes. The consequences of a missed appendicitis are serious and can even be life-threatening through perforation, peritonitis and sepsis. Making a timely diagnosis is challenging, especially in younger children and various clinical decision rules have been developed such as the Alvarado score and Paediatric Appendicitis score. Unfortunately, the reported sensitivities and specificities of these decision rules vary and so their usefulness is limited. Diagnostic tests such as radiologist performed ultrasound and CT and MRI scans can give more accurate diagnoses with sensitivities and specificities from systematic reviews of CT for appendicitis of 94% and 95% and 96.5% and 96.1% for MRI scanning. However, these scans are not always readily available and can take time and in the case of CT expose the child to radiation. To improve the diagnostic process POCUS has been employed to aid clinicians who see children with suspected acute appendicitis.

Experts advocate different techniques but the linear probe is usually the best probe to use although in more obese patients the curvilinear probe can be used. The patient should have had appropriate analgesia and be laid flat on the bed with their right leg crossed over their left as this can move the appendix more anteriorly. The simplest and often fastest technique to use is to place the probe gently in the area of maximum tenderness and scan around this area. If you don’t immediately see the appendix other techniques include scanning along the right iliac artery as the appendix can lie anterior to it and just medial to the psoas muscle. The POCUS Atlas give a great summary here. One caveat to be aware of is that POCUS has a lower sensitivity for a perforated appendix as the classic tubular shape is lost.  

A recent systematic review by Benabbas et al 2017 looked at the role of POCUS in diagnosing acute appendicitis in children as well as the physical examination, blood tests and Paediatric Appendicitis Score (PAS). Five POCUS studies including a total of 461 patients found pooled sensitivities of 86% and specificity of 91%. The reference test in all studies was surgical and histopathological tissue findings. The paper concluded that ‘no single history, physical examination, laboratory test finding, or PAS cut-off point to be sufficiently robust enough to rule out AA and eliminate the need for using CT scan or MRI’ and that a positive ED point-of-care ultrasound is diagnostic.

Intussusception

Intussusception is the most common cause of bowel obstruction in children. It is caused when the ileum ‘telescopes’ into the caecum leading to compression of the mesentry and congestion of the venous and lymphatic systems. If undetected it can lead to gut ischaemia, perforation and significant morbidity. Symptoms are non-specific with less than half of children having the classical triad of abdominal pain, mass and bloody stools and as the typical age of presentation is 6-36 months history is limited also. Diagnosis is typically made by radiologist ultrasound but a recent systematic review and meta-analysis have shown that POCUS by emergency physicians has a pooled 95.1% sensitivity and 98.1% specificity (Lin-Martore et al., 2022) Academic Life in Emergency Medicine has another great summary here of images and scanning techniques.

Typically POCUS findings are “target or donut sign” where one part of the bowel (intussusceptum) telescopes into another part of the bowel (intussuscipiens). Another feature is the “pseudokidney” sign where the hyperechoic intussusceptum telescopes into the hypoechoic intussuscipiens.

Testicular Torsion

https://www.thepocusatlas.com/pediatrics

The acute scrotum is another common presentation to Emergency Departments. The causes can be relatively benign such as epididymitis but the most serious cause is testicular torsion. Diagnostic uncertainty occurs due to overlapping of symptoms and so many children are taken for an unnecessary scrotal surgical exploration to exclude a torsion. Ultrasound has been used to help with the diagnostic workup but any delays to surgery in true testicular torsion can increase the risk of losing the testis and subsequent future fertility risks as well as concerns about ensuing litigation. Evidence shows that patients who receive surgery within 6 hours of onset of pain almost always manage to keep the testis whereas after 24 hours the chance of saving the testis is low (Gopal et al., 2021).

The evidence for POCUS in paediatric populations is limited to mainly case reports but one retrospective study has shown promise. In 120 patients presenting with an acute scrotum, POCUS detected all 12 cases of torsion with one false positive which turned out to be a torsion of the testicular appendage. (Friedman et al., 2019)

Results for the correct diagnosis of all causes of acute scrotal pain showed 70% accuracy (95% confidence interval 62-78%) which is much less than for torsion but it can be argued that the emergency physician’s primary goal in the management of an acute scrotum is not to miss testicular torsion and this study shows excellent sensitivity for that. The study also found that POCUS was performed a median of 73 minutes faster than formal radiology ultrasound which would significantly reduce time to surgery and Emergency department length of stay. (Friedman et al., 2019)

A more recent systematic review of four studies totalling 784 patients has shown excellent sensitivity and specificity of 98.4% and 97.2% for the diagnosis of paediatric POCUS for testicular torsion although the risk of bias in the studies was thought to be high.

A 2021 study from the U.K. has shown that only 24.5% of cases of scrotal pain that proceed to scrotal surgical exploration actually have testicular torsion. They have proposed a diagnostic strategy that incorporates the use of POCUS to try to reduce the unnecessary numbers of negative scrotal explorations (Gopal M., et al 2021).

The authors of this paper are planning a study comparing the usual practice to a strategy that utilizes the testicular workup for ischaemia and suspected torsion (TWIST) score and POCUS to see if diagnostic accuracy improves. This will be a significant area of future research and could further define the role of POCUS in the assessment of the acute scrotum (Gopal M., et al 2021). Another future planned diagnostic POCUS trial Rescue aims to further define the role of POCUS in suspected torsion- watch this space!

Conclusion

I must admit I was a little bit disingenuous to Sir John Forbes with the initial quote. In later versions of the review the quote was removed as Sir John had clearly changed his mind,

‘I have no doubt whatever, from my own experience of its value, that it will be acknowledged to be one of the greatest discoveries in medicine by all those who are of a temper, and in circumstances, that will enable them to give it a fair trial.’

I think it’s great that after a few years of practice and experience with using the stethoscope, Sir John had come to a different conclusion. This perfectly demonstrates the learning curve that all of us experience with learning new skills be that driving, dancing or POCUS! The evidence supporting the use of POCUS in children is mounting. It has clear benefits in emergency medicine for respiratory, cardiac, musculoskeletal and abdominal conditions and helping to gain intravenous access. The evidence doesn’t support POCUS use in trauma (although it does have good specificity) and must be used with caution if at all in cardiac arrests.

As with all diagnostic tests the results need to be interpreted in the clinical context of the child and in the cases where the sensitivity of that test isn’t sufficient to rule out disease then other tests need to be sought.

Another caveat is that the evidence needs to be interpreted with caution as most of these studies are done by enthusiasts and the results are not always generalisable to the novice scanner. Ultimately, it’s up to each individual clinician to invest in their own education to make sure they are as competent as they can be in scanning and use POCUS for the conditions where the evidence is strongest.

Thanks for reading and happy scanning! Hopefully, you’re already convinced about the benefits of paediatric POCUS but if you’re not like Sir John you’ll have a change of heart! Keep an eye out for part II coming soon……

Pete

Further reading

The CACTUS course is a great introduction to paediatric POCUS https://ics.ac.uk/learning/cactus.html

The POCUS Manifesto– not necessarily aimed at paediatric POCUS but a great read about the history of diagnostics and development of POCUS

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