The impact of ultrasound imaging on patient management – Let's practice the evidence

Abstract

As a novice researcher, I worked with a cardiology professor who was driven by clinical evidence. Clinical trials were his bread and butter, and leading guideline writing groups became his passion. The most memorable take-home message for me was this: Before you do any test, a clinician should ask themselves, ‘Will this change management? And if so, how?’ A clinician should know what they will do if the test is positive or negative and be able to articulate that. Sadly, this is not always the case. And whilst it might be ‘nice to know’, the cost of confirmatory tests is certainly not insignificant.

When I trained in ultrasound, we still called it ‘diagnostic ultrasound’ to differentiate it from therapeutic ultrasound, but this also highlighted the immense and unique diagnostic properties of ultrasound. Increasingly, ultrasound is used to not only diagnose, but also to monitor and screen for conditions, as well as to aid in management and prognosis. While all of these are laudable uses, I still think it is helpful when we can link our imaging directly to change in management.

In this issue of AJUM, Smith and Mistry¹ present research documenting the impact of formal echocardiography (echo) on patient management in a small clinical audit of formal echos in their intensive care unit (ICU). Although half of the patients had critical findings found on formal echo, only 25% resulted in management change. Perhaps, the remainder of the critical findings were either already suspected, and therefore being treated; or had been anticipated. Indeed, it is possible that a point of care ultrasound (POCUS) had already given them some clinical cues, and thus, the formal echo was simply confirmatory. In a reasonable number of patients, the formal echo helped make the decision to proceed with palliation and this seems an entirely reasonable reason to do an extra imaging test.

Also, in the ICU setting, Xin et al.² report on the use of Tissue Doppler Imaging (TDI) of the diaphragm to optimise the timing of weaning from mechanical ventilation in ICU patients. Using TDI to measure the low velocity motion of heart muscle is fundamental to echocardiography, so the extension to the diaphragm seems a logical extension of practice. But a good idea still needs to be tested and shown to aid patient management. Innovation needs to be effective.

Innovation is a key part of medicine, and finding new applications for imaging is part of that. Lau et al.³ applied shear wave elastography to patients in a case–control study comparing patients with COVID-19 with controls and found that patients with recent (<6 months) COVID-19 had increased liver stiffness. They were prompted to do the study after observing elevated liver enzymes in these patients. But as the authors point out, these may be transient changes, and data are needed to see whether these abnormalities are associated with persistent liver injury.

Staying on the topic of ultrasound evaluation of the liver, attenuation imaging (ATI) is a relatively new ultrasound technique providing a quantitative assessment of attenuation that may assist in evaluating hepatic steatosis, or fatty liver disease. Tan et al.⁴ present their data on patients who had undergone ultrasound and liver biopsy on the same day and concluded that although ATI strongly correlated with histological grading of steatosis, the radiologists' qualitative impression was actually the best correlate of histological findings. This is an example of where ATI did not contribute to the diagnosis, and further begs the question, if these patients still get a liver biopsy, is there really a point of adding ATI to the ultrasound? The answer to that question is evidence.

When I started my ultrasound journey, the gold standard for diagnosing heart valve disease was invasive cardiac catheterisation. But innovative research performed by forward thinking clinician scientists provided evidence, such that now, echocardiography is the gold standard for quantification of heart valve disease.

Ultrasound has power to transform, but we need evidence. Whilst I think it is great that we are finding new clinical applications for ultrasound and using the newer technologies being developed, it is important that we measure the clinical effectiveness of these techniques, as these papers have done. And we need to abandon new techniques if they do not add clinical value, indeed some may do harm. The additional clinical benefit for the patient from the imaging should be evident, and imaging should not routinely be used as another confirmatory or reassuring test. Although, of course, there are circumstances where the latter is entirely clinically appropriate.

Exploration of clinical applications for emerging ultrasound technologies has an important role; however, as these papers have shown, research should include the clinical effectiveness of these techniques as stand-alone tests, not just confirmatory reassurance.