The construction of this study is based on ample literature that indicates how ultrasound can be considered the imaging technique of choice both in the ordinary European hospital environment and, thanks to its low cost and easy transportability, in low-resource contexts such as intra/extra-hospital emergencies or healthcare in developing countries. Another important reason is the consideration that the relationship between medicine and the population of developing countries is often influenced by cultural backgrounds rooted in distant traditions that clash with Western medicine’s invasiveness. Ultrasound can therefore fill the role of a modern magic mirror that allows the doctor to “look inside” the patient without breaking through the “protective barrier” that surrounds the patient according to the animist culture. For this reason, it is often well accepted by people allowing for a great compliance between doctor and patient. Moreover, portability, costs, and steep learning curve on how to use the ultrasound machine make ultrasonography the most feasible imaging technique in this context.
As far as concern our results, abdominal pain was the most frequent symptom of presentation. In Sierra Leone, the only CT is a 3-hour drive from the HSH and the only imaging test locally available is plain X-ray, that is far less sensitive in the abdominal pain diagnostic pathway [5]. Taking this into account, US drastically improved the diagnostic possibility in our context. Moreover, the strongest barrier against the feasibility of US is not a big deal in Sierra Leone with only 3% of the population with a BMI >30 [6].
As mentioned in the results, most of the patients (78%) reported more than one complaint. In this situation, it is very likely to have a broad spectrum of differential diagnosis in which the US has been of paramount importance in leading to their reduction. In our primary outcome, it seems that with the US exam we obtained only a slight reduction in differential diagnoses from 1.8 diagnoses per patient to 1.5. Actually, we had a rule-out rate of 45% of pre-US diagnoses with 33% of new post-US diagnoses. This high turnover has led to the final result that can therefore be considered impressive. Moreover, the introduction of new potential and clinically unexpected diagnoses can be a valuable point since it can changes the management of the patient.
We noticed that the half of new unexpected diagnosis came in male patients, but male were only one-third of our sample. For this, the percentage of new unexpected diagnosis among men is nearly double than among women (56% for male, 32% for women, χ
2 = 5.5; 1 df; p < 0.02). This could be quite surprising if we consider that one would expect to find with the US something unexpected in a female abdomen due to the greater amount of organs and therefore make the differential diagnosis of abdominal symptoms harder. Something was missing also in the possible explanation, given that abdominal presentation was fourfold in females rather than males. Analyzing our sample, we tried to find the confounding variable dividing abdominal or non-abdominal patients on the basis of the presenting symptom. Observing the odds ratio of new diagnosis, it came out that abdominal presentation did not conduce to greater number of diagnosis as being male did instead (OR 3.2; CI 1.04.9.81). This tells us that male presentation was probably a risk factor itself. The explanation could lay in two possible facts that we are not completely able to analyze: male patients came with worse clinical pictures in comparison with women or the visiting doctor formulated less diagnostic hypotheses when facing a man. This second explanation came out to be unlikely, since the average of differential diagnosis was not related to sex and average of new unexpected diagnosis was not correlated to the number of differential diagnosis.
The non-homogeneous distribution of new differential diagnosis prompted by the US thoraco-abdominal exam in comparison to sole abdominal or sole cardiac has to be related with the request of the complete abdominal-thoracic exam in the cases in which the physician was less sure of his diagnostic hypotheses.
Another strong point of US is the possibility to make some final diagnoses which would otherwise be impossible. For example, in two cases we have diagnosed an aortic dilation that has led to a follow-up for the patient. In the same way, we have diagnosed one case of nephrolithiasis (rare in African population) and one of cholecystolithiasis which could not have been recognized without the US.
Analyzing the differences in therapy before and after the US examination, we can underline some issues. As far as the therapeutic strategy is concerned, we can notice how 74% of unnecessary surgeries expected before the US have been avoided. On one hand, without US three cases would not have been referred in the right hospital and two patients would not have had the early surgery they needed. On the other hand, the changes in drugs prescription, the decrease in PPI, and eradication therapy can be explained with the PUD and gastritis diagnoses reduction. These diagnoses were typically general and not specific, made by the caring physician when there were no clear features of the abdominal pain referred by the patient. With the US exam, we increased the diagnostic performance of the caring physician on the abdominal pain, the most frequent main complaint. The most important variation between pre- and post-US therapy we observed was in NSAID prescription and was probably due to the after-US new diagnoses of painful abdominal masses, abscesses, and muscular pain. In the end, although the diagnosis of cardiomyopathy decreased after the US exam, the increase in spironolactone prescription can be explained with the increase in cirrhosis diagnosis.
This study presents some merits and limitations. Its one-hospital setting cannot be clearly representative of the whole population of all low-income countries; moreover, even in low-income countries there are differences in distribution of healthcare facilities and Sierra Leone itself represents one of most deprived countries. Despite an intuitive and consolidated idea of ultrasound utility in both high and low-income countries, the ability of the physician to give the right indication for US remains a big problem to deal with. Our hospital may have had physicians that are probably different in number, experience, and ability from the physicians of another service; specifically our visiting doctor were one young general practitioner from Pakistan, one older general practitioner from Nigeria, one surgeon, and one pediatrician. One big limit is due to the absence of a certain diagnosis to compare the variation in differential diagnosis to a standard reference. This problem is widespread and, in a certain sense, it will persist in those contexts in which diagnostic facilities, whether ultrasound or other, are unaffordable to people and services. Another limit is that, even with a good sample size, our 105 patients are not enough to make reliable deductions on the single pathologies encountered, since each pathology accounts for very few cases. We were not able to fulfill the typical features of point-of-care ultrasound [7] given that our examinations were not made directly by the caring physician. This was due to the lack of doctors trained in ultrasound at all. Actually, we decided to train a nurse in ultrasound for the low doctor/population ratio of Sierra Leone that amounted at 2.2 every 100,000 population [8]. For this reason, many medical competencies, that in Western countries are doctors’ prerogative, in Sierra Leone can often be guaranteed by nurses, especially in rural zones. Finally, since US examination can be reassuring, the level of confidence of the visiting physician may have also risen because of this.
On the other hand, this study provide an example of well-integrated clinical and imaging diagnostic service, in which a point-of-care level of ultrasound facility was implemented by the collaboration between the visiting physician on duty and the sonographer, matching their ideas on the same patient in nearly real time. Both the reduction and emergence of new unexpected diagnoses are important parts of the diagnostic process and US showed to be a useful means to face this step. The confidence level of the caring physician is a point of great importance, since physician–patient relationship cannot relinquish a certain grade of confidence on the most probable diagnosis. In this context also blood tests are very expensive and limited in spectrum. Since US could aid to complete diagnostic needs, the introduction of widespread US could improve the diagnostic accuracy of local physician. The possibility to indicate an appropriate treatment instead of another, in particular a surgical one, is of paramount importance, from the point of view of safety, prognosis, and economic affordability. Finally, to our knowledge this is the first study exploring the gain in diagnostic accuracy after an ultrasound examination made by a specifically trained local nurse practitioner. In contexts with a severe lack of physician, like Sierra Leone, the results of our research highlight the usefulness of US training programs, which can be extended to all low-income countries.
Further studies are needed to explore other strong outcomes like mortality, length of stay in hospital, and money saved with the implementation of ultrasound services in low-income countries. Moreover, the Ebola epidemic brought many humanitarian resources to Sierra Leone, which could be useful to arrange a multicentric study, similar to this one, that can strengthen the results of this study.