Introduction

Over the past few decades we have seen a gradual aging of the general population and a change in clinical characteristics of internal medicine (IM) patients: older; affected by chronic illnesses with acute exacerbation, by multiple, often unacknowledged, co-morbidities, by a complex profile and by frailty [1–3]. We have, therefore, moved from a disease-oriented vision of medicine to an integrated multidisciplinary holistic person-oriented approach [4].

In this context, we have also moved to a new organization of the entire medical network, both outside and inside the hospital (i.e. hub and spoke hospitals). Organization of acute care hospitals and IM departments are changing according to the intensity of care and nursing complexity to assure the real need of hospitalization [5], taking into account health care demand and cost restraints in the concept of an economically sustainable health system.

Optimizing the use of limited resources is, therefore, fundamental to appraise the role of old, simple and accurate, best clinical practice, such as history and physical examination [6], and new simple diagnostic approaches, such as bedside US [7–9].

In recent years, technological improvements have allowed the development of miniaturized US devices comparable to personal computers, tablets and even to smart phones. For many years clinicians with US expertise have supported the bedside use of US; more recently, a huge amount of evidence has established the indications and the advantages of a clinical US approach, in the concept of an ultrasound stethoscope [10–12].

Because US is an extremely user-dependent technique, we now need (a) to ensure training, during and after a medical degree, (b) to define the different levels of competence, indications, limits and characteristics of different devices (c) to establish the advantages of an appropriate use of US, integrating physical examination and clinical data. The purpose of this is to limit an approach, used increasingly more often in daily clinical practice, that is based on a direct prescription of instrumental or laboratory tests. Stimulated by the constant search for maximum efficiency, this approach is often unnecessary and costly, at the expense of the traditional physical examination.

SIMI Ultrasound Study Group

With this in mind, since 2005 the Italian Society of Internal Medicine (SIMI) has been organizing the Summer School of US, a national annual course, dedicated to IM residents. In 2009, the SIMI Study Group on US was founded to define the SIMI learning program in US. We identified all Italian IM departments with US expertise able to provide the training stages to IM residents attending the SIMI Summer School of US (Fig. 1). A national SIMI network of bedside US schools was then organized for all IM specialists who want to learn and to obtain the SIMI certificate in bedside US (Fig. 2).

Fig. 1
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Italian distribution of US SIMI centres willing to accept students of postgraduate course of specialization school (residents) in IM who have attended the SIMI Summer School of US. Different colour areas are related to the number of US examinations per year (1,500–2,000 blue, 2,000–4,000 green, 4,000–9,000 yellow, more than 9,000 pink)

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Fig. 2
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Italian distribution of SIMI Schools that organize theoretical and practical course of bedside US for all Internal Medicine specialists

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The SIMI Working Group of US first defined bedside US as all examinations performed bedside by the clinician with small, portable or transportable instruments. The recent introduction of miniaturized devices made a further distinction necessary: first level bedside US, performed with pocket size devices that we will call “Echoscopy” (ES), and second level “Point of Care US” (POCUS) performed with portable instruments, as recently also stated in the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) [13]. In fact, the technical resolution, the size of the screen, the absence of spectral or power Doppler and different probes limit the diagnostic power of pocket size devices used for ES. On the positive side, they have the advantage of being hand-held, fitting in pockets and thus easily available to integrate every physical examination, from emergency conditions to daily examinations performed bedside, both in clinical departments as well as in the ambulatory settings (Fig. 3). POCUS can also be used in the same settings, but, although they are bulkier and heavier, they do have better resolution, a larger screen, and the technological improvements mentioned above, that provide greater diagnostic power (Fig. 4).

Fig. 3
figure 3

Echoscopy with a “pocket size” instrument in an IM department. US scan of left kidney performed by a resident under supervision

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Fig. 4
figure 4

Point of Care US performed bedside by a “tablet” like instrument. US scan of abdominal aorta

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As concerns training and skills in the first and second levels of bedside US, the SIMI Group stated that the SIMI certificate of competence of first level of bedside US or ES is achieved by participation in (1) theory bedside US course (4 h of didactics) held every year in the SIMI National Congress, (2) theory and practical bedside US one-week course (36 h of training consisting in the participation in 75 US exams, 50 as an observer and 25 performed under an expert’s supervision) in a SIMI school, according to the educational program shown in Table 1 [14].

Table 1 Echoscopy—diagnostic power and use
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By means of ES, the competence acquired makes it possible to answer general questions usually in terms of the presence or absence of simple, macroscopical, US findings (i.e. is pleural or pericardial or abdominal effusion present? Is the lung wet or dry? Is there a solid or liquid mass?), postponing more complex diagnosis to the second level of bedside US.

The SIMI certificate of competence of second level bedside US or POCUS is achieved by means of (1) obtaining the certificate for the first level of competence, (2) participation in one theory bedside US course (6 h of didactics), organized by one of the SIMI national schools and (3) theory and practical bedside US two-week course (72 h of training consisting of the participation in 150 US exams, 100 as an observer and 50 performed under an expert’s supervision) in a SIMI school, according to the educational program shown in Table 2 [15, 16]. The teaching program of POCUS is, therefore, more complex and divided into five learning modules. With the use of POCUS, we, therefore, increase not only the clinical applications of bedside US (i.e. deep venous thrombosis, heart morphology and function, characterization of various abdominal lesions, pulmonary end neck pathologies) but we also achieve a more accurate and precise diagnosis than obtained at the preliminary ES evaluation. The competence acquired with the second level permits identification of all the conditions shown in Tables 1 and 2. In case of doubt, the patient will be re-evaluated with a “second opinion” expert physician [17], using the same device or a better performing one (i.e. transportable), or transferring the patient to the hospital US centre.

Table 2 Point of Care US, diagnostic power and use
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To better explain the training program for the second level of bedside US, we will now briefly describe the principal applications and advantages of POCUS in various clinical settings, as summarized in Table 2, according not to the importance of the technique in each clinical setting but to the methodology of the physical exam. This strengthens the message of a first level of bedside US for internists, as ES and POCUS, which concludes the history and physical examination, and increases the clinician’s accuracy of the latter as an “extension of the internist’s hand”. Moreover, the SIMI US Study Group have planned multicenter studies aimed at evaluating the benefit of bedside US on the outcome of patients and costs in general, as a reduction of diagnostic tests and of hospital stays, in patients admitted to Internal Medicine departments.

In the 1st module we address the basic concepts of US (i.e. physics, semiotics, technical methodology of performing a US examination), the different US devices, in part mentioned above, and finally the appropriate indications for a second opinion complete US examination. All these topics are well known and widely described in the literature [18–21].

Patients with neck nodules

POCUS is a useful tool to integrate the physical examination of the neck in case of (a) a palpable nodule or mass; (b) appearance of compressive symptoms such as dysphagia, dysphonia, pain on chewing, and (c) clinical suspicion of disease, e.g. in the case of a clinical laboratory framework suggestive of hyper-hypothyroidism [22]. A mass in the neck can be due to several structures and causes: vessels and nerves, lymph nodes, salivary glands, thyroid and parathyroids. US allows not only a quick differential diagnosis between solid vs cystic masses but also identifies the mass, and the areas within the mass where we can guide a fine needle aspiration biopsy [23, 24].

To examine the neck by US we need high-frequency linear probes (7.5–13 MHz); no preparation is required. The swellings of the suprahyoid region are, in most of the cases, caused by an increase in volume of the salivary glands due to a salivary duct stone, or to inflammatory or expansive disease. By means of POCUS we can easily recognize (a) volume gland increases, (b) intraparenchymal hypoechoic areas due to widespread inflammation, (c) dilatation of the main duct with endoluminal lithiasis, (d) intraparenchymal hyso-hyper echoic nodules, in case of benign tumour, (e) or roundish–oval hypoechoic nodules, sometimes with calcifications and aspects of invasiveness of nearby organs, in the case of malignant disease [25, 26]. Similarly by US we can easily identify diffuse or nodular pathologies of the thyroid and differentiate solid and liquid nodules [27, 28]. Lymph nodes can increase in size in response to infectious (tuberculosis, mononucleosis, toxoplasmosis, etc.) or inflammatory (sarcoidosis, Castleman disease, etc.) and neoplastic diseases (Hodgkin’s disease, metastases of solid tumours). On the basis of US findings we can define lymph nodes as normal or reactive versus pathological ones [29, 30]. In case of reactive lymph node the US architecture is preserved, the cortex is uniformly thickened and the hilum is visible and in central position. In malignant conditions the lymph nodes are frequently enlarged, with rounded shape, irregular margin, altered echo pattern and eccentrical hilum [31, 32]. For specific US findings of various pathologies of the neck we refer to related extensive and specific literature on these topics.

Patients with cardio-respiratory diseases

Dyspnea represents the most common symptom encountered in internal medicine practice in a hospital setting [33], very often associated with a multidisease condition. For this reason, a holistic clinical approach and an integrated bedside US cardiopulmonary evaluation of a dyspnoic patient represents a major challenge for internists, both in terms of appropriate diagnosis/therapy and health resource use.

While US has been for years considered inadequate to explore the lung, evidence has now been collected demonstrating that lung US offers high accuracy not only in the identification and quantification of pleural effusion [34, 35], but also in the differential diagnosis of respiratory insufficiency [36]. Pneumothorax [37], pulmonary edema [36, 38], and pneumonia [39] are indeed recognized with an accuracy definitely higher than the standard chest X-ray study. In addition, a preserved sonographic ‘normal’ pattern in the presence of a dyspnoic patient and congruent anamnestic/laboratory data, may guide the clinician towards the diagnosis of recurrent acute phase of chronic obstructive pulmonary disease or pulmonary embolism (PE) [36]. A recent document from the Consensus Conference on Lung US [40] reported a large number of studies showing the potentiality of lung US in triage, diagnosis, follow-up and even prognosis, of patients referred for dyspnoea. Lung US is easily performed with portable devices and most of the evidence has been collected in the emergency setting, searching for mainly dichotomous answers to basic clinical questions (Is there pleural effusion? Is there a sign of pneumothorax, pulmonary edema or interstitial disease, pneumonia or atelectasia?). It has been demonstrated that a short training period is required to correctly recognize pneumothorax, pulmonary edema or signs of pulmonary fibrosis [41–43]; pleural fluid as well as diffuse interstitial syndrome are easily detected even with pocket size US devices, such as ES described above [43–45].

The same approach has been applied in the last decade to echocardiography and it has been demonstrated that even briefly trained physicians can obtain crucial information regarding heart dimension and function with good reproducibility compared to expert echocardiographers, thus implementing physical examination even by means of ES [46–49]. Of course, a clinician at the bedside cannot substitute extensive echocardiograpy; nevertheless, with the help of ES the clinician can rapidly obtain important information about the diagnosis and the optimal treatment management: is a significant systolic or diastolic dysfunction present? Are there signs of pericardial effusion, cardiac tamponade or a hemodynamically significant pulmonary embolus [50]?

Lung and cardiac US, associated with evaluation of the inferior vena cava (IVC) for estimation of intravascular volume status, can furnish an integrated approach (Fig. 5), useful not only for diagnosis but also for monitoring critical patients and guiding therapeutic intervention—for example during fluid [51] or diuretic administration [52]. In the same context as the multiorgan approach, it has been demonstrated that adding compression US (CUS) to lung and cardiac US (is there a deep vein thrombosis?) increases the accuracy of diagnosis of PE, reducing the need for computed tomography pulmonary angiography (CTPA) [53].

Fig. 5
figure 5

Example of a normal subjects (‘a’ panels) and a heart failure patient (HF) (‘b’ panels); scans have been obtained with pocket size ultrasound device. Notice in normal subject preserved dimensions of left atrium and ventricle (a1, a2), collapsibility of IVC during inspirations (a4) and ‘dry’ lung (a5); in HF: dilatated left atrium and ventricle (b1, b2), non collapsibility of IVC (b4) and ‘wet lung’ characterized by multiple B-lines (b5)

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Patients with abdominal diseases

Acute abdominal pain represents one of the most frequent causes of admission in internal medicine departments; moreover, it is also a symptom often arising during the hospital stay. The clinical approach to acute abdominal pain is now particularly enriched by small bedside US machines, as an excellent integrated tool to physical examination. Bedside US in abdominal pathology often allows a rapid and definitive diagnosis, excludes suspected diseases or indicates successive and appropriate investigations. In fact, by mean of ES we can immediately define the presence or absence of macroscopic pathology, described in Table 1 [13], and by mean of POCUS we can detect a larger number of the abdominal diseases listed in Table 2 [7, 8].

Bedside US can clearly demonstrate the presence or absence of peritoneal effusion as its quantification and represents a quick and secure method for paracentesis, performed for both therapeutic and diagnostic purposes, particularly useful in the latter case when the amount of fluid is small [54–56]. Abdominal masses such as abdominal aortic aneurysms (AAA) are also easy diagnosed with a sensitivity and specificity in emergency departments of 99 and 98 %, respectively [57]. Bedside US, performed as ES or POCUS, can clearly determine the presence of the aneurysm but with the second method we can better measure its diameter, define the morphology and its localization (above and below the renal arteries), evaluate thrombosis, and recognize cases that require urgent computed tomography (CT) angiography and surgery [58]. Hypertrophy and atrophy of the abdominal viscera (liver, spleen, kidney, etc.), like abdominal pathologies that present other morphologic changes are examples of important advantages and opportunities of bedside US [59].

A recent study shows that simple ES is sufficient both to delineate abdominal disease, and to detect abdominal focal lesions larger than 2 cm in diameter in 97.4 % and in 97 % of cases, respectively [49]. In cases of fortuitously discovered liver lesions, a precise characterization can be reached at second opinion level in the hospital US centre by contrast-enhanced US (CEUS) [60, 61]. This approach, that starts from ES and arrives at CEUS, makes it possible to select patients who may benefit from CEUS, contrast-enhanced computed tomography (CECT) or contrast-enhanced magnetic resonance imaging (CEMRI), and is not only accurate but also appropriate and inexpensive [62]. Jaundice, suspicion of biliary colic or acute cholecystitis, are easy to diagnose by ES as a dilatation of the intrahepatic bile ducts, gallbladder hydrops and large gallbladder stones. In the same clinical conditions, POCUS can document with more detail the morphological US signs of acute cholecystitis (presence of thickened walls or fluid peripheral collections), presence of biliary sludge or pus, infundibulum microlithiasis, and causes of distal common bile duct obstruction.

Similarly, in acute renal failure a simple ES allows the differential diagnosis between obstructive and non-obstructive diseases (i.e. bladder globe, hydronephrosis) and, in cases of renal colic, POCUS can better document small stones [63]. Gastrectasia and the diagnosis of the severity of bowel obstruction [64] are also easy to show by ES. Although US of the gastrointestinal tract is generally a second level survey, by means of POCUS, as an adjunct to clinical and laboratory data, it can help to diagnose some diseases or indicate successive investigations: such as for bowel wall thickening or “pseudokidney” in the case of diverticulitis, inflammatory bowel disease, appendicitis or tumours [64–67].

Patients with limb edema

“Swollen leg” represents a frequent clinical case in internal medicine, which can be from a number of possible causes, [68] and whose early diagnosis can indicate the best medical treatment that may prevent possible complications [69]. In fact, swollen leg, especially when unilateral, can be due to deep vein thrombosis (DVT), and this requires prompt diagnosis and treatment to avoid the risk of PE. Clinical examination, even if carried out with the aid of a suitable pre-test score [70–72], does not always enable an accurate diagnosis. US findings, provided by colour and power Doppler, integrate clinical information and represent the fastest way to reach a definitive diagnosis [73, 74]. Technological US innovation is today available to clinicians with instruments that are easy to use and compact in size, very suitable for point of care diagnosis without specialized backgrounds necessarily needed. In particular, CUS for the diagnosis of DVT is a very easy manoeuvre, that can be acquired with a brief period of training, and that can be done easily with a linear probe and a simple B-Mode US system. The deep venous vessels of the lower limbs are compressed with the probe, and their complete collapsibility makes it possible to exclude DVT [75]. In this “facilitated” or simplified way, CUS is confined to the femoro-popliteal segments [76] (the only one validated in the literature), and the presence of thrombosis is confirmed when complete compressibility of the vessel is not possible (Fig. 6). Proximal venous thrombosis exposes the patient to a higher risk of PE if compared to the distal forms, and US recognition of the two forms is, therefore, important both for diagnosis and treatment [77, 78]. This does not exclude a time-delayed study of the entire venous system that may be performed with more complex ultrasound equipment and by highly skilled operators.

Fig. 6
figure 6

Point of Care US performed bedside with superficial probe. Acute deep vein thrombosis of the popliteal vein (short axis): the vessel is enlarged, filled with echoes and not compressible

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The use of bedside US evaluation of patients with signs and symptoms of PE has been controversial [79]. CTPA is considered the gold standard for the diagnosis of PE, and is frequently performed in patients with cardiopulmonary complaints. However, indiscriminate use of CTPA results in significant exposure to ionizing radiation and contrast. Recently a screening ultrasound protocol has been proposed for patients suspected of having PE to predict the need for CTPA: the examination consists of a limited echocardiogram, thoracic ultrasonography and lower extremity deep venous compression study [80]. This protocol has been considered suitable for the diagnosis of PE with high specificity, especially for pregnant women to avoid the high foetal radiation exposure risk. However, its poor sensitivity implies that further testing may be necessary to fully rule out a pulmonary embolism. Moreover, the venous compression study may be applied at the same time and in the same way to exclude superficial venous thrombosis (SVT) that, when located near a junction with the deep venous system, requires the same treatment as DVT because of the exposure of the subject to the same high risk of PE [74, 78]. As for other applications of bedside US, this technique needs basic knowledge of normal and pathological findings (in this case regarding superficial and deep venous systems and other nearby structures), it requires a short period of training with expert tutors for the correct application of the methodology [81], and should be considered a routine part of the learning paths of all doctors of internal medicine.