2.1 Introduction

The resolving power of an ultrasound probe is directly proportional to the frequency emitted: with a frequency of 7.5 MHz, widely used in EUS, the spatial resolution is in the order of 1 mm. On the other hand, the depth of field that can be analyzed is inversely proportional to the frequency used (Table 1).

Table 1 EUS transducer frequency and depth of field

In recent years, equipment manufacturers have increased the range of frequencies that can be used on the same endoscope by adding relatively low frequencies (5 and 6 MHz), which allow accurate analysis to a depth of 6–8 cm, thus achieving better management of some pancreatic disorders.

2.2 Equipment

Two types of ultrasound technique are used in endoscopic ultrasound.

2.2.1 Radial imaging

Radial imaging provides 360° ultrasound images perpendicular to the axis of the endoscope.

This technique has many advantages, namely:

• Excellent image quality, allowing real-time study of the circumference of the digestive tract through 360° (Fig. 1), making the examination easier overall for all types of gut pathology, particularly for assessing locoregional involvement of cancers and their surveillance or other indications related to diseases of the gastrointestinal wall

• The ability to visualize constantly the major vascular landmarks, facilitating localization of pathology regardless of the oblique optics of the ultrasound image obtained, thus allowing precise evaluation of the structures and organs around the intestinal lumen, particularly the pancreaticobiliary region.

Figure 1 Normal gastric wall with five layers. Electronic radial scope. (1) interface between the gastric lumen and the epithelium, (2) mucosa including muscularis mucosae, (3) submucosa, (4) muscularis propria, (5) serosa and interface with the perigastric fat.

Its main drawback is that it is impossible to carry out EUS-FNA as the path of the needle passes through the plane of the ultrasound image and cannot therefore be monitored in real-time.

Because radial imaging is long-established and relatively easy to perform, it currently remains the most widely used EUS technique. Three types of apparatus have been developed as a result:

• Video-EUS (Fig. 2) for the study of the esophagus, stomach, duodenum, pancreaticobiliary region, anal canal, rectum and colon, with the option of simultaneously visualizing the ultrasound image and the endoscopic image. There are two types of radial video-EUS:

Rotating mechanical: this is the oldest type (developed in the early 1980s). It is used increasingly rarely and Doppler studies are not possible.

Electronic in B-mode. The three companies that manufacture echoendoscopes supply this type of apparatus. The endoscopic view is either end-viewing (Pentax, Fig. 2A, or Fujinon, Fig. 2B), or oblique-forward (Olympus, Fig. 2C). The instruments produce several frequencies (5–12 MHz) and thus allow Doppler studies and power Doppler sonography. The latest instruments, which are connected to very sophisticated ultrasound consoles, allow contrast harmonic ultrasound after intravenous injection of ultrasound contrast agents.

• Rigid probes are designed for examination of the anal canal and its sphincters and the lower and mid-rectum. Both rotating mechanical or electronic transducers are available.

• Miniprobes (Fig. 3) can be introduced into the operating channel of conventional endoscopes, and are particularly suited to the use of very high frequencies (20 and 30 MHz). They were developed in the mid-1990s, and are used before curative endoscopic treatment of superficial flat cancers of the digestive tract (0–IIa, b, c) and high-grade dysplasia; these very high frequency miniprobes allow accurate patient selection for curative endoscopic treatment of superficial cancers whether for endoscopic mucosectomy, submucosal dissection, photodynamic therapy or radiofrequency ablation.

• Mid-way between the miniprobe and the echoendoscope, is the ‘blind’ probe (Fig. 4; Box 1), a flexible instrument with a small diameter (7.8 mm) and lacking endoscopic optics, with a miniature transducer at its end; it uses the rotating mechanical radial technique, emitting at 7.5 MHz, and is tapered at its end (3 mm). The blind probe can be passed over a guidewire previously positioned under endoscopic control. It is intended for the examination of stenotic esophageal or rectal lesions.

Figure 2 (A) Pentax EUS scopes, radial and linear. (B) Fujinon EUS scopes, radial and linear. (C) Olympus EUS scopes, radial and linear.

Figure 3 Olympus high frequency (mechanical radial) miniprobe (30 MHz) used through a standard gastroscope.

Figure 4 Olympus blind probe MH 908 (mechanical radial 7.5 MHz).

Box 1 Blind probe (Olympus GIF-MH908)

For the esophagus, use a transnasal or pediatric gastroscope, which can pass through the stenosis without previous dilation. Aspirate the air present in the gastric lumen, position a 0.035 inch guidewire in the stomach, withdraw the endoscope, slide the blind probe onto the guidewire and insert, under ultrasound control, into the stenosis, moderately inflating the balloon to facilitate its passage. Then advance the probe into the stomach (celiac region). The examination is performed by withdrawing the probe under ultrasound control as far as the cervical esophagus.

2.2.2 Curved linear array (Fig. 2)

The ultrasound image obtained in electronic B mode is a sagittal image (Figs 5, 6) provided by an electronic transducer. The plane of the image is parallel to the axis of the endoscope.

Figure 5 Aorta. 3–5 cm under the cardia seen in longitudinal view with celiac and superior mesenteric artery (SMA) take-off. Olympus linear scope coupled with Aloka α10 console.

Figure 6 Pancreatic cancer located within uncinate process, invading the posterior side of the SMV. IVC, inferior vena cava. Electronic linear scope.

The main advantage of this technique is the ability to carry out intra- or transmural EUS-guided FNA (Fig. 7) as the path of the needle to the target can be followed in real time on the ultrasound image.

Figure 7 (A) EUS-guided FNA of a malignant (15 mm in diameter) lymph node located along the liver under the cardia. (B) Pancreatic adenocarcinoma located within the body with involvement of the celiac axis (left) with EUS-guided FNA (right) using a Pentax linear scope coupled with a Hitachi console. (C) EUS-guided FNA of a pancreatic cystic lesion (left) and a malignant lymph node (right), using a Fujinon scope coupled with a Toshiba console.

As a result of this option, therapeutic EUS uses echoendoscopes with a large operating channel.

The drawback of this type of equipment is the nature of the sagittal images as these are inappropriate for studying the circumference of the GI tract and thus assessing locoregional involvement prior to treatment or surveying cancers of the GI tract.

Two types of instrument use this technique: video-echoendoscopes and rigid probes.

• Video-echoendoscopes can be used to study the esophagus, stomach, duodenum, pancreaticobiliary region, anal canal, rectum, and colon. They are less suited to examining the esophagus, common bile duct, anal canal and rectum than instruments using the radial technique, because of the nature of the images obtained. They are also more difficult to use for the stomach and duodenum. On the other hand, they allow very satisfactory examination of the pancreas and the peripancreatic region, particularly its vascular aspect, and the posterior mediastinum.

• Rigid probes are designed for examination of the anal canal and rectum. Although the image obtained is not very practical for studying the anal sphincters and the pre-treatment assessment of rectal and anal cancers, it nevertheless allows an accurate measurement of the distance between the lower margin of a rectal cancer, the pelvic floor and the internal anal sphincter, thus providing valuable information on whether intersphincteric resection is indicated for low rectal cancers. Rigid probes are also very well suited to dynamic studies in patients with pelvic floor disorders since they allow the simultaneous examination of the lower part of the anterior rectal wall, the anal sphincters, the urethra and bladder, and the rectovaginal septum. Hitachi consoles can provide a useful three-dimensional evaluation of the mesorectal region.

2.3 Sedation analgesia and general anesthesia

EUS, even if performed without FNA sampling, usually requires intravenous sedation or light general anesthesia because the procedures can be prolonged and require the patient to remain completely still. The use of a benzodiazepine (Midazolam) may be sufficient for examination of the esophagus, stomach and mediastinum. Combining this with an opiate or Propofol, to produce short-term general anesthesia may be necessary for pancreaticobiliary examination or for any EUS-FNA, depending on local custom. This means that EUS needs to be performed at centers with appropriate outpatient facilities.

In contrast, endorectal or endoanal ultrasound without FNA may be performed without sedation (except for painful cancer of the anal canal, or perianal abscess or fistula).

2.4 How to position the patient, doctor, and console

2.4.1 Patient position

• For gastroesophageal or duodenal examination, the left lateral decubitus position is usual. The patient’s head and chest may be raised if water is instilled into the stomach or duodenum.

• For pancreaticobiliary examination, left lateral decubitus, tilted forwards by 30°–45°, is the best position (Fig. 8A). The left shoulder should therefore be moved back and the right leg brought to the front. If the patient is very thin, it is often useful to have him/her lie almost prone, to examine the common bile duct and pancreatic head.

• For anorectal examination, supine is the simplest position. Instilled water pools at the most dependent point and therefore indicates the posterior wall of the lower and mid-rectum at the bottom of the screen, and the anterior wall at the top of the screen, the right wall to the right of the screen and the left wall to the left of the screen.

Figure 8 (A) Position of the patient for pancreaticobiliary examination. (B) The neutral position of the echoendoscope handle: the front of the handle is facing the patient. (C) The open position of the echoendoscope handle. (D) The closed position of the echoendoscope handle. (E) The extreme closed position of the echoendoscope handle. (F) The open position facing the console located at the patient’s feet is used for the examination of the posterior mediastinum.

2.4.3 Position of the echoendoscope handle

Definitions concerning the position of the echoendoscope handle:

• The neutral position (Figs 8B, 9) is where the front of the handle is facing the patient.

• The open position (Figs 8C, 9) is where the front of the handle is facing the patient’s feet. It is reached by turning anti-clockwise through 90° from the neutral position.

• The closed position (Figs 8D, 9) is the opposite of the open position. It is reached by turning clockwise through 90° from the neutral position.

• The extreme closed position (Figs 8E, 9) is reached by continuing to turn the handle clockwise through a further 90° by shoulder rotation, bringing the handle opposite the neutral position.

• The neutral and open positions account for at least 75% of the positions used for pancreaticobiliary and rectal examination.

• The closed position is used to examine the pancreatic tail and is one of the three positions used to examine the uncinate process of the pancreas.

• The extreme closed position is used for pancreatic tail biopsy and is one of the three positions used to biopsy the uncinate process of the pancreas.

• When the ultrasound console is at the patient’s head (Fig. 10), the closed position of the handle (facing the console) is used for examination of the posterior mediastinum: the spine and the aorta (posterior) being at the bottom of the screen and the left atrium (anterior) at the top of the screen; the right side of the screen then corresponds to the left of the posterior mediastinum and the left side of the screen to the right of the posterior mediastinum.

• When the console is at the patient’s feet, the open position (Fig. 11) of the handle (which is facing the console) is used (Fig. 8F) for examination of the posterior mediastinum: the spine and aorta (the back) are at the top of the screen and the left atrium (the front) is at the bottom of the screen; the right side of the screen then corresponds to the right side of the posterior mediastinum and the left side of the screen to the left of the posterior mediastinum.

Figure 9 Position of the echoendoscope handle for EUS.

Figure 10 Console adjacent to the patient’s head. The closed position (3) is the most natural. The extreme closed position (4) is easy to obtain. The neutral position (1) is easy to obtain. The open position (2) is very difficult to sustain for any length of time. Passing from the neutral to the open position has to be very precise. This position is used when biopsying the tail or neck of pancreas.

Figure 11 Console adjacent to the patient’s legs. The open position (2) is the natural position. The neutral position (1) is very easy to obtain. The closed position (3) is easy to obtain. The extreme closed position (4) is very difficult to sustain for any length of time. Passing from the closed (3) to the extreme closed position (4) has to be very precise. This position of the console is used for 90% of EUS procedures.

2.4.4 Console position

• The console position is unimportant if there is a second monitor positioned behind the patient’s back. If not, you can choose between the top and bottom of the patient.

• The majority of endosonographers place the console (and therefore the screen) at the patient’s head (Fig. 10), i.e. to the right of the examiner when he/she is facing the patient. As such, the most natural position of the handle is facing the screen, which corresponds to the closed position described. For the handle to face the patient, i.e. in the neutral position, it must be turned anti-clockwise through 90° from the most natural position and this is not problematic. On the other hand, it is difficult to continue to turn the handle anti-clockwise through a further 90° to reach what is described as the open position because the screen is then 180° opposite this position.

It is because the neutral position and the open position account for three-quarters of the positions that are useful for pancreaticobiliary and rectal examination that this console position has not been considered.

• It is advisable to place the console alongside the patient’s legs (Fig. 11). The open position of the handle (Fig. 8C,F) is therefore the natural position, because the examiner is then positioned at an angle of 45° in relation to the screen. The neutral position (Fig. 8B) is easy because the examiner is then facing the patient. The closed position (Fig. 8D) is easy because the left hand, which is holding the endoscope handle, is up against the examiner’s right clavicle and you are facing the patient. Only one handle position is uncomfortable for the examiner when the console is placed at the patient’s feet: this is the extreme closed position (Fig. 8E), i.e. with the handle opposite the patient. It is then difficult to see the screen positioned along the patient’s legs, while maintaining this extreme closed position for any length of time. This handle position is useful only for biopsying certain tumors of the uncinate process and pancreatic tail. In these two situations, it is advisable to change the position of the console and place it at the patient’s head.

• In summary:

It is best to have a second monitor positioned behind the patient’s back

Otherwise, it is best to position the console beside the patient’s legs, since this facilitates pancreaticobiliary and rectal examination (Fig. 12) in which the extreme closed position is rarely used and since this does not complicate esophageal or mediastinal examination; on the contrary, the right side of the screen corresponds well to the right part of the patient’s mediastinum and the left side of the screen to the left part of the patient’s mediastinum.

Figure 12 Examination of the rectum and anus. Patient in supine position. Console next to the patient’s abdomen, alongside their right arm. The positions of the handle that are used are the neutral (1) and the open positions (2). (3) closed position of the handle, is used to pass the scope through the junction sigmoid rectum.

3.1 General technique

EUS examination uses two different methods that are sometimes combined to obtain a satisfactory acoustic window between the transducer and the gut wall, as well as the surrounding region. The first is the balloon method, and the second is the instillation of water through the operating channel of the echoendoscope.

3.2 Examination technique using miniprobes

The miniprobes are introduced into the endoscope operating channel and slid in endoscopic view over the lesion to be studied:

4.1 Indications and contraindications

There is a broad range of indications for EUS-FNA and these are outlined in Box 2.

These indications will continue to evolve, especially with advances in oncology, e.g. restaging after neoadjuvant therapy or to provide tissue for molecular genetic analysis to guide treatment and/or prognosis.

4.2 General aspects

EUS-FNA requires adequate sedation or general anesthesia and patient monitoring for at least 4–6 h afterwards. Many factors influence the success of EUS-FNA (Box 5).

The lesions can be located using either radial or linear EUS. The linear scope is then used to perform EUS-FNA. A balloon is not useful in this setting.

Upwards deflection of the scope tip keeps the transducer tip pressed against the wall and creates a shallow exit angle for the needle. The needle is advanced from its sheath and applied against the gut wall at an exit angle pre-determined by the endoscope being used. The path of the needle towards the target must take account of this predetermined angle making pre-positioning of the echoendoscope in relation to the target essential. Once pre-positioned against the wall, it may be necessary (depending on the needle type) to retract the small central stylet by 5 mm (if there is a blunt end) in order to be able to pass through the wall, especially with 19-gauge needles.

The latest generation Olympus and Pentax echoendoscopes have an elevator and are therefore easier to handle than older echoendoscopes, because the angle of passage through the digestive wall to the target can be adjusted. This is particularly useful for lesions that are difficult to access, notably those of the uncinate process, for lesions remote from the digestive wall (more than 15 mm away), or for very small lesions (≤1 cm in diameter). The Fujinon echoendoscope has a virtual target line (Fig. 7C) that shows the operator the path the needle will take. The exit angle of the needle is very shallow and is comparable, without an elevator, to that provided by Olympus and Pentax instruments when used with their elevators.

4.3 Antibiotic prophylaxis

The value of intravenous antibiotic prophylaxis is debatable for solid lesions unless indicated for prevention of infective endocarditis. Antibiotic prophylaxis is essential for biopsy of a cystic lesion, whether of the pancreas or digestive wall. It is also required if the patient is using gastric antisecretory drugs (PPI) since this type of product encourages gastroduodenal microbial overgrowth. Antibiotic prophylaxis is also required for transrectal FNA. The antibiotic therapy must be continued orally for 3 to 5 days.

4.4 Pancreatic cancer biopsy

A 22 G needle is advanced under ultrasound control into the tumor. Once in position, the stylet, if it has been partially retracted, is pushed back into the needle so that any fragment of the digestive wall present at the tip of the needle will not obstruct it; the stylet is then removed completely and a 10–20 cc syringe, preferably with a continuous negative pressure instrument, is fitted to the needle. Once continuous negative pressure has been obtained, the needle should be moved slowly to and fro several (about 20) times in the lesion without hurrying, without removing the needle from the lesion, and trying, if possible, to change the angle of penetration of the lesion; this is helped by having an elevator, if the target is small and close to the lesion or if the lesion is soft, which is rare in cancer of the pancreas; if, as is more common in pancreatic cancer, the lesion is large, far from the probe or hard, angulation of the endoscope should be adjusted (from up to down angulation) to change the path of the needle in the lesion.

The needle must always be monitored in real time on the screen, during these movements, to avoid vascular or organ injury. To be sure that the needle is correctly centered in the lesion during aspiration, make small clockwise and anti-clockwise movements of the handle. Avoid penetrating any vascular and particularly arterial structures which may be present between the digestive wall and the target. Power Doppler imaging should be used for this purpose. On the other hand, unexpected passage through intramural or adjacent collateral venous circulation does not usually cause any significant complications if the vein is <3 mm in diameter. As little healthy pancreatic tissue should be traversed as possible, in order to limit the risk of acute pancreatitis. It is also advisable to avoid penetrating the common bile duct and main pancreatic duct, particularly if the latter is dilated upstream of a tumor, since the risk of acute pancreatitis is then increased. Do not puncture the gallbladder or the common bile duct above the pancreas owing to the risk of biliary leakage. Once the biopsy has been completed, release the negative pressure otherwise tumor cells may be deposited in the needle tract as it is withdrawn. Once negative pressure has been released, the needle is withdrawn into its protective sheath and the EUS-FNA needle is removed from the operating channel of the echoendoscope, which is left in position over the lesion. The biopsy sample is then checked. It is ideal to have a cytologist present in the biopsy room since he/she can immediately assess the quality of the sample. If there is no cytologist available, several biopsy passes (two to three on average) should be made in the tumor. The sample should preferably be placed in a tube containing formaldehyde or formalin so that histology can be performed on a cell block preparation. For this purpose, the stylet is advanced through the needle, gradually expelling the sample. Once a sufficient sample has been obtained for histological study, the remainder is divided, giving preference to smears (two to three slides should be prepared), and the rest is placed in CytoLyt medium for liquid-based cytology. This is particularly useful if the sample is poor or liquid, as in cystic tumors of the pancreas. Liquid-based cytology involves the automated concentration of the cells and produces a slide that is easy to process with a thin, even layer of cells. Liquid-based cytology can also be used for immunohistochemistry, unlike slide smears. Once the three types of sample have been obtained, the stylet should be withdrawn and the needle purged, using a 10 cc syringe filled with air, onto slides, yielding a further 1–3. The inside of the needle should be purged with 30 cc of physiological saline between biopsies. If the same patient with pancreatic cancer has several targets, the procedure should start with a biopsy of a hepatic metastasis, then a lymph node biopsy and finally the tumor itself. For lymph node biopsies, start with the lymph node least likely to be involved by tumor and end with the most suspicious.

The biopsy procedure must be stopped if blood is aspirated into the syringe.

If the pancreatic cancer is very hard and the sample is very poor (just some serous fluid) and there is no cytologist available in the examination room, a 50 cc or 60 cc suction syringe should be used. For cancer of the pancreatic body or tail, the needle can also be changed for a 19 G needle combined with a 50 cc or 60 cc suction syringe.

4.5 Biopsy of a cystic lesion

For a cystic lesion biopsy, puncture only once to avoid introducing infection. A cystic lesion should be punctured boldly and cleanly by quick, firm pressure so as not to tear the wall (this can happen if you push in the needle slowly while the patient’s respiratory movement causes the lesion to move). After withdrawing the stylet, attach a 10 or 20 cc suction syringe, according to the volume to be aspirated. If no fluid is visible after a few seconds, check that the needle is positioned correctly. If it is, wait because this means that the fluid is viscous (IPMN or mucinous cystadenoma).

Where possible, i.e. if the cystic lesion is not too large, it should be drained completely, in particular if it is a cystic lesion of the pancreas. Cystic lesions of the mediastinum, esophagus or rectum should not be punctured since several cases of abscess formation and in particular mediastinitis have been reported in the literature. The same applies to infected necrosis following acute pancreatitis.

4.6 Lymph node biopsy

For lymph node biopsy, adjust the needle and sampling technique according to the suspected nature of the lymph node and its size.

4.7 Difficult biopsies

Some lesions are difficult to biopsy, for example some benign or malignant pancreatic tumors, either because they are hard (or very fibrotic) or because they are very small (usually endocrine tumors), because they are far from the gut wall, or because they are in areas where the needle has little penetration force.

4.8 Renal cancer metastases and endocrine tumor

The biopsy technique for a pancreatic mass suspected of being an endocrine tumor or a renal cancer metastasis must be different as regards the suction force exerted. Make several back and forth movements without suction, then lightly aspirate using a 2 cc syringe for 1–2 s. Cells from this type of cancer, which are very fragile, thus remain analyzable. This also lowers the risk of post-biopsy hematoma (see Fig. 138) associated with these hypervascular tumors.

4.9 Complications of EUS-FNA

To summarize, EUS-FNA is an invasive technique with low morbidity but it is nevertheless associated with a small number of severe complications.

The indication for performing EUS-FNA should thus be considered carefully and based on an assessment of the risk-benefit ratio – the patient should be fully informed of this.

5.1 General points

After upper endoscopy (EGD) to identify the location of the tumor (distance from the incisors, length, circumferential involvement, degree of stenosis and ulceration), EUS begins in the stomach, 45–50 cm from the incisors, over the posterior side of the lesser curve, at the junction between the upper and middle thirds of the lesser curve. The echoendoscope must be pressed (by up angulation) against the lesser curve, between the liver (segment II) and the junction between the pancreatic neck and body. The air present in the stomach must have been completely aspirated beforehand, especially if EGD has been carried out previously.

The celiac region and the subcardial and left gastric artery lymph node areas are examined by progressively withdrawing the echoendoscope, keeping the transducer pressed against the wall by up angulation of the scope tip.

The anterior subcardial lymph node areas between the anterior surface of the upper part of the stomach and the apex of the left lobe of the liver should also be examined. The splenic hilum should also be examined; this can be a drainage region, in the event of subcardial involvement by esophageal cancer, following the splenic artery and vein to the spleen. If a suspicious lymph node is discovered in the celiac region, the examination should be continued as far as the second part of the duodenum, to examine the retroduodenopancreatic and lumbar aortic lymph node areas and the hepatic pedicle, which may be affected.

By withdrawing the instrument into the posterior mediastinum, the esophagus and peri-esophageal region can be visualized:

Figure 13 (A) Radial examination of the esophagus in the cervical region with visualization of the cricoid cartilage (white arrow), with the console positioned beside the patient’s feet using the open position of the echoendoscope handle. (B) Radial examination of the esophagus in the cervical region with visualization of the thyroid lobes and the common carotid arteries on both sides of the trachea. (C) Small metastatic lymph node (M1a) in the upper thorax in the left tracheo-esophageal angle in a patient with an esophageal cancer at 35 cm arising in Barrett’s esophagus. (D) Small metastatic lymph node in the aorto-pulmonary window in a patient with squamous lung cancer. (E) Subcarinal lymph node. Note the triangular shape and the central area (white arrow) highly suggestive of benign appearance.

Generally speaking, the lymph node drainage areas of esophageal cancers are often ipsilateral (right or left) to the predominant spread of the cancer on one or other of the lateral walls.

Five major regions should be examined very closely for metastatic adenopathy. They are, from the top down:

Tumor stenoses are impassable in only a few cases if a gastroscope has passed through beforehand. If a stenosis is impassable, a blind probe, capable of passing through almost 95% of malignant stenoses, should preferably be used. If a blind probe is unavailable, cautious dilation can be considered. Dilation up to a diameter of 13 mm is usually sufficient to allow the latest generation echoendoscopes to pass through. This type of dilatation is usually safe. The use of a 7.5 or 12 MHz miniprobe is a less satisfactory alternative to a blind probe.

5.2 Special features of radial examination

While studying an esophageal tumor using a radial echoendoscope fitted with a balloon, the balloon should be inflated moderately so that the endoscope can be advanced and retracted without creating an oblique image. The endoscope should be kept angulated so that the transducer remains perpendicular to the lesion examined. This means making sure that the muscle layer is visible through 360° around the lesion examined. For a small lesion, the inflated balloon should be positioned between the lesion and the transducer, with the aid of sufficient angulation so that it is not pressed against the lesion.

5.3 Special features of linear examination

5.3.3 Examination of the posterior mediastinum with linear instruments

The lymph node areas of the posterior mediastinum and the celiac and mesenteric region should be examined in patients with cancer of the esophagus and cardia, when assessing bronchogenic cancer or in patients with benign or malignant mediastinal masses.

The examination always begins in the stomach over the celiac region. The left adrenal gland, readily located by turning the endoscope handle clockwise from the celiac trunk, should then be examined. The left lobe of the liver is easy to locate by turning the handle anti-clockwise from the celiac trunk.

The endoscope is then brought up to the cardia (40 cm from the incisors), following the aorta longitudinally. At this point the suprahepatic venous confluence at the inferior vena cava (Fig. 14A) and the dome of the liver, which is located around it, can be observed by turning the handle clockwise and anti-clockwise, then climbing along the inferior vena cava as far as the right atrium (Fig. 14B). When the right atrium disappears on withdrawal of the endoscope (35 cm from the incisors), the left atrium (Fig. 14C) can be examined by making small clockwise or anti-clockwise turns of the handle, and the endoscope is brought up along the central part of the left atrium (the largest part) as far as its upper margin (28–30 cm from the incisors). On withdrawal, the subcarinal region then appears and the screen shows, below the transducer, from top to bottom, the air present in the trachea and carina, the subcarinal region, the right pulmonary artery in cross-section (Fig. 14D) and the upper part of the left atrium. Turning the handle clockwise and anti-clockwise then allows all the subcarinal lymph nodes (Fig. 14E) to be examined (the right group, which is close to the large azygos vein, the central group between the esophagus and the right pulmonary artery, and the left group near the descending aorta).

Figure 14 (A) Suprahepatic venous confluence seen with a linear scope. (B) Right atrium seen with a linear scope. (C) Right atrium and left atrium seen with linear scope. (D) Subcarinal region with the left atrium, the right pulmonary artery (RPA) and the superior vena cava (SVC) seen with linear scope.(E) Central subcarinal lymph node below the carina in front of the right pulmonary artery (RPA) above the left atrium (LA) seen with linear scope. (F) Aorto-pulmonary window (AP window) between the aortic arch (AO arch) and the left pulmonary artery (LPA) seen with a linear scope. (G) Left common carotid artery (LC) branching from the aortic arch (AO) seen with a linear scope. (H) Left subclavian artery (LSCA) branching from the aortic arch (AO) seen with a linear scope.

With maximum up angulation, withdrawing the endoscope 1–2 cm and turning the handle anti-clockwise, the aortopulmonary window (region IVL) will become visible between the aortic arch, round in section, at the top of the screen, and the left pulmonary artery, round in section, at the bottom of the screen (Fig. 14F).

Continuing withdrawal of the endoscope reveals the supraaortic (left paratracheal and para-esophageal) region with the left common carotid artery (Fig. 14G) and the left subclavian artery (Fig. 14H), then the origin of the left vertebral artery and the left retroclavicular lymph node region, finally, above the left thyroid lobe.

If the handle is turned clockwise from the aortic arch, the trachea, then the supra-azygos region (above the arch of the azygos vein), and if the endoscope is retracted keeping the same image plane, the brachiocephalic trunk will appear followed by its bifurcation into the right subclavian and right carotid artery, the origin of the right vertebral artery, then the right thyroid lobe.

6.1 Introduction

It is advisable to almost always start with a radial instrument. It is far easier and more comprehensive. The linear instrument can be used first only if the examiner has to biopsy a large submucosal tumor suspected of being a GIST. By contrast with conventional teaching, it is advisable to instil water into the stomach only very rarely, because it is usually ineffective and may cause pulmonary aspiration.

6.2 Examination of the stomach with a radial instrument

For malignant or suspected malignant tumor disease, the examination begins in the duodenum, as for pancreaticobiliary examination, looking for retropancreatic and interaortocaval metastatic adenopathy, particularly at the base of the posterior segment of the hepatic pedicle. Returning into the bulb allows examination of the preportal (pyloric) hepatic chain. Moving into the stomach allows examination of the left gastric, celiac and cardiac lymph node regions. Each part of the stomach should be examined systematically, the antrum, body and fundus, to be sure you have examined the lymph node areas adjacent to these regions. The liver is the key landmark anteriorly, the pancreas is the key landmark posteriorly, the spleen for the greater curve, and the lesser curve can be readily located at the junction between the posterior and anterior walls (Fig. 15).

Figure 15 (A) Radial examination of the lesser curve (1), between the posterior side (2), the anterior side (3), in front of the greater curve (4) between the left lobe of the liver (6) and the body of the pancreas (5). (B) Radial examination of the gastric antrum. The scope being pushed immediately upstream the pylorus maintaining maximum up angulation. The lesser curve (1) is between the anterior side of the antrum which is facing the gallbladder (5) and the liver (6). (4) posterior side and the antrum. (2) greater curve of the antrum.

The key to success when performing EUS of the gastric wall is to try to obtain a study of the layers of the wall so that they are perpendicular to the ultrasonic beam (Fig. 1). EUS is not possible across the whole circumference of the stomach simultaneously. In other words, once the anomaly to be examined has been located roughly on one wall of the stomach, focus on this anomaly so that the layers of the wall over and below the anomaly, but also at its edges, are clearly individualized. It is only by proceeding in this manner that you can be sure that the EUS abnormalities are real and not due to an ‘oblique image’ which may be misinterpreted (overlapping of several structures creating false images that suggest serosal involvement of a tumor or wrongly attributing the anomaly to a layer other than the one in which it is actually located). Examination of the fundus is sometimes difficult when the lesion in question is small. It is sometimes easier to perform the examination without instillation of water, after aspirating all the air present. It is sometimes necessary to work with the echoendoscope in retroflexion to visualize the anomaly if it is small. Examination of the body of the stomach is easy, and examination of the antrum is equally easy for the horizontal portion. On the other hand, examination of the incisura is more problematic. The best solution is to inflate the balloon immediately upstream of the pylorus, maintaining maximum up angulation, to check that the gallbladder is facing the anterior side, which means that the lesser curve is then at the bottom of the screen and the greater curve at the top. Once this has been confirmed, withdrawal of the echoendoscope, with the balloon inflated and up angulation, usually means that it can remain perpendicular to the lesser curve, whether in the horizontal portion, the incisura itself or the vertical portion immediately above the incisura. Examination of an immediate prepyloric lesion is difficult because it is often impossible to avoid oblique images of the pylorus itself which will give the impression that there is a submucosal tumor in the muscle layer. This is a frequent cause of false positive results for stromal tumors. This type of error obviously occurs only with small tumors, since large tumors are usually clearly visible, regardless of the image plane used.

6.3 Examination of the stomach with a linear instrument

It is advisable to use a linear instrument only to biopsy a submucosal tumor whose exact location has already been determined by UGIE or by a radial examination performed immediately beforehand.

7.1 Essential anatomic knowledge for correctly performing a pancreaticobiliary examination

Familiarity with the celiac and mesenteric anatomy is required: