Using the Endoscope for Endobronchial Ultrasound in the Esophagus

Summary

Transesophageal ultrasound (EUS-B) is a safe and feasible procedure using the echoendobronchoscope (EBUS) in esophagus and stomach. After identifying six anatomical landmarks, additional structures can be identified and biopsied, sparing subsequent diagnostic sessions. Thus, EUS-B is an ideal continuation of bronchoscopy and EBUS in diagnosing lung cancer and other diseases.

Abstract

EUS-B is a procedure using the echoendobronchoscope in the esophagus and stomach. The procedure is a minimally invasive, safe, and feasible approach that pulmonologists can use to visualize and biopsy structures adjacent to the esophagus and stomach. EUS-B gives access to many structures of which some may also be reached by EBUS (mediastinal lymph nodes, lung or pleural tumors, pericardial fluid) while others cannot be reached such as retroperitoneal lymph nodes, ascites, and lesions in the liver, pancreas or left adrenal gland. The procedure is a pulmonologist- and patient- friendly version of the gastroenterologists' EUS using the thin EBUS endoscope that the pulmonologist already masters. Thus EUS-B training should be easy and a natural continuation of EBUS. With the patient under conscious sedation and in the supine position, the echoendoscope is introduced either through the nostril or mouth into the oropharynx. Then the patient is encouraged to swallow while the endoscope is slowly bent posteriorly and introduced into the esophagus and stomach. Using the ultrasonic image, the operator identifies the six landmarks by EUS-B and EUS: the left liver lobe, abdominal aorta (with the celiac trunk and superior mesenteric artery), left adrenal gland, and mediastinal lymph node stations 7, 4L, and 4R. Biopsies can be taken from suspected lesions under real-time ultrasonographic guidance- fine needle aspiration (EUS-B-FNA) using a technique similar to that used with EBUS-TBNA. The biopsy order is M1b-M1a-N3-N2-N1-T (M = metastasis, N = lymph node, T = tumor) to avoid iatrogenic upstaging. Pre- and post-procedural observation is similar to that of bronchoscopy. EUS-B is safe and feasible in the hands of experienced interventional pulmonologists and provides a significant expansion of the diagnostic possibilities in providing safe, fast, and thorough diagnosis and staging of lung cancer.

Introduction

Endoscopic ultrasound is a key procedure in the diagnosis and staging of lung cancer and allows safe sampling from mediastinal or hilar lymph nodes^1,2. Endoscopic ultrasound comprises endobronchial (EBUS) and transesophageal ultrasound (EUS), are considered complementary procedures².

Interventional pulmonologists are trained with the EBUS endoscope but are rarely familiar with the larger EUS endoscope (Figure 1), which requires special training to handle correctly³. EBUS and EUS are often performed by different departments and on separate sessions/days⁴. However, trained pulmonologists experienced with EBUS techniques can insert the smaller EBUS endoscope into the esophagus and perform safe examination and biopsy sampling from mediastinal lymph nodes and other lesions adjacent to the esophagus and stomach - a technique termed as EUS-B⁵. This leads to extension of pulmonologists' ability to safely and conclusively sample lesions in many different anatomical sites such as lung⁶, pleura⁷, pericardial effusion⁸, mediastinal lymph nodes^1,5, left liver lobe and retroperitoneal lymph nodes⁹, pancreas¹⁰ and the left adrenal gland^11,12 (Figure 2).

The EUS-B procedure is a pulmonologist friendly version of the gastroenterologists´ EUS using an endoscope that the pulmonologist already masters. The EUS procedure is performed with a gastroendoscope which is both larger and heavier than the EBUS endoscope, has a different handle (with wheels, see Figure 1) and is unlike EBUS performed with the patient in left lateral decubitus. Learning EUS as a pulmonologist is challenging and requires a lot of training and supervision².

EUS-B and EUS are so far very similar regarding diagnostic yield when performed in the field of pulmonology^5,13,14,15. EUS-B is patient friendly since the endoscope is significantly thinner than that of EUS, and therefore less unpleasant for the pharynx and esophagus. Unlike EBUS, EUS-B does not cause direct airway irritation and is therefore safe to use in patients with suspected cancer resulting in severe respiratory impairment due to mediastinal tumor masses¹⁶.

The combination of EBUS and EUS-B is preferred over either test alone in any patient suspected of lung cancer, but EUS-B should especially be considered in patients with suspicious lesions out of reach by EBUS, but within range by transesophageal ultrasound (Figure 2). Adding EUS-B to EBUS in lung cancer work-up expands the interventional pulmonologists´ ability to perform diagnostic work-up during a single session using the same endoscope by one proceduralist, which is more convenient for the patient, saving both time and costs.

The complication risk of EUS-B is extremely low and is to our knowledge only limited to infectious complications^17,18. EUS-B training should be easy and a natural continuation of EBUS, and the following protocol will describe how to perform EUS-B in mild sedation in an out-patient clinical setting.

Protocol

The following protocol developed at our institution (Zealand University Hospital) follows the Danish national guidelines on human research ethics.Written and informed consent was obtained from the human subjects.

1. Preparation for EUS-B

NOTE: This procedure requires experience in performing bronchoscopy / EBUS, thus the following instruction will not include details on basic steps such as sedation, monitoring etc. which are common for bronchoscopy, EBUS and EUS-B.

1. Evaluate available computed tomography (CT) or positron emission tomography (PET)-CT scans in order to locate target lesions reachable by EUS-B (see Figure 2). Make sure that antithrombotic therapy is paused according to guidelines. Obtain patient's informed consent.
2. Exclude patients with increased risk of perforation (e.g., recent bowel surgery, bowel obstruction, esophageal stenosis), coagulopathy or impaired platelet function.
3. Position the patient in a supine position and apply monitoring similar to bronchoscopy or EBUS according to institutional standards. Many sites continuously monitor 3-lead telemetry, oxygen saturation, pulse and intermittent blood pressure.
4. Initiate conscious sedation similar to bronchoscopy or EBUS according to institutional standards, such as IV midazolam 2.5 mg (for sedation) and IV Fentanyl 25 µg (for cough and pain).

2. Performing EUS-B

1. Perform EUS-B using the EBUS echoendoscope, which is typically 60 cm long (EUS is 125 cm) and the average diameter of the regular scope is between 6 and 7 mm (EUS is 12 - 14 mm).
2. Stand behind the patient´s head who is in a supine position. Hold the handle of the endoscope with the left hand with the thumb on the lever and hold the distal end of the endoscope with the right hand.
3. Apply local anesthetic gel (nasal route) or spray (oral route) on the mucosa 1-2 min before endoscopy.
4. Introduce the endoscope into the oropharynx, either orally or through the nostril, after applying local anesthetic gel on the tip of the endoscope.
5. Advance into the laryngopharynx while the epiglottis is in front of the scope and visualize the vocal cords using the bronchoscopic view.
   1. Turn the scope left or right to direct the scope lateral to the arytenoids. Ask the patient to swallow and slowly bend the endoscope posteriorly and introduce it into the esophagus. Never use force but follow the downward direction of the patient's voluntary swallowing movement, where the esophageal lumen is widened. Patient-operator coordination is vital.
   2. Spray 2 mL of topical lidocaine in the oropharynx if the endoscope is not successfully introduced into the esophagus.
6. Shift to the ultrasonic image and introduce the endoscope into the stomach, and start identifying the six EUS landmarks in a stepwise and chronological order as described in¹⁹ and below (Figure 3).
   1. The left liver lobe - turn the endoscope slightly counterclockwise (Landmark 1).
   2. The abdominal aorta with the celiac trunk and superior mesenteric artery - turn the scope clockwise (Landmark 2).
   3. The left adrenal gland - turn the scope further clockwise (Landmark 3).
   4. Mediastinal lymph node station 7 -retract the endoscope to the mediastinum. This is situated close to the left atrium and right pulmonary artery (Landmark 4).
   5. Mediastinal lymph node station 4L - retract the endoscope a few centimeters and notice the reflections from the trachea. Then, turn the endoscope counterclockwise and find 4L between the aortic arch and the left pulmonary artery (the mickey mouse sign; Landmark 5).
   6. Mediastinal lymph node station 4R - turn the endoscope clockwise, pass the trachea and find the azygos vein (confirm by retracting the scope and the vein should disappear into the superior vena cava). 4R is near the azygos vein (Landmark 6).

3. Tissue sample collection

1. Take tissue samples from suspected lesions under real-time ultrasonographic guidance using the FNA needle. The needles on the market are slightly different, but the principles for their use are the same.
   1. Insert the sheath in the endosope and adjust the length so that the tip is 1 mm outside the endoscope and lock it.
   2. Move the needle with the stylet forward and retract the stylet a few millimeters (if the tip is rounded) to make the needle sharp. This step is not needed if the stylet is sharp.
   3. Hit the target, retract the stylet, and apply suction to the needle.
   4. Move the needle back and forth. Then remove suction, lock the needle in the upper position and remove the equipment from the endoscope.
2. Make sure that the biopsy order is M1b-M1a-N3-N2-N1-T (M = metastasis, N = lymph node, T = tumor) to avoid iatrogenic upstaging.

Results

The described technique allows the EBUS-skilled pulmonologist to safely and efficiently sample lesions adjacent to the esophagus and stomach - above or below the diaphragm - using the EBUS echoendoscope (Figure 1 and Figure 2). Table 1 shows that diagnostic hit rates vary according to location, with slightly higher diagnostic success rates of intrathoracic lesions.

The systematic six...

Discussion

EUS-B has significantly changed the field of interventional pulmonology^2,5,6,13. EUS-B allows the pulmonologist to access lesions not reachable with EBUS, simply by using the EBUS endoscope in a new way. A patient with a central lung tumor, enlarged mediastinal lymph nodes and abnormal left adrenal gland can have all lesions sampled with one endoscope in a single interventional session, saving ...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
22 Gauge FNA needle system	Olympus Medical Systems	Vizishot
EBUS echoendoscope	Olympus Medical Systems	BF-UC190F
EVIS Exera II endoscopy tower with EVIS X1 video processor	Olympus Medical Systems	CV-1500
Lidocaine gel	Multiple (e.g. Aspen Pharma)	Xylocain 2%
Lidocaine spray	Multiple (e.g. Aspen Pharma)	Xylocaine Pump Spray