Inside Endoscopic Ultrasound

Technological advancements in endoscopic ultrasound (EUS) have created an imaging and informational tool of great facility. The technology has advanced at great speed, and it’s not finished yet.

The concept of endocsopic ultrasound (EUS) began in the early 1980s as a research-type tool, combining the technologies of ultrasonography and endoscopy. The merging of these two technologies into one delivery system produces high-frequency sound waves to provide imaging and information about the digestive tract and the surrounding tissues and organs. Initially investigational, the technology has evolved, and EUS has found a clinical niche in cancer staging and diagnosis.

The rapidly evolving technology of EUS is also being used in the following applications:

• Staging of cancers of the esophagus, lungs, stomach, pancreas and rectum
• Evaluating chronic pancreatitis and other masses or cysts of the pancreas
• Studying bile duct abnormalities, including stones in the bile duct or gallbladder, or bile duct, gallbladder or liver tumors
• Studying the muscles of the lower rectum and anal canal in evaluating reasons for fecal incontinence
• Studying submucosal lesions that may be present in the intestinal wall.¹

In EUS, a small ultrasound transducer embedded with a microchip television camera is installed on the tip of an endoscope, which is inserted into the upper or lower digestive tract. The transducers can scan either in a plane perpendicular to the endoscope, in the manner of radial endoscopes, or in a plane along the axis of the endoscope, as with linear scanning echoendoscopes. The transducer’s close proximity to the organs of interest provides images that are frequently more accurate and more detailed than images obtained by traditional ultrasound. EUS can also provide information about the layers of the intestinal wall, as well as adjacent areas such as lymph nodes and blood vessels.

Fine needle aspiration (FNA) is a procedure used to visualize and biopsy tumors. “You locate the tumor, you spot it, the scope has an ultrasound probe attached to it,” says Felix Tiongco, MD, FACP, assistant professor of clinical medicine, Eastern Virginia Medical School, Norfolk, Va. “The probe seeks the tumor, it tells us how deep it is, whether there are any adjacent lymph nodes involved, and by locating that we are able to guide a fine needle into that lesion to obtain biopsies.”

EUS has several important advantages over other diagnostic and therapeutic imaging systems:

• EUS has very high resolution.
•  EUS combines diagnostic imaging with tissue sampling and directed therapy in a single endoscopic modality.
• EUS is performed in real time (unlike CT-guided biopsies) allowing second-tosecond adjustment and precise localization of needle placement.
• EUS makes it possible to perform FNA directly through the lumen of the gastrointestinal tract. This is advantageous because the needle pathway is often resected in the subsequent surgical procedure, so the potential for tumor spread along the needle pathway is minimized.²

“It’s the best modality in staging certain cancer tumor invasion or depth of involvement — how deeply it goes through tissue” says Tiongco. “Particularly esophageal cancer, rectal cancer, gastric cancer and pancreatic obiliary type malignancies.”

The advantages to this relatively new technology are seen by many as a godsend. “For 23 years I used to open bellies, and I used to see things done by what references they had before,” says Karen Beukers, RN, CNOR, RNFA, clinical coordinator of the EMB suite, Fox Chase Cancer Center, Philadelphia. “But now to see all the advancements that we can do pre-operatively in the endoscopy suite to help with the surgery is amazing to me. Rather than open up and invade a body to get a diagnosis, we can get it through a tissue diagnosis here, and maybe be able to tell it’s not a resectable tumor. That’s a big help. It’s marking out all the areas that a surgeon is going to encounter before he goes in there and he’s hit with a surprise. It’s really nice to be able to map everything out with the lymph nodes, the vessels or the thickness of the tumor wall.”

“It takes a skilled eye to read,” continues Beukers. “It’s a whole new advanced skill for the physician — not just any endoscopist can do it. It’s kind of like saying that’s why regular physicians have radiologists or ultrasound people read their film, because they might know so much of it, but not advanced to the point of where a seasoned interventional endoscopist is.”

“The state of the technology has evolved to amazing speed,” says Tiongco. “It used to be that we were limited by the flexibility of the scope, the frequency of the transducers attached to the endoscopes. But now scopes have been developed that pretty much surpass that — you get better scope flexibility, better tip-bending radius, smaller caliper scopes, and better frequency of the transducers used in the scopes.”

“This technology makes it a total team effort between the medical oncologist, the interventional endoscopist, and if need be, the surgical oncologist,” says Beukers. “It really combines the team into one for the betterment of the patient. Everybody’s on the same page.”

“I think it’s a great tool for the continuing care of the patient,” continues Beukers. “What’s nice is before your patient goes into surgery, you call the surgeon and say, let me show you this, let me show you exactly what I’m looking at. After all those years in the OR, I just think this is a wonderful advancement. And if people don’t see that, they have their blinders on. Well then, they’re keeping themselves behind. It’s time to catch up with the times, because this is the future.”

The Down Side?

Are there any disadvantages to EUS technology? “Obviously it is an invasive procedure, but that is a very minimal disadvantage to it,” says Tiongco. “But if you look at current observational studies, it pretty much supports the safety of this procedure. Although it’s invasive, the risks are not that significantly different from standard endoscopy. Now, if you do apply fine needle aspiration biopsy, a word of caution: biopsies of cystic lesions have a higher risk of bleeding. And obviously passing the scope through stenotic or tight areas, there is a slightly increased risk for perforation, because of the relatively larger diameter of the endoscope.”

Beukers can only think of one improvement that could be made. “I wish it would write a check out for me every once in awhile!”

Training the Endonurse

For the skilled endonurse to be profficient with EUS technology, just what is involved?

“The training of an endonurse really should be hands-on,” says Tiongco. “There’s no better way than for an endonurse to really stand side by side with an endosonographer. The endoscopy nurse is going to another level, another notch higher. Aside from their training with endoscopy, they should be familiar with the ultrasound machine and what they see on the screen. The nurse will be very important in adjusting certain knobs on the machine, making sure they know what buttons to place and to punch for Doppler mode, holding the scope, torquing the scope, making sure the scope is in correct position to safely pass a needle. In private practice, that is the main role of the endonurse. In academic institutions, there will always be a fellow assisting the endosonographer, but in real life it’s just the doctor and the nurse.” “There’s a certain skill for the nurses in preparing the scopes,” says Beukers. “We have to put ultrasound covers, or condoms, on the tips. We’ll tie them on with dental floss. They have to be tested to make sure there is no air in the condom, because that can air bubble can show up as something on the ultrasound screen.”

“I’ll have the sales rep in to explain the machines because I feel that they just won’t miss things,” continues Beukers. “I utilize them because I feel that that’s a service they need to provide. Then I have a one-on-one with the trained nurses for a good month until the nurse feels that she can function on her own and troubleshoot. We’ll also have the sales rep go over a lot of the troubleshooting issues.”

“The No. 1 challenge would be becoming familiar with the aspiration biopsy needle apparatus,” says Tiongco. “There are several delivery systems made by different manufacturers and vendors that have different styles. With regard to the actual technique of endoscopy itself, it’s almost the same as any other technique. It’s almost like ERCP (endoscopic retrograde cholangiopancreatography), but instead of looking at the fluoroscopy machine you’re looking at the ultrasound machine.”

“Since you are actually using a needle device, precaution against needlestick injuries is very important,” cautions Tiongco. “Learning how to handle the needle sample, and the fact that we are working also with a cytopathologist who is frequently in the room, the nurse should be familiar with the way the cytopathologist wants the sample delivered onto the slide or into any specimen container. Cytopathologists have different ways of collecting samples. Be familiar with that method.”

What kind of glitches can come up? “Not having the condom on correctly, not being able to get the bubbles out,” says Beukers. “For some reason you may not have a picture on the screen — that’s because something might not have connected. The machines are pretty much self-sufficient and will come up with a default number if something is wrong with the monitor. A lot of things are common sense. Let’s say the picture goes off. Well, don’t just start pushing buttons on the front of the monitor. See if somebody tripped over the plug. Because this is something brand new, and it’s a little intimidating, people tend to panic. Start from the beginning: is it still plugged in? You just don’t want them to panic in a room just because it’s new to them, and because we stress the importance of how much money is involved.”

“People will say that their scope is their baby,” says Beukers. “Well, this is my critical-care baby. Because we do so much of it, if that scope goes down, I’ve got to hope that the place I get my scope from has a loaner for me — it would really stop a lot of our cases from getting done.”

“We go from a regular viewing picture, like with a regular endoscope, and we do an upper endoscopy report,” says Beukers. “Then we want to correspond the pictures with the upper report. There’s a switch that you have to flip to make sure that you’re now on the ultrasound pictures. What happens is the ultrasound picture gets taken and they’re on a totally different report. We have to go behind the scenes in the computer and play around with that. But one thing that we’ve decided to start doing in concert with the Joint Commission on the Accreditation of Healtcare Organizations (JCAHO) recommendations, is a ‘time-out.’ Correct patient, correct X-rays, etc. We’re taking a time-out to make sure that: 1. We have the correct patient, and 2. We have the correct report ready before we start. When we change over from regular endoscopy to ultrasound, we do a time-out again to make sure that the switch has been made. It’s another pause for safety that I enforce.”

Beukers has found that the time-out is a valuable safety net in an atmosphere where a lot is going on. “Our tech would run out with one scope to change to another scope,” she says. “At the same time, the scope is being withdrawn from the patient’s mouth, so I have my conscious sedation nurse sitting there. This is a time where you’ve really got to pay attention to the patient. You don’t want to be walking away to change the monitor. So what we do is, we pause and say, ‘Is the monitor changed over?’ The person who is free — it could be a tech walking by at that moment — switches it over.”

“As far as the rest of the stuff, it’s just a matter of learning how to use the equipment,” says Beukers. “Again, I utilize my sales reps when I have new employees. And I like to have them come in every once in awhile to refresh people. Because it’s not all the time that everybody does the ultrasound.”

What’s Ahead

“One thing I’d like to see is already happening,” says Tiongco. “More maneuverable endoscopes, multi frequency scopes where you can vary the frequency. As we know in physics, the higher the frequency of the endoscope transducer, the finer the detail you get. The lower the frequency of the transducer, the deeper you can see into the tissue. So you want a scope that is versatile, that is able to provide you detail, but also will provide you depth, so you can actually see what’s beyond.”

Multi-purpose scopes, says Tiongco, are currently in evolution. “Mutli-purpose, meaning combining ERCP with EUS. I believe there are certain companies that have developed that.”

“Since almost all of these scopes are basically tangential or side-viewing scopes, you would ideally want a frontviewing scope, and Pentax has developed that,” says Tiongco. “They have a forward- viewing scope that allows the easy passage of the endoscope. It’s forwardviewing as opposed to side-viewing. The nice thing about multi-purpose scope, it has Doppler capability, which has never been available in standard radial scopes.”

“Probably most important is the evolution from the mechanical scope to the electronic-type scopes” continues Tiongco. “The initial scopes are mechanical, meaning that there are a lot of moving parts. For the sonographic transducer to the release soundwaves, it uses certain gears and knobs, which turn the crystal around. The newer electronic scopes have less moving parts. Henceforth they are believed to be sturdier, with fewer repairs and less service.”

“I think this technology is really on an upswing,” says Tiongco. “I think there’s increased utilization in the community. The oncologists, the thoracic surgeons and the pulmonary people especially, which are non-GI, have begun to see the utility of this technology in their own realm. With lung cancer and the diagnosis and identification of mediastinal lesions, we’ve pretty much gone beyond the GI track and now are kind of sharing this technology with thoracic surgeons and pulmonary specialists in diagnosing lung cancer and mediastinal disease.”

But we’re not quite there yet, says Tiongco. “I think there are a lot of things that need to be done. Right now, the technology is still on an upswing. The future of this technology will be the application of therapeutics. The same way that ERCP started as a diagnostic tool, now it’s evolving into a therapeutic tool. One of the therapeutic uses of this technology will be pain management in pancreatic cancer patients via celiac plexus block. You can actually do a nerve block of the celiac plexus to alleviate pain in pancreatic cancer patients. You can drain pancreatic pseudocysts utilizing this technology. Lately there’s been a description of stents into the pancreatic or bile ducts utilizing these EUS scopes, called EUS antigrade pancreatography. Hopefully there will be some cancer treatment potentials for this, maybe introducing vectors for chemotherapeutic agents into tumor areas. These are the things that hopefully I will see evolve over the next decade or so.”