New Endoscopic Technologies
CT colonography, also known as virtual colonoscopy, utilizes the X-ray technology of a CT scan combined with computer software to create an image of the inside of the colon (large intestine). In addition, views of the other intra abdominal organs are obtained. These images can be configured to resemble what one would see during a colonoscopy. Colonoscopy, by contrast, looks directly at the inside of the colon through a video-equipped scope passed through the anus into the colon.
CT colonography is performed and interpreted by radiologists in most circumstances. The test is similar to colonoscopy in that the bowel must be cleansed of fecal material prior to the scan. The colon is distended by air or carbon dioxide introduced through the rectum, and the CT scan is completed over approximately 10 minutes. CT colonography is done without sedation. If polyps are found on CT colonography, colonoscopy will then be necessary to remove the polyps. Colonoscopy is the only method that allows for both the detection and removal of polyps.
Recent studies show that CT colonography is effective in identifying medium to large polyps, but is ineffective in identifying small polyps. CT colonography may be best for low-risk patients who cannot undergo or who failed a conventional colonoscopy. The procedure is not currently covered by Medicare as an initial screening test.
High Definition Scopes/Narrow Band Imaging/Chromoendoscopy
Just as technology continues to improve our television images with new high definition sets, endoscopic images are following a similar path. A new generation of endoscopes are being developed that utilize high definition imaging with stunning detail. Not only does high definition provide a clearer picture for the doctor to look at, but it literally gives more information due to the increased resolution of the picture. When endoscopists are trying to find small polyps, early cancer and flat lesions, the addition of high definition may further improve identification of these abnormalities.
Along with a high definition picture, new techniques are being developed to enhance certain mucosal or vascular characteristics so that abnormal growths are visualized better. One example is a technology called Narrow Band Imaging (NBI) (Olympus America, Center Valley, PA). NBI uses a special filter to illuminate tissue with light at specific wavelengths which enhances underlying vasculature and produces the greatest contrast between the vessels and surrounding mucosa. This can help the physician see the margins of an abnormal growth better and assist in determining which areas are the best to biopsy. Fujinon Intelligent Color Enhancement (FICE; Fujinon, Inc. Wayne, NJ) and I-scan (Pentax Medical Montvale, NJ) are similar technologies that use computer processing to enhance mucosal detail.
Chromoendoscopy is a special technique used in conjunction with endoscopy to improve visualization of the mucosa or lining of the intestine. Chromoendoscopy can help the endoscopist find abnormalities that are present during the endoscopic examination which may be difficult to identify using only “white light” endoscopy. Chromoendoscopy is performed by spraying specialized nonpermanent stains or dyes on the lining of the intestine during the endoscopic procedure.
Once the area of interest has been sprayed, the dye works either as a direct contrast agent or is absorbed by the cells of the lining of the intestine. In either case, a color change occurs and the endoscopist evaluates the surface appearance to detect a characteristic appearance which is either normal or abnormal. If an abnormal appearance is detected the endoscopist may then perform tissue sampling of the area (endoscopic biopsy), treat the abnormal area or remove the area of abnormality.
Chromoendoscopy is used to evaluate a variety of conditions including cancer of the mouth, esophagus, stomach and colon, and a number or premalignant or precancerous conditions. These include Barrett’s esophagus, a change in the lining of the esophagus which may increase the risk of esophageal cancer, and ulcerative colitis, one of the two types of inflammatory bowel disease involving the colon. Chromoendoscopy can also be used to evaluate benign (noncancerous) conditions in the gastrointestinal tract including Helicobacter pylori infections and abnormal, but not precancerous, gastric mucosa found in the esophagus or small intestine.
Endoscopic Mucosal Resection (EMR)
Endoscopy allows direct visualization of the inner most lining of the gastrointestinal tract as the scope passes through the hollow lumen. This inner lining is called the mucosa. Many cancers originate from the mucosa of the gastrointestinal tract. Some examples include colon, esophageal and stomach cancer.
Precancerous changes and early stage cancers can be removed through an endoscope provided the cancer has not spread beyond the surface layers of the gastrointestinal lining. An important technique in removing these lesions is endoscopic mucosal resection (EMR). In this technique, a needle is passed through the endoscope and a liquid solution is injected under the area of interest, in effect “lifting” the abnormal tissue and separating it from the deeper intestinal layers. The abnormal lesion is then removed (“resected”) with a snare; the tissue is subsequently retrieved and sent to pathology for evaluation.
Endoscopic Ultrasound (EUS)/Fine Needle Aspiration (FNA)
Endoscopic ultrasound (EUS) is a technique using sound waves known as ultrasound during an endoscopic procedure to look at or through the wall of the gastrointestinal tract. This technique allows physicians to see organs and structures not typically visible during gastrointestinal endoscopy, such as the layers of the gastrointestinal tract wall, the liver, pancreas, lymph nodes, and bile ducts. The scope used for EUS is similar to a regular endoscope with the added component of an ultrasound transducer. Under continuous real-time ultrasound guidance, a thin needle can be advanced into these structures to obtain an aspirate of the tissue. This technique is known as a fine needle aspirate (FNA). The cells obtained from the FNA can be smeared on a slide and analyzed for abnormalities such as cancer. The cell analysis is called cytology.
EUS with FNA has revolutionized the ability to diagnose and stage cancers of the gastrointestinal tract and assess the pancreas. Gastrointestinal cancers can be looked at with EUS and their depth of penetration into the intestinal wall can be determined. Any suspicious appearing lymph nodes can be biopsied using EUS/FNA. The pancreas is another organ that is well visualized with EUS. Abnormalities such as tumors and cysts of the pancreas can be carefully evaluated using EUS and then biopsied with FNA.
Lung cancer is also routinely staged by performing an EUS/FNA of the lymph nodes in the chest that can be seen by looking through the esophagus, as these nodes are often the first location to which lung cancer spreads. If a malignant (cancerous) node is confirmed on EUS/FNA, the patient will often require medical therapy first before considering lung surgery. In this way, EUS/FNA can help direct the appropriate first line of therapy.
There are many new applications of EUS using FNA. Researchers are looking to deliver chemotherapeutics into small pancreatic cancers and cysts. Nerve blocks using EUS/FNA to inject numbing medicines into the celiac ganglia, a major nerve cluster are now routinely performed in patients with pain due to pancreatic cancer.
NOTES® (Natural Orifice Translumenal Endoscopic Surgery®)
Natural Orifice Translumenal Endoscopic Surgery® (NOTES®) is a new type of hybrid endoscopic/surgical procedure currently being studied at hospitals and research facilities around the world. NOTES® represents the next frontier of surgical principles and endoscopic techniques. The standard approach to reaching the peritoneal cavity (that portion of the abdomen where organs such as the gallbladder and liver are found) is via a surgical incision of the skin or puncturing the skin allowing the introduction of small cameras deep into the abdomen. The latter technique is known as laparoscopic surgery.
Portions of the gastrointestinal tract such as the stomach and colon commonly examined with endoscopy (such as for colon cancer screening) also reside in the peritoneal cavity. Perforation (inadvertent puncture creating a hole) of the gastrointestinal tract has been traditionally considered an undesirable event. Interventions using NOTES®, however, intentionally perforate the stomach, bowel or vagina thereby allowing the operator to access the peritoneal cavity using a normal body orifice as a conduit. Here, any peritoneal structure is theoretically approachable.
As an example, in natural orifice surgery the gallbladder might be removed through the mouth. The doctor would insert a tube down the esophagus, make a small incision in the stomach wall to gain access to the abdominal peritoneal cavity and take the organ out by the same route. Potential advantages of the NOTES® technique include reduced post-operative pain, shortened recovery times, and improved cosmesis (lack of surgical incision scars).
A range of procedures might be performed this way, such as gastric bypass, fallopian tubal ligation, removal of the ovaries and diagnostic work. Some operations might be done via the rectum, vagina, urethra or bladder as well. Because NOTES® is so new, research generally has been confined to animals, mainly pigs. Recently, however, human studies have emerged that report the procedures to be feasible. Further studies involving a variety of NOTES® procedures, under close supervision by medical experts and Institutional Review Boards, are being performed.
The NOTES® initiative is a joint effort of the American Society for Gastrointestinal Endoscopy (ASGE) and the Society for American Gastrointestinal and Endoscopic Surgeons (SAGES). Together, these societies have formed the Natural Orifice Surgery Consortium for Assessment and Research® (NOSCAR®), a group that provides guidance and oversight and evaluation of NOTES techniques and the related research required.
Mucosal Ablation Therapies
Mucosal ablative techniques are methods of destroying the superficial lining, or “mucosa,” of the gastrointestinal tract. This is usually done when the mucosa is bleeding or when there are precancerous changes which need to be treated. Once the superficial, diseased mucosal layer is destroyed, a new, healthy layer regenerates. For example, some patients have damage to the colon from previous radiation treatment for prostate cancer, with chronic bleeding from the colon lining. The lining can be ablated or destroyed, and a new lining grows back in its place. One area of considerable interest for mucosal ablation is Barrett’s esophagus, a change in the lining of the esophagus which is sometimes found in people with chronic acid reflux disease. People with Barrett’s esophagus are at increased risk for developing cancer of the esophagus, so they have periodic endoscopy to biopsy this lining and look for progression of the precancerous changes. If advanced precancerous changes are found, the risk of developing cancer of the esophagus is much higher, and treatment to ablate the Barrett’s esophagus can be considered.
There are a number of devices which can be used to ablate mucosa, and the choice of a particular instrument depends on the area being treated as well as the experience of the endoscopist. These devices include catheters or probes which are passed through an endoscope and burn the GI tract lining through electricity or heat when the probe touches the lining. Another catheter conducts electricity through inert argon gas, so that the catheter does not actually have to touch the mucosa. This technique called argon plasma coagulation helps the physician to treat a larger area at once. Cryotherapy is a method of spraying a cold substance, usually liquid nitrogen, on the tissue. When tissue is frozen, it dies and sloughs off, allowing new, healthy tissue to grow back. Cryotherapy has been used in other parts of the body for many years (for example, to treat precancerous cells of the cervix) and is now being used in the GI tract as a means of mucosal ablation.
Another newer method of mucosal ablation, called radiofrequency ablation, has generated much interest. One radiofrequency device has been developed specifically for the ablation of Barrett’s esophagus. This is a cylinder shaped balloon passed over a guidewire. Once in position it is inflated bringing the wall of the balloon in contact with the precancerous Barrett’s mucosa. The physician presses a foot pedal and radiofrequency energy is delivered over the entire surface area of the balloon. The delivery of the energy takes about one second and results in a very superficial burn of the esophageal lining. Once the Barrett’s tissue sloughs off, a new, healthy esophagus lining grows back. There is a smaller, rectangular shaped radiofrequency instrument which can be used to “touch up” places where small pieces of Barrett’s esophagus might have been missed. The studies which have been done suggest this method of ablating Barrett’s esophagus is safe, effective, and easy to use.