Tuesday, March 13, 2012

Gastrointestinal Endoscopy

Author: Dr Brian Fennerty Oregon Health and Science University 2008-07-28

I. Introduction to gastrointestinal endoscopy

Direct visualization of the gastrointestinal (GI) tract was largely limited to viewing the small section at the top of the digestive system, the esophagus (swallowing tube), and the very end part, the rectum, through rigid instruments using light shining down the shaft of the instrument. This remained the case until the development of flexible fiberoptic instruments in the 1960-70s that allowed light to bend with the instruments (endoscopes) so that organs beyond the very top and bottom of the gastrointestinal tract could now be reached and visualized, such as the whole colon, stomach, duodenum, and upper portion of the small intestine, the jejunum.
Further refinements in endoscopes including video instruments  has allowed for improved visualization of the GI tract, ability to sample tissues and apply therapy, and reach even the most inaccessible of GI locations (the entire small bowel including all of the jejunum and ileum). Most recently, capsule endoscopes have become available that allows for visualization of certain areas of the bowel without the “scope,” simply by swallowing a big pill with a recording and transmitting device.
Patients undergo endoscopy because they either have symptoms suggestive of digestive disease or because they are being screened for cancer or precancerous conditions affecting the digestive tract. For example, the most common reason for a patient to have an upper endoscopy (that allows for inspection of the esophagus, stomach, and upper small bowel [duodenum]) is either the presence of heartburn or indigestion, or when screening patients with long standing heartburn for a precancerous condition called Barrett’s esophagus.  The most common reason a patient would have a lower endoscopy, or colonoscopy, is screening for cancer or precancerous polyps or in the evaluation of rectal bleeding or diarrhea.
In general, gastrointestinal endoscopy is a safe and well tolerated procedure when performed by a trained and skilled practitioner who is experienced in managing the digestive diseases one may encounter (ulcers, esophagitis, colon polyps, cancers of the intestines, etc.). It is most often performed in an ambulatory outpatient setting in a doctor’s office, endoscopy center, or outpatient hospital-based endoscopy department. As the presence of food or intestinal contents will obscure the ability to examine the lining of the digestive system and hinder identification of the abnormality or diseases being looked for, patients undergoing gastrointestinal endoscopy are not allowed to eat for many hours prior to the procedure and when the colon is being examined patients will also need to undergo a bowel purge prior to the procedure. Additionally, as most patients undergoing endoscopic procedures in the United States have sedation to allow a more comfortable examination, there is the added need to have someone accompany them to and from the procedure. In general, resuming work on the same day as these procedures is not feasible. Thus, endoscopy can be an “inconvenience.”

II. Types of gastrointestinal endoscopy

Upper gastrointestinal endoscopy (video of the first part of an upper endoscopy) is also commonly referred to as EGD or esophagogastroduodenoscopy, as it allows the endoscopist to examine the esophagus (swallowing tube), stomach (gastro), and first part of the small bowel called the duodenum (video of an upper endoscopy after the esophagus has been entered including the esophagus, stomach and duodenum).  EGD allows one to see and diagnose:    
·         inflammation of the gut (esophagitis, gastritis, or duodenitis)
·         ulcers (esophageal ulcers, gastric ulcers, and duodenal ulcers
·         strictures or narrowings (esophageal strictures usually found at the junction of the esophagus and stomach, and pyloric strictures found at the pylorus located at the junction of the stomach and duodenum)
·         presence of food or foreign material indicating abnormal emptying of the esophagus or stomach in the fasting patient
·         tumors of the esophagus, stomach, or duodenum
·         sites of bleeding in the esophagus, stomach, or duodenum
·         presence of abnormal blood vessels found in patients with liver disease (esophageal or gastric varices and or portal hypertensive gastropathy)
·         a pre-cancerous esophageal condition called Barrett’s esophagus in patients with chronic heartburn
·         a malabsorptive process in the duodenum called sprue or celiac disease
·         other abnormal conditions of this section of the GI tract
Often, biopsies are obtained during EGD to confirm the presence or type of inflammation, ulceration, tumors, precancerous conditions, or sprue. If bleeding is active or likely to occur, procedures can be performed through the scope that halt the bleeding or prevent it from recurring (such as banding of varices in those with liver disease, cauterization, injection, and or clipping of ulcer vessels bleeding or likely to rebleed). Narrowings or strictures can be dilated or stretched open with balloons or bougie devices inserted through the scope or after the scope is withdrawn from the patient. Tumors can be treated with resection, heating, or other chemicals to cause them to regress or disappear entirely.
Colonoscopy (Video of the upper part of a normal colonoscopy) or endoscopy of the lower GI tract allows the endoscopist to examine the entire large bowel, and if needed, the very end of the small bowel called the terminal ileum. Colonoscopy allows one to see and diagnose:
·         polyps (video of a polyp and diverticulosis)
·         tumors
·         inflammation (colitis, ileitis)
·         diverticulosis (video of a polyp and colon diverticulosis)
·         hemorrhoids
·         presence of abnormal blood vessels (AVMs)
·         sites of bleeding (usually diverticuli, AVMs, or tumors)
Biopsies can easily, painlessly, and safely be obtained during colonoscopy, and evaluated by a pathologist for the presence of specific types of inflammation or to confirm the benign or malignant nature of a tumor. Additionally, polyps are usually easily removed and submitted for pathology analysis as the type, size, number, and microscopic nature of the polyp will determine if any follow up is needed and if so how soon that follow-up colonoscopy should occur. Usually, precancerous polyps indicate that the next exam should take place in about 5 years but occasionally it needs to be sooner (e.g., 6 months to assure complete removal, 2-3 years because the polyp was larger or had more advanced features). Polyps or tumors to large to remove can sometimes be destroyed by laser or other cautery techniques and tumors blocking the bowel can be opened by placing a metal stent, allowing bowel contents to get through and the blockage to be relieved.
Sigmoidoscopy is a limited form of colonoscopy and because it exams only the end part of the colon (about ¼ of the colon’s length), sigmoidoscopy does not require: 1) sedation, 2) fasting, or 3) a full bowel preparation. The preparation for sigmoidoscopy usually is just enema(s) prior to the procedure. While biopsy can be performed during sigmoidoscopy, polypectomy is usually not done as the finding of a polyp usually will require a full colonoscopy to make sure other polyps are not present farther up in the large colon. The limitation of sigmoidoscopy is that it only examines a small portion of the colon, therefore other abnormalities and diseases of the colon can be overlooked
ERCP or endoscopic retrograde cholangiopancreatography is a form of upper endoscopy combined with radiology imaging of the bile ducts and pancreatic duct system. ERCP allows one to see and treat diseases of the bile ducts and pancreas such as:
·         bile duct stones
·         bile duct narrowings (strictures)
·         bile duct tumors
·         pancreatic duct stones and narrowings
·         pancreatic tumors
·         Sphincter of Oddi (SOD) dysfunction
During ERCP, the Sphincter of Oddi muscle can be cut to remove stones, allow passage of dilators, brushes, forceps, cameras, or stents to diagnose and or treat bile and pancreatic duct strictures or as a primary treatment of SOD dysfunction.
EUS, or endoscopic ultrasound, is a special type of upper or lower endoscope fitted with an ultrasound device that allows for close and high-resolution depiction of tumors, polyps, and lymph nodes near the bowel wall and adjacent organs such as the lung, pancreas, and liver. EUS allows diagnosis and treatment of:
·         tumors and cysts of the pancreas
·         tumors (both benign and malignant) arising from the gut wall
·         lymph nodes near the gut wall
·         bile duct stones
During EUS, a needle can be advanced into lesions within and outside the bowel wall to obtain tissue for a diagnosis as well as to inject material into the abnormality as treatment.

III. Indications for gastrointestinal endoscopy

There are a variety of indications for endoscopy, but the following are the most common reasons for a person to be referred for one of these exams:
·         dyspepsia (indigestion or upper abdominal pain)
·         reflux (GERD or heartburn)
·         trouble or painful swallowing
·         nausea and or vomiting
·         unexplained weight loss
·         suspected peptic ulcer
·         loss of appetite or inability to finish a normal sized meal
·         evidence of bleeding (vomiting of blood, anemia or passage of blood)
·         screening for Barrett’s esophagus in those with chronic heartburn or GERD
·         screening for esophageal varices (abnormal blood vessels) in patients with chronic liver disease
·         screening for polyps or colon cancer
·         follow up of prior precancerous polyps or cancer
·         surveillance of long-standing ulcerative colitis or Crohn’s colitis
·         suspected ulcerative colitis or Crohn’s colitis
·         unexplained diarrhea
·         unexplained rectal bleeding
·         screening for polyps or colon cancer
·         suspected ulcerative colitis or Crohn’s colitis
·         unexplained diarrhea
·         unexplained rectal bleeding
·         removal of bile duct stones
·         placement of a bile duct stent
·         confirmation of suspected bile duct cancer
·         treatment of suspected Sphincter of Oddi dysfunction
·         removal of pancreatic duct stones
·         placement of a pancreatic duct stent
·         confirmation of suspected pancreatic tumors
·         evaluation of suspected sclerosing cholangitis
·         staging cancers of the esophagus, rectum and pancreas
·         sample lymph nodes near the bowel wall
·         evaluate and diagnose tumors or cysts seen on x-ray studies or prior endoscopy
·         treat pancreatic pseudocysts

IV. Preparation(s) for gastrointestinal endoscopy

When a patient is going to have an endoscopic procedure what will they experience?
First, the bowel must be made ready for an endoscope so that the surface lining (mucosa) can be observed in its entirety, and no abnormalities missed (or at least the chance of missing an abnormality is minimized). For an upper endoscopy that means not eating or drinking anything for about 8 hours prior to the procedure so that the stomach is completely empty, as is the first portion of the small bowel called the duodenum. For a colonoscopy or enteroscopy, the bowel must be further emptied of its normal contents (intestinal chyme in the small bowel and stool in the colon) by performing a bowel prep the day prior to, and/or the day of the procedure. Typically one of two prep types are used: 1) ingestion of a PEG-based 4 liter ( approximately one gallon) salty solution, examples of which are Golytely, Nulytely, etc. or 2) a smaller amount of a phosphate solution such as Fleet’s oral prep along with large amounts of fluid. Some centers also use a laxative to help the purging process. The result is evacuation of the entirety of intestinal contents and this is the part of the colonoscopy many patients find the most bothersome, although many patients find it not so difficult.
Second, in the United States most gastrointestinal endoscopy is performed with the patient under mild to moderate sedation (a relaxed sleepy state, somewhat like just before you fall asleep or awaken fully) although there is an emerging trend to use even deeper sedation (very sleepy and unaware of your surroundings), with a drug called propofol. However, many patients also may choose to have unsedated procedures as this allows them to drive themselves to and from the test as well as to resume a normal diet and return to work immediately following the procedure. In motivated patients, unsedated gastrointestinal endoscopy can be accomplished in most cases.
When sedation is used for gastrointestinal endoscopy, an 8-hour fast is necessary to avoid the risk of stomach contents being regurgitated when sedated, and to prevent lung problems (aspiration). Additionally, if sedation is used the patient is not allowed to drive (or operate other dangerous machinery) the rest of the day so another individual needs to accompany the patient and transport them home after the procedure. Once the patient reaches the endoscopy center, an IV will be started and medicine (usually a narcotic like fentanyl and a sedative like versed, although recently propofol is being more commonly used) is given intravenously, to accomplish the degree of sedation needed for patient comfort. The intent of sedation is to a) relieve any anxiety related to the procedure, and b) minimize any discomfort that occurs during the procedure. Upper endoscopy is for the most part painless, but can be anxiety provoking as the instrument bypasses the breathing tube and is inserted into the digestive tract. Thus, most patients do fine with light to moderate sedation for these type procedures. Younger patients and those taking pain medicines or sedatives on a regular basis are more difficult to sedate and often require more intensive sedation to perform these procedures. Colonoscopy can be associated with discomfort. While the colon does not feel most things, it can be very sensitive to air distension or stretching, both necessary parts of performing this procedure. While many patients tolerate colonoscopy very well with minimal or no sedation, allowing them to observe the procedure and talk with the doctor performing the procedure throughout their exam, others require deeper sedation to allow the exam to be completed.
Once the procedure is completed, most patients feel normal within 30-60 minutes and are sent back home. There may be some residual mild abdominal discomfort, but most patients are usually completely pain free, hungry, and ready to eat real food! Increased gassiness is noted by many the rest of that day and stools return to normal usually by the day following. In almost all cases, full activity can be resumed the following day including a normal diet and activity including work and exercise.

V. Diagnostic and therapeutic gastrointestinal endoscopy

While most endoscopic procedures are performed for what turns out to be symptoms that are not associated with any identifiable gastrointestinal abnormalities (a normal endoscopic examination where nothing else is done during the procedure other than “looking” at the lining of the GI tract), many exams end up being accompanied by either a diagnostic test or a therapy applied at the time of the endoscopy.
The most common diagnostic parts of an endoscopic procedure are a biopsy or polypectomy. Biopsies of tissue are usually obtained using a biopsy forceps inserted through a channel built into the endoscope itself, that allows the doctor to remove a small portion of the surface lining of the bowel. These endoscopic biopsies are painless and safe and are extremely common. Biopsies are usually obtained when inflammation or infection is suspected based on the appearance of the bowel wall or based on the patients symptoms, such as diarrhea. Deeper tissue biopsy or more extensive tissue biopsy can also be obtained when necessary by using special needles for deeper tissue or large resection devices for more extensive tissue removal or sampling (such as Endoscopic Mucosal Resection, or EMR). These more extensive biopsy procedures do not result in any pain but do have a risk for bleeding and/or causing a hole (perforation) in the bowel wall, both of which can be serious complications.
Polypectomy, or taking off a polyp, using small snare-like devices inserted through a built in channel in the endoscope occurs in about 1/3 of patients having screening colonoscopy. They are usually painless and rarely associated with any serious complications such as bleeding or perforation, although larger polyps or the use of cautery for polypectomy increases this risk.
Therapies most often applied during endoscopy are cauterization (heat) or injection (usually adrenalin) for bleeding or dilation of scars/strictures that are blocking the bowel. Cauterization or injection is applied using specially constructed accessory devices that are inserted through the endoscope and applied directly to the site that is or has been thought to have been bleeding (ulcers, abnormal blood vessels, diverticuli, etc.). It is unusual for bleeding to be uncontrolled using these systems. Another means of avoiding or treating bleeding is to apply a small, tight rubber band around a bleeding vessel, such as the esophageal varices seen in some patients with advanced chronic liver disease.

Dilation during gastrointestinal endoscopy is usually performed using balloons directly inserted across the narrowing, using the endoscopic view as the guide and then stretching the blockage open. Sometimes x-ray guidance is needed to guide the dilation or other types of dilators are used to stretch the narrowing open. Once open, some strictures require plastic stents or metal stents be inserted to keep the dilated section open. This is most true when the narrowing or stricture is due to a cancer. Stenting is usually not necessary for benign causes of narrowing or stricture in the gut. Plastic type stents are removable whereas most metal ones are not.

VI. Complications of gastrointestinal endoscopy

While endoscopy is a remarkably safe procedure, complications can arise during or afterward, although serious complications are very rare. The most common complications with all endoscopic procedures include:
a)      cardiac or lung problems related to the sedation
b)      bleeding that is usually related to a therapy that was applied, such as the removal of a polyp
c)      perforation or tearing a hole in the bowel wall
d)     missing important diseases (especially missing polyps or cancers on colonoscopy)
e)      infection
With ERCP the following complications can also occur in addition to those noted above:
f)       inflammation of the pancreas
g)      infection of the bile duct
What would happen if one of these complications were to occur? When it is a sedation-related problem, causing your breathing to become to shallow or stop, the procedure may need to be aborted, the sedation medicine may need to be reversed, and or your breathing supported with a mask or tube until the effect wears off. Heart rhythm problems or heart attacks rarely occur unless there is a breathing problem causing insufficient oxygen to get to the tissues. If a prolonged decrease in breathing and therefore oxygen delivery does occur, the heart and other organs can be at risk. Fortunately, serious breathing problems are rare because if sedation is used during endoscopy, monitoring of breathing, oxygenation of blood, and the heart rhythm is universally applied. Additionally, the nurse present during the procedure has a primary focus on patient monitoring during the gastrointestinal endoscopy, thus these risks, although potentially very serious, are rare.
Bleeding can occur during an endoscopy especially when a therapy is applied such as removing a polyp, dilating (stretching) open a stricture (scar), cutting the bile duct sphincter, etc. When this occurs, the endoscopist likely will stop the bleeding by applying cautery or injecting adrenalin into the site using special tools that go through the scopes. The more common scenario is bleeding days or weeks after a polyp was removed. This occurs because the cautery used to take the polyp off causes an ulcer to form at the site and these ulcers can present with delayed bleeding many days later. Usually this bleeding stops on its own and just needs to be monitored. Any bleeding during or after an endoscopy that does not stop or is severe will require the patient to be hospitalized and attempts at control may include endoscopy, radiology, and or surgery. Although surgery to stop bleeding is rare it can be necessary in some severe cases.
Perforation is probably the most feared endoscopic complication and although rare, almost always requires surgery to repair the hole caused by the endoscopic procedure. Most perforations occur during colonoscopy, are recognized during the procedure, and usually require the patient to go to surgery without delay. Often the hole can be repaired without any temporary diversion of the colon, but some patients will require a temporary colostomy for 3-4 months and a second surgery to put things back together once things heal up.
Missing an ulcer, polyp, or cancer is considered a complication because of the potential that it can harm the patient by delaying treatments aimed at cure. It is important for patients to realize the limitations of the endoscopist to discover all important bowel abnormalities, and to seek care if symptoms arise, not simply accepting that a disease process has already been excluded because of a prior endoscopy. The bottom line is that endoscopy is an accurate test but not perfect!

VII. References

Preparation of Patients for Gastrointestinal EndoscopyGastrointest Endosc 2003;57:446-450
The Role of Endoscopy in DyspepsiaGastrointest Endosc 2007;66:1071-1075
Role of Endoscopy in the Management of GERDGastrointest Endosc 2007;66:219-224
Complications of Upper GI EndoscopyGastrointest Endosc 2002;55:784-793
Colorectal Cancer Screening and SurveillanceGastrointest Endosc 2006;63:546-557
Complications of ColonoscopyGastrointest Endosc 2003;57:441-445
Appropriate Use of Gastrointestinal EndoscopyGastrointest Endosc 2000;52:831-83

VIII. Web resources

http://www.asge.org/   (The official website for the American Society for Gastrointestinal Endoscopy containing patient education brochures and other useful information)
http://www.asge.org/Apps/FindADoctor/search.aspx   (The link to the official Web site for the American Society for Gastrointestinal Endoscopy “find an” endoscopy doctor)
http://www.nlm.nih.gov/medlineplus/ency/article/003338.htm (Contains descriptions of endoscopy procedures)
http://www.guideline.gov/summary/summary.aspx?ss=15&doc_id=5680&nbr=3818 (Contains descriptions of endoscopy preparations and procedures)
http://www.endoatlas.com/atlas_1.html  (Contains endoscopic photographs of various GI disease states)
http://www.gastrointestinalatlas.com/  (Contains endoscopic photographs of various GI disease states)
http://dave1.mgh.harvard.edu/ (Contains endoscopic photographs and videos of various GI disease states)