Acs0518 Gastrointestinal Endoscopy 2006


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Acs0518 Gastrointestinal Endoscopy 2006

  1. 1. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 1 18 GASTROINTESTINAL ENDOSCOPY Alicia Fanning, M.D., and Jeffrey L. Ponsky, M.D., F.A.C.S. Since the beginning of the 1970s, flexible endoscopy of the gas- the intestinal absorptive cells of the columnar epithelium. Darkly trointestinal tract has been the dominant modality for the diag- stained areas may be biopsied for confirmation. nosis of gastrointestinal disease. Over the same period, develop- As the endoscope is advanced, insufflation is continued, and the ments in technology and methodology have made possible the curve of the lumen is followed to the left as the esophagus traverses use of endoscopy to treat a host of conditions that once were the diaphragm to enter the stomach.There is a pinched area where considered to be manageable only by means of open surgical the diaphragm compresses the esophagus; the pinching is exagger- procedures. The integration of flexible endoscopic techniques ated when the patient is asked to sniff. If gastric folds are seen above into the armamentarium of the GI surgeon permits a more mul- this pinched area, a hiatal hernia is present. When the stomach is tidimensional approach to the treatment of digestive disease. entered, the tip of the endoscope is elevated so as to center it with- The modern GI surgeon should be conversant in and adept at in the gastric lumen. It should be noted that with the patient lying many of these procedures. in the left lateral decubitus position, the stomach is also on its side, with the greater curvature at 6 o’clock, the lesser curvature at 12 o’clock, the posterior wall at 3 o’clock, and the anterior wall at 9 Diagnostic Esophagogastroduodenoscopy o’clock. Air should be insufflated to distend the stomach fully and Diagnostic esophagogastroduodenoscopy (EGD) is indicated permit careful inspection of the mucosal surfaces. when a patient has abnormal findings on traditional GI x-ray As the instrument is advanced toward the gastric antrum, its series, dysphagia, odynophagia, epigastric pain that does not tip should be slightly elevated because the stomach has a J shape respond to medical therapy, persistent heartburn, or upper GI and the prepyloric region curves upward. The pylorus is nor- bleeding; it is also indicated for surveillance of patients at high mally round and may be seen to open and close with gastric peri- risk for malignancy and for sampling of GI tissue or fluid. One stalsis. With the tip of the endoscope positioned at the proximal prepares for the examination by ensuring the patient’s hemody- gastric antrum, just under the incisura angularis, a retroflex view namic stability, having the patient fast for 6 to 8 hours before- of the cardia and the fundus is obtained by elevating the tip of hand, and performing conscious sedation, which generally the scope and rotating the shaft to the left. This maneuver pro- involves applying a topical anesthetic to the posterior pharynx vides visual and therapeutic access to the proximal stomach. and administering a narcotic and a benzodiazepine intravenous- After the stomach has been viewed, the instrument is ly. Monitoring of arterial blood pressure and oxygen saturation advanced under direct vision through the pylorus and into the throughout the procedure is now standard practice. duodenal bulb. Insufflation of air should continue as the scope is TECHNIQUE With the patient in the left lateral decubitus position, a topi- cal anesthetic is applied to the posterior pharynx and an intra- venous sedative administered. The forward-viewing panendo- scope—a small-caliber instrument that is long enough to permit examination of the foregut from the mouth to the third portion of the duodenum—is employed. The endoscope may be introduced either blindly, via finger- guided palpation of the pharynx, or under direct vision.The latter approach is preferable. In this approach, the instrument is ad- vanced slowly until the epiglottis and vocal cords are visualized [see Figure 1]; it is then angled posteriorly to the esophageal introitus and gently advanced as the patient is asked to swallow. Insufflation of air is begun to distend the esophagus, which appears as a long, round tube. Frequent peristaltic waves are seen; these are normal. Mucosal surfaces must be closely inspected for signs of ulceration, stricture, tumor, or Barrett’s (columnar) epithelium, which mani- fests itself as orange patches in otherwise pale salmon-pink esoph- ageal (squamous) mucosa.When abnormalities are noted, biopsy, brushing for cytologic evaluation, or both should be performed. Figure 1 Diagnostic esophagogastroduodenoscopy. As the endo- Staining of the esophagus with methylene blue may be useful in scope is introduced under direct vision, the vocal cords are clearly the search for Barrett’s mucosa: the blue dye is avidly absorbed by noted. The esophageal opening is posterior to the cords.
  2. 2. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 2 pressed against the pylorus to facilitate passage of the instru- a a ment.The scope tends to pop into the duodenal bulb rather than slide smoothly; it should be pulled back slightly to allow one to observe the mucosal surfaces of the bulb before moving ahead. Unlike the rest of the small bowel, the duodenal bulb has no semicircular folds. The tip of the scope must be rotated slightly to permit examination of the walls of the bulb. It is advisable to pull the instrument back into the stomach while observing the walls of the bulb and the pyloric channel for lesions; several such withdrawals may be required for full assessment of this area. Once the duodenal bulb has been examined, the endoscope is advanced just past the bulb to the point where the first duodenal folds are observed. Here, the duodenum turns sharply to the rear b b and downward as it becomes retroperitoneal. Advancement of the scope into the second portion of the duodenum is one of the few endoscopic maneuvers that cannot be accomplished under direct vision. Because of the sharp angle of the turn, one will experience a moment of so-called red out as the tip of the endoscope touch- es the mucosa during the turn. To ensure that the turn is accom- plished safely, the instrument is advanced as far through the bulb as is possible under direct vision. The control handle of the scope is then rotated approximately 90° to the right as the tip of the scope is turned to the right and angled first upward, then down- ward. As the second portion of the duodenum appears, the scope Figure 2 Therapeutic esophagogastroduodenoscopy: control of is rotated back to its neutral position. When done correctly, the variceal hemorrhage. (a) A plastic tip on the endoscope is used to turn is actually quite easy. It should never be forced: if the instru- create a chamber. (b) An esophageal varix is suctioned into the ment does not proceed easily into the descending duodenum, the chamber, and a rubber band is released around it. scope should be pulled back and the attempt repeated. Pushing against resistance may result in perforation. Entering the descending duodenum causes the scope to form a ties are to establish a secure airway and to ensure hemodynamic large loop in the stomach. Therefore, once the second portion of stability. These priorities must be addressed before endoscopy is the duodenum is successfully entered, the shaft of the instrument attempted. If the bleeding is thought to be coming from esopha- is pulled back. Paradoxically, as this movement straightens the gas- geal varices, it is frequently useful to perform endotracheal intuba- tric loop, it also advances the tip of the instrument deeper into the tion for control of the airway before the endoscopic intervention. duodenum. Further advancement of the instrument under direct Technique vision often permits entry into the third or even the fourth portion of the duodenum. Once the distal limit of intubation is reached, the A rapid but complete diagnostic upper GI endoscopic proce- scope is withdrawn and the luminal surfaces are carefully exam- dure is performed to determine whether varices are present and ined. Rotating the scope with small right-left movements of the to identify the exact site of hemorrhage. Endoscopic therapy for controls and side-to-side movements of the control handle itself variceal disease is then delivered by means of either sclerother- will help demonstrate the more subtle details of duodenal anatomy. apy or rubber band ligation. Often, the upper GI tract is inspected more completely while the Sclerotherapy is commenced in the distal esophagus at the site instrument is being withdrawn than while it is being advanced. of active or suspected bleeding: 2 to 3 ml of a sclerosant solution Mucosal abnormalities should be biopsied; liberal use of brush (e.g., sodium tetradecyl sulfate) is injected directly into the lumen cytology in combination with biopsy enhances the yield. of the varix. Additional varices can be treated in the same fashion. After the bleeding has stopped, further therapy is usually delivered COMPLICATIONS at weekly intervals until total variceal obliteration is achieved. EGD is an extremely safe procedure. Perhaps the most common Rubber band ligation of varices has become extremely popular problems associated with the technique arise from the preparatory and has been shown to possess some clear advantages over scle- sedation and analgesia. Respiratory depression and aspiration may rotherapy [see Figure 2]. Originally, multiple passages of the endo- occur during the procedure. Careful attention must be paid to the scope were required to allow for reloading of the bands; however, patient’s state of consciousness and airway during the endoscopic newer ligating devices permit ligation of as many as 10 varices with procedure, appropriate drugs must be available to reverse sedative a single passage of the endoscope. As with sclerotherapy, the site effects, and a suction apparatus must be ready for use at all times. of active or suspected bleeding is attacked first; it is most often Blind advancement of the endoscope by force may lead to perfora- near the esophagogastric junction.The offending varix is centered tion of the esophagus; this problem may be avoided by taking care in the field of view, and suction is applied to pull it into the ligator never to advance the instrument against resistance. cup, which sits on the end of the endoscope. When the varix is deep within the cup, the trigger string on the ligator is pulled, and a rubber band is released around the varix. Suction is then Therapeutic Esophagogastroduodenoscopy released, and the ligated varix is visualized. Additional ligations may be performed at the initial session; follow-up sessions are usu- CONTROL OF VARICEAL HEMORRHAGE ally held at weekly intervals until total variceal obliteration is In patients with massive upper GI hemorrhage, the first priori- achieved.
  3. 3. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 3 a b Figure 3 Therapeutic esophagogastroduodenoscopy: dilation of esophageal strictures. (a) A hydrostatic dilating balloon filled with a contrast agent is inflated within the stricture under fluoroscopic guidance. Initially, a “waist” appears at the stricture site. (b) Inflation of the balloon is continued until the waist is ablated, which indicates complete dilation of the stricture. Complications therapy is performed around the bleeding lesion to create edema Because aspiration of blood and gastric contents may occur and vasospasm in the area. The bipolar coagulator or the heater during endoscopic control of variceal hemorrhage, endotracheal probe is applied directly to the bleeding lesion in an attempt to intubation must be considered when bleeding is massive. In many coapt the bleeding vessel as heat is delivered. Frequently, injec- cases, general anesthesia will permit adequate airway control and tion therapy is employed in conjunction with coagulation; this a quiet operating field. Violent patient motion when the injection combination is very effective. needle is in a varix may result in perforation of the esophagus.This If there is a clot covering the ulcer base, it must be removed with is a rare complication, however; tearing of the varix, with resultant suction or a snare before coagulation is attempted. If a rapidly bleed- hemorrhage, is more frequent. Injection of excessive amounts of ing lesion is present, the best approach often is injection therapy in sclerosant may lead to significant ulceration and necrosis of esoph- adjacent areas to slow or stop the bleeding, followed by coagula- ageal tissue. Fever, severe infection, pleural effusion, and subse- tion by direct coaptation.Vascular lesions are often multiple or diffuse, quent esophageal stricture occasionally occur after sclerotherapy. as in so-called watermelon stomach. Such lesions are most effec- Ulceration and necrosis of tissue, with subsequent stricture, occur tively treated by means of modalities that can be applied in a spray- after rubber band ligation as well, but severe infection is less com- ing fashion, such as the Nd:YAG laser or the argon beam coagulator. mon in this setting. Complications CONTROL OF NONVARICEAL HEMORRHAGE Nonvariceal hemorrhage is successfully controlled by endoscopic Bleeding from peptic ulcer disease, gastritis, or vascular malfor- means in more than 90% of cases. At times, however, attempts at mations is a common indication for EGD. Once the patient has endoscopic control may exacerbate the bleeding. Several therapeu- been adequately resuscitated, endoscopy should be performed, tic modalities should always be available: one may succeed when and the entire esophagus, stomach, and duodenum should be another fails. Excessive injection therapy or persistent attempts at examined thoroughly. Before the procedure is begun, the stomach coagulation may lead to tissue necrosis and subsequent perfora- should be vigorously irrigated through a large-bore tube so that as tion. Although the argon beam coagulator can injure tissue only to much clotted blood as possible can be evacuated. If a pool of a depth of several millimeters, excessive application may result in blood is noted in the stomach, the position of the patient should massive distention of the bowel if care is not taken to aspirate the be changed so as to move the pool and permit complete examina- constantly infused argon gas frequently.The Nd:YAG laser has the tion of the stomach. potential to cause full-thickness injury to the gastric wall. The therapeutic modalities available for control of nonvar- DILATION OF ESOPHAGEAL STRICTURES iceal bleeding include (1) the injection of hypertonic saline, epi- nephrine (in a 1:10,000 solution), or 98% alcohol, (2) bipolar When patients complain of dysphagia or odynophagia, prompt en- electrocoagulation, (3) the use of heater probes, (4) argon beam doscopic investigation is warranted. Strictures may be secondary to coagulation, (5) the application of acrylic glue, (6) the applica- reflux disease, secondary to caustic burns, or of neoplastic origin. tion of hemostatic clips, and (7) the use of the neodynium:yttri- Technique um-aluminum-garnet (Nd:YAG) laser. Endoscopy is performed in the usual fashion. It is imperative Technique that the endoscope be advanced only under direct vision. When The most popular therapeutic modalities are injection thera- a stricture is encountered, its location, morphology, and length py, bipolar coagulation, and the use of the heater probe. Injection should be determined. Biopsy and cytology specimens should be
  4. 4. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 4 gathered from the circumference of the stricture. When a stric- Technique ture is present at the esophagogastric junction and the scope can Modern esophageal prostheses are placed under fluoroscopic easily be passed by the stricture, it is helpful to view the area guidance, frequently after endoscopic balloon dilation of the tumor. from below with the tip of the scope retroflexed. During the endoscopic examination, it is useful to inject a small Stricture dilation can be accomplished in several different ways amount of water-soluble contrast material into the muscular wall and with several different kinds of dilators. One commonly em- of the esophagus just above and below the tumor; this enables one ployed method is to use the endoscope to guide the passage of a to measure the length of the tumor and select the correct stent. soft-tipped guide wire through the stricture; the scope is then re- Once the tumor has been dilated and marked endoscopically, the moved, leaving the wire in place. Subsequently, dilators are passed scope is removed, and the expandable stent is passed into the over the guide wire, usually under fluoroscopic control. Another esophagus and positioned between the endoscopic injection mark- method for endoscopic dilation of strictures is the use of through- ings seen on fluoroscopy. The stent is then deployed and allowed the-scope (TTS) hydrostatic dilating balloons. A balloon of the to expand [see Figure 4].The endoscope may then be reintroduced appropriate inflated diameter (usually no larger than 18 mm or 54 to ensure that the prosthesis is patent and is correctly placed. French) is selected, passed through the biopsy channel of the endo- scope, and advanced under direct vision until its middle portion Complications passes through the stricture. At the stricture site, the balloon is Incorrect positioning of the prosthesis is a frequent problem. At- compressed, giving the appearance of a waist. The balloon is then tention to the details of endoscopic marking is very important. Also inflated until the waist is fully expanded [see Figure 3]. Full expan- crucial is correct selection of a stent: stents shorten from both ends sion is verified by fluoroscopic surveillance and the use of contrast as they are deployed, and this must be taken into account in select- to inflate the balloon. This second method is extremely useful for ing the correct stent length. On occasion, the stent may migrate as a initial dilation of tight strictures in preparation for the use of other, result of tumor-related necrosis or incorrect placement. If it migrates nonendoscopic dilators or the placement of an esophageal stent. into the stomach, it can usually be captured in a snare and retrieved. Complications RETRIEVAL OF FOREIGN BODIES Dilation of esophageal strictures may result in bleeding (usual- Many ingested foreign bodies pass through the GI tract ly minor) or perforation of the esophagus. When a patient experi- uneventfully, but a good number must be removed by endo- ences severe pain after dilation, a chest x-ray is imperative.The finding scopic means—in particular, foreign bodies in the esophagus, of mediastinal or subcutaneous air should prompt the immediate sharp objects that are likely to perforate the bowel, and objects performance of a contrast study with a water-soluble agent to deter- that do not progress from the stomach. mine whether a perforation is present. Some small perforations If the ingested object is of an unfamiliar type, it is an extremely can be managed with intravenous antibiotics and observation, but good idea to practice with a similar object outside the patient most must be managed surgically. The incidence of perforation before attempting endoscopic retrieval. This preparatory step can be minimized by avoiding excessive or forceful dilation. allows one to select the most appropriate accessory and technique for removing the object. STENTING OF ESOPHAGEAL TUMORS Under optimal circumstances, esophageal tumors should be Technique treated by means of extirpative surgery. When surgical cure or Objects with sharp edges should be removed with the sharp palliation seems to have little to offer, placement of an esophageal end trailing to prevent perforation. In some cases, this means prosthesis by endoscopic means is a reasonable approach. that the object must be pushed into the stomach and turned a b c d Figure 4 Therapeutic esophagogastroduodenoscopy: stenting of esophageal tumors. (a) An esophageal tumor is dilated. (b, c) A compressed expandable metal stent is positioned within the tumor and deployed. (d) The expanded stent yields a large enough lumen to permit the patient to continue oral alimentation.
  5. 5. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 5 around before being removed. If multiple foreign bodies are present or if it is highly likely that the foreign body will injure the esophagus if removed in the standard manner, an overtube should be placed over the scope before insertion. The overtube enables one to pass the instrument several times and retrieve any sharp objects without injuring the esophagus; it also helps ensure that the object is not aspirated into the airway. If the patient is a child, general anesthesia may be advisable. Perhaps the best method of removing foreign bodies is to sur- round them with a simple polypectomy snare and secure them in the endoscope’s grasp. Meat boluses that form in the esoph- agus or proximal to a gastric band may be extremely difficult to dislodge; the use of a variceal ligator cap to produce a suction chamber can be helpful in such situations. Complications Endoscopic removal of foreign bodies is extremely safe and effective. Care must be taken to ensure that the esophagus is not injured during removal of the object. If the object is deeply em- bedded or refractory to removal, a surgical approach is preferred. PERCUTANEOUS ENDOSCOPIC GASTROSTOMY Since 1980, endoscopically guided placement of a tube gas- trostomy has been widely employed to provide access to the GI tract for feeding or decompression. Indications for percutaneous endoscopic gastrostomy (PEG) include various disease processes that interfere with swallowing, such as severe neurologic impair- ment, oropharyngeal tumors, and facial trauma. PEG has also been Figure 5 Therapeutic esophagogastroduodenoscopy: percuta- neous endoscopic gastrostomy. The first steps in the procedure employed to establish a route for recycling bile in patients with involve selecting a proper site in the stomach and using a snare to malignant biliary obstruction, to provide supplemental feeding in surround a needle that has been passed through the abdominal and selected patients with inflammatory bowel disease, and to accom- gastric walls. plish gastric decompression in patients with conditions such as carcinomatosis, radiation enteritis, and diabetic gastropathy. Technique The patient fasts for 8 hours beforehand, and a single pro- phylactic dose of an antibiotic is administered just before the procedure is begun.The patient is placed in the supine position, a topical anesthetic is applied to the posterior pharynx, and intravenous sedation is begun. A forward-viewing endoscope is passed into the esophagus and advanced into the stomach. The abdomen is prepared in a sterile fashion and draped. The stom- ach and the duodenum are then inspected. The room lights are dimmed, and the light of the endoscope is used to transilluminate the abdominal wall so as to indicate a point where the gastric wall and the abdominal wall are in close prox- Figure 6 Therapeutic esophagogastroduodenoscopy: percuta- imity. Finger pressure is applied to various areas of the abdomen neous endoscopic gastrostomy. After the suture is retrieved from until a spot is identified at which such pressure produces clear the stomach, it is affixed to the gastrostomy tube and used to pull indentation of the gastric wall. An endoscopic snare is deployed the tube back into the stomach and out the abdominal wall. The through the biopsy channel of the endoscope to cover this spot, gastroscope is reinserted to follow the process and ensure that the and a local anesthetic is infiltrated into the overlying skin [see final position of the tube is correct. Figure 5]. A 1 cm skin incision is made at the chosen spot, and a needle is passed through the incision and into the gastric lumen. The endoscopic snare is tightened around the needle, and a wire abdominal wall.The crossbar should remain several millimeters is passed through the needle and into the gastric lumen.The snare from the skin to prevent excessive tension, which would cause is moved so as to surround the wire, which is then pulled out of ischemic necrosis of the underlying tissue. the patient’s mouth. The gastrostomy tube is fastened to the wire Complications and pulled in a retrograde manner down the esophagus and into the stomach.The gastroscope is subsequently reinserted to ensure Local wound infections are the most common complications that the head of the catheter is correctly positioned against the gas- of PEG. They can be minimized by administering preoperative tric mucosa [see Figure 6]. antibiotics and ensuring that excessive tension is not applied to An outer crossbar is put in place to prevent inward migration the crossbar at the end of the procedure.When such infections do of the tube and to hold the stomach in approximation to the occur, they can usually be treated via simple drainage and local
  6. 6. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 6 wound care; sacrifice of the gastrostomy is rarely necessary. lead to acinarization, or rupture of the small ductules, with extra- Several other complications, such as early extrusion of the tube, vasation of contrast material into the pancreatic parenchyma; progressive enlargement of the tract, and separation of the gastric pancreatitis is a frequent consequence of acinarization. Cho- and abdominal walls with leakage of feedings into the abdominal langitis may result when contrast is injected proximal to an ob- cavity, are also most often attributable to excessive crossbar ten- struction of the biliary tree. When obstruction is demonstrated, sion and subsequent ischemia. Gastrocolic fistula can occur after drainage of the system by means of stone extraction, stenting, or PEG. This problem may not be obvious for months afterward, nasobiliary intubation is important to prevent cholangitis. but severe diarrhea after feedings is grounds for suspicion. Once the PEG tract is mature, gastrocolic fistulas usually close quick- ly after simple removal of the gastrostomy tube. Therapeutic Endoscopic Retrograde Cholangiopancreatography Therapeutic interventions that may be accomplished at the time Diagnostic Endoscopic Retrograde of ERCP include sphincterotomy for ductal access or ampullary Cholangiopancreatography stenosis, removal of CBD stones, dilation of benign and malignant Endoscopic retrograde cholangiopancreatography (ERCP) is biliary strictures, and insertion of stents to maintain ductal paten- an advanced procedure that is technically more challenging cy. Pancreatic duct interventions include removal of stones, bridg- than standard upper GI endoscopy; however, it can be mastered ing of ductal disruptions, and drainage of pseudocysts. by most endoscopists who are willing to dedicate sufficient time TECHNIQUE to learning the method. ERCP yields a radiologic image of the pancreatic and biliary trees, and in many cases, it provides All therapeutic applications of ERCP must begin with selective access for therapy. Indications for ERCP include suspected cannulation of the duct being treated. Frequently, a guide wire is benign or malignant maladies of the common bile duct (CBD), then introduced deep into the duct to provide a means of obtain- the ampulla of Vater, or the pancreas. Cholelithiasis per se is not ing access to the duct on an ongoing basis and to ensure correct an indication for ERCP unless choledocholithiasis is suspected. TECHNIQUE a As with standard upper GI endoscopy, the patient fasts for 6 to 8 hours beforehand. Intravenous sedation is administered, and prophylactic antibiotics are given when biliary obstruction is sus- pected. The patient is initially placed in the left lateral decubitus position but is later rotated to the prone position after the scope is in place in the second portion of the duodenum. A side-viewing endoscope is employed because it allows the best visualization of the ampulla of Vater.The instrument is passed into the esophagus and maneuvered through the stomach, across the pylorus, and into the duodenum. Manipulation of a side-viewing instrument is a bit awkward for the novice but is easily learned. Once the endoscope is in the second portion of the duodenum, it is pulled back so that the gastric loop is straightened and the tip of the scope occupies a better position with regard to the papilla. This so-called short scope position is generally best for work in the CBD [see Figure 7]. The papilla of Vater (also known as the b major duodenal papilla) appears as a small longitudinal nubbin crossing the horizontal semicircular folds of the duodenum, gen- erally in the 12 to 1 o’clock position. At its tip, a small, soft, retic- ulated area may be noted; this is the papillary orifice. Often, a small mucosal protuberance is seen just proximal and to the right of the papilla of Vater; this is the minor duodenal papilla. A small plastic cannula is passed through the channel of the endoscope and introduced into the ampullary orifice, and contrast material is injected under fluoroscopic control to provide visual- ization of the CBD and the pancreatic duct.The two may share a single orifice within the ampulla or may have separate orifices.The CBD exits the papilla in a cephalad direction, tangential to the duodenal wall. The bulge of the ampulla within the duodenum represents the intramural segment of the duct. The orifice of the CBD is typically found at the 11 o’clock position in the ampulla.The pancreatic duct leaves the papilla in a perpendicular fashion. Its orifice is usually in the 1 o’clock area of the papilla [see Figure 8]. Figure 7 Diagnostic endoscopic retrograde cholangiopancreatog- COMPLICATIONS raphy. (a) The so-called short scope position, along the lesser curve of the stomach, is usually the most effective in biliary interven- When contrast material is being injected into the pancreatic tions. (b) The so-called long scope position may be necessary at ductal system, care must be taken to avoid overfilling, which can times.
  7. 7. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 7 positioning for intraductal manipulations. After electrosurgical divi- sion of the papilla, biliary stones are retrieved with balloon or bas- kets [see Figure 9]. Often, large stones can be captured within the duct in mechanical lithotripsy baskets and crushed before removal. Strictures should be brushed for cytologic evaluation once they have been traversed by a wire. They may then be dilated with hydrostatic balloons under fluoroscopic guidance and stented [see Figure 10]. Plastic stents are used for most benign and many malignant strictures; however, self-expanding metal stents are now being used more frequently for malignant stric- tures because they remain patent longer [see Figure 11]. COMPLICATIONS Perforation can occur during endoscopic sphincterotomy as a result of extension or tearing of the papilla beyond the junction of the CBD with the duodenal wall. Retroperitoneal or free intraperitoneal air may be seen. In many cases, intravenous antibiotics, hydration, and avoidance of oral intake are sufficient to manage such complications. If the patient’s condition deteri- orates, surgical exploration is indicated. Figure 8 Diagnostic endoscopic retrograde cholangiopancreatog- Bleeding may also occur with sphincterotomy. It is usually raphy. The so-called long scope position, along the greater curve of controllable with injection of epinephrine solution (1:10,000), the stomach, may be useful in some pancreatic interventions; electrocoagulation, or balloon tamponade. Arteriographic em- shown is the pancreatic duct orifice. bolization of the gastroduodenal artery may be helpful in some cases. As with diagnostic ERCP, pancreatitis may occur; it usu- ally responds to conservative measures. a b b Diagnostic Colonoscopy Colonoscopy has become one of the most frequently per- formed endoscopic examinations. It has revolutionized the diag- nosis and treatment of colonic disease and offers the promise of reducing the occurrence of colon cancer. Indications for colonoscopy include iron deficiency anemia, frank or occult rec- tal bleeding, a history of colonic cancer in the patient or in first- degree family members, a history or suspicion of colonic polyps, inflammatory bowel disease, and a persistent change in bowel habits. Preparation involves purging the bowel mechanically by placing the patient on a clear liquid diet for several days, then giv- ing cathartics and enemas; alternatively, one may use osmotic lavage, in which 1 gal of lavage fluid is administered orally over a period of 4 hours. It is often helpful to administer 10 mg of meto- clopramide to enhance gastric motility as preparation begins. TECHNIQUE c c d d Sedation is accomplished as for upper GI endoscopy, and the patient fasts for 6 to 8 hours before the procedure. With the patient in the left lateral decubitus position, a rectal examina- tion is performed. This step helps relax the anal sphincter in preparation for insertion of the scope and ensures that low-lying rectal lesions are not overlooked. The colonoscope is introduced into the rectal vault, and insufflation of air is commenced. The instrument is advanced only when the lumen is clearly apparent. At times, only a por- tion of the lumen may be visible, but this is usually enough to guide advancement of the scope. Frequently, when the lumen itself is not visible, light reflected onto the colonic folds can guide one to the lumen, with the concavity of the fold indicating the direction of the lumen. In contrast with upper GI endos- Figure 9 Therapeutic endoscopic retrograde cholangiopancreatog- copy, in which torsion on the shaft of the endoscope is rarely raphy. After endoscopic sphincterotomy, CBD stones may be necessary, such torsion is the rule in colonoscopy. The shaft of retrieved with balloons (a) or baskets (b, c, d). the instrument is rotated with the right hand to facilitate
  8. 8. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 8 a b Figure 10 Therapeutic endoscopic retrograde cholangiopancreatography. CBD strictures (a), whether benign or malignant, may be dilated effectively with hydrostatic balloons under fluoroscopic guidance (b). straightening and intubation of the colon. By applying torsion to lenge, in which case placement of the patient on the back or the the shaft frequently and pulling back the scope as necessary, one abdomen to change the orientation may be helpful. Once again, can pleat the colon on the instrument as it is advanced. Pulling pulling back and straightening the scope is a highly useful back is one of the most useful techniques for advancing the colon- maneuver. Once the scope is in the hepatic flexure looking down oscope through the colon. the right colon, pulling back, counterclockwise torsion, and the The colon exhibits a number of characteristic anatomic features application of suction may all assist in advancing the instrument that are readily observed during colonoscopy. The sigmoid colon, into the cecum. Changing the patient’s position or applying pres- because of its frequent turns, yields elliptical views of the lumen. sure to various points in the abdomen may also be helpful. Once The descending colon appears as a long, round tunnel with little the cecum is reached, the instrument is slowly withdrawn while haustration.The transverse colon has well-defined triangular folds, the colonic parietes are carefully examined. Biopsy and cytolog- and the hepatic flexure may exhibit a blue hue resulting from the ic brushing may be done as appropriate, and colonic contents proximity of the liver.The cecum is recognized on the basis of the may be aspirated into a suction trap for examination. appearance of the ileocecal valve on the lateral wall, the conver- COMPLICATIONS gence of the colonic taenia to form the cecal strap (the so-called Mercedes sign), and the presence of the appendiceal orifice. Perforation is the most common complication of diagnostic Insertion of the colonoscope as far as the hepatic flexure is colonoscopy. It may result from direct tip pressure, bowing of rarely difficult. Occasionally, the sigmoid colon presents a chal- the shaft of the scope while a large loop is being formed, blowout of a diverticulum secondary to air insufflation, or tear- ing of an adhesion of the colon to an adjacent structure. The risk of perforation can be minimized by observing the lumen directly as the scope is advanced, avoiding excessive insuffla- tion, and minimizing loop formation. Close attention to patient discomfort is important. If the patient feels poorly after the pro- cedure, an upright chest x-ray, an upright abdominal x-ray, or a lateral decubitus abdominal x-ray should be obtained to deter- mine whether there is any free air, which would indicate a per- foration. Such situations have been successfully managed by nonoperative means in some cases, but in most cases, prompt operative intervention with primary repair of the perforation is the best approach. Therapeutic Colonoscopy By far the most common use of therapeutic colonoscopy is for the excision of polyps. Other applications include control of bleeding, dilation of strictures, and placement of enteral stents. TECHNIQUE The development of colonoscopic polypectomy—electrosur- gical excision of the polyp with a wire snare—has rendered oper- Figure 11 Therapeutic endoscopic retrograde cholangiopancre- ative colotomy unnecessary in the management of colonic atography. Self-expanding metal stents may provide effective long- polyps. Pedunculated polyps are approached by placing the term palliation of malignant biliary obstruction. snare over the polyp’s head and tightening the loop around the
  9. 9. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 9 a a a b b b b c c d c c Figure 12 Therapeutic colonoscopy. Shown is removal of a pedunculated colonic polyp by means of snare excision at Figure 13 Therapeutic colonoscopy. Illustrated is piecemeal the stalk. excision of a sessile colonic polyp. stalk near the junction of the head and the stalk [see Figure 12]. Because the stalk is an extension of normal mucosa, it is unnec- essary—and often unwise—to excise the stalk close to the colonic wall; excision near the head of the polyp is usually sufficient. Short bursts of coagulating current are applied to transect the stalk. During excision, the polyps must be moved around to pre- vent conduction burns to the opposing colonic wall. Once tran- section is complete, if the polyp is small, it may be suctioned into a trap; if it is large, it may be suctioned onto the tip of the scope and retrieved or captured in a snare or basket. Sessile polyps are more challenging and risky to excise. Accordingly, it is often preferable to excise such polyps in a piecemeal fashion [see Figure 13]. The snare is applied several times to successive portions of the polyp until it is excised down to the colonic wall.The excised fragments are then retrieved. Difficult or large sessile polyps may be elevated before excision by injecting epinephrine solution or saline submucosally into the polyp or the surrounding tissue.This maneuver makes transmural injury less likely (see below). Although the use of colonoscopy to define the site of colonic Figure 14 Therapeutic colonoscopy. Shown is an angiodysplasia bleeding is commonplace, its use to treat such bleeding is not. of the right colon, a frequent cause of lower GI hemorrhage.
  10. 10. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 10 Chromoendoscopy The development of extirpative endoscopy has allowed physi- cians to treat several conditions that previously required open or laparoscopic surgical procedures. However, it is not always possible to see the difference between diseased and healthy tissue on endoscopy, and this limitation has precluded one-stage procedures. Identification of tissue types required biopsy, and lesion margins were impossible to determine at the time of the procedure. Chromoendoscopy can help to identify diseased tissue and define lesion borders.This process is essentially an in vivo staining technique in which a variety of specialized stains are applied to tis- sues to improve their characterization. It differs from carbon-dye injection (tattooing), a technique that is used for later surgical identification, in that the stains used for chromoendoscopy are specific to the anatomic area being examined. Several chromoen- doscopic dyes are commercially available in the United States [see Table 1]. Selection of a particular agent is based on the type of tis- sue being studied, the disease state, and physician familiarity. Figure 15 Therapeutic colonoscopy. Shown is a right colonic One of the first agents used for chromoendoscopy was methyl- angiodysplasia after treatment with bipolar electrocoagulation. ene blue. It was initially used in Japan in the 1970s to detect intestinal metaplasia in the stomach. Subsequent studies in the Diverticular bleeding often stops when colonoscopy is done, and United States, Japan, and Europe independently demonstrated only in rare instances is the actual bleeding diverticulum seen. In that methylene blue will selectively stain metaplasia in Barrett’s such cases, injection of epinephrine solution around the mouth of esophagus (see above). On routine screening endoscopy in the offending diverticulum is often effective. Angiodysplasias are patients with Barrett’s esophagus, methylene blue chromoen- frequently found in the right colon, though they are rarely identi- doscopy offers improved detection of dysplasia and early malig- fied while they are bleeding [see Figure 14]. They may be treated nancy compared with four-quadrant random biopsy studies. with a variety of modalities, including bipolar electrocoagulation, Other reported applications include esophageal carcinoma, gas- injection of a sclerosant solution, and laser therapy [see Figure 15]. tric metaplasia, oropharyngeal cancer, mucosal lesions, and het- Currently, the argon plasma coagulator is often employed for erotopic gastric mucosa. obliteration of these lesions.This device has the advantage of being able to obliterate angiodysplasias with minimal wall penetration, Endoscopic Mucosal Resection thereby increasing the safety of this intervention in the thin-walled right colon. Endoscopic polypectomy marked the beginning of extirpative Strictures may occur in the colon, as in the rest of the GI procedures. Subsequently, endoscopic resection techniques have tract. Colonic strictures usually develop at an anastomosis, continued to advance, as a result of improvements in imaging and though they may also be the result of ischemia. Hydrostatic bal- instrumentation, along with the development of chromoendoscopy loon dilation is very effective in treating such strictures.The bal- and specific techniques designed as adjuncts to tissue removal. One loon is introduced through the lumen of the endoscope, and such technique is endoscopic mucosal resection (EMR). dilation is carried out under direct vision, often in conjunction EMR has its basis in the anatomy of the GI tract. with fluoroscopic observation to confirm that dilation is com- Histologically, the GI tract has three layers: a superficial muco- plete. In patients with fully or almost fully obstructing tumors sal, a middle submucosal, and an outer muscular layer. EMR is of the colon, self-expanding metal stents may be placed to pro- designed to help the endoscopist remove superficial mucosal tis- vide decompression and at least temporary relief of obstruction. sue while leaving the deeper submucosal and muscular layers This step may avert emergency surgery or, if the tumor is inop- intact. These layers can be relatively easily separated from each erable, provide palliation. other by injecting a liquid that spreads within the plane of injec- tion. This step elevates the layers superficial to the injection, thus COMPLICATIONS facilitating the resection of those layers. Advantages over other Perforation may occur as a result of transmural thermal injury resection techniques include the preservation of histologic archi- during polypectomy. Some perforations are immediately apparent, tecture (in contrast to electrocautery or laser ablation), which but others may not be noticed for several days. When perforation allows improved pathologic assessment; the ease with which is documented, surgical exploration is indicated. Occasionally, a EMR can be combined with endoscopic ultrasonography; and its patient may present with fever and abdominal tenderness several safety and minimal invasiveness. days after polypectomy but show no free air on abdominal films. EMR was first described in 1955, when submucosal saline Such a patient may have a thermal injury to the bowel wall or so- injections through a rigid sigmoidoscope were used in the resec- called postpolypectomy syndrome and can usually be treated with tion of rectal and sigmoid polyps. In 1973, a submucosal saline intravenous fluids, antibiotics, and observation. Bleeding from the injection was employed to assist with the removal of sessile polyps stalk of a pedunculated polyp may occur after excision; it may pre- throughout the colon. Additional development was accomplished sent immediately or may be delayed until the coagulum on the in Japan in 1983, when mucosal resection was used in the treat- stalk separates 3 to 5 days after polypectomy. Such bleeding is a ment of early gastric carcinoma in a technique termed strip-off rare occurrence.When it does occur, it can be treated by injecting biopsy.The technique has been refined and is now routinely used epinephrine solution (1:10,000) into the stalk. for lesions in the esophagus, stomach, duodenum, colon, and rec-
  11. 11. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 11 tum. It is widely incorporated into aggressive screening programs Table 1 Special Stains Used in Endoscopy designed to detect early GI cancers. EMR can be used to treat dysplastic and other premalignant Stain Site of Use Comment lesions, as well as superficial cancers of the GI tract. One must be careful to comply with all standard principles of cancer resection, Normal mucosa stains including knowledge of the depth of the lesion, its radial extent, Lugol solution green-brown (as a Esophagus result of intracellular and staging. Consequently, several criteria must be fulfilled (2% iodine) glycogen); dysplastic before EMR can be viewed as a curative intervention. Classifica- cells do not stain tion of lesions on the basis of their endoscopic appearance can be Enhances contour of combined with information obtained through the use of chro- Indigo carmine mucosa, giving tissue a Stomach, colon moendoscopy and EUS to determine the potential for EMR. (0.4% solution) three-dimensional Lesion location within the GI tract is important with respect to appearance long-term outcomes. For example, EMR can be used to treat cir- Absorbed by the nucleic cumferential colonic lesions but is inappropriate for esophageal Toluidine blue Oropharynx, acid component of esophagus malignant epithelial lesions that extend beyond one third of the circumference, cells because of the risk of a late stricture. Although specific methods differ among practitioners, several Acid-secreting Turns a blue-black color Congo red areas of gastric generalizations about the technical aspects can be made. First, a mucosa when pH < 3 liquid must be injected deep to the mucosal layer, allowing sepa- ration of the wall components. Although the ideal solution for Absorbed only by Intestinal meta- dysplastic tissue; injection has not been determined, the liquid chosen must be Methylene blue plasia, Barrett’s however, absorption biodegradable, biocompatible, noninflammatory, and have vis- (0.5% solution) esophagus decreases as severe coelastic properties allowing the development of an adequate dysplasia develops bleb. Saline, hypertonic saline, epinephrine, hyaluronic acid, and glycerol solutions are all in current use.The elevated tissue is then held in place with a grasper or suction mechanism, and snares, needle knives, or lasers are used to cut the tissue at its base. rate staging of tumors—information that is sometimes unobtain- Optimal results are obtained on nonulcerated lesions that are less able from other imaging techniques. than 2 cm after elevation; other lesions have a high probability of This technology has now been firmly established as an accurate submucosal lymphatic and vascular invasion. way to identify carcinoma. Subsequent developments are allowing Although complications can occur, with proper patient selec- EUS to expand from the field of diagnosis into the realm of inter- tion and procedural refinement they are relatively rare. vention. Examples of EUS-guided procedures include fine-needle Perforation has been noted, particularly when submucosal bleb aspiration, lymph node sampling, and drainage of pancreatic formation is suboptimal. Inadequate blebs may result from insuf- pseudocysts. ficient liquid being injected, improper needle depth, or severe EUS devices come in both linear and radial transducers. Radial scarring of the local tissues. Bleeding has been reported to occur transducers have the advantage of providing circumferential visu- in 1.6% of EMR cases. This complication is relatively easily han- alization that parallels the standard modes of perceiving the GI dled with a combination of electrocautery and epinephrine injec- tract. Linear images allow EUS-directed biopsies and have the tion. Infection in the absence of perforation is uncommon. potential to provide color and pulsed Doppler imaging. Probes Overall, EMR provides a minimally invasive means to treat can be mounted on the top of an oblique viewing fiberoptic scope, early cancers in favorable locations. Patients must understand or come in an over-the-wire format for use in the pancreaticobil- that additional resection may be required if histopathologic iary tree. A series of frequencies is available, with the higher fre- assessment does not show curative margins. Future development quencies providing greater resolution but less tissue depth pene- of endoscopic instruments and injection liquids will likely broad- tration. Lower-frequency probes allow deeper tissue assessment en the applicability of the procedure. and a broader view, but at the price of reduced resolution. Never- theless, any form of EUS will provide better resolution than trans- cutaneous ultrasonography, allowing markedly improved two- Endoscopic Ultrasonography point discrimination and hence more accurate tissue diagnosis. The 1980s saw the introduction of EUS. Extracavitary ultra- The benefits of accurate staging of GI tumors paved the way sonographic methods have been hampered by the presence of air for EUS development. Tissue sampling techniques are further within the GI tract, which precludes high-resolution imaging. benefited by this technology.The sensitivity of EUS makes it one Consequently, they had been relegated to gross estimates of dis- of the best modalities for the evaluation and detection of pancre- ease and detection of displacement of other tissues or fluid accu- atic tumors. Its sensitivity, which is in excess of 95%, contrasts mulation proximal to stenoses, such as ductal dilation in patients favorably with those of other modalities, including ultrasonogra- with common bile duct stones. phy (75%), computed tomography (80%), and angiography Three advances have proved invaluable in allowing EUS to (89%). The accuracy of T staging by EUS in esophageal cancer carve out a niche in the field of GI diagnosis. First is the improve- (80% to 90%) is greater than that of staging determined by CT ment in endoscopes that allows transducer and receiver channels scanning (50% to 60%).This finding has led to the development to traverse a tortuous path. Second is the development of multi- of several staging schemes that are based solely on EUS findings. ple frequency options in conjunction with circumferential visual- EUS has established a role in the identification of early pancre- ization. Higher frequencies provide higher resolutions, allowing atitis; the detection of common bile duct stones and mediastinal useful differentiation of the various layers of the intestinal tract. masses; and the assessment of anastomotic strictures, thickened Third is the evolution of treatment protocols keyed to the accu- gastric folds, and the integrity of the anal sphincter. It has also
  12. 12. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 18 GASTROINTESTINAL ENDOSCOPY — 12 proved a useful adjunct in the determination of whether a tumor plications of other endoscopic techniques. Despite the develop- is amenable to EMR techniques or is better served by adjuvant ment and commercial availability of numerous devices, howev- therapies or surgical interventions. er, design problems have relegated most applications to investi- The sensitivity of EUS is rooted in its ability to delineate the gational status. For such devices to enter clinical practice, they various layers of the alimentary canal. Experienced endoscopists must encompass fundamental surgical techniques: the ability to can easily evaluate the submucosa and differentiate intramural cut, suture, tie knots, and staple. These are critical for maintain- from extrinsic masses. Characteristic patterns are readily learned ing hemostasis and constructing durable anastomoses. Although and rapidly recognized, obviating tissue diagnoses in straightfor- these techniques are plausible with modern devices, continued ward cases. Criteria have also been established to aid in the dif- innovation and experience in conjunction with a new paradigm ferentiation of benign and malignant lesions. With the continued of disease management will direct the future of endoscopic use of this technique, additional algorithms will be established in interventions. conjunction with more innovative interventional adjuncts. However, two limitations have caused many practitioners to remain skeptical: cost and training issues. Other imaging modal- Natural Orifice Transvisceral Endoscopic Surgery ities, such as CT and magnetic resonance imaging, have also A new area of endoscopic exploration is emerging—namely, made tremendous strides in the recent past. Although these vari- the performance of intraperitoneal surgical procedures by means ous modalities are often considered competitors—a view arising of a flexible endoscope passed through the wall of a gastrointesti- from the perceived need for a single imaging modality—the issue nal viscus. This approach, referred to as natural orifice transvis- of which is superior to the others pales in comparison to the ben- ceral endoscopic surgery (NOTES), is still investigational, but it efits that can be gained from combining imaging techniques in has generated a great deal of excitement in the surgical and gas- appropriate circumstances. troenterologic communities.Transgastric gastrojejunostomy, liver biopsy, tubal ligation, and splenectomy in a porcine model have been reported. In addition, there have been anecdotal reports Endoscopic Suturing and presentations of natural orifice transvisceral appendectomy The ability to suture through an endoscope would open up an in human beings in India; however, to date, there have been no entire arena of new possibilities, including antireflux proce- published cases. Extensive laboratory investigation and clinical dures, morbid obesity surgery, and advances in the control of trials will have to be carried out before the true utility and safety acute hemorrhage, as well as improved ability to manage com- of NOTES can be established. Recommended Reading Abi-Hanna D,Williams SJ: Advances in gastrointestinal Endoscopic gastrojejunostomy with survival in a Philadelphia, WB Saunders Co, 1991, p 22 endoscopy. Med J Aust 170:131, 1999 porcine model. Gastrointest Endosc 62:287, 2005 Schuman BM, Sugawa C: Diagnostic endoscopy of Acosta MM, Boyce HW Jr: Chromoendoscopy—where Matsuda K: Introduction to endoscopic mucosal resec- upper gastrointestinal bleeding. Gastrointestinal Bleed- is it useful? J Clin Gastroenterol 27:13, 1998 tion. Gastrointest Endosc Clin N Am 11:439, 2001 ing. Sugawa C, Schuman BM, Lucas CE, Eds. Igaku Brugge WR: Endoscopic ultrasonography: the current Ponchon T: Endoscopic mucosal resection. J Clin Shoin, New York, 1992, p 222 status. Gastroenterology 115:1577, 1998 Gastroenterol 32:6, 2001 Soetikno R, Inoue H, Chang KJ: Endoscopic muscosal Canto M: Methylene blue chromoendoscopy for Ponsky JL: Atlas of Surgical Endoscopy. Mosby–Year resection: current concepts. Gastrointest Endosc Clin Barrett’s esophagus: coming soon to your GI unit? Book, St. Louis, 1992 N Am 10:595, 2000 Gastrointest Endosc 54:403, 2001 Swain CP: Endoscopic sewing and stapling machines. Ponsky JL, King JF: Endoscopic marking of colonic Cotton PB, Williams CB: Practical Gastrointestinal lesions. Gastrointest Endosc 22:42, 1975 Endoscopy 29:205, 1997 Endoscopy, 3rd ed. Blackwell Scientific, Oxford, 1990 Rosch T, Lightdale CJ, Botel JF, et al: Localization of Venu RP, Geenen JE: Overview of endoscopic sphinc- Hawes RH: Endoscopic ultrasound. Gastrointest pancreatic endocrine tumors by endoscopic ultra- terotomy for common bile duct stone. Endoscopic Endosc Clin N Am 10:161, 2000 sound. N Engl J Med 326:1721, 1992 Approach to Biliary Stones. Kozarek RA, Ed. Hawes RH: Perspectives in endoscopic mucosal resec- Rosen M, Ponsky JL: Endoscopic therapy for gastro- Gastrointest Endosc Clin N Am 1:3, 1991 tion. Gastrointest Endosc Clin N Am 11:549, 2001 esophageal reflux disease. Semin Laparosc Surg 8:207, Inoue H: Endoscopic mucosal resection for the entire 2001 gastrointestinal mucosal lesions. Gastrointest Endosc Schrock T: Colon and rectum: diagnostic techniques. Acknowledgment Clin N Am 11:459, 2001 Shackelford’s Surgery of the Alimentary Tract. Vol 4: Kantsevoy SV, Jagannath SB, Niiyama H, et al: Colon and Anorectum, 3rd ed. Condon R, Ed. Figures 2, 4a, 4b, 4c, 5, 6, 9 12, 13 Tom Moore.