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| CECIL |
| TEXT BOOK of MEDICINE |
Section XII Gastrointestinal Diseases
| 136 GASTROINTESTINAL ENDOSCOPY Pankaj Jay Pasricha • |
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IMPORTANCE AND USE OF ENDOSCOPY
Technologic advances in radiologic and endoscopic imaging have transformed medicine in the past few decades. With its remarkable accessibility, the gastrointestinal tract, perhaps more than any other organ system, has particularly benefited from the endoscopic approach. The major advantages of endoscopy over contrast radiography in evaluation of diseases of the alimentary tract include direct visualization, resulting in a more accurate and sensitive evaluation of mucosal lesions; the ability to obtain biopsy specimens from superficial lesions; and the ability to perform therapeutic interventions. These advantages make endoscopy the procedure of choice in most cases in which mucosal lesions or growths are suspected. Conversely, contrast radiography may be indicated when extrinsic or intrinsic distortions of anatomy are suspected, such as volvulus, intussusception, subtle strictures, or complicated postsurgical changes. For most upper gastrointestinal lesions, however, the sensitivity (about 90%) and specificity (nearly 100%) of endoscopy are far higher than those of barium radiography (about 50 and 90%, respectively).
Diagnostic endoscopy (Table 136-1) is usually a remarkably safe and well-tolerated procedure. However, complications do occur and need to be carefully explained to the patient as part of the informed consent process; patients must also be prepared appropriately to reduce complication rates (Table 136-2). In general, diagnostic and uncomplicated therapeutic endoscopy can be done in most patients with a combination of benzodiazepines and narcotics to produce moderate (conscious) sedation (Chapter 458). Propofol, which provides faster and deeper sedation with rapid recovery but is generally administered by an anesthesiologist, is increasingly popular, especially for prolonged procedures such as endoscopic retrograde cholangiopancreatography and endoscopic ultrasonography.
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LUMINAL ENDOSCOPY
Specific Indications
Most indications for gastrointestinal endoscopy are based on the presenting symptoms of the patient (e.g., dysphagia, bleeding, diarrhea). In other instances, endoscopy is required to evaluate specific lesions found by other diagnostic imaging, such as a gastric ulcer or colon polyp discovered by barium radiography. Finally, screening endoscopy is often performed in asymptomatic individuals on the basis of their risk for commonly occurring and preventable conditions, such as colon cancer (see later).
Implicit in the decision to perform endoscopy is the assumption that it will have a bearing on future management strategy. In dealing with the evaluation of gastrointestinal symptoms, several questions need to be addressed by the referring physician and the endoscopist. Which patients need endoscopy? When should the endoscopy be done? What is the endoscopist looking for? What endoscopic therapy, if any, should be planned?
Gastroesophageal Reflux and Heartburn (Chapters 139 and 140)
Gastroesophageal reflux disease (GERD) is an extremely common condition in the general population. The fact that its cardinal symptom, heartburn, is relatively specific for this condition justifies an empirical approach to treatment by a combination of lifestyle modifications and over-the-counter or even prescription drugs. Endoscopy is not therefore necessary to make the diagnosis of GERD. Indeed, normal findings on endoscopy do not rule out the diagnosis of GERD because the overall sensitivity of endoscopy in GERD is only about 70%. If necessary, further evaluation with ambulatory pH monitoring may be indicated to establish the diagnosis. However, there are several circumstances in which endoscopy should be considered for patients with reflux, including patients with associated warning symptoms (“red flags”) such as dysphagia, odynophagia, regurgitation, weight loss, gastrointestinal bleeding, or frequent vomiting (Fig. 136-1). These symptoms imply either the development of a GERD-related complication (erosive esophagitis, stricture, or adenocarcinoma) or another disorder masquerading as GERD (esophageal cancer or a gastric-duodenal lesion such as cancer or peptic ulcer). Another group of patients who are candidates for endoscopy are those with severe or persistent or frequently recurrent symptoms that suggest significant esophagitis and hence a risk for complications, such as stricture or Barrett's esophagus (intestinal metaplasia of the esophageal lining).
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| FIGURE 136-1 • Severe reflux esophagitis (left) with mucosal erythema and linear ulcers with yellow exudates (∗). It is thought that such changes eventually lead to Barrett's esophagus (right), in which the normal white squamous epithelium (SE) is replaced by red columnar epithelium (BE). These pictures are from different patients. |
If a significant length of Barrett's esophagus is discovered (see Fig. 136-1), most experts recommend some form of periodic surveillance endoscopy because these patients are at increased risk for the development of adenocarcinoma. Barrett's esophagus, once established, does not generally regress despite adequate control of reflux by either pharmacologic or surgical means. To eliminate the small but definite risk of cancer associated with this lesion, various methods to ablate this epithelium have been attempted, with the rationale that the esophageal lining is reconstituted by squamous epithelium under conditions of acid suppression. For patients who have high-grade dysplasia associated with Barrett's esophagus and who are at high risk for surgery or wish to avoid it, endoscopic ablation or resection may provide a potentially curative alternative to esophagectomy. In patients without dysplasia, the benefit (i.e., reduction in the risk of cancer) remains to be established, and ablation should be considered experimental in this setting. Ablation can be achieved by electrical cautery, argon plasma coagulation, high-energy laser, radio frequency, and photodynamic therapy. However, these approaches do not allow a full pathologic examination and are associated with a small risk of regrowth of Barrett's tissue in ectopic locations, such as the submucosa, where it may subsequently escape detection. An evolving technique is en bloc resection of the mucosa, a procedure that allows complete removal and pathologic analysis.
Endoscopic techniques of therapy for GERD itself include radio frequency to produce a scar and to tighten the lower esophageal sphincter, suturing or plication devices to restructure the area below the sphincter, and injection of different polymers to “bulk up” the gastroesophageal junction. Although initial results were promising, long-term outcomes have been less positive.
Heartburn in immunocompromised patients often indicates an esophageal infection. The most common causes in patients with human immunodeficiency virus (HIV) infection are Candida, cytomegalovirus, herpesvirus, and idiopathic esophageal ulcers. Because most patients with the acquired immunodeficiency syndrome and esophagitis have candidiasis, an empirical 1- to 2-week course of antifungal therapy may be justified. Patients who do not respond to this approach, however, should almost always have endoscopy and biopsy so that more specific therapy can be instituted.
The PillCam is a capsule capable of taking bidirectional digital photographs and transmitting 14 wireless images per second to an external data recorder. Patients can swallow this capsule easily and, within seconds, have a nearly complete noninvasive examination of the esophageal lining. This technique has the potential to replace traditional endoscopy for indications such as GERD and cirrhosis, in which screening for complications (Barrett's esophagus or varices, respectively) is of value.
Dysphagia (Chapter 140)
Dysphagia can often be categorized as oropharyngeal on the basis of the clinical features of nasal regurgitation, laryngeal aspiration, or difficulty in moving the bolus out of the mouth. These symptoms are usually associated with a lesion in the central or peripheral nervous system. Although endoscopy is often performed in these patients, videofluoroesophagography (modified barium swallow or cine-esophagogram) is the procedure of choice as it allows a frame-by-frame evaluation of the rapid sequence of events involved in transfer of the bolus from the mouth to the esophagus. Common causes of esophageal dysphagia include malignant as well as benign processes (peptic strictures secondary to reflux, Schatzki's rings) and motility disturbances of the esophageal body or the lower esophageal sphincter. Endoscopic examination is considered mandatory in all patients with esophageal dysphagia. However, contrast esophagography may also be helpful; it can provide guidance for endoscopy that is anticipated to be difficult (e.g., a patient with a complex stricture), suggest a disturbance in motility, and occasionally detect subtle stenoses that are not appreciated on endoscopy (the scope diameter is typically 10 mm or less, whereas some symptomatic strictures can be considerably wider).
Endoscopic treatment options are available for many causes of esophageal dysphagia. Tumors may be dilated mechanically, ablated by thermal means (cautery or laser), or stented with prosthetic devices. Metallic expandable stents have become the palliative procedure of choice for most patients with symptomatic esophageal cancer. Benign lesions of the esophagus, such as strictures or rings, can also be dilated endoscopically, usually with excellent results. Finally, some motility disturbances, such as achalasia, are best approached endoscopically with the use of large balloon dilators for the lower esophageal sphincter or with the local injection of botulinum toxin.
Dyspepsia (Chapter 139)
Dyspepsia, which is chronic or recurring pain or discomfort centered in the upper abdomen, is a common condition that can be caused by a variety of disorders, including peptic ulcer, reflux esophagitis, gallstones, gastric dysmotility, and, rarely, gastric or esophageal cancer. However, up to 60% of patients with chronic (>3 months) dyspepsia belong to the so-called functional category in which there is no definite structural or biochemical explanation for the symptoms. Although Helicobacter pylori gastritis is found frequently in these patients, there is no definite evidence to prove a cause-and-effect relationship between these two findings. The optimal diagnostic approach to dyspepsia is somewhat controversial and is still evolving (see Fig. 139-2). If a diagnostic test is to be performed, endoscopy, sometimes with biopsies to detect H. pylori, is clearly the procedure of choice, with an accuracy of about 90% (compared with about 65% for double-contrast radiography). There has been a move toward empirical approaches to dyspepsia because only a minority of patients with dyspepsia have peptic ulcers, and gastric cancer is extremely rare in Western countries. However, dyspepsia is a recurrent condition, and patients who do not respond to empirical therapy eventually almost always undergo endoscopy. Many gastroenterologists therefore opt for early endoscopy, if only for the reassurance that a normal examination provides.
Upper Gastrointestinal Bleeding (Chapter 137)
Acid peptic disease (including ulcers, erosions, and gastritis), variceal bleeding, and Mallory-Weiss tears account for most cases of upper gastrointestinal bleeding. Other less common but important lesions are angiomas, gastric vascular ectasia (“watermelon” stomach), and the rarer Dieulafoy's lesion (a superficial artery that erodes through the gut mucosa). Finally, upper gastrointestinal cancers are occasionally associated with significant bleeding. Endoscopy is mandatory in all patients with upper gastrointestinal bleeding, with the rare exception being the terminally ill patient in whom the outcome is unlikely to be affected. Endoscopy is able to detect and to localize the site of the bleeding in 95% of cases and is clearly superior to contrast radiography (with an accuracy of only 75 to 80%). The endoscopic appearance of bleeding lesions can also help predict the risk of rebleeding, thus facilitating the triage and treatment process. Bleeding can be effectively controlled during the initial endoscopic examination itself in the majority of cases. The risk of recurrent bleeding is diminished, resulting in a shorter duration of hospital stay as well as a reduction in the need for surgery.
In general, endoscopy should be performed only after adequate stabilization of hemodynamic and respiratory parameters. The role of gastric lavage before endoscopy is controversial; some endoscopists prefer that it be done, occasionally even with use of a large-bore tube, whereas others avoid such preparation because of the fear of producing artifact. The timing of subsequent endoscopy depends on two factors: the severity of the hemorrhage and the risk status of the patient. Patients with active, persistent, or severe bleeding (>3 units of blood) require urgent endoscopy. Endoscopy in these patients is best performed in the intensive care unit because they are at particular risk for aspiration and may require emergent intubation for respiratory protection and ventilation. Patients with slower or inactive bleeding may be evaluated by endoscopy in a “semielective” manner (usually within 12 to 20 hours), but a case can be made to perform endoscopy early even in these stable patients (perhaps in the emergency department itself) to allow more confident triage and efficient resource management.
Most bleeding from upper gastrointestinal lesions can be effectively controlled endoscopically. The endoscopist considers factors such as age (older patients have a higher risk of rebleeding) and the severity of the initial hemorrhage (which has a direct correlation with the risk of rebleeding) in addition to the appearance of the lesion in determining the need for endoscopic therapy. Nonvariceal bleeding vessels can be treated by a variety of means, including injections of various substances (epinephrine, saline, sclerosants), thermal coagulation (laser or electrocautery), and mechanical means (clipping). In the United States, the most popular approach to a bleeding peptic ulcer lesion is a combination of injection with dilute epinephrine and electrocoagulation. Initial hemostasis can be achieved in 90% or more of cases; rebleeding, which may occur in up to 20% of cases, responds about half of the time to a second endoscopic procedure. Patients who continue to bleed (typically patients with large ulcers in the posterior wall of the duodenal bulb) are usually managed angiographically (with embolization of the bleeding vessel) or surgically.
Variceal bleeding is also effectively managed endoscopically, with a success rate similar to that with bleeding ulcers (Fig. 136-2). Hemostasis is achieved by band ligation (Fig. 136-3), sclerotherapy, or a combination of both. Increasingly, patients who do not respond to endoscopic treatment are considered candidates for a transjugular intrahepatic portosystemic shunt; traditional shunt surgery for bleeding varices is rarely performed. Even if initial endoscopic hemostasis is successful, long-term prevention of rebleeding requires a program of ongoing endoscopic sessions until variceal obliteration is complete. Ligation is the preferred approach in this setting because it is associated with fewer side effects. An ongoing area of investigation is whether endoscopic therapy, in the form of ligation, should be performed in patients whose large esophageal varices have never bled (primary prophylaxis). Currently, β-blockers are considered first-line treatment in this scenario, but there is increasing evidence to suggest that endoscopic band ligation may be useful in selected patients.
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| FIGURE 136-2 • Endoscopic view of esophageal varices (left) in the wall of the esophagus (V). Right, image of a varix that has been endoscopically ligated with a band. |
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| FIGURE 136-3 • Endoscopic variceal ligation technique. A, The endoscope, with attached ligating device, is brought into contact with a varix just above the gastroesophageal junction. B, Suction is applied, drawing the varix-containing mucosa into the dead space created at the end of the endoscope by the ligating device. C, The tripwire is pulled, releasing the band around the aspirated tissue. D, Completed ligation. |
Acute Lower Gastrointestinal Bleeding (Chapter 137)
The most common cause of acute lower gastrointestinal bleeding is angiodysplasia, followed by diverticulosis, neoplasms, and colitis. In about 10% of patients presenting with hematochezia, a small bowel lesion may be responsible. In contrast to upper gastrointestinal bleeding, there is no single best test for acute lower gastrointestinal bleeding (Fig. 136-4). In young patients (<40 years) with minor bleeding, features that are highly suggestive of anorectal origin (e.g., blood on the surface of the stool or on the wipe) may warrant only flexible sigmoidoscopy. Conversely, patients presenting with hemodynamic compromise may need upper endoscopy first to exclude a lesion in the upper gastrointestinal tract (typically postpyloric) bleeding so briskly that it arises as hematochezia. Colonoscopy has traditionally been recommended after bleeding has slowed or stopped and the patient has been given an adequate bowel purge. However, a disadvantage of delaying endoscopy is that when a pathologic lesion such as an arteriovenous malformation (see Fig. 136-4) or diverticulum is found, it may be impossible to implicate it confidently as the site of bleeding (complementary information by radiography or scintigraphy becomes particularly important in this situation). Some experts therefore recommend urgent diagnostic endoscopy with little or no preparation for acute lower gastrointestinal hemorrhages and have reported significant diagnostic as well as therapeutic success rates. However, such recommendations have not been universally accepted and remain logistically difficult to implement in most hospital settings.
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| FIGURE 136-4 • Mucosal telangiectasia (arteriovenous malformation) in the colon. The patient presented with hematochezia. The lesion was subsequently cauterized endoscopically. |
It is not uncommon for gastrointestinal bleeding to develop or to be discovered in hospitalized patients who have had a recent myocardial infarction. In many cases, the bleeding is of a microscopic nature, and endoscopic evaluation can be deferred until the patient has fully recovered from the cardiac event. In other cases, however, bleeding is more significant, and its risks outweigh the potential adverse effects of endoscopic intervention. In patients with recent myocardial infarctions, upper endoscopy and colonoscopy are associated with a higher risk of cardiovascular complications, but they are usually transient and minor.
Occult Gastrointestinal Bleeding or Iron Deficiency Anemia (Chapter 137)
Normal fecal blood loss is usually less than 2 to 3 mL/day. Most standard fecal occult blood tests detect only blood loss of 10 mL/day or more. Therefore, even if this test result is negative, patients with iron deficiency anemia and no other obvious source of blood loss should always undergo aggressive gastrointestinal evaluation, which uncovers a gastrointestinal lesion in the majority of cases. Although most lesions that cause overt gastrointestinal bleeding can also cause occult blood loss, occult bleeding should almost never be ascribed to diverticulosis or hemorrhoids. Endoscopy is always preferable to radiographic studies for evaluation of occult blood loss or iron deficiency anemia because of its ability to detect flat lesions, particularly vascular malformations, which may be found in 6% or more of patients. If the findings on both upper and lower endoscopy are normal, a small bowel radiographic series (preferably enteroclysis) to look for gross lesions often completes the evaluation. If the patient continues to have symptomatic bleeding, enteroscopy (the use of a long upper endoscope to intubate the small bowel) and capsule endoscopy may be helpful to detect small bowel lesions, such as tumors or angiomas.
An innovation has been the development of capsule endoscopy, which consists of a disposable capsule that can be swallowed and that takes color video images as it travels through the digestive tract. These images are received and recorded by a device that the patient wears as a belt while carrying out his or her routine activities. At the end of the procedure, the information is downloaded to a computer, processed, and scanned for detectable abnormalities. The capsule itself passes out harmlessly in the stool. The capsule is not useful, in its present form, as a method for imaging the upper gastrointestinal tract or the colon; further, it is contraindicated in patients with suspected narrowing or strictures of the small bowel. Nevertheless, capsule endoscopy has become the diagnostic procedure of choice in patients with obscure gastrointestinal bleeding (with normal findings on upper and lower endoscopies) and when mucosal lesions of the small bowel are suspected. Diagnosis is limited by the inability to obtain tissue for histologic analysis, and treatment typically requires open surgery. A double-balloon endoscopy approach potentially allows observation and treatment of the entire small bowel, so in the future, most if not all small bowel lesions may be treated effectively by endoscopy.
Colorectal Neoplasms (Chapter 203)
Colonoscopy is the most accurate test for detecting mass lesions of the large bowel that are suspected on clinical or radiologic grounds. However, the greatest impact of endoscopy on colorectal neoplasia may be in the area of screening and prevention. The adenoma to carcinoma sequence of progression in colorectal cancer provides a unique opportunity for prophylaxis. Thus, if screening programs can identify patients with polyps and if these polyps are removed, cancer can largely be prevented. Various techniques are available for safe and effective polypectomy, depending on the size, presence of a stalk, and location (Fig. 136-5). Colonoscopy is being increasingly accepted as the procedure of choice for screening patients at average risk, that is, anybody older than 50 years. When patients have been found to harbor adenomatous polyps, they should be entered into a surveillance program; the frequency of colonoscopic examinations is still not settled but varies in practice from 1 to 3 years.
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| FIGURE 136-5 • Endoscopic polypectomy. Left, a snare (S) has been passed through the endoscope and positioned around the polyp (P). Right, subsequently, cautery was applied and the polyp guillotined, leaving behind a clean mucosal defect. |
More aggressive screening strategies are required for patients considered at high risk for colorectal cancer, including patients with well-defined hereditary syndromes as well as those with a history of colorectal cancer in a first-degree relative. In addition, patients with ulcerative colitis with long-standing (more than 8 years) disease affecting the entire colon have an increased risk for development of colon cancer, about 0.5 to 3% after 20 years. Periodic colonoscopic surveillance (every 1 to 2 years with biopsies) is therefore recommended for patients with long-standing disease (8 years with pancolitis, 12 to 15 years with left-sided colitis); the discovery of dysplasia or cancer is an indication for colectomy.
“Virtual colonoscopy” (Chapter 135), which involves the digital construction of an endoluminal view of the colon on the basis of data from abdominal computed tomography, is not yet accurate enough for general screening. However, technical advances in this procedure may change this in the near future.
Chronic Diarrhea (Chapter 143)
Endoscopy may be a valuable aid in the evaluation of patients with persistent diarrhea. The timing of the endoscopy in these patients often depends on the clinical features of the illness. Patients with bloody diarrhea should have lower endoscopy as part of their initial evaluation to look for inflammatory bowel disease (Chapter 144). In most patients with chronic diarrhea, endoscopy is often done when initial routine testing does not yield a specific diagnosis. Both upper and lower endoscopies may be used, depending on the clinical presentation. Thus, the patient suspected of having a malabsorptive process may require upper endoscopy with jejunal or duodenal biopsies to look for celiac sprue or rarer lesions such as lymphoma or Whipple's disease (endoscopic biopsy has largely replaced blind intestinal biopsies for these conditions). Conversely, patients thought to have a secretory cause of diarrhea require a colonoscopy with biopsies to look for overt inflammatory bowel disease or more subtle variants such as microscopic or lymphocytic colitis, in which cases the diagnosis requires careful examination of the biopsy specimens.
The endoscopic approach to diarrhea in immunocompromised patients, such as those with HIV infection, is guided by the degree of immunosuppression and the need to find treatable infections. When results of routine stool tests are negative, patients with CD4 counts less than 100/mm3 should undergo endoscopic evaluation to detect pathogens such as cytomegalovirus, Mycobacterium avium complex, and microsporidiosis. Small-volume stools with tenesmus suggest a proctocolitis, for which sigmoidoscopy (rather than a full colonoscopy) with biopsies is usually adequate. In patients with upper gastrointestinal symptoms (large-volume diarrhea, bloating, and dyspepsia), upper endoscopy with biopsy may be attempted first.
Miscellaneous Indications
The upper endoscope has provided a relatively quick and noninvasive means for removal of accidentally or deliberately ingested foreign bodies. Timing is critical for removal, however, because objects are usually beyond endoscopic retrieval when they reach the small bowel. Any foreign object that is causing symptoms should be removed, as should potentially dangerous devices such as batteries and sharp objects. In general, objects larger than 2.5 cm in width or 13 cm in length are unlikely to leave the stomach and so should also be removed. On occasion, patients with food impacted in the esophagus require endoscopic removal (Fig. 136-6). This condition almost always indicates an underlying functional or structural problem (Chapter 140) and should prompt a thorough diagnostic evaluation after the acute problem has been addressed.
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| FIGURE 136-6 • Impacted food bolus in a young male patient who was found to have a ringed esophagus on endoscopy. This presentation is characteristic and may be either congenital or acquired secondary to reflux-induced or eosinophilic esophagitis. |
Because of the relatively poor correlation between oropharyngeal lesions and more distal visceral injury, upper endoscopy is usually recommended urgently in patients with corrosive ingestion (Chapter 111). Endoscopy allows patients to be divided into high- or low-risk groups for complications, with institution of appropriate monitoring and therapy.
Among the myriad causes of nausea and vomiting, a few, such as mucosal lesions and unsuspected reflux disease, are amenable to endoscopic diagnosis. Patients with new-onset constipation (Chapter 138), particularly those who are older than 40 years, should also undergo a colonoscopic evaluation to exclude an obstructing carcinoma. Colonoscopy is also useful in patients with pseudo-obstructive (nonobstructive) colonic dilation or Ogilvie's syndrome (Chapter 138); such patients are at risk for colonic rupture at diameters above 9 to 12 cm, and colonoscopic decompression is often required, sometimes on an emergent basis.
Malignant obstruction of the gastrointestinal lumen including the esophagus (Fig. 136-7), pylorus or duodenum, and colon can now be safely and effectively palliated endoscopically by expandable metal stents, avoiding the need for surgery in these patients. A major advance in enteral feeding has been the introduction of percutaneous endoscopic gastrostomy (PEG), a relatively quick, simple, and safe endoscopic procedure that has virtually eliminated surgical placement of gastric tubes. A variation of PEG is percutaneous endoscopic jejunostomy (PEJ), in which a long tube is passed through the gastric tube, past the pylorus, and into the jejunum. The most common indication for these procedures is the need for sustained nutrition in patients with neurologic impairment of swallowing or with head and neck cancers. Patients with a short life expectancy are not suitable candidates for PEG and can be managed by nasoenteral tubes. Further, despite its intuitive appeal, there is little or no evidence that PEG feeding alters clinical or nutritional outcomes or significantly improves quality of life.
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| FIGURE 136-7 • Large malignant mass at the gastroesophageal junction as seen endoscopically. |
PEJ was originally introduced to prevent aspiration, but it does not prevent this complication; the major indication for PEJ is significant impairment of gastric emptying. Retrograde tube migration with PEJ is common, however, and PEJ may require frequent replacement.
PANCREATOBILIARY ENDOSCOPY (IMAGING)
Endoscopic retrograde cholangiopancreatography (ERCP) involves a special side-viewing endoscope (the duodenoscope) that is used to gain access to the second part of the duodenum. A small catheter is then introduced into the bile or pancreatic duct, and radiographic contrast medium is injected under fluoroscopic monitoring. Successful cannulation and imaging can be achieved in up to 95% of cases. In some centers, a fine-caliber “baby” endoscope can also be introduced into the duct of interest (cholangioscopy or pancreaticoscopy), allowing the direct visualization of intraductal disease. ERCP is perhaps the technically most demanding of gastrointestinal endoscopic procedures, and it is associated with the highest risk of serious complications (notably pancreatitis, in about 5% of cases).
Suspected Biliary Disease (Chapters 149 and 159)
The diagnostic approach to patients with cholestasis begins with an attempt to differentiate obstructive from hepatocellular causes. The most common causes of obstructive jaundice are common bile duct stones and tumors of the pancreatic and bile ducts. Less invasive conventional imaging with ultrasonography, computed tomography, or magnetic resonance imaging demonstrates dilated bile ducts and mass lesions but is not sensitive or specific in detecting or delineating pathologic change in the distal common bile duct and pancreas, two regions where the majority of obstructing lesions are found. Furthermore, some biliary diseases, such as sclerosing cholangitis, do not result in dilated ducts but have a characteristic appearance on cholangiography. Finally, the ability to use devices such as cytology brushes and biopsy forceps during cholangiography provides an additional aid in the diagnosis of biliary lesions. Both percutaneous and endoscopic cholangiographic techniques are associated with a high rate of success in experienced hands, but the endoscopic approach allows visualization of the ampullary region and the performance of sphincterotomy, and it also avoids the small risk of a biliary leak associated with puncture of the liver capsule.
In the last few years, magnetic resonance cholangiopancreatography, a digital reconstruction technique based on an abdominal magnetic resonance imaging scan, has become popular as an imaging modality for the pancreatobiliary system, with excellent sensitivity and specificity. Because of its relative safety, many experts now advocate this procedure for screening patients with a low likelihood of disease. In those with a higher probability, ERCP is still the procedure of choice because of its therapeutic options.
Of the approximately 600,000 patients undergoing cholecystectomy in this country, 5 to 10% may present with bile duct stones before or after the surgery. Endoscopic stone removal is successful in 90% or more of these cases and usually requires a sphincterotomy (Fig. 136-8). The sphincter of Oddi is a band of muscle that encircles the distal common bile duct and pancreatic duct in the region of the ampulla of Vater; cutting of this muscle, or sphincterotomy, is one of the mainstays of endoscopic biliary treatment and is accomplished with a special tool called a papillotome or sphincterotome. This procedure is often sufficient for the treatment of small stones in the bile ducts, but larger stones may require additional procedures, such as mechanical, electrohydraulic, or laser lithotripsy, which can be performed endoscopically. In addition to stone disease, sphincterotomy can be curative for patients with papillary stenosis or muscle spasm (termed sphincter of Oddi dysfunction). Finally, by enlarging the access to the bile duct, sphincterotomy facilitates the passage of stents and other devices into the bile duct. Sphincterotomy carries an additional small risk of bleeding, but its associated morbidity is about one third that of surgical exploration and its cost is only about 20% as high.
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| FIGURE 136-8 • Biliary sphincterotomy and stone removal from the bile duct. Left, endoscopic retrograde cholangiographic image showing stones (arrow) in the distal common bile duct. Center, endoscopic image of a sphincterotome in the bile duct with the wire cutting the roof of the ampulla (sphincter). Right, a stone is being removed from the bile duct by an endoscopically passed basket. |
Endoscopic therapy has also revolutionized the palliative approach to malignant biliary obstruction. The technique, which requires the placement of indwelling stents, is superior to both radiologic and surgical techniques. Plastic stents have been the mainstay of treatment, but metal stents last longer and are perhaps preferred in patients with longer life expectancies.
Pancreatic Disease (Chapters 147 and 205)
ERCP is also useful in patients with pancreatic diseases that do not always arise with obstructive jaundice, such as pancreatic cancer of the body and tail and, less commonly, chronic pancreatitis. It is also indicated for patients with acute or recurrent pancreatitis without any obvious risk factors on history or routine laboratory evaluation. Imaging of the pancreatic duct may delineate anatomic abnormalities that may be responsible for the pancreatitis, such as congenital variants (pancreas divisum, annular pancreas), intraductal tumors, or possibly sphincter of Oddi dysfunction. In such cases, bile can be collected from the bile duct for microscopic examination for crystals (so-called microlithiasis) that can result in pancreatitis in some patients even in the absence of macroscopic stones. In patients with chronic pancreatitis, which is most often due to excessive alcohol intake, pancreatography can confirm the diagnosis, provide useful information about the severity of the disease, and identify ductal lesions that may be amenable to therapy by either endoscopic or surgical means. In more subtle cases, collection and analysis of pancreatic juice after stimulation with secretin may be useful in establishing exocrine impairment and hence in confirming chronic pancreatic injury.
ERCP also has a role in some patients with acute pancreatitis (Chapter 147) that is probably caused by obstructing biliary stones. Patients presenting with severe biliary pancreatitis may benefit from urgent ERCP early in their course, with the intention of detecting and removing stones from the common bile duct. Similarly, patients who have smoldering acute pancreatitis that does not appear to be improving satisfactorily with conservative treatment may require ERCP for identification and treatment of any obstructing lesions in the pancreatic or distal biliary duct.
Therapeutic endoscopy for chronic pancreatic disease is still evolving. Relief of ductal obstruction (e.g., by endoscopic removal of pancreatic stones or dilation of strictures) can provide short to intermediate pain relief in some patients with chronic pancreatitis. Endoscopic pseudocyst drainage by a variety of techniques is now technically feasible, with results that appear to be comparable to those of surgical or radiologic techniques. Patients with ductal disruptions (e.g., those with pancreatic ascites) can often be treated successfully with endoscopic stent placement. Pancreatic papillotomy may also be useful for some patients with recurrent pancreatitis, such as when pancreas divisum is thought to play a role. Although the ability to approach these difficult clinical entities by the relatively less invasive endoscopic techniques represents a major accomplishment, the treatment of pancreatic diseases remains a multidisciplinary process with important and in some cases dominant roles played by surgeons and interventional radiologists.
TRANSLUMINAL IMAGING: ENDOSCOPIC ULTRASONOGRAPHY
The incorporation of an ultrasonic transducer in the tip of a flexible endoscope or the use of stand-alone ultrasound probes has now made it possible to obtain images of gastrointestinal lesions that are not apparent on superficial views, including lesions within the wall of the gut as well as those that lie beyond (e.g., pancreatic or lymph node lesions). A further role of endoscopic ultrasonography (EUS) is to guide fine-needle aspiration, which often provides pathologic confirmation of suspicious lesions (Fig. 136-9). In many cases, this approach appears to be even more accurate than conventional radiologic techniques like abdominal ultrasonography and computed tomography. Thus, EUS is probably the single best test for diagnosis of pancreatic tumors (Chapter 205), particularly the small endocrine varieties, with sensitivities approaching 95%. It is also the procedure of choice for imaging of submucosal and other wall lesions of the gastrointestinal tract (overall accuracy of 65 to 70%) as well as for staging of a variety of gastrointestinal tumors (overall accuracy of 90% or more). Preoperative staging is a critical element in the management strategy for tumors such as esophageal and pancreatic cancer, and EUS can complement more conventional radiologic tests to help determine the resectability and curative potential of surgery in these cases.
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| FIGURE 136-9 • Biopsy of a pancreatic mass guided by endoscopic ultrasonography (A) and the placement of a stent into a malignant bile duct stricture with endoscopic retrograde cholangiopancreatography (B). (From Brugge WR, Van Dam J: Pancreatic and biliary endoscopy. N Engl J Med 1999;341:1808-1816. Copyright ©1999 Massachusetts Medical Society. All rights reserved.) |
In addition to its valuable diagnostic role, EUS is rapidly emerging as a therapeutic tool. One example is EUS-directed celiac plexus neurolysis, a technique that appears to be effective for the treatment of pain in patients with pancreatic cancer. Unfortunately, this approach does not appear to work as well in patients with chronic pancreatitis.
EVOLVING TECHNIQUES AND FUTURE DIRECTIONS
Recent innovations with much promise include endoscopic optical coherence tomography (Fig. 136-10) and confocal microscopy. These techniques have the ability to provide microscopic images of cells at the surface as well as within deeper layers, thereby providing virtual real-time histology.
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| FIGURE 136-10 • A, Optical coherence tomography of the stomach, an endoscopic procedure currently under investigation that provides high-resolution images of the superficial epithelium comparable to those of microscopy. Scale bar = 500 μm. B, Magnified view of A. Gastric pits can be clearly identified as areas of relatively low reflectance within the glandular epithelium (arrowheads). C, Histology corresponding to B. Gastric pits are marked by arrowheads (hematoxylin and eosin stain, original magnification ×40). (From Bouma BE, Tearney GJ, Compton CC, Nishioka NS: High-resolution imaging of the human esophagus and stomach in vivo using optical coherence tomography. Gastrointest Endosc 2000;51:467-474.) |
Intraluminal or, potentially, transluminal (i.e., entering the peritoneal cavity through a deliberate incision in the wall of the stomach or other organ) endoscopic approaches may provide less invasive treatment of a variety of diseases including obesity, gastrointestinal anastomoses, and even organ resection.
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