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Methylene blue chromoendoscopy for Barrett's esophagus: Coming soon to your GI unit?
EDITORIALS Methylene blue chromoendoscopy for Barrett’s esophagus: Coming soon to your GI unit? The continued rise in the incidence of adenocarcinoma of the esophagus has fueled resurgent interest in the use of a variety of endoscopic and nonendoscopic techniques to improve the diagnosis of Barrett’s esophagus and associated dysplasia/cancer. In recent years, the endoscopic techniques have included vital staining, enhanced high-magnification endoscopy, laser-induced fluorescence endoscopy, photodynamic diagnosis, endoscopic optical coherence tomography (OCT), and high-frequency EUS. Why has there been such a plethora of new imaging techniques for Barrett’s esophagus? The diagnosis of Barrett’s esophagus and associated dysplasia/early-stage cancer continues to be problematic. The current definition of Barrett’s esophagus no longer hinges on an estimated length of pink columnar mucosa. Rather, it requires that there be both endoscopically visible columnar lined esophagus (CLE) and the histologic identification of characteristic specialized intestinal-type metaplasia (SIM) in the tissue samples from CLE. Although gastric fundictype and junctional-type metaplasia have been described in CLE, it is SIM that defines Barrett’s esophagus and confers the increased risk for adenocarcinoma. The diagnosis of Barrett’s esophagus usually becomes problematic only in patients with short lengths of CLE, in whom SIM may not be present or may be present in a focal or patchy distribution. With short Barrett’s esophagus, there are also the inherent problems of esophageal motility, asymmetry of the gastroesophageal (GE) junction, delineation of CLE from columnar mucosa in the cardia, and the need for precise sampling of cells containing SIM from the CLE. Consequently, only 28% to 46% of patients with short CLE may ultimately be proven to have SIM by using the random biopsy technique.1,2 Furthermore, 20% of patients studied with conventional EGD and random biopsies will not have SIM confirmed in a second procedure.3 Overdiagnosis or underdiagnosis of Barrett’s esophagus caused by mistaking columnar mucosa in a hiatal hernia for CLE and by use of random biopsy technique has significant implications for clinical practice. Copyright © 2001 by the American Society for Gastrointestinal Endoscopy 0016-5107/2001/$35.00 + 0 37/70/117958 doi:10.1067/mge.2001.117958 VOLUME 54, NO. 3, 2001
The other reason for the increased interest in new diagnostic modalities for Barrett’s esophagus is the well-known difficulty of diagnosing dysplasia and early-stage carcinoma in the absence of an endoscopically evident mucosal irregularity or lesion. Hence, some investigators have proposed routine use of a rigid, systematic biopsy protocol involving intense sampling of the Barrett’s mucosa (“the Seattle protocol”) for surveillance of Barrett’s esophagus. The prolonged time and high cost for obtaining and examining multiple biopsy specimens by using the Seattle protocol has led to criticism of this method. Two national surveys in the United States have shown that there is no widely accepted, optimal technique for endoscopic surveillance for detection of dysplasia and early-stage carcinoma.4,5 The majority of practicing gastroenterologists in the United States do not use the “jumbo” biopsy forceps, and a fourth of endoscopists do not follow any biopsy protocol.4,5 Vital staining is an “old” endoscopic technique that involves the application of vital stains or dyes for purposes of improving visualization, diagnosis, or characterization. It has been of interest as a “novel” diagnostic modality for Barrett’s esophagus because it is safe, inexpensive, readily available, and potentially clinically useful. Lugol’s iodine, toluidine blue, cresyl violet, and methylene blue have been used for Barrett’s esophagus during the last 2 decades. Methylene blue is a blue dye that is readily taken up by intestinal-type absorptive cells in the GI tract. The technique of methylene blue chromoendoscopy was originally described in 1979 by Japanese investigators as a means for detecting intestinal metaplasia in the stomach. Because of the similarity of SIM with incomplete intestinal metaplasia in the stomach, methylene blue chromoendoscopy was first reported in 1996 as a new technique to aid detection of Barrett’s esophagus.2 The original technique6,7 involves removal of surface mucus with an agent such as a 10% solution of Nacetylcysteine by spraying it on the Barrett’s mucosa with a special washing catheter that creates a fine mist. Next, a 0.5% solution of methylene blue is sprayed on the CLE before vigorous washing with tap water. A 1- to 2-minute wait is needed to allow the mucolytic agent to work and also for the dye to be absorbed. The volumes of mucolytic agent and methylene blue dye required vary according to the length of the columnar mucosa being stained. The original technique involves the use of approximately 10 mL of acetylcysteine and 20 mL of methylene blue dye for every 5 cm of circumferential CLE.6,8 The endpoint of staining is the point at which the surrounding or adjacent squamous epithelium is free of dye and the staining pattern within the CLE GASTROINTESTINAL ENDOSCOPY
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B Figure 1. A, Endoscopic view of focal methylene blue staining of nondysplastic specialized intestinal metaplasia in an ultrashort tongue of columnar mucosa (arrow) and under the Z line. B, Endoscopic view of diffuse, homogeneous staining of a short circumferential length of nondysplastic specialized intestinal metaplasia in nondysplastic Barrett’s esophagus. Biopsy specimens from the small unstained area (arrow) showed gastric-type metaplasia.
Figure 2. A, Endoscopic views of nondysplastic long Barrett’s esophagus with diffuse, homogeneous staining. B, Endoscopic view of long Barrett’s esophagus without an associated lesion showing multiple, focal unstained areas (yellow arrows) within heterogeneously stained mucosa (“speckled” appearance) within the proximal portion. Specimens from these abnormally stained areas showed specialized intestinal metaplasia with high-grade dysplasia. No dysplasia was found elsewhere in multiple specimens from the stained Barrett’s esophagus.
appears stable.2,9 Positive staining is defined as the presence of blue-stained, noneroded mucosa that persists despite vigorous water irrigation. Methylene blue staining adds an average of 5 to 7 minutes to the procedure time2 and less than $9 to procedure cost2 (not including the cost of the catheters). The cost could potentially be reduced further by using methylene blue dye that is not injectable grade and dilute acetic acid rather than acetylcysteine as the mucolytic agent. Because methylene blue specifically stains SIM, fewer biopsy specimens are needed to make a diagnosis compared with random biopsy.6,10
In subsequent studies in the United States, Japan, and Germany, investigators6-11 have confirmed that methylene blue selectively stains SIM in Barrett’s esophagus and that vital staining with directed biopsies can significantly increase the rate of detection of SIM, compared with random biopsies,6,7,9,10 even in patients who have CLE greater than 3 cm in length.6 Nondysplastic SIM in short CLE will appear moderate or dark blue in a focal (Fig. 1A) or diffuse pattern (Figs. 1B, 2B), depending on its distribution and the length of CLE. Most cases of long CLE with nondysplastic SIM have a diffuse staining pattern (Fig. 2B). The sensitivity for the
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diagnosis of SIM in biopsy specimens from stained nondysplastic Barrett’s esophagus is 95% to 98%.6-9 The high sensitivity and high negative predictive value of methylene blue staining for SIM can be used in clinical practice to confirm the absence of SIM in patients with short CLE in whom biopsies have consistently shown only gastric-type metaplasia (Fig. 3). In this issue of Gastrointestinal Endoscopy, Sharma et al.10 further define the patients who may potentially benefit from methylene blue chromoendoscopy. Their prospective, controlled study involving a large number of patients demonstrates the superiority of the methylene blue-directed biopsy technique over random biopsy for the diagnosis of SIM in short (<3 cm) CLE. Vital staining with methylene blue significantly improved detection of SIM and reduced the number of biopsies required. Moreover, by stratifying patients according to the length of CLE, Sharma et al.10 showed that the diagnostic benefits of methylene blue staining were primarily due to improved visualization of focal SIM in CLE 1 cm or greater in length. In patients with 1 to less than 3 cm of columnar mucosa, methylene blue detected SIM in 77% to 90%, compared with 45% to 58% of the patients in whom the random biopsy technique was used.10 Hence, the endoscopist’s “take-home” message from this study should be that, even with fewer biopsies, methylene bluedirected biopsy is better than random biopsy in confirming the presence of SIM in patients with CLE that is 1 or more cm in length and not in those in whom the squamocolumnar junction is irregular. In the latter group, the prevalence of SIM is low, similar to that described for intestinal metaplasia at the GE junction and cardia. Hence, vital staining adds little to random biopsy. The most clinically relevant application of methylene blue chromoendoscopy is the detection of endoscopically inapparent dysplasia and early-stage cancer in Barrett’s esophagus. Nondysplastic circumferential Barrett’s esophagus generally exhibits a diffuse, homogeneous, dark blue staining pattern (Figs. 1B, 2A) because the methylene blue is readily absorbed into the columnar cytoplasm and numerous goblet cells (Fig. 4A). In contrast, severely dysplastic or malignant Barrett’s epithelium exhibits increased nuclear size, decreased cytoplasm, and decreased to absent goblet cells (Fig. 4B). The latter two features result in decreased uptake of methylene blue, which in turn results in the endoscopic appearance of focal light blue or pink (unstained) (Fig. 5A and B) or heterogeneously stained (“specked”) mucosa (Fig. 2B) within diffusely stained CLE. An increasing grade of dysplasia is significantly associated with decreasing stain intensity (Figs. 2B, 5A, 5B) and increasing hetVOLUME 54, NO. 3, 2001
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B Figure 3. Endoscopic views of short length of columnar-lined esophagus before (A) and after (B) methylene blue staining. A prior endoscopy procedure with random biopsy technique disclosed only gastric-type metaplasia. After methylene blue staining, there is no significant positive staining, indicating the absence of intestinal metaplasia, which was confirmed by multiple biopsies. The small amount of dye visible in the hiatal hernia refluxed from the stomach.
erogeneity8 (Fig. 2B). Abnormal methylene blue staining (particularly moderate to marked heterogeneity) is an excellent marker of severe dysplasia and/or early-stage cancer, even better than an endoscopically evident lesion.12 Hence, abnormal staining can be used to select patients in whom numerous biopsy specimens should be obtained. It can also help direct biopsies to SIM with dysplasia or early-stage adenocarcinoma in the absence of a visible associated lesion6,8 or localize an area for endoscopic therapy.13,14 When used during routine endoscopic surveillance, methylene blue staining can improve the detection of dysplasia and early-stage cancer and significantly decrease the overall cost of endoscopic surveillance GASTROINTESTINAL ENDOSCOPY
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Figure 4. A, Photomicrograph showing nondysplastic distinctive Barrett’s esophagus (intestinal metaplasia) with the characteristic crypts and villi lined by mucus-secreting columnar cells and goblet cells (H&E, orig. mag. ×100). With increasing grade of dysplasia, there is loss of goblet cells and increased ratio of nuclei to cytoplasm. B, Photomicrograph showing severely dysplastic Barrett’s esophagus; methylene blue is not readily absorbed into cells and results in decreased to absent staining.
compared with the 4-quadrant random biopsy.6 The lower cost is due to the improved diagnostic yield and decreased number of biopsy specimens needed.6,7,15 Sixteen studies are available on methylene blue staining for diagnosing SIM and/or dysplasia in Barrett’s esophagus that are published in preliminary form or peer-reviewed journals; 716-22 have less satisfactory results and 92,6-10,14,15,23 have positive results. The discrepancy in the overall results in published and preliminary reports has resulted in controversy regarding the role of vital staining in Barrett’s esophagus and has slowed the diffusion of this highly promising endoscopic technology into routine clinical practice. The report by Wo et al.22 in this issue of the Journal highlights not only the controversy itself but also the reasons behind the controversy. There are multiple reasons for the variability of the results in studies of methylene blue chromendoscopy in Barrett’s esophagus. First of all, there is variability in the staining technique used in different studies. Some endoscopists use a more concentrated (1%)9 solution of methylene, which may potentially 406
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B Figure 5. A, Endoscopic views of Barrett’s esophagus with no apparent lesion after methylene blue staining performed during routine endoscopic surveillance. Methylene-blue directed biopsy specimens from 2 focal, confluent areas of unstained columnar mucosa identified low-grade dysplasia in a tongue (A) and high-grade dysplasia in an island (B). Note homogeneous dark blue staining of adjacent nondysplastic specialized intestinal metaplasia.
increase the rate of false-positive staining, decrease specificity, and prolong the washing time. Others use a different (“gentle”) washing technique.9,19 In our experience, vigorous washing provides the best results, decreases false-positive staining, and shortens the washing time. The endoscopy assistant needs to hold a large 60-mL syringe with 2 hands to forcefully apply the water wash through the spray catheter. A short dwell time between application of reagents is generally recommended, but Wo et al.22 do not describe any dwell time in the Methods section of their study. They also used a fixed volume of water wash instead of the accepted endpoint for VOLUME 54, NO. 3, 2001
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washing. Hence, the volumes for the water wash were lower and the likelihood of decreased specificity from underwashing is high. Figure 1 in the report by Wo et al.22 demonstrates the effect of underwashing, with persistent blue-stained squamous mucosa adjacent to blue-stained CLE. Clearly, more research is needed to compare the relative benefits and performance characteristics of the various techniques for methylene blue chromoendoscopy to determine the optimal staining technique. The second possible explanation for the variability in results among available studies is difficulty with the interpretation of staining results and the targeting of biopsies. Interpretation of methylene blue staining is not as straightforward as it is with Lugol’s chromoendoscopy. It requires an understanding of the different staining characteristics of gastric- and intestinal-type metaplasia and of nondysplastic and dysplastic SIM. The pattern of methylene blue staining of SIM may be focal (Fig. 1A) or diffuse (Figs. 1B, 2A and B) because of the variable distribution of epithelial subtypes in short and long Barrett’s esophagus. When MB staining is performed for the diagnosis of short Barrett’s esophagus (i.e., <3 cm), biopsy specimens should be obtained of both stained and unstained columnar mucosa proximal to the GE junction. The latter may be either gastric-type metaplasia or dysplastic SIM in the distal esophagus. Partially stained gastric mucosa within the GE junction or herniated stomach resulting from incomplete washing can be misinterpreted as Barrett’s mucosa.16 If methylene blue staining is performed to detect dysplasia or early-stage cancer, endoscopic biopsy should be preferentially directed toward light blue, unstained, or heterogeneously stained areas because these are more likely to be dysplastic. Biopsy specimens should also be obtained from stained mucosa because Barrett’s esophagus with low-grade dysplasia stains variably.8 About 60% to 80% of Barrett’s esophagus with lowgrade dysplasia and 80% to 100% of Barrett’s esophagus with high-grade dysplasia or early-stage cancer will exhibit this abnormal staining pattern.8 The third possible reason for the variable outcomes with methylene blue in Barrett’s esophagus is variability in training and experience. As with many endoscopic techniques, the technique of methylene blue chromoendoscopy is limited by the subjective nature of the interpretation of staining results and the operator-dependent technical aspects of the staining procedure itself, particularly the decision as to endpoint. This may lead to errors in interpretation and suboptimal results of staining in inexperienced hands. There is clearly a learning curve for this technique. The level of experience needed to arrive at optimal accuracy has not been studied and VOLUME 54, NO. 3, 2001
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is undefined. However, the results of studies, whether positive or negative, appear to be directly correlated with the sample size, which suggests that training or experience is a main limiting factor. The overall sensitivity and diagnostic yield of methylene blue staining for the diagnosis of intestinal metaplasia in Barrett’s esophagus has been shown to be high (95% to 98%) in studies involving large numbers of patients and investigators experienced with the technique.2,6-8,10,14,15 In studies with low numbers of patients,16-19 the results are not as good. Chromoendoscopy is not routinely taught in most gastroenterology training programs in North America, and there is limited educational material available. Most endoscopists who use this technique are self-taught and perform it on a regular basis. Endoscopists who persist at learning this technique usually obtain satisfactory results. As a fourth explanation, negative results with methylene blue chromoendoscopy may be directly related to the quality of the scientific study. The study of Wo et al.22 attempted to compare the relative diagnostic yield of methylene blue-directed biopsy with random biopsy for the diagnosis of SIM and dysplasia. These investigators report a low sensitivity and specificity for the diagnosis of SIM (51% and 48%) and dysplasia, with no difference in diagnostic yield for methylene blue chromoscopy compared with conventional 4-quadrant random biopsy. Unfortunately, Wo et al. used a staining and biopsy technique that is different from that used by other investigators with much better results. More importantly, the study has multiple methodologic and analytic problems that make the conclusions difficult to interpret. First, the investigators were not blinded to the results of the methylene blue-enhanced and conventional endoscopy because Dr. Wo was present for 91% of the former and 83% of the latter. Second, the randomization method was only by simple coin toss, which indicates a lack of rigor in the experimental design. Third, only 35 of 47 patients randomized underwent both endoscopic techniques; therefore the data were presented and analyzed according to the evaluable patients rather than an “intent-to-treat” approach. No information is given concerning the patients that dropped out and it is not possible to determine whether they were significantly different from those who completed the study. Fourth, no statistical correction was made for multiple comparisons of the data in the same groups of patients. Fifth, the most serious limitation of the study is the lack of any run-in phase or prior estimation of sample size requirements. Hence, the study’s small sample size has resulted in insufficient power with respect to the ability to make any scientifically GASTROINTESTINAL ENDOSCOPY
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sound, definitive conclusions. In summary, the “takehome” message for the study by Wo et al. is that it cannot provide valid additional information about the relative performance of methylene blue-directed biopsy over random biopsy technique. Interest in chromoendoscopy will grow as more well-designed studies confirm its efficacy and experience with the technique increases. As experience with vital staining increases, ways will be found to overcome its limitations and expand its clinical applications in the GI tract. The problem of poor visualization of minute foci of SIM in the distal esophagus and the imprecision inherent in obtaining biopsy specimens of short Barrett’s esophagus may potentially be solved by use of a high magnification endoscope with a fitted cap and small-cup biopsy forceps. Such technology is already available. When combined with chromoendoscopy, high magnification videoendoscopy may also improve visualization of mucosal detail to enhance discrimination of SIM from gastric metaplasia.14,24 Techniques that combine methylene blue with other vital stains (such as cresyl violet to stain nuclei) may also further improve visualization and characterization of dysplastic and malignant Barrett’s esophagus.14 Currently, chromoendoscopy is a technique that can be of assistance in the diagnosis of SIM in short CLE and endoscopically inapparent dysplasia or cancer. In the future, it may also increase our knowledge of the way in which SIM develops in GERD and how rapidly SIM progresses in extent over time. By allowing localization and mapping of dysplastic SIM, more might be learned about the natural history of dysplastic SIM. With improvements in technique and increased experience, methylene blue chromoendoscopy may prove to be more cost-effective for the practicing gastroenterologist than evolving sophisticated diagnostic technologies such as endoscopic OCT and laser-induced fluorescence endoscopy. Is chromoendoscopy coming to your GI unit? Like any new technology, adoption of this endoscopic technique by gastroenterologists will occur only if scientific evidence supports its use, if it clearly benefits patients, and if billing and reimbursement issues are resolved. It is clear that more work is needed before vital stains become a standard part of the endoscopic practice. Marcia Irene Canto, MD, MHS The Johns Hopkins Division of Gastroenterology and Hepatology Baltimore, Maryland REFERENCES 1. Chalasani N, Wo JM, Hunter JG, Waring JP. Significance of intestinal metaplasia in different areas of esophagus including esophagogastric junction. Dig Dis Sci 1997;42:603-7. 408
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2. Canto MI, Setrakian S, Petras RE, Blades E, Chak A, Sivak MV Jr. Methylene blue selectively stains intestinal metaplasia in Barrett’s esophagus. Gastrointest Endosc 1996;44:1-7. 3. Kim SL, Waring JP, Spechler SJ, Sampliner RE, Doos WG, Krol WF, et al. Diagnostic inconsistencies in Barrett’s esophagus. Department of Veterans Affairs Gastroesophageal Reflux Study Group. Gastroenterology 1994;107:945-9. 4. Gross CP, Canto MI, Hixson J, Powe NR. Management of Barrett’s esophagus: a national study of practice patterns and their cost implications. Am J Gastroenterol 1999;94:3440-7. 5. Falk GW, Ours TM, Richter JE. Practice patterns for surveillance of Barrett’s esophagus in the United States. Gastrointest Endosc 2000;52:197-203. 6. Canto MI, Setrakian S, Willis J, Chak A, Petras R, Powe NR, et al. Methylene blue-directed biopsies improve detection of intestinal metaplasia and dysplasia in Barrett’s esophagus. Gastrointest Endosc 2000;51:560-8. 7. Canto M, Wu TT. Methylene blue staining predicts dysplasia in Barrett’s esophagus [abstract]. Gastrointest Endosc 1999:49;AB50. 8. Canto M, Setrakian S, Willis J, Petras R, Chak A, MV Sivak J. Methylene blue staining of dysplastic and nondysplastic Barrett’s esophagus: an in vivo and ex vivo study. Endoscopy 2001;33:391-400. 9. Kiesslich R, Hahn M, Herrmann G, Jung M. Screening for specialized columnar epithelium with methylene blue: chromoendoscopy in patients with Barrett’s esophagus and a normal control group. Gastrointest Endosc 2001;53:47-52. 10. Sharma P, Topalovski M, Mayo M, Weston A. Methylene blue chromoendoscopy for detection of short segment Barrett’s esophagus. Gastrointest Endosc 2001;54:000-000. 11. Canto MIF, Wu T-T, Kalloo AN. High magnification endoscopy with methylene blue chromoendoscopy for improved diagnosis of Barrett’s esophagus and dysplasia [abstract]. Gastrointest Endosc 2001;53:AB140. 12. Canto M, Kantsevoy S, Wu T, Montgomery E, Kalloo A. MB predicts dysplasia in Barrett’s esophagus [abstract]. Gastrointest Endosc 1999;49:AB50. 13. Ell C, May A, Gossner L, Pech O, Gunter E, Mayer G, et al. Endoscopic mucosal resection of early cancer and high-grade dysplasia in Barrett’s esophagus. Gastroenterology 2000;118: 670-7. 14. Sueoka N, Tabuchi M, Nishigaki H, Sakamoto C, Kobayashi M, Sasajima K. Magnification endoscopy with vital dye staining for detection of a minute focus of early adenocarcinoma in Barrett’s esophagus [abstract]. Gastrointest Endosc 2001;53:AB150. 15. Gossner L, May A, Pech O, Stolte M, Ell C. Chromoendoscopy for detection of dysplasia or mucosal cancer in Barrett’s esophagus [abstract]. Gastrointest Endosc 2000;51:AB3537. 16. Gangarosa LM, Halter S, Mertz H. Methylene blue staining and endoscopic ultrasound evaluation of Barrett’s esophagus with low-grade dysplasia. Dig Dis Sci 2000;45:225-9. 17. Dave U, Shousha S, Westaby D. Methylene blue staining: Is it really useful in Barrett’s esophagus? Gastrointest Endosc 2001;53:333-5. 18. Jobson B, Goenka P, Manalo G, Thomas E. Methylene blue staining for intestinal metaplasia in Barrett’s esophagus—is it as good as we think? [abstract]. Gastrointest Endosc 1999; 49:AB 52. 19. Breyer HP, Maguilnik I, Barros SG. Methylene blue can disclose intestinal metaplasia in Barrett’s esophagus? [abstract]. Gastrointest Endosc 2000;51:AB116. 20. Egger K, Roesch T, Allescher H-D, Ott R, Kurjak M, Werner M, et al. Videoendoscopy and stepwise biopsy of Barrett’s VOLUME 54, NO. 3, 2001
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esophagus are still necessary despite sophisticated diagnostic methods [abstract]. Gastrointest Endosc 2000;51:AB115. 21. Horwhat JD, Famos F, Celna R, Maydonovitch CL, Wong RKH. A prospective controlled study to compare the diagnostic yield of methylene blue-detected biopsies versus 4-quadrant random biopsies to identify the presence and grade of dysplasia in Barrett’s esophagus [abstract]. Gastroenterology 1999;116:A189. 22. Wo J, Ray M, Mayfield-Stokes S, Al-Sabbagh G, Gebrail F, Slone S, et al. Comparison of methylene blue directed biopsies and conventional biopsies in the detection of intestinal meta-
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plasia and dysplasia in Barrett’s esophagus. Gastrointest Endosc 2001. In press. 23. Sueoka N, Tabuchi M, Fujimori T. Videoendoscopy with vital double dye staining (crystal violet and methylene blue) for detection of a minute focus of early adenocarcinoma in Barrett’s esophagus: a case report [abstract]. Gastrointest Endosc 2000;51:AB117. 24. Sharma P, Weston AP, Sampliner RE. Magnification chromoendoscopy for the detection of intestinal metaplasia and dysplasia in Barrett’s esophagus [abstract]. Gastrointest Endosc 2001;53:AB62.
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The other reason for the increased interest in new diagnostic modalities for Barrett’s esophagus is the well-known difficulty of diagnosing dysplasia and early-stage carcinoma in the absence of an endoscopically evident mucosal irregularity or lesion. Hence, some investigators have proposed routine use of a rigid, systematic biopsy protocol involving intense sampling of the Barrett’s mucosa (“the Seattle protocol”) for surveillance of Barrett’s esophagus. The prolonged time and high cost for obtaining and examining multiple biopsy specimens by using the Seattle protocol has led to criticism of this method. Two national surveys in the United States have shown that there is no widely accepted, optimal technique for endoscopic surveillance for detection of dysplasia and early-stage carcinoma.4,5 The majority of practicing gastroenterologists in the United States do not use the “jumbo” biopsy forceps, and a fourth of endoscopists do not follow any biopsy protocol.4,5 Vital staining is an “old” endoscopic technique that involves the application of vital stains or dyes for purposes of improving visualization, diagnosis, or characterization. It has been of interest as a “novel” diagnostic modality for Barrett’s esophagus because it is safe, inexpensive, readily available, and potentially clinically useful. Lugol’s iodine, toluidine blue, cresyl violet, and methylene blue have been used for Barrett’s esophagus during the last 2 decades. Methylene blue is a blue dye that is readily taken up by intestinal-type absorptive cells in the GI tract. The technique of methylene blue chromoendoscopy was originally described in 1979 by Japanese investigators as a means for detecting intestinal metaplasia in the stomach. Because of the similarity of SIM with incomplete intestinal metaplasia in the stomach, methylene blue chromoendoscopy was first reported in 1996 as a new technique to aid detection of Barrett’s esophagus.2 The original technique6,7 involves removal of surface mucus with an agent such as a 10% solution of Nacetylcysteine by spraying it on the Barrett’s mucosa with a special washing catheter that creates a fine mist. Next, a 0.5% solution of methylene blue is sprayed on the CLE before vigorous washing with tap water. A 1- to 2-minute wait is needed to allow the mucolytic agent to work and also for the dye to be absorbed. The volumes of mucolytic agent and methylene blue dye required vary according to the length of the columnar mucosa being stained. The original technique involves the use of approximately 10 mL of acetylcysteine and 20 mL of methylene blue dye for every 5 cm of circumferential CLE.6,8 The endpoint of staining is the point at which the surrounding or adjacent squamous epithelium is free of dye and the staining pattern within the CLE GASTROINTESTINAL ENDOSCOPY
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B Figure 1. A, Endoscopic view of focal methylene blue staining of nondysplastic specialized intestinal metaplasia in an ultrashort tongue of columnar mucosa (arrow) and under the Z line. B, Endoscopic view of diffuse, homogeneous staining of a short circumferential length of nondysplastic specialized intestinal metaplasia in nondysplastic Barrett’s esophagus. Biopsy specimens from the small unstained area (arrow) showed gastric-type metaplasia.
Figure 2. A, Endoscopic views of nondysplastic long Barrett’s esophagus with diffuse, homogeneous staining. B, Endoscopic view of long Barrett’s esophagus without an associated lesion showing multiple, focal unstained areas (yellow arrows) within heterogeneously stained mucosa (“speckled” appearance) within the proximal portion. Specimens from these abnormally stained areas showed specialized intestinal metaplasia with high-grade dysplasia. No dysplasia was found elsewhere in multiple specimens from the stained Barrett’s esophagus.
appears stable.2,9 Positive staining is defined as the presence of blue-stained, noneroded mucosa that persists despite vigorous water irrigation. Methylene blue staining adds an average of 5 to 7 minutes to the procedure time2 and less than $9 to procedure cost2 (not including the cost of the catheters). The cost could potentially be reduced further by using methylene blue dye that is not injectable grade and dilute acetic acid rather than acetylcysteine as the mucolytic agent. Because methylene blue specifically stains SIM, fewer biopsy specimens are needed to make a diagnosis compared with random biopsy.6,10
In subsequent studies in the United States, Japan, and Germany, investigators6-11 have confirmed that methylene blue selectively stains SIM in Barrett’s esophagus and that vital staining with directed biopsies can significantly increase the rate of detection of SIM, compared with random biopsies,6,7,9,10 even in patients who have CLE greater than 3 cm in length.6 Nondysplastic SIM in short CLE will appear moderate or dark blue in a focal (Fig. 1A) or diffuse pattern (Figs. 1B, 2B), depending on its distribution and the length of CLE. Most cases of long CLE with nondysplastic SIM have a diffuse staining pattern (Fig. 2B). The sensitivity for the
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diagnosis of SIM in biopsy specimens from stained nondysplastic Barrett’s esophagus is 95% to 98%.6-9 The high sensitivity and high negative predictive value of methylene blue staining for SIM can be used in clinical practice to confirm the absence of SIM in patients with short CLE in whom biopsies have consistently shown only gastric-type metaplasia (Fig. 3). In this issue of Gastrointestinal Endoscopy, Sharma et al.10 further define the patients who may potentially benefit from methylene blue chromoendoscopy. Their prospective, controlled study involving a large number of patients demonstrates the superiority of the methylene blue-directed biopsy technique over random biopsy for the diagnosis of SIM in short (<3 cm) CLE. Vital staining with methylene blue significantly improved detection of SIM and reduced the number of biopsies required. Moreover, by stratifying patients according to the length of CLE, Sharma et al.10 showed that the diagnostic benefits of methylene blue staining were primarily due to improved visualization of focal SIM in CLE 1 cm or greater in length. In patients with 1 to less than 3 cm of columnar mucosa, methylene blue detected SIM in 77% to 90%, compared with 45% to 58% of the patients in whom the random biopsy technique was used.10 Hence, the endoscopist’s “take-home” message from this study should be that, even with fewer biopsies, methylene bluedirected biopsy is better than random biopsy in confirming the presence of SIM in patients with CLE that is 1 or more cm in length and not in those in whom the squamocolumnar junction is irregular. In the latter group, the prevalence of SIM is low, similar to that described for intestinal metaplasia at the GE junction and cardia. Hence, vital staining adds little to random biopsy. The most clinically relevant application of methylene blue chromoendoscopy is the detection of endoscopically inapparent dysplasia and early-stage cancer in Barrett’s esophagus. Nondysplastic circumferential Barrett’s esophagus generally exhibits a diffuse, homogeneous, dark blue staining pattern (Figs. 1B, 2A) because the methylene blue is readily absorbed into the columnar cytoplasm and numerous goblet cells (Fig. 4A). In contrast, severely dysplastic or malignant Barrett’s epithelium exhibits increased nuclear size, decreased cytoplasm, and decreased to absent goblet cells (Fig. 4B). The latter two features result in decreased uptake of methylene blue, which in turn results in the endoscopic appearance of focal light blue or pink (unstained) (Fig. 5A and B) or heterogeneously stained (“specked”) mucosa (Fig. 2B) within diffusely stained CLE. An increasing grade of dysplasia is significantly associated with decreasing stain intensity (Figs. 2B, 5A, 5B) and increasing hetVOLUME 54, NO. 3, 2001
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B Figure 3. Endoscopic views of short length of columnar-lined esophagus before (A) and after (B) methylene blue staining. A prior endoscopy procedure with random biopsy technique disclosed only gastric-type metaplasia. After methylene blue staining, there is no significant positive staining, indicating the absence of intestinal metaplasia, which was confirmed by multiple biopsies. The small amount of dye visible in the hiatal hernia refluxed from the stomach.
erogeneity8 (Fig. 2B). Abnormal methylene blue staining (particularly moderate to marked heterogeneity) is an excellent marker of severe dysplasia and/or early-stage cancer, even better than an endoscopically evident lesion.12 Hence, abnormal staining can be used to select patients in whom numerous biopsy specimens should be obtained. It can also help direct biopsies to SIM with dysplasia or early-stage adenocarcinoma in the absence of a visible associated lesion6,8 or localize an area for endoscopic therapy.13,14 When used during routine endoscopic surveillance, methylene blue staining can improve the detection of dysplasia and early-stage cancer and significantly decrease the overall cost of endoscopic surveillance GASTROINTESTINAL ENDOSCOPY
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Figure 4. A, Photomicrograph showing nondysplastic distinctive Barrett’s esophagus (intestinal metaplasia) with the characteristic crypts and villi lined by mucus-secreting columnar cells and goblet cells (H&E, orig. mag. ×100). With increasing grade of dysplasia, there is loss of goblet cells and increased ratio of nuclei to cytoplasm. B, Photomicrograph showing severely dysplastic Barrett’s esophagus; methylene blue is not readily absorbed into cells and results in decreased to absent staining.
compared with the 4-quadrant random biopsy.6 The lower cost is due to the improved diagnostic yield and decreased number of biopsy specimens needed.6,7,15 Sixteen studies are available on methylene blue staining for diagnosing SIM and/or dysplasia in Barrett’s esophagus that are published in preliminary form or peer-reviewed journals; 716-22 have less satisfactory results and 92,6-10,14,15,23 have positive results. The discrepancy in the overall results in published and preliminary reports has resulted in controversy regarding the role of vital staining in Barrett’s esophagus and has slowed the diffusion of this highly promising endoscopic technology into routine clinical practice. The report by Wo et al.22 in this issue of the Journal highlights not only the controversy itself but also the reasons behind the controversy. There are multiple reasons for the variability of the results in studies of methylene blue chromendoscopy in Barrett’s esophagus. First of all, there is variability in the staining technique used in different studies. Some endoscopists use a more concentrated (1%)9 solution of methylene, which may potentially 406
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B Figure 5. A, Endoscopic views of Barrett’s esophagus with no apparent lesion after methylene blue staining performed during routine endoscopic surveillance. Methylene-blue directed biopsy specimens from 2 focal, confluent areas of unstained columnar mucosa identified low-grade dysplasia in a tongue (A) and high-grade dysplasia in an island (B). Note homogeneous dark blue staining of adjacent nondysplastic specialized intestinal metaplasia.
increase the rate of false-positive staining, decrease specificity, and prolong the washing time. Others use a different (“gentle”) washing technique.9,19 In our experience, vigorous washing provides the best results, decreases false-positive staining, and shortens the washing time. The endoscopy assistant needs to hold a large 60-mL syringe with 2 hands to forcefully apply the water wash through the spray catheter. A short dwell time between application of reagents is generally recommended, but Wo et al.22 do not describe any dwell time in the Methods section of their study. They also used a fixed volume of water wash instead of the accepted endpoint for VOLUME 54, NO. 3, 2001
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washing. Hence, the volumes for the water wash were lower and the likelihood of decreased specificity from underwashing is high. Figure 1 in the report by Wo et al.22 demonstrates the effect of underwashing, with persistent blue-stained squamous mucosa adjacent to blue-stained CLE. Clearly, more research is needed to compare the relative benefits and performance characteristics of the various techniques for methylene blue chromoendoscopy to determine the optimal staining technique. The second possible explanation for the variability in results among available studies is difficulty with the interpretation of staining results and the targeting of biopsies. Interpretation of methylene blue staining is not as straightforward as it is with Lugol’s chromoendoscopy. It requires an understanding of the different staining characteristics of gastric- and intestinal-type metaplasia and of nondysplastic and dysplastic SIM. The pattern of methylene blue staining of SIM may be focal (Fig. 1A) or diffuse (Figs. 1B, 2A and B) because of the variable distribution of epithelial subtypes in short and long Barrett’s esophagus. When MB staining is performed for the diagnosis of short Barrett’s esophagus (i.e., <3 cm), biopsy specimens should be obtained of both stained and unstained columnar mucosa proximal to the GE junction. The latter may be either gastric-type metaplasia or dysplastic SIM in the distal esophagus. Partially stained gastric mucosa within the GE junction or herniated stomach resulting from incomplete washing can be misinterpreted as Barrett’s mucosa.16 If methylene blue staining is performed to detect dysplasia or early-stage cancer, endoscopic biopsy should be preferentially directed toward light blue, unstained, or heterogeneously stained areas because these are more likely to be dysplastic. Biopsy specimens should also be obtained from stained mucosa because Barrett’s esophagus with low-grade dysplasia stains variably.8 About 60% to 80% of Barrett’s esophagus with lowgrade dysplasia and 80% to 100% of Barrett’s esophagus with high-grade dysplasia or early-stage cancer will exhibit this abnormal staining pattern.8 The third possible reason for the variable outcomes with methylene blue in Barrett’s esophagus is variability in training and experience. As with many endoscopic techniques, the technique of methylene blue chromoendoscopy is limited by the subjective nature of the interpretation of staining results and the operator-dependent technical aspects of the staining procedure itself, particularly the decision as to endpoint. This may lead to errors in interpretation and suboptimal results of staining in inexperienced hands. There is clearly a learning curve for this technique. The level of experience needed to arrive at optimal accuracy has not been studied and VOLUME 54, NO. 3, 2001
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is undefined. However, the results of studies, whether positive or negative, appear to be directly correlated with the sample size, which suggests that training or experience is a main limiting factor. The overall sensitivity and diagnostic yield of methylene blue staining for the diagnosis of intestinal metaplasia in Barrett’s esophagus has been shown to be high (95% to 98%) in studies involving large numbers of patients and investigators experienced with the technique.2,6-8,10,14,15 In studies with low numbers of patients,16-19 the results are not as good. Chromoendoscopy is not routinely taught in most gastroenterology training programs in North America, and there is limited educational material available. Most endoscopists who use this technique are self-taught and perform it on a regular basis. Endoscopists who persist at learning this technique usually obtain satisfactory results. As a fourth explanation, negative results with methylene blue chromoendoscopy may be directly related to the quality of the scientific study. The study of Wo et al.22 attempted to compare the relative diagnostic yield of methylene blue-directed biopsy with random biopsy for the diagnosis of SIM and dysplasia. These investigators report a low sensitivity and specificity for the diagnosis of SIM (51% and 48%) and dysplasia, with no difference in diagnostic yield for methylene blue chromoscopy compared with conventional 4-quadrant random biopsy. Unfortunately, Wo et al. used a staining and biopsy technique that is different from that used by other investigators with much better results. More importantly, the study has multiple methodologic and analytic problems that make the conclusions difficult to interpret. First, the investigators were not blinded to the results of the methylene blue-enhanced and conventional endoscopy because Dr. Wo was present for 91% of the former and 83% of the latter. Second, the randomization method was only by simple coin toss, which indicates a lack of rigor in the experimental design. Third, only 35 of 47 patients randomized underwent both endoscopic techniques; therefore the data were presented and analyzed according to the evaluable patients rather than an “intent-to-treat” approach. No information is given concerning the patients that dropped out and it is not possible to determine whether they were significantly different from those who completed the study. Fourth, no statistical correction was made for multiple comparisons of the data in the same groups of patients. Fifth, the most serious limitation of the study is the lack of any run-in phase or prior estimation of sample size requirements. Hence, the study’s small sample size has resulted in insufficient power with respect to the ability to make any scientifically GASTROINTESTINAL ENDOSCOPY
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sound, definitive conclusions. In summary, the “takehome” message for the study by Wo et al. is that it cannot provide valid additional information about the relative performance of methylene blue-directed biopsy over random biopsy technique. Interest in chromoendoscopy will grow as more well-designed studies confirm its efficacy and experience with the technique increases. As experience with vital staining increases, ways will be found to overcome its limitations and expand its clinical applications in the GI tract. The problem of poor visualization of minute foci of SIM in the distal esophagus and the imprecision inherent in obtaining biopsy specimens of short Barrett’s esophagus may potentially be solved by use of a high magnification endoscope with a fitted cap and small-cup biopsy forceps. Such technology is already available. When combined with chromoendoscopy, high magnification videoendoscopy may also improve visualization of mucosal detail to enhance discrimination of SIM from gastric metaplasia.14,24 Techniques that combine methylene blue with other vital stains (such as cresyl violet to stain nuclei) may also further improve visualization and characterization of dysplastic and malignant Barrett’s esophagus.14 Currently, chromoendoscopy is a technique that can be of assistance in the diagnosis of SIM in short CLE and endoscopically inapparent dysplasia or cancer. In the future, it may also increase our knowledge of the way in which SIM develops in GERD and how rapidly SIM progresses in extent over time. By allowing localization and mapping of dysplastic SIM, more might be learned about the natural history of dysplastic SIM. With improvements in technique and increased experience, methylene blue chromoendoscopy may prove to be more cost-effective for the practicing gastroenterologist than evolving sophisticated diagnostic technologies such as endoscopic OCT and laser-induced fluorescence endoscopy. Is chromoendoscopy coming to your GI unit? Like any new technology, adoption of this endoscopic technique by gastroenterologists will occur only if scientific evidence supports its use, if it clearly benefits patients, and if billing and reimbursement issues are resolved. It is clear that more work is needed before vital stains become a standard part of the endoscopic practice. Marcia Irene Canto, MD, MHS The Johns Hopkins Division of Gastroenterology and Hepatology Baltimore, Maryland REFERENCES 1. Chalasani N, Wo JM, Hunter JG, Waring JP. Significance of intestinal metaplasia in different areas of esophagus including esophagogastric junction. Dig Dis Sci 1997;42:603-7. 408
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2. Canto MI, Setrakian S, Petras RE, Blades E, Chak A, Sivak MV Jr. Methylene blue selectively stains intestinal metaplasia in Barrett’s esophagus. Gastrointest Endosc 1996;44:1-7. 3. Kim SL, Waring JP, Spechler SJ, Sampliner RE, Doos WG, Krol WF, et al. Diagnostic inconsistencies in Barrett’s esophagus. Department of Veterans Affairs Gastroesophageal Reflux Study Group. Gastroenterology 1994;107:945-9. 4. Gross CP, Canto MI, Hixson J, Powe NR. Management of Barrett’s esophagus: a national study of practice patterns and their cost implications. Am J Gastroenterol 1999;94:3440-7. 5. Falk GW, Ours TM, Richter JE. Practice patterns for surveillance of Barrett’s esophagus in the United States. Gastrointest Endosc 2000;52:197-203. 6. Canto MI, Setrakian S, Willis J, Chak A, Petras R, Powe NR, et al. Methylene blue-directed biopsies improve detection of intestinal metaplasia and dysplasia in Barrett’s esophagus. Gastrointest Endosc 2000;51:560-8. 7. Canto M, Wu TT. Methylene blue staining predicts dysplasia in Barrett’s esophagus [abstract]. Gastrointest Endosc 1999:49;AB50. 8. Canto M, Setrakian S, Willis J, Petras R, Chak A, MV Sivak J. Methylene blue staining of dysplastic and nondysplastic Barrett’s esophagus: an in vivo and ex vivo study. Endoscopy 2001;33:391-400. 9. Kiesslich R, Hahn M, Herrmann G, Jung M. Screening for specialized columnar epithelium with methylene blue: chromoendoscopy in patients with Barrett’s esophagus and a normal control group. Gastrointest Endosc 2001;53:47-52. 10. Sharma P, Topalovski M, Mayo M, Weston A. Methylene blue chromoendoscopy for detection of short segment Barrett’s esophagus. Gastrointest Endosc 2001;54:000-000. 11. Canto MIF, Wu T-T, Kalloo AN. High magnification endoscopy with methylene blue chromoendoscopy for improved diagnosis of Barrett’s esophagus and dysplasia [abstract]. Gastrointest Endosc 2001;53:AB140. 12. Canto M, Kantsevoy S, Wu T, Montgomery E, Kalloo A. MB predicts dysplasia in Barrett’s esophagus [abstract]. Gastrointest Endosc 1999;49:AB50. 13. Ell C, May A, Gossner L, Pech O, Gunter E, Mayer G, et al. Endoscopic mucosal resection of early cancer and high-grade dysplasia in Barrett’s esophagus. Gastroenterology 2000;118: 670-7. 14. Sueoka N, Tabuchi M, Nishigaki H, Sakamoto C, Kobayashi M, Sasajima K. Magnification endoscopy with vital dye staining for detection of a minute focus of early adenocarcinoma in Barrett’s esophagus [abstract]. Gastrointest Endosc 2001;53:AB150. 15. Gossner L, May A, Pech O, Stolte M, Ell C. Chromoendoscopy for detection of dysplasia or mucosal cancer in Barrett’s esophagus [abstract]. Gastrointest Endosc 2000;51:AB3537. 16. Gangarosa LM, Halter S, Mertz H. Methylene blue staining and endoscopic ultrasound evaluation of Barrett’s esophagus with low-grade dysplasia. Dig Dis Sci 2000;45:225-9. 17. Dave U, Shousha S, Westaby D. Methylene blue staining: Is it really useful in Barrett’s esophagus? Gastrointest Endosc 2001;53:333-5. 18. Jobson B, Goenka P, Manalo G, Thomas E. Methylene blue staining for intestinal metaplasia in Barrett’s esophagus—is it as good as we think? [abstract]. Gastrointest Endosc 1999; 49:AB 52. 19. Breyer HP, Maguilnik I, Barros SG. Methylene blue can disclose intestinal metaplasia in Barrett’s esophagus? [abstract]. Gastrointest Endosc 2000;51:AB116. 20. Egger K, Roesch T, Allescher H-D, Ott R, Kurjak M, Werner M, et al. Videoendoscopy and stepwise biopsy of Barrett’s VOLUME 54, NO. 3, 2001
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esophagus are still necessary despite sophisticated diagnostic methods [abstract]. Gastrointest Endosc 2000;51:AB115. 21. Horwhat JD, Famos F, Celna R, Maydonovitch CL, Wong RKH. A prospective controlled study to compare the diagnostic yield of methylene blue-detected biopsies versus 4-quadrant random biopsies to identify the presence and grade of dysplasia in Barrett’s esophagus [abstract]. Gastroenterology 1999;116:A189. 22. Wo J, Ray M, Mayfield-Stokes S, Al-Sabbagh G, Gebrail F, Slone S, et al. Comparison of methylene blue directed biopsies and conventional biopsies in the detection of intestinal meta-
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plasia and dysplasia in Barrett’s esophagus. Gastrointest Endosc 2001. In press. 23. Sueoka N, Tabuchi M, Fujimori T. Videoendoscopy with vital double dye staining (crystal violet and methylene blue) for detection of a minute focus of early adenocarcinoma in Barrett’s esophagus: a case report [abstract]. Gastrointest Endosc 2000;51:AB117. 24. Sharma P, Weston AP, Sampliner RE. Magnification chromoendoscopy for the detection of intestinal metaplasia and dysplasia in Barrett’s esophagus [abstract]. Gastrointest Endosc 2001;53:AB62.
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