REVIEW

Rev esp enfeRm Dig (MadridVol. 107, N.º 7, pp. 430-435, 2015

Submucosal chromoendoscopy. A technique that highlights epithelia and differentiates histological components, and renders colon polypectomy easier and saferCarlos Dolz-Abadía and Angels Vilella-Martorell

Department of Digestive Diseases. Hospital Son Llatzer. Palma de Mallorca. Spain

1130-0108/2015/107/7/430-435Revista española De enfeRmeDaDes DigestivasCopyRight © 2015 aRán eDiCiones, s. l.

ABSTRACT

Submucosal chromoendoscopy involves the injection of a solution containing a vital stain, usually indigo carmine, into the intestinal wall submucosal layer. This allows to: Better delimit and characterize the various epithelia present (colonic mucosa, adenoma, hyperplastic polyp, serrated polyp, small bowel mucosa); expose and delimit lesion implantation areas; cooperate in the lifting of resectable lesions; ensure section across the submucosal plane; identify intestinal wall structures; render complex polypectomy feasible; and facilitate the identification of perforations.

The present paper offers information on the endoscopic technique for submucosal injection, solution preparation and concentration, and on the potential benefits it may provide for polypectomy or endocopic mucosal resection whether en block or piecemeal. This endoscopic technique simultaneously combines a diagnostic and a therapeutic aspect, since lesion lifting in association with better delimited contours may improve not only accuracy but also endoscopic resection safety and feasibility.

Key words: Chromoendoscopy. Colonic polypectomy.

INTRODUCTION

Chromoendoscopy or chromoscopy is defined as the topical application of dyes during endoscopy in order to highlight tissue characteristics (1). The dyes used for digestive chromoendoscopy are categorized according to their absorption. The first group includes absorbable dyes such as methylene blue, lugol, toluidine blue, and crystal violet. Dyes in the second group are not absorbed, and include indigo carmine. Finally, dyes in the third group modify their color according to pH, as is the case with congo red and phenol red (2).

Indigo carmine is the most widely used stain for colo-rectal endoscopy. It occurs naturally in the sap of the shrub Indigofera tinctoria, but is currently manufactured syn-thetically. It may be used as a food coloring in sweets (for

instance, in violet-colored candy), drinks, and ice cream. It also serves as pH indicator.

The classical technique for topical chromoendoscopy involves the instillation of indigo carmine over the colon-ic epithelium and lesions. This requires an optimal or at least adequate level of cleanliness. Some authors previ-ously administer a mucolytic agent (N-acetylcysteine) to cleanse as thoroughly as possible the target area. Atropine, butylhyoscine bromide or glucagon may be administered to obtain a hypokinetic bowel (3).

Then the dye is injected through a spray catheter at a con-centration ranging from 0.1% to 0.8%. Once injected, the dye may be washed out with water or air through the same spray catheter should the stain be too dark (2). Mucosal irregularities and pit patterns are then carefully examined, usually with Kudo’s pit pattern (4,5) (Fig. 1) and Sanos’s capillary pattern (Fig. 2) classifications (6,7). In non-con-trolled studies aimed at identifying colonic preneoplastic lesions, indigo carmine increased detection rates for flat and smaller lesions overlooked by conventional colonoscopy (8-11). Randomized controlled studies comparing conven-tional white-light colonoscopy and chromoendoscopy have shown strong evidence that the latter enhances premalignant polyp detection in the colon and rectum (12-16). Moreover, the sensitivity of indigo carmine to predict polyp histology (adenomatous vs. hyperplastic) was 82% and 95%, with a specificity of 64% and 95%, respectively.

The injection of indigo carmine into the submucosal layer, or submucosal chromoendoscopy, is a variant of the above classical modality used to verify the submucosal loca-tion of the injected solution. The injection of any solution into the submucosal layer results in a bulging that will not develop during injection into the muscular layer. The addi-tion of indigo carmine to the injected solution colors the resulting bulge and confirms its location within the submu-cosa. This averts perforation risk during polypectomy (17).

Dolz-Abadía C, Vilella-Martorell A. Submucosal chromoendoscopy. A tech-nique that highlights epithelia and differentiates histological components, and renders colon polypectomy easier and safer. Rev Esp Enferm Dig 2015;107:430-435.

Received: 25-09-2014Accepted: 07-01-2015

Correspondence: Carlos Dolz Abadía. Department of Digestive Diseases. Hos-pital Son Llatzer. Ctra. Manacor, km. 4. 07198 Palma de Mallorcae-mail: cdolzaba@gmail.com

Vol. 107, N.º 7, 2015 SubMuCOSAL CHROMOeNDOSCOPy. A TeCHNIque THAT HIgHLIgHTS ePITHeLIA AND DIFFeReNTIATeS 431 HISTOLOgICAL COMPONeNTS, AND ReNDeRS COLON POLyPeCTOMy eASIeR AND SAFeR

Rev esp enfeRm Dig 2015; 107 (7): 430-435

I Round pit (normal pit) Normal

II Asteroid pit Hyperplasic

IIIS

Tubular or round pit that is smaller than the normal pit (type I)

Adenoma

IIIL

Tubular or round pit that is larger than the normal pit (type I)

Adenoma

IV Dendritic or gyrus-like pit Adenoma

VI

Irregular arrangement and sizes of IIIS, III

L, IV type

pit patternCarcinoma

VN

Loss or decrease of pits with an amorphous structure

Carcinoma

Fig. 1. Kudo’s pit pattern classification for the colonic mucosa.

Capillary pattern I II IIIA IIIB

Schema

Endoscopic findings

Capillary characteristics

Meshed capillary vessels (-)Meshed capillary vessels (-)Capillary vessel sureounds mucosal glands

Meshed capillary vessels characterized by: Blind ending, branching and curtailed irregularly

Lack of uniformityHigh density of capillary vessels

Nearly avascular or loose micro capillary vessels

A. Type I CP: MC (-), capillaries not visible with NBI. Hyperplastic polyp. Non-neoplastic lesions.B.1. and B.2. Type II CP: MC (+), capillaries visible, regularly distributed around crypts. Adenomas (tubular and villous, respectively).

Neoplastic lesions.Type II I CP: MC (+), irregular capillaries visible. Cancer. Neoplastic lesions.C.1. Type IIIA CP: Increased capillary vessel density and loss of capillary vessel uniformity. Compromised m/ssm (m: mucosa; ssm:

superficial submucosa < 1,000 mcm).C.2. Type IIIB CP: Avascular areas. Compromised dsm (deep submucosa ≥ 1,000 mcm).

Fig. 2. Sano’s microvascular pattern classification for colon adenomas.

432 C. DOLz-AbADíA AND A. VILeLLA-MARTOReLL Rev esp enfeRm Dig (maDRiD)

Rev esp enfeRm Dig 2015; 107 (7): 430-435

both the muscularis propria and the submucosal fibrotic tissue are weakly stained by indigo carmine. The muscula-ris propria layer is seen as concentric white fibers whereas fibrosis appears as a dense white-yellowish structure (3,18).

Most of the available information on the submucosal injection of indigo carmine involves the study of adeno-mas, colon cancer, and ulcerative colitis (12-16,19,20). In the last few years the submucosal injection of indigo car-mine has been widely used for endoscopic submucosal dis-section (21,22). However, overall, the injection of indigo carmine into the submucosa is a non-standard technique, and information available is scarce on the how, when and where of its use.

This manuscript is an attempt to offer information on the way submucosal chromoendoscopy may be carried out, and on the benefits it may provide.

ENDOSCOPIC TECHNIQUE

First, the target lesion is identified and cleansed, and secretions are aspirated. A hypokinetic agent is given for excessive intestinal peristaltism. We use glucagon rather than butylhyoscine bromide (buscapine, buscopan) as the latter more commonly increases heart rate.

Once the lesion’s surface is attentively examined its attachment is delimited and established. Pedicled lesion resection usually entails no difficulties, but sessile or flat lesions may be challenging or even impossible to excise. In such cases delimiting the lesion’s attachment extent and contour is crucial. It is here that submucosal chro-moendoscopy may be of invaluable help, as it will lift and more clearly delineate the lesion’s base by highlighting its contours. This is feasible even for lesions spanning two aspects of a haustrum or fold. In other words, it may render feasible a lesion initially deemed impossible to resect.

Injected solution composition

No recommendations are available regarding the com-ponents of solutions for submucosal chromoendoscopy and their concentrations. There is only some consensus in the endoscopic submucosal dissection setting, but modifica-tions according to authors are many (23-28).

In this paper we shall not refer to the solution used for endoscopic submucosal dissection. Instead, we shall refer to the solution used for classical polypectomy, endoscop-ic mucosal resection or fragmented resection -anyway, a resection that will not in theory take longer than 15-20 minutes. The composition we recommend in table I is the result of a number of combinations tried in our practice, the one we finally deemed more appropriate.

The liquid base we shall use is a saline solution (0.9% sodium chloride) in a 100-cc container. Reloading from a 100-cc bag-container is more efficient and convenient as compared to filling 10-cc syringes. We add adrenaline, 1 mg per 100 cc of saline. This concentration is 10 times lower than usual when attempting to achieve hemostasis for active bleeding. We must underscore two reasons for the addition of adrenaline to a submucosal chromoendoscopy solution: First, to prevent potential bleeding; second, to obtain vasoconstric-tion in highly vascular epithelia, as is the case with some ade-nomas. We have seen that adenomas become paler following this sort of injection, and that such decoloration helps indigo carmine in delimiting the various epithelia present. We deem a higher adrenaline concentration unnecessary, but could be used to manage potential bleeding following resection.

Indigo carmine is available at several concentrations ranging from 0.1% to 0.8%. Its dosing at such concentra-tions, with no dilution, provides a deep blue color that precludes differentiating the various components of intes-tinal wall layers. When injecting a dye into the wall our goal is obtaining information on the various components we may come across in order to make better decisions. We must find a blue hue allowing differentiation between collagen fibrous tissue and muscle tissue, veins and arter-ies, fat from submucosa, etc. Having obtained a number of dilutions we believe that adding 0.4 cc of 0.8% indigo carmine to 100 cc of saline results in an appropriate blue hue for our purposes (Table I). Other compositions and combinations have also been used, as the one suggested by bourke -succinate-polymerized gelatin plus indigo car-mine 80 mg in 500 ml of solution plus adrenaline 1:10.000 (1 ml per 10 ml injected) (28).

Perilesional injection

The method and sequence of the injection procedure are very important. The final result of a consensus on the

Table I. Composition and concentrations of the solution used for submucosal chromoendoscopy

Substance and material Dose/Measure Comments

Saline 100 ml More practical than filling 10-20 cc syringes. Enough for a complete day of work

Adrenaline 1 mg Concentration 10 times lower than for hemostasis. Highlights more vascular epithelia

Indigo carmine 0.4 cc of a 0.8% solution Pastel blue hue adequate for the purposes pursued

Injection needle 25 G = 0.5 mm Greater diameter = solution leaks from puncture holes

Vol. 107, N.º 7, 2015 SubMuCOSAL CHROMOeNDOSCOPy. A TeCHNIque THAT HIgHLIgHTS ePITHeLIA AND DIFFeReNTIATeS 433 HISTOLOgICAL COMPONeNTS, AND ReNDeRS COLON POLyPeCTOMy eASIeR AND SAFeR

Rev esp enfeRm Dig 2015; 107 (7): 430-435

technique, with the different authors using differing meth-ods. However, the recommendations issued by bourke are highly useful (28) and may be considered a reference. A first option would consist of starting the injection at the lesion’s posterior aspect so that the bulging obtained brings the lesion toward us, from back to front. Once the pos-terior aspect is lifted, the bulging should be induced on both sides, left and right, in a symmetrical, matching way. Finally, we must examine the lesion on its anterior aspect. Injection at this level may also be required, but always in smaller volumes as compared to the posterior and lateral procedures; failure to comply with this would mar the pre-viously obtained visual plane. This is common in narrower colonic segments such as the sigmoid colon.

It should be noted the perilesional mucosal bulging detracts from endoscopic view, hence it is recommended that the needle be slowly withdrawn into the endoscope’s working channel as the bulging develops (Fig. 3-6).

The needle recommended for injection should have a rather small bore to prevent the injected solution from leaking towards the intestinal lumen. A 25 g (0.5 mm) size seems appropriate to us.

The volume to be injected oscillates according to lesion dimensions. A sessile lesion about 25 mm in diameter may admit 5-20 cc of solution. More is better than less since the bulging slowly but steadily flattens over time; however, the injected volume is not to block the visual field thus precluding adequate lesion delimitation.

Some drops of injected solution usually leak from puncture orifices. This should entail no difficulties -rather, superficial epithelial staining helps define their character-istics and better delineate lesion borders.

Lesion resection

After submucosal injection completion we shall have a clearer view of the lesion’s attachment base, which will

Fig. 3. Ileocecal valve. Transition between ileum and tubular adenoma epithelium (arrow).

Fig. 4. LST-G polyp in the ascending colon. With and without (white light) (A) and submucosal chromoendoscopy (B).

Fig. 5. Flat polyp. Tubular adenoma in the ascending colon. A small trickle of blood from the injection site may be seen.

Fig. 6. Pedunculated polyp. Tubular adenoma. A submucosal injection of indigo carmine allows to precisely delimit the transition between the pedicle’s normal mucosa and the adenoma.

A B

434 C. DOLz-AbADíA AND A. VILeLLA-MARTOReLL Rev esp enfeRm Dig (maDRiD)

Rev esp enfeRm Dig 2015; 107 (7): 430-435

allow an estimation of the lesion’s histological nature and invasion depth by using the Kudo and Sano classi-fications (4,5,7). With this we are in a better position to decide whether the lesion should be excised and the best therapeutic modality to be used (Figs. 1 and 2). be as it may, the final objective should be visual reassurance that a complete resection, that is, an R0 resection was obtained of the neoformed tissue. Factors in favor of submucosal injection (submucosal chromoendoscopy) include bet-ter lesion exposure from the lifting action exerted with a potential disappearance of the haustra effect, and complete exposure of difficult-to-identify neoplastic tissue as occurs with some serrated polyps. Some of these serrated polyps, the so-called SSA/P-D (sessile serrated adenomas/polyps) growths, have a non-dysplastic component that may be easily overlooked, thus resulting in incomplete endoscopic resection (29-33).

better lesion exposure permits a safer, more accurate endoscopic resection. Similarly, lesion lifting averts perfo-ration risk by increasing intestinal wall thickness, and may minimize bleeding risk as a result of the vasoconstriction provided by the diluted adrenaline associated with indigo carmine.

Often, a lesion initially considered non-resectable becomes endoscopically resectable in just one fragment, which allows the pathology study of a single block and ensures a precise histological characterization. A second option is fragmented (piecemeal) resection following sub-mucosal injection. Piecemeal resection entails uncertain pathological diagnosis and uncertain cure, hence must be considered a valid though not preferable option. With good visual access, a resection en block should have margins < 25-30 mm in the distal colon and rectum, and < 20-25 mm in the right colon (28).

Once resection is completed, the bluish tinge of the sub-mucosa grants that it took place along that plane, and lower perforation risks. The sight of linear, parallel, whitish struc-tures will suggest the muscle layer was reached, and depth was excessive. Small ectopic fat collections may be identi-fied in the submucosa, particularly in the proximal colon, which should not be mistaken for peritoneal fat; the latter would suggest perforation. Red areas may also be identi-fied that represent submucosal bleeding and should not be mistaken for muscle fibers, which are a whitish pale color (18). Prior staining with India ink, as in a tattoo, may confer a typical blackish hue to the submucosal layer, and result in wall fibrosis and loss of elasticity, which translates into higher perforation risk after endoscopic resection; from all the above, endoscopic resection should be avoided on previ-ously tattooed segments if possible (34,35). The use of pro-phylactic endoscopic procedures to avoid digestive bleed-ing after the endoscopic resection of large colonic lesions (including the use of clips to bring together the borders of the mucosal defect left after the excision) is now open to debate (36). Closing the resection base may reduce bleeding risk (37). Thus, the prophylactic use of clips may reduce the

risk for complications following polypectomy for lesions greater than 2 cm in size, although controlled, randomized studies are needed to demonstrate this in a prospective man-ner. Reinjecting the indigo carmine solution is also useful when in doubt regarding potential microperforations. Rein-jection may confirm an appropriate resection plane, thus reducing the risk for delayed perforation (17).

In summary, submucosal chromoendoscopy may attain several goals:

– better delimitation and characterization of the differ-ent epithelia present, thus telling the normal colonic mucosa from that of lesions.

– exposure and definition of a lesion’s attachment base and its morphology (this may render feasible the resection of a lesion previously considered non-resectable).

– Confirmation that resection took place along the sub-mucosal layer.

– Improved perforation detection.

REFERENCES

1. Devuni D, Vaziri H, Anderson JC. Chromocolonoscopy. gastroenterol Clin North Am 2013;42:521-45. DOI: 10.1016/j.gtc.2013.05.002

2. Wong KeeSong LM, Adler Dg, Chand b, et al. Chromoendoscopy. ASge Technology Committee. gastrointest endosc 2007;66:639-49.

3. Mönkemüller K, Wilcox CM. Interventional chromoendoscopy. gas-trointest endosc 2013;78:346-50. DOI: 10.1016/j.gie.2013.04.181

4. Kudo S, Hirota S, Nakajima T, et al. Colorectal tumours and pit pattern. J Clin Pathol 1994;47:880-5. DOI: 10.1136/jcp.47.10.880

5. Kudo S, Tamura S, Nakajima T, et al. Diagnosis of colorrectal tumour-ous lesions by magnifying endoscopy. gastrointest enodsc 1996;44:8-14. DOI: 10.1016/S0016-5107(96)70222-5

6. Fu KL, Sano y, Kato S, et al. Chromoendoscopy using indigo carmine dye sparring with magnifying observation is the most reliable method for differential diagnosis between non-neoplastic and neoplastic color-rectal lesions: A prospective study. endoscopy 2004;36:1089-93. DOI: 10.1055/s-2004-826039

7. uraoka T, Saito y, Ikematsu H, et al. Sano’s capillary pattern classifica-tion for narrow-band imaging of early colorectal lesions. Dig endosc 2011;23(Supl. 1):112-5. DOI: 10.1111/j.1443-1661.2011.01118.x

8. Hurlstone DP, Sanders DS, Cross SS, et al. Colonoscopic resection of lateral spreading tumours: A prospective analysis of endoscopic mucosal resect. gut 2004;53:1334-9. DOI: 10.1136/gut.2003.036913

9. Rembacken bJ, Fujii T, Cairns A, et al. Flat and depressed colonic neo-plasms: A prospective study of 1000 colonoscopies in the uK. Lancet 2000;355:1211-4. DOI: 10.1016/S0140-6736(00)02086-9

10. Lee JH, Kim JW, Cho yK, et al. Detection of colorectal adenomas by routine chromoendoscopy with indigo carmine. Am J gastroenterol 2003;98:1284-8. DOI: 10.1111/j.1572-0241.2003.07473.x

11. brown SR. baraza W. Chromoscopy versus convetional endoscopy for the detection of polyps in the colon and rectum. Cochrane Database Syst Rev 2010;(10):CD006439.

12. brooker JC, Saunders bP, Shah Sg, et al. Total colonic dye-spray increases the detection of diminutive adenomas during routine colonos-copy: A randomized controlled trial. gastrointest endosc 2002;56:333-8. DOI: 10.1016/S0016-5107(02)70034-5

13. Hurlstone DP, Cross SS, Slater R, et al. Detecting diminutive colorectal lesions at colonoscopy: A randomised controlled trial of pan-colonic versus targeted chromoscopy. gut 2004;53:376-80. DOI: 10.1136/gut.2003.029868

14. Lapalus Mg, Helbert T, Napoleon b, et al. Does chromoendoscopy with structure enhance the colonoscopic adenoma detection rate? endoscopy 2006;38:444-8.

Vol. 107, N.º 7, 2015 SubMuCOSAL CHROMOeNDOSCOPy. A TeCHNIque THAT HIgHLIgHTS ePITHeLIA AND DIFFeReNTIATeS 435 HISTOLOgICAL COMPONeNTS, AND ReNDeRS COLON POLyPeCTOMy eASIeR AND SAFeR

Rev esp enfeRm Dig 2015; 107 (7): 430-435

15. Le Rhun M, Coron e, Parlier D, et al. High resolution colonoscopy with chromoscopy versus standard colonoscopy for the detection of colonic neoplasia: A randomized study. Clin gastroenterol Hepatol 2006;4:349-54. DOI: 10.1016/j.cgh.2005.12.009

16. Stoffel eM, Turgeon DK, Stockwell DH, et al. great Lakes New eng-land Clinical epidemiology and Validation Center of the early Detection Research Network. Chromoendoscopy detects more adenomas than colo-noscopy using intensive inspection without dye spraying. Cancer Prev Res (Phila) 2008;7:507-13. DOI: 10.1158/1940-6207.CAPR-08-0096

17. Holt bA, Jayasekeran V, Sonson R, et al. Topical submucosal chro-moendoscopy defines the level of resection in colonic eMR and may improve procedural safety (with video). gastrointest endosc 2013;77:949-53. DOI: 10.1016/j.gie.2013.01.021

18. Tutticci N, bourke MJ. Interventional chromoendoscopy: Specific aspects for the colon. gastrointest endosc 2014;79:536-8. DOI: 10.1016/j.gie.2013.09.002

19. Matsumoto T, Iwao y, Igarashi M, et al. endoscopic and chromoendo-scopic atlas featuring dysplastic lesions in surveillance colonoscopy for patients with long-standing ulcerative colitis. Inflamm bowel Dis 2008;14:259-64. DOI: 10.1002/ibd.20267

20. Kiesslich R, Neurath MF. Chromoendoscopy in inflammatory bow-el disease. gastroenterol Clin North Am 2012;41:291-302. DOI: 10.1016/j.gtc.2012.01.016

21. Herreros de Tejada A. eSD training: A challenging path to excel-lence. World J gastrointest endosc 2014;6:112-20. DOI: 10.4253/wjge.v6.i4.112

22. Saito y, uraoka T, yamaguchi y, et al. A prospective, multicenter study of 1111 colorectal endoscopic submucosal dissections (with video). gastrointest endosc 2010;72:1217-25. DOI: 10.1016/j.gie.2010.08.004

23. Conio M, Rajan e, Sorbi D, et al. Comparative performance in the porcine esophagus of different solutions used for submucosal injec-tion. gastrointest endosc 2002;56:513-6. DOI: 10.1016/S0016-5107(02)70435-5

24. Hyun JJ, Chun HR, Chun HJ, et al. Comparison of the charac-teristics of submucosal injection solutions used in endoscopic mucosal resection. Scand J gastroenterol 2006;41:488-92. DOI: 10.1080/00365520500325994

25. Kantsevoy SV, Adler Dg, Conway JD, et al. endoscopic mucosal resection and endoscopic submucosal dissection. ASge Technol-ogy Committee. gastrointest endosc 2008;68:11-8 DOI: 10.1016/j.gie.2008.01.037

26. Matsui y, Inomata M, Izumi K, et al. Hyaluronic acid stimulates tumor-cell proliferation at wound sites. gastrointest endosc 2004;60:539-43. DOI: 10.1016/S0016-5107(04)01890-5

27. bures J, Kopácová M, Kvetina J, et al. Different solutions used for sub-mucosal injection influence lyhealing of gastric endoscopic mucosal resection in a preclinical study in experimental pigs. Surgendosc 2009;23:2094-101.

28. bourke MJ. endoscopic mucosal resection in the colon: A practical guide. Tech gastroientest endosc 2011;13:35-49. DOI: 10.1016/j.tgie.2011.01.002

29. Pohl H, Srivastava A, bensen SP, et al. Incomplete polyp resec-tion during colonoscopy-results of the complete adenoma resection (CARe) study. gastroenterology 2013;144:74-80 DOI: 10.1053/j.gastro.2012.09.043

30. gancayco J, Siddiqui uD, Jain D, et al. Narrow band imaging features and pathological correlations of sessile serrated polyps. Am J gastro-enterol 2011;106:1559-60 DOI: 10.1038/ajg.2011.122

31. Tadepalli uS, Feihel D, Miller KM, et al. A morphologic analysis of sessile serrated polyps observed during routine colonoscopy. gastroin-test endosc 2011;74:1360-8. DOI: 10.1016/j.gie.2011.08.008

32. Hazewinkel y, López-Cerón M, east Je, et al. endoscopic features of sessile serrated adenomas: Validation by international experts using high-resolution white-light endoscopy and narrow-band imaging. gastrointest endosc 2013;77:916-24. DOI: 10.1016/j.gie.2012.12.018

33. burgess Ng, Tutticci NJ, Pellise M, et al. Sessile serrated adenomas/polyps with cytologic dysplasia: A triple threat for interval cancer. gastrointest endosc 2014;80:307-10. DOI: 10.1016/j.gie.2014.03.050

34. Trakarnsanga A, Akaraviputh T. endoscopic tattooing of colorec-tal lesions: Is it a risk-free procedure? World J gastrointest endosc 2011;3:256-60.

35. Moss A, bourke MJ, Pathmanathan N. Safety of colonic tattoo with sterile carbon particle suspension: A proposed guideline with illus-trative cases. gastrointest endosc 2011;74:214-8. DOI: 10.1016/j.gie.2011.01.056

36. bourke MJ. bleeding following wide-field endoscopic resection in the colon. gastroenterol Hepatol 2011;7:814-7.

37. Liaquat H, Rohn e, Rex DK. Prophylactic clip closure reduced the risk of delayed postpolypectomy hemorrhage: experience in 277 clip large sessile or flat colorectal lesions and 247 control lesions. gastrointest endosc 2013;77:401-7. DOI: 10.1016/j.gie.2012.10.024