Version May 2024
INTRODUCTION — Precise localization of lesions or specific sites within the gastrointestinal tract is important for subsequent surgical or endoscopic intervention and/or for follow-up surveillance endoscopy. Tattooing is the most common method for marking a gastrointestinal lesion or site, although other methods (eg, endoscopic clip placement combined with imaging) are also available. Tattoos are most often placed in the colon, although any area of the luminal gastrointestinal tract can be marked for future reference (eg, small bowel).
This topic will discuss methods to localize gastrointestinal lesions or specific sites, with a focus on the application of endoscopic techniques for tattooing. Other issues related to colonoscopy including indications, patient preparation, technical aspects, and complications are discussed separately. (See "Overview of colonoscopy in adults" and "Bowel preparation before colonoscopy in adults".)
TATTOOING
General principles
Goal — The goal of tattooing is to facilitate accurate localization of a gastrointestinal mucosal lesion (or the site of an endoscopic resection) during a follow-up surgical or endoscopic procedure. Anatomic descriptions (eg, transverse colon) refer to a general location but are often imprecise for identifying specific areas in the small or large bowel. (See 'Other methods for localization' below.)
Deciding to tattoo based on lesion's location — Tattoos can be applied to any portion of the gastrointestinal mucosa and are most frequently used in the colon; however, colonic lesions located in the cecum or rectum generally do not require tattooing prior to resection if they are readily visible because of the ease of identifying these locations endoscopically. For example, a large polyp (≥2 cm) in the cecum or the proximal ascending colon that will be referred to an advanced endoscopist for resection can be photographed rather than placing a tattoo, provided that the appendiceal orifice and/or ileocecal valve is in view or close proximity [1]. Alternatively, the resection site of a small rectal neuroendocrine (carcinoid) tumor (<1 cm) may be marked by the advanced endoscopist so that the site can be more easily identified during a follow-up surveillance procedure. (See 'Surveillance examination' below and "Staging, treatment, and post-treatment surveillance of non-metastatic, well-differentiated gastrointestinal tract neuroendocrine (carcinoid) tumors", section on 'Rectum'.)
Clinical applications
Surgical or endoscopic localization — Tattooing is used primarily in the colon for patients who have a lesion suspicious for cancer (eg, exophytic mass) or a large polyp (≥2 cm) that is detected during colonoscopy and requires subsequent surgical or endoscopic resection [2-4]. (See "Clinical presentation, diagnosis, and staging of colorectal cancer", section on 'Colonoscopy'.)
Lesions in the colon that require surgical excision using laparotomy may sometimes be palpable or easily recognized during surgery. However, small lesions can be difficult to localize, and large lesions may not be palpable by the surgeon if they are soft and compressible [5].
Tattooing is particularly useful for patients undergoing laparoscopic-assisted colonic resection as the surgeon cannot palpate the colon [6,7]. Thus, it is important to have a marker that can be easily seen laparoscopically.
Surveillance examination — If endoscopic resection of the lesion is performed during the index colonoscopy, tattooing can be used to facilitate identifying the resection site during the follow-up endoscopy, detecting residual tissue, and monitoring for recurrence (picture 1) [8]. The mucosal ulcer at the resection site may heal within approximately eight weeks, and a tattoo will serve as a marker at the site in the absence of an ulcer. (See "Endoscopic removal of large colon polyps".)
Other uses — Other uses for tattoos in the gastrointestinal tract include marking the point of maximal insertion during small bowel enteroscopy so that it can be identified subsequently (eg, during capsule endoscopy or surgery). (See "Overview of deep small bowel enteroscopy", section on 'Balloon-assisted enteroscopy'.)
Tattoos have also been used to mark other gastrointestinal lesions because of the lesion's limited visibility. For example, a Dieulafoy lesion in the fundus of the stomach may be localized during surgery by identifying a tattoo placed at the time of a previous endoscopy; thus, the need for intraoperative endoscopy can be avoided [9]. A Dieulafoy lesion is an aberrant vessel that may be difficult to identify endoscopically in the absence of active bleeding, and this is discussed separately. (See "Causes of upper gastrointestinal bleeding in adults", section on 'Dieulafoy's lesion'.)
Types of ink
Carbon black — Carbon black is a permanent ink that is used in the gastrointestinal tract, and it is available in two formulations:
●Pure carbon black – A sterile and prediluted suspension of carbon black particles (Spot endoscopic marker) is commercially available for endoscopic injection and results in a permanent stain [10].
●India ink – The India ink formulation of carbon black has been traditionally used for tattooing, and the stain persists for a minimum of 10 years without fading (picture 2) [11,12]. India ink is black drawing ink made with carbon particles. However, India ink contains several other substances that are immunologically active (eg, carriers, stabilizers) and may be associated with rare complications [1]. (See 'Complications' below.)
India ink is less convenient when compared with Spot endoscopic marker because India ink must be sterilized and diluted prior to use. However, the immunologic properties of India ink may be partially reduced by dilution of the ink while maintaining its visibility. Ink diluted to 1:100 with saline produces as dark a spectrophotometric pattern as undiluted India ink, and the tattoo made by 1:100 diluted India ink is visible from both the luminal and serosal surfaces.
Tattoo placement
Preparation — Prophylactic antibiotics are not necessary before injecting carbon black formulations [13]:
●Pure carbon black – Pure carbon black (Spot endoscopic marker) is commercially available as a sterile and prediluted suspension that is ready for use.
●India ink – India ink must be diluted and sterilized prior to use. This can be accomplished by treating a diluted solution in an autoclave. As an alternative, the ink can be rendered bacteriologically sterile by passing the diluted solution through a 0.22 micron Millipore filter, which is interposed between the syringe containing the dilute solution of India ink and the injection needle [14]. To prevent clogging, it is helpful to use two filters in tandem: the first (0.44 micron) filters large particles while the second (0.22 micron) filters bacteria.
Injection technique — The goal of the injection technique is to place the ink into the submucosal space because the stain will be visible from the gastrointestinal lumen and from the peritoneal cavity [1]. A catheter with an injection needle (23 or 25 gauge) is passed through the endoscope's channel, and then either of the following injection techniques is used:
●Direct injection method – For the direct injection method, the needle enters the mucosa so that the beveled tip of the needle is entirely beneath the mucosa to permit injections into the submucosa. The standard volume of ink injection for each site is 0.5 to 0.75 mL (if using Spot endoscopic marker), but in practice, the endoscopist may use a larger volume of injectate based on personal preference. If India ink is being used, refer to the manufacturer's instructions for the recommended volume of ink per injection.
When the needle is in the submucosal plane, a bleb will develop during injection. If a submucosal blue or black bleb is not immediately seen during an injection, then the needle is either too far into the intestinal wall, causing the injection solution to flow into the peritoneal cavity, or it is too superficial, causing the carbon suspension to leak out the needle and into the intestinal lumen. If it is suspected that the needle may have penetrated the full thickness of the intestinal wall, the needle should be pulled back slightly since the carbon suspension may have been injected into the peritoneal cavity. When the needle is repositioned into the submucosal space, the ink can be injected. Intraperitoneal spillage of small amounts of ink does not appear to result in any adverse effects [2,15].
●Saline bleb method – The saline bleb method involves first creating a bleb by injecting 0.5 to 1 mL of isotonic saline solution into the submucosa. Next, the needle of the catheter containing tattoo ink enters the saline bleb, and the ink for tattooing is injected. The rationale for the saline bleb is that it will prevent insertion of the needle through the bowel wall and subsequent injection of ink into the peritoneal cavity.
Selecting tattoo site — The specific site(s) and number of tattoo injections depend on whether the lesion will require surgical or endoscopic intervention:
●Pre-surgical tattooing – For pre-surgical marking, the tattoo injection is placed 3 cm distal to the lesion and at three sites, each located in different quadrants of the intestinal lumen to increase the likelihood of visualization (picture 3) [11,16,17].
●Endoscopic tattooing – The approach to endoscopic marking depends on whether the lesion will be resected at a later time or if removal occurs during the index procedure, and on the endoscopist's personal preference:
•For endoscopic marking a lesion for resection at a later date, there are two options. One option is to place the tattoo 3 cm distal to the lesion. The tattoo should not be placed directly adjacent to or under the lesion because of the potential for submucosal fibrosis and muscle injury, which may increase the risk of perforation during subsequent endoscopic resection [18,19]. Another option is to tattoo the intestinal wall opposite the lesion, and some advanced endoscopists prefer this approach. (See "Endoscopic removal of large colon polyps", section on 'Effect of prior polyp manipulation'.)
•For tattoo placement following endoscopic resection, the tattoo is placed after the resection is completed and the site is closed with endoscopic clips, if they are needed. Tattooing is performed either near the resection site or on the intestinal wall opposite the resection site, and the relationship between the resection site and the tattoo is specifically noted in the endoscopy procedure note. (See 'Documentation' below and "Endoscopic removal of large colon polyps", section on 'Preventing bleeding'.)
Documentation — The endoscopy report should include the following information for each tattoo placement:
●Location of the tattoo in relation to the lesion (eg, distal)
●Number of tattoos associated with each lesion
●Anatomic location of the lesion and tattoo (eg, ascending colon, transverse colon)
For example, the endoscopy report may state that in the transverse colon, 0.75 mL of Spot endoscopic marker were injected submucosally on the wall opposite a 3 cm lateral spreading lesion.
Efficacy — Tattooing malignant-appearing colon lesions is associated with lower rates of lesion localization error at the time of surgery, and most endoscopic tattoos are visualized intraoperatively on the serosal surface of the colon. In a meta-analysis of 22 observational studies including over 2500 patients with colorectal cancer, the pooled rate of localization error was lower for tattooed lesions compared with no tattoo (6.5 versus 13.7 percent; mean difference 7.2, 95% CI 2.02–12.38) [17]. Studies on tattoo placement for marking a colonic neoplasm show intraoperative tattoo visualization rates ranging from 78 to 100 percent [2,7,11,16,17,20,21]. In addition, tattoos were associated with reduced operative time and reduced blood loss compared with no tattoos [7].
Complications — The overall risk of complications of tattooing is low and depends on the type of ink and, in some cases, the location of the ink:
●Type of ink – Pure carbon black in sterile formulation (Spot endoscopic marker) has not been associated with complications such as infection or chronic inflammation [22]. Complications related to the use of India ink are rare; however, reported adverse events include sterile abscess formation at the site of injection, peritonitis, and development of inflammatory bowel disease [23-26]. Complications associated with India ink may be related to immunologically active compounds contained in the solution such as carriers, stabilizers, binders, and fungicides. (See 'Types of ink' above.)
●Tattoo placement – Placement of a tattoo under a mucosal lesion may result in submucosal fibrosis that can interfere with advanced endoscopic resection techniques and may increase the risk of incomplete resection and perforation when resection is performed at a later time [18,19,27]. (See "Endoscopic removal of large colon polyps", section on 'Tattooing'.)
OTHER METHODS FOR LOCALIZATION
Endoscopic clips — One or more metal clips can be placed endoscopically to mark the site of a mucosal lesion, and they are often used in conjunction with an imaging modality (eg, fluoroscopy, ultrasound) to locate the clip at a later date [28,29]. Clips placed preoperatively can be located by either laparoscopic ultrasonography or by fluoroscopy. While laparoscopic ultrasonography is a more rapid method for identifying the clips compared with fluoroscopy, its accuracy may be limited by intestinal gas [30]. Intraoperative fluoroscopy has also been used to locate endoscopic clips placed on colorectal cancers during preoperative colonoscopy [30].
The use of clips is limited because they are not permanent and the duration of the mucosal attachment is variable, ranging from days to months (average duration of approximately ten days) [31]. Thus, the clip(s) may detach prior to the follow-up procedure. The risk of failing to localize the site due to clip detachment may be reduced by placing two or more clips at the target location because this approach may increase the likelihood that at least one clip remains attached. In a study of 11 patients with colorectal tumors marked with at least one endoscopic clip, the localization error rate varied depending on the number of clips used. When one clip was used, the error rate was 60 percent, but if two or more clips were used, the error rate was zero [32].
Intraoperative colonoscopy — The location of a colonic neoplasm or a polypectomy site can be identified by performing intraoperative colonoscopy prior to or during the resection, although in practice this is rarely performed [5,33,34]. A potential issue with intraoperative colonoscopy is that the volume of gas needed to insufflate the colon and permit localization may interfere with surgical techniques. In addition, the polypectomy site may not be endoscopically visible because the mucosal defect may heal before the surgical procedure is performed.
Methods to avoid — Localization by measuring the number of centimeters that an instrument is inserted into the colon is a relatively inaccurate method for lesion localization [35,36]. The number of centimeters inserted may not correspond to the colonoscope tip's location within the colon unless both the colon and the colonoscope are relatively straight. Colonic loops may affect the amount of endoscope inserted and may cause the endoscopist to overestimate the distance from the anal verge, whereas a straight endoscope, without any loops, can give a more accurate estimation of the distance from the anal verge (figure 1) [37,38]. (See "Overview of colonoscopy in adults", section on 'Looping'.)
SUMMARY AND RECOMMENDATIONS
●The goal of tattooing is to facilitate accurate localization of a gastrointestinal mucosal lesion (or the site of an endoscopic resection) during a follow-up surgical or endoscopic procedure. Anatomic descriptions (eg, transverse colon) refer to a general location but are often imprecise for identifying specific areas in the bowel. (See 'Goal' above.)
●Examples of clinical applications for tattooing include (see 'Clinical applications' above):
•For patients who have a colorectal lesion suspicious for cancer (eg, exophytic mass) that is detected during colonoscopy but is not located in the cecum or rectum, tattooing is typically used to facilitate subsequent surgical resection.
•For patients who undergo endoscopic resection of a large lesion (eg, ≥2 cm) during the index colonoscopy, tattooing is used to facilitate finding the resection site during the follow-up surveillance examination.
•For patients undergoing small bowel enteroscopy, tattoo placement marks the point of maximal endoscope insertion so that it can be identified subsequently (eg, during capsule endoscopy or surgery).
●Carbon black is a permanent ink that is used in the gastrointestinal tract, and it is available in two formulations (see 'Types of ink' above):
•Pure carbon black – A sterile and prediluted suspension of carbon black particles (Spot endoscopic marker) is commercially available for endoscopic injection.
•India ink – The India ink formulation of carbon black is less convenient compared with Spot endoscopic marker because of the need to sterilize and dilute it prior to use.
●The specific site(s) and number of tattoo injections depend on whether the lesion will require surgical or endoscopic intervention (see 'Selecting tattoo site' above):
•Pre-surgical tattooing: For pre-surgical marking, we place the injection 3 cm distal to the lesion and we tattoo three sites (each located in different quadrants of the intestinal lumen to increase the likelihood of visualization) (picture 3).
•Endoscopic tattooing: The approach to tattooing to facilitate future endoscopy depends on whether the lesion is resected during the index procedure or if it will be removed at a later time and on the endoscopist's personal preference.
●The endoscopy report should include the following information for each tattoo placement (see 'Documentation' above):
•Location of the tattoo in relation to the lesion (eg, tattoo was placed 3 cm distal to lesion)
•Number of tattoos associated with each lesion
•Anatomic location of the lesion and tattoo (eg, transverse colon)
●For patients with malignant-appearing lesions found during colonoscopy in locations other than the cecum or rectum, we suggest endoscopic tattooing because it is associated with lower rates of lesion localization error at the time of surgery (Grade 2C). (See 'Deciding to tattoo based on lesion's location' above and 'Efficacy' above.)
●Tattoo placement directly underneath a mucosal lesion may result in submucosal fibrosis that can interfere with advanced endoscopic resection techniques and may increase the risk of incomplete resection and perforation when resection is performed at a later time. (See "Endoscopic removal of large colon polyps", section on 'Tattooing' and 'Complications' above.)
ACKNOWLEDGMENT — The authors and UpToDate thank Dr. Jerome Waye, who contributed to earlier versions of this topic review.
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