Laterally spreading tumors (LSTs)[ ¹] are mainly located in the cecum and rectum and endoscopic mucosal resection (EMR) is the therapeutic choice[ ^{2 , 3}] because of their lower incidence of submucosal (sm) invasion. Involvement of the ileocecal valve with possible spreading to the terminal ileum, however, complicates the EMR and resulting in piecemeal resection in which persistent recurrence leads to surgery even for adenomas and intramucosal cancers[ ⁴]. In addition, the thin wall of the narrow ileum increases the risk of perforation during EMR[ ⁵].

Our experience suggests that the well-established endoscopic submucosal dissection (ESD) also produces good results in colorectal cases as in early gastric cancer treatment[ ⁶]. Unlike the stomach, colonic ESD presents high risk of complications[ ⁷] and increased patient discomfort. These factors motivated us to develop better techniques to achieve successful ESDs such as using a bipolar needle knife (B-Knife ^® Zeon Medical Co. Tokyo, Japan)[ ⁸] to reduce the risk of perforation and carbon dioxide (CO ₂) instead of conventional air insufflation for patient comfort[ ⁹].

A 76-year-old woman was referred to our hospital for endoscopic treatment of a neoplastic lesion located at the cecum. Conventional colonoscopy revealed a broad base, flat tumor. After 0.4% indigo-carmine dye spraying, the margin of the 70 mm-lesion was clearly delineated (Figure 1A and B). High-magnification colonoscopy (PCF-Q240ZI; Olympus Optical Co. Ltd, Tokyo, Japan) disclosed a non-invasive pit pattern[ ^{10 - 12}] indicating an intramucosal cancer despite the lesion’s large size (Figure 1C). Extension onto the terminal ileum until 1.5 cm from the ileocecal valve was also observed (Figure 1D). After diagnosing a Is+IIa, LST granular type (LST-G), we performed ESD using B-Knife and insulation-tip knife (IT-Knife) (Olympus Optical Co., Tokyo, Japan) (Figure 2A). During the procedure, we used CO ₂ instead of air insufflation to reduce patient’s intraoperative abdominal discomfort. This is a safe and effective technique suitable in lengthy colonic endoscopic procedures with the patient under conscious sedation[ ¹³]. Following the injection of glycerol and sodium hyaluronate solution into the sm layer[ ^{14 , 15}], a circumferential incision was made using a B-Knife. The thickened sm layer was then dissected (oral to anal) across the ileocecal valve using both the B-Knife and IT-Knife. Finally, hemostasis was carefully checked throughout the ileocecal region (Figure 2B and C). The procedure took 150 min and neither perforation nor delayed bleeding was recognized. Hospitalization lasted four days with no further complications. Histopathology disclosed that the 70 mm resected specimen was an intramucosal cancer with tumor-free margins (Figure 2D). Although some retraction of the ileocecal valve could be observed, follow-up examinations after 6 mo revealed no residual tumor or recurrence (Figure 3A and B).

In the present report, en-bloc resection was successfully achieved by ESD using B-Knife and IT-Knife, despite the difficult location involving the ileocecal valve and terminal ileum and the large size of the lesion. IT-Knife, a developed insulation-tipped monopolar electrosurgical knife for removing large gastric lesions en-bloc, is not widely accepted in the colorectum because of its technical difficulty and the risk of complications, such as perforation and bleeding. On the other hand, a bipolar current minimizes the damage to deeper tissues. Thus, the current flow characteristics of the B-Knife reduce the vertical damage and risk of perforation demonstrating its utility for ileocecal ESDs[ ^{9 , 10}].

Another important consideration was patient discomfort with air insufflation in long procedures. The supply of air can easily flow into the ileum causing painful distension even in EMRs for cecal lesions. In an earlier study aimed at reducing abdominal discomfort using CO ₂ in colorectal ESDs, we demonstrated the advantages and safety of CO ₂ compared to conventional air[ ¹⁴]. This factor was evident in the present case. Although a large amount of CO ₂ was supplied to the ileum, only a small amount of midazolam (4 mg in both cases) was required for intra-operative sedation.

Considering the indications for colorectal ESD, we generally recommend ESD for LST-non granular type lesions > 20 mm and planned piecemeal EMR for LST-Gs M < 40 mm[ ³]. In these four cases, we decided to perform ESD because of the LST-Gs large size, their location at the ileocecal valve and terminal ileum spreading, the probability of sm infiltration, and an increased likelihood of incomplete resections and recurrence.