Reply to Krakamp et al.: Is Water Immersion Necessary in Colorectal Cancer Staging Using Balloon-Sheathed Miniprobes?

Previous reports have shown that miniprobe ultrasonography is superior to conventional endoscopy ultrasonography (EUS) in the staging of colorectal cancer, especially in tumors with tight strictures and in flat or small lesions [1] [2] [3]. In our experience, most colon cancers are moderately advanced (higher than the T2 stage) at presentation and are usually accompanied by tight stricture formation. Conventional EUS is unable to pass through the stricture in about 11 % of these lesions, so that clear cross-sectional images are obtained in only 89 % of cases [3]. In our study, however, clear cross-sectional images were obtained using a balloon-sheathed miniprobe in 96.5 % of the patients.

When EUS examinations are being carried out in the colon, bowel gas is a major hindrance to obtaining clear images. The balloon at the tip of the balloon sheath can usually be expanded to a maximal diameter of about 2.5 cm after water infusion. This is advantageous in evaluating moderate to severely stenosed lesions, without further need for water immersion. However, if direct contact between the lesion and the balloon is relied upon in small and/or flat lesions, the abundance of bowel gas in the relatively larger bowel lumen will almost always distort the images. If this is encountered, suctioning out the air in the bowel lumen is the preferred remedy. However, this collapses the colon wall and can obscure the anatomical relationship between the lesion and the wall, in turn affecting the accuracy of staging. We strongly believe that the best way of expanding the lumen is with water infusion, which is definitely not time-consuming. In the study, however, water immersion over the balloon-sheathed miniprobe arm was not required in 35 % of the patients, since maximum inflation of the balloon was sufficient to achieve apposition between the lesion and the balloon.

With regard to the report by Krakamp et al., the first question is what the type and characteristics were of the lesions they encountered. More advanced lesions with tight strictures would not require water immersion, as explained above, while small lesions would most likely require water immersion. This finding is supported by our study, in which all lesions staged as T1 and 86 % of those staged as T2 required water immersion.

The outer diameter of a balloon sheath is about 3.6 mm, which is larger than the working channel of the conventional colonoscope. We therefore agree with Krakamp et al. that a scope with a working channel larger than 3.7 mm should be used. However, it should be emphasized that it is more convenient to use a scope with two channels, so that infusion or suction of water can be carried out through one channel while simultaneously keeping the probe in place in the other channel.

Another aspect that needs to be considered is how the life of the balloon sheath can be prolonged. Before the balloon-sheathed miniprobe is inserted into the working channel, it is highly advisable to apply some lubricating jelly to the tip of the balloon sheath.

Reference

• 1 Yoshida M, Tsukamoto Y, Niwa Y. et al . Endoscopic assessment of invasion of colorectal tumors with a new high-frequency ultrasound probe.  Gastrointest Endosc. 1994;  41 587-592
• 2 Saitoh Y, Obara T, Einami K. et al . Efficacy of high-frequency ultrasound probes for the preoperative staging of invasion depth in flat and depressed colorectal tumors.  Gastrointest Endosc. 1996;  44 34-39
• 3 Tsuda S, Hoashi T, Yao T. Endoscopic ultrasonography versus probe for diagnosis of depth of infiltration of colorectal cancer.  Endoscopy. 1998;  30 A85-87
• 4 Mo L R, Tseng L J, Jao Y T. et al . Balloon sheath miniprobe compared to conventional EUS in the staging of colorectal cancer.  Hepatogastroenterology. 2002;  49 980-983