Experience with Ultrasound Miniprobes in the Staging of Colorectal Cancer

In the July 2002 edition of Endoscopy, Tseng et al. [1] reported on their experience using an Olympus balloon-sheathed miniprobe for endosonographic examination during diagnostic colonoscopy for colon cancer. There was 85 % agreement between the miniprobe findings and the intraoperatively identified tumor spread. Lymph nodes were identified correctly, with sensitivity and specificity rates of 74 % and 71 %, respectively - a rate that is higher than that achieved with radiographic methods. In contrast to conventional endosonography, the miniprobe was generally found to be particularly suited to investigating proximal and stenotic segments of the colon, particularly in T1 and T2 tumors. The specificity and sensitivity rates were highest in the rectum, for anatomical reasons.

During the last 3 years, Fuji 12-MHz and 20-MHz miniprobes have also been used in our hospital, supplemented with a balloon water-supply line developed in collaboration with Hitachi (Fig. [1], [2]). This unit has been used both for colonoscopy and upper endoscopy. In 54 patients with colon cancer, the specificity and sensitivity rates obtained with this system during preoperative staging were also similar to the intraoperative results. Unlike the study group mentioned above, however, the miniprobe was used exclusively with a balloon water-supply line, without infusing an additional 50 - 100 ml of water. After an initial learning phase, this method makes straightforward operations even easier. It was possible to insert the miniprobe into the water-supply line without any complications and to place the rotating crystal in such a way that it was encompassed by the water-supply line. Finally, the balloon was filled with 5 - 6 ml of fluid through a side arm, allowing any air bubbles arising to be sucked out. The probe fitted to the water-supply line in this way can easily be pushed through working channels with diameters of 3.8 - 4.2 mm during the examination. This procedure only added an extra 5.5 min to procedure times in comparison with conventional colonoscopy. The water-supply line can be disinfected and re-used up to six times, but this is an indication of its durability rather than a general recommendation for multiple use.

This novel system therefore provides an inexpensive and easily manageable method that can significantly expand the value of colonoscopy in the preoperative staging of gastrointestinal tumors and in searching for recurrent tumors.

Figure 1 The Fujinon miniprobe with an uninflated Hitachi balloon water-supply line.

Figure 2 The Fujinon miniprobe with the Hitachi balloon water-supply line inflated.

Reference

• 1 Tseng L J, Jao Y TFN, Mo L R. Preoperative staging of colorectal cancer with a balloon-sheathed miniprobe.  Endoscopy. 2002;  34 564-568