Endoluminal US for stool liquefaction

Dr. Lyndon HernandezLyndon V. Hernandez, MD, MPH from GI Associates in Milwaukee, Wisconsin and the Medical College of Wisconsin discusses his New Methods article “A pilot study of endoluminal US for stool liquefaction” from the March issue.

The purpose of this study was to find out if ultrasound can efficiently liquefy stools. It is difficult to clear the intestinal wall of solid stools and blood clots using conventional water spray and suction. Poor bowel preparation increases the duration of examination, and more importantly increases the chance of missing adenomatous poylps. Many patients undergo repeat procedures in order for the endoscopist to get a better view, which is costly in an era of bundled, value-based payments. Miniaturized ultrasound (US) has been extensively used in intra-vascular thrombolysis, and is a good candidate for liquefying stools intraprocedurally. Time reversal acoustics (TRA) is a simple method that allows the placement of an US transducer outside the body, while using disposable beacons wrapped around the colonoscope to reflect US energy into the intestinal lumen.

Figure 4Figure 4. Representative images demonstrating the enhanced ability to detect a colon polyp in a phantom colon model, after solid stool (C) was mostly cleared after ultrasonic liquefaction (D) and suction (E).

In our bench studies, we noted that low-frequency US (< 100 kHz) successfully dissolved solid stools (Figure 4). Later, we obtained an increase in liquefaction speed by a factor of 50 and 100 times compared to control in our dosimetry studies of various US parameters. There was a significant difference in change in weight between the 20 kHz treated sample (Figure 5 ) compared to controls (P=<.0001), 231 kHz (P=<.0001), and 85 kHz (P=<.0001). In our TRA experiment, the focusing resolution of the ultrasonic field  yielded accurate US focusing in the colon.

Low frequency sonication should lead to stool dissolution more rapidly than water-spray alone, thereby optimizing colonoscopic evaluation in vivo.

Read this article on pages 508-513 of the journal or find it online.

Figure 5Figure 5. Stool dissolution plot of stool liquefaction after various sonication frequencies (5 trials per transducer).

The information presented in Endoscopedia reflects the opinions of the authors and does not represent the position of the American Society for Gastrointestinal Endoscopy (ASGE). ASGE expressly disclaims any warranties or guarantees, expressed or implied, and is not liable for damages of any kind in connection with the material, information, or procedures set forth.

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