Abstract
Background/Aims
Poor bowel preparation is encountered in over 20% of colonoscopies & it increases the duration of the procedure while it impairs adenoma detection. Ultrasound is already being used in catheter-based intravascular thrombolysis. Our aim was to evaluate the efficacy & safety of a novel, miniaturized endoluminal ultrasound in dissolving stool, as a means to salvage poorly prepared colonoscopies.
Methods
We evaluated a range of ultrasound parameters from frequencies of 20 kHz to 1 MHz, & ultrasonic intensities from 1 to 4 W/cm2 in the dissolution of porcine stool samples in water & compared them to non-sonicated controls. We then carried out a safety study on freshly harvested porcine colon, & exposed colon sections to various ultrasound exposure parameters. There were 3 groups: ultrasound-treated with waterspray (n=3), waterspray alone (n=3), and control (n=3). Stool dissolution was measured in terms of weight of stool before & after ultrasound exposure. The stool samples were categorized as type 4 by the Bristol Stool Scale. Ultrasound exposure safety was evaluated histologically by a blinded pathologist. Finally, we developed an ultra-low-profile transducer & mounted it on the tip of a colonoscope (figure not shown).
Results
In preliminary studies, 20 mL porcine stool was exposed to ultrasound with a frequency of 20 kHz, & the samples dissolved completely within a one minute time frame (Figure 1). Stool samples were then exposed to a wide range of ultrasound frequencies & a sub-100 kHz frequency showed the most dissolution efficacy. Depending on pulse rate, acoustic intensity, & duration, an increase in liquefaction speed by a factor of 50-100 times was observed. The effect of ultrasound was profound in a way that solid stool samples in saline turned into fully dispersed liquid sludge within seconds. Figure 2 compares the percent change in weight between the sonicated group & control, showing a significant difference (p=0.004) between sub-85kHz & control. In further experimentation, porcine stool was exposed to ultrasound within a range of 20 kHz to 80 kHz, & the sample dissolved to approximately 75% of their initial weight within 60 min & was suctioned out immediately. Ultrasound with slight agitation &/or water spray at 300 mL/min further decreased dissolution time by 10-fold. Using H&E stain, there was no appreciable difference in sloughing of mucosa or mechanical injury among the groups; histology showed only minor acute damage & slight sloughing of mucosa for all groups.
Conclusion
Endoluminal ultrasound can efficiently liquefy stools at acoustic exposure levels that do not damage ex vivo colonic mucosa. Our ultrasound-assisted colonoscopy device should be able to dissolve stools in vivo more rapidly than water-spray alone & should optimize colonoscopic evaluation to its successful completion.
Poor bowel preparation is encountered in over 20% of colonoscopies & it increases the duration of the procedure while it impairs adenoma detection. Ultrasound is already being used in catheter-based intravascular thrombolysis. Our aim was to evaluate the efficacy & safety of a novel, miniaturized endoluminal ultrasound in dissolving stool, as a means to salvage poorly prepared colonoscopies.
Methods
We evaluated a range of ultrasound parameters from frequencies of 20 kHz to 1 MHz, & ultrasonic intensities from 1 to 4 W/cm2 in the dissolution of porcine stool samples in water & compared them to non-sonicated controls. We then carried out a safety study on freshly harvested porcine colon, & exposed colon sections to various ultrasound exposure parameters. There were 3 groups: ultrasound-treated with waterspray (n=3), waterspray alone (n=3), and control (n=3). Stool dissolution was measured in terms of weight of stool before & after ultrasound exposure. The stool samples were categorized as type 4 by the Bristol Stool Scale. Ultrasound exposure safety was evaluated histologically by a blinded pathologist. Finally, we developed an ultra-low-profile transducer & mounted it on the tip of a colonoscope (figure not shown).
Results
In preliminary studies, 20 mL porcine stool was exposed to ultrasound with a frequency of 20 kHz, & the samples dissolved completely within a one minute time frame (Figure 1). Stool samples were then exposed to a wide range of ultrasound frequencies & a sub-100 kHz frequency showed the most dissolution efficacy. Depending on pulse rate, acoustic intensity, & duration, an increase in liquefaction speed by a factor of 50-100 times was observed. The effect of ultrasound was profound in a way that solid stool samples in saline turned into fully dispersed liquid sludge within seconds. Figure 2 compares the percent change in weight between the sonicated group & control, showing a significant difference (p=0.004) between sub-85kHz & control. In further experimentation, porcine stool was exposed to ultrasound within a range of 20 kHz to 80 kHz, & the sample dissolved to approximately 75% of their initial weight within 60 min & was suctioned out immediately. Ultrasound with slight agitation &/or water spray at 300 mL/min further decreased dissolution time by 10-fold. Using H&E stain, there was no appreciable difference in sloughing of mucosa or mechanical injury among the groups; histology showed only minor acute damage & slight sloughing of mucosa for all groups.
Conclusion
Endoluminal ultrasound can efficiently liquefy stools at acoustic exposure levels that do not damage ex vivo colonic mucosa. Our ultrasound-assisted colonoscopy device should be able to dissolve stools in vivo more rapidly than water-spray alone & should optimize colonoscopic evaluation to its successful completion.
| Original language | English |
|---|---|
| Pages (from-to) | AB429-AB430 |
| Journal | Gastrointestinal Endoscopy |
| Volume | 77 |
| Issue number | 5 |
| State | Published - 2013 |