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Colon cleaning during colonoscopy: a new mechanical cleaning device tested in a porcine model
Colon cleaning during colonoscopy: a new mechanical cleaning device tested in a porcine model Annette Fritscher-Ravens, MD, C. Alexander Mosse, PhD, Tim Mills, PhD, Keiichi Ikeda, MD, Paul Swain, MD London, United Kingdom
Background: Poor colon cleaning frequently impairs colonoscopy. The aim of the study was to develop a method of cleaning the colon during colonoscopy. Methods: A soft-tipped catheter with a water jet spray at its tip was designed to break up and propel stool contents in the direction of the anus. Stool contents were collected in a container attached to an endoscopy trolley. Observations: In bench tests, colon models filled with porridge were rapidly cleaned. Unprepared colons (n Z 15) of anesthetized pigs were cleared in a few minutes by using this device at colonoscopy, by advancing the catheter under direct vision into concretions, which were rapidly broken down. There was minimal trauma to mucosa in these survival studies. Conclusions: A colon cleaning method for use at colonoscopy was highly effective in cleaning colon models and in unprepared pig colon. This device may have a role in cleaning the colon in unprepared or poorly prepared patients.
Copyright ª 2006 by the American Society for Gastrointestinal Endoscopy 0016-5107/$32.00 doi:10.1016/j.gie.2005.05.023
Warm water (w30 C) was pumped from a reservoir with a volumetric pump, i.e., a pump that uses a piston to deliver a constant flow rate with an overpressure cutout. This was chosen so that if the attached catheter burst, the flow would not increase. This pump is likely to be safer than a pump that delivers a constant pressure. The disposable catheters, made of flexible nylon, were 240-cm long and, at the tip, had 4 radial nozzles through which the water was pumped. The catheter tip had a rounded nosepiece made from silicon rubber to minimize trauma to the mucosa. Technical details of catheter design and function are given in Table 1. A metal-tipped catheter used in the first two animals was found to produce linear red streaks on the mucosa and, consequently, the tip was modified. The nozzle diameter and flow rate were selected for animal testing after a series of bench tests, where a stoolfilled colon was simulated by a thin-walled, collapsible nylon tube filled with porridge to which was added 2.5% cooking oil. Once the stool was broken up and diluted, it was removed from the bowel by allowing about 200 mL to accumulate and then gently withdrawing the colonoscope with the water still flowing. This produced a cascade of water and fecal matter out of the anus. This was collected by using a polyethylene bag. A suction connector was designed to fit onto the accessory channel port with a switch to allow suction through the channel, bypassing the valve and the umbilicus of the colonoscope.
www.giejournal.org
Volume 63, No. 1 : 2006 GASTROINTESTINAL ENDOSCOPY 141
Unlike upper-GI endoscopy, colonoscopy requires a bowel preparation to allow visualization of the colonic mucosa. Unfortunately, incomplete bowel preparation is reported in up to 20% of patients, resulting in aborted procedures in 6%.1-6 Moreover, inadequate bowel preparation has been shown to increase costs of colonoscopy by 12% to 22%4 and contributes to missed pathology and procedure-related complications. Therefore, it would be beneficial if a method were available to complete the bowel preparation safely and efficiently in those patients for whom bowel preparation is unsatisfactory or is difficult to achieve. The aim of the study was to design and to test a method for cleaning the poorly prepared colon during colonoscopy.
MATERIAL AND METHODS The device consists of an external pump that is connected to a catheter via a handle with a trigger (Fig. 1), which activates the water flow. The tip of the catheter (Fig. 2) can be advanced, under direct vision, through the accessory channel of the endoscope into the feces so that when water is pumped through, even impacted stool can be broken up into slurry. The water and the broken-up stool are flushed or suctioned out of the colon into a collection system.
Colon cleaning during colonoscopy
Fritscher-Ravens et al
Capsule Summary What is already known on this topic d
Poor preparation for colonoscopy is reported in up to 20% of patients, resulting in aborted procedures in 6%, missed abnormalities, and repeat procedures.
What this study adds to our knowledge d
Figure 1. A view of the hand control for the colon cleaning device.
A colon-cleaning method that sprays water through a catheter at colonoscopy was highly effective in cleaning colon models and unprepared pig colon.
TABLE 1. Catheter specifications
Catheter Catheter Nozzle size length diameter 7F/10F
240 cm
Flow rate
0.5 mm 14 mL/s
Pressure Pressure drop drop across across nozzle catheter 4 bar
11 bar
water pump was started by using the trigger, and the stool was broken up. The resultant slurry was propelled to the rectum where it tended to collect before passing out of the anus. Pulling the colonoscope backward while pumping water through the catheter was an effective cleaning maneuver. It also was found helpful to hold the anus open to allow passage of stool and water into a disposable plastic bag, designed for this purpose, in a container made in our laboratory, which was attached to the examination bed. Figure 2. The tip of the catheter spraying water.
For experimental colon cleaning for colonoscopy, 15 domestic pigs (25-45 kg) were used. These studies were approved by the ethical review board of the Royal Veterinary College and by the Home Office (government review board). The pigs were fasted overnight before the colonoscopy. They had no oral purgative medication or enemas before colon cleaning. The cleaning catheter was passed through a 165-cm long Olympus videocolonoscope (CF 140 L; Olympus Optical Co Ltd, Tokyo, Japan). During colon cleaning, the flow rates were measured, and, after the cleaning, the mucosa of the pigs was inspected for any mucosal damage, which was recorded on videotape. The time to clean the colon was documented, as well as the efficacy of cleaning, which was measured by using a visual analogue scale of 0 to 10, from bad to very good. Ten pigs had a repeat colonoscopy 1 to 2 weeks later to identify possible lesions caused by the first examination. The catheter was advanced by 2 cm or more beyond the tip of the colonoscope into stool collections. The 142 GASTROINTESTINAL ENDOSCOPY Volume 63, No. 1 : 2006
RESULTS The device was tested in unprepared pig colons in 15 animals. The colons were cleared in a few minutes (a median of 12 minutes, range 9-20 minutes), by advancing the catheter under colonoscopic vision into concretions, which were rapidly broken down. It required a mean of 6 insertions (range 2-10) of the colonoscope into the colon, with subsequent washing when using the colon cleaning device to clear the unprepared pig colon to 120 cm, measured once redundant loops had been straightened. All animals had a rectum filled with feces that caused a dark colonoscopic image once the anus was crossed. The stool content was assessed as soft in 8, fibrous but firm in 12, and constipated in 4. The stool appeared to form a continuous column in all but one of the animals, which only had a few lumps of stool to clear. Filling the colon with water was observed to induce a propulsive contraction, which tended to push feces www.giejournal.org
Fritscher-Ravens et al
toward the anus. Gentle abdominal pressure sometimes helped evacuation. The retrograde direction of the water jet tended to break up stool ahead of the endoscope under direct vision and to propel the material coaxial to the endoscope, which allowed the colonoscope to image the way ahead. The water jet spray sometimes reduced the quality of the endoscopic image for a few seconds. The colonoscope channels did not become blocked in the course of the cleaning studies. Visual analog scores assessed the quality of the preparation as a median of 9/10 (range 7-10). Most of the preparations were totally atraumatic. It was possible to identify red streaks on the mucosa in the first 2/15 preparations when pulling or pushing a metal catheter tip across the mucosal surface with an early prototype catheter. This trauma was reduced by designing a softer tip for the catheter, which was used in subsequent studies. The washing process itself was not observed to produce visible trauma or to raise blebs or to cause submucosal edema. One pig had self-limited diarrhea for 12 hours after the procedure. All other pigs were well after the examination, and, in particular, there were no perforations, delayed bleeding, or deaths. The mucosa of the colon was always normal at repeat examination at 7 of 14 days after colon cleaning.
DISCUSSION A simple method for cleaning the colon is presented. It was used in pig studies and allowed successful colonoscopy. The pig colon is nearly twice as long as the human colon and includes a spiral loop that is fixed in a fibrous sheath. We found that the progress of conventional colonoscopes was limited by the tightening spiral at 120 cm. It was possible to clean a few centimeters beyond this distance by advancing the catheter beyond the colonoscope. It seems unlikely that differences between pig and human colonic anatomy should influence cleaning efficacy and safety. Further studies are needed to demonstrate the usefulness of this technique during colonoscopy in patients with poor preparation. Washing and flushing devices have been used to clear blood, especially in the upper-GI tract,7 but have been little studied for bowel cleaning during colonoscopy. Per-anal catheters have been used to assist bowel preparation.8 Possible limitations to this method might include mucosal trauma, bleeding, perforation, clogging of the colonoscope channels, and electrolyte imbalance. Randomized, blinded studies may yield lower scores assessing efficacy of colon cleaning.
www.giejournal.org
Colon cleaning during colonoscopy
This newly developed cleaning procedure may offer some advantages to current practice. It could be used selectively in the endoscopy unit during colonoscopy and might reduce the number of procedures that require to be repeated because the preparation is poor. It is not likely to prolong the procedure by more than a few minutes. Patient compliance and normal colonic motility is not needed, and the cleaning procedure itself is not difficult to do. DISCLOSURE This study also was supported by an educational grant from Ethicon Endosurgery, Cincinnati, Ohio, USA. A provisional patent application has been filed by the authors.
REFERENCES 1. Neidich RL, Zuckermann GR. Patient preparation. In: Raskin JB, Nord HJ, editors. Colonoscopy: principles and techniques. New York: Igaku Shoin; 1995. p. 53-83. 2. DiPalma J. Preparation for colonoscopy. In: Waye JD, Rex DK, Williams CB, editors. Colonoscopy: principles and practice. Oxford: Blackwell; 2003. p. 210-20. 3. Toledo TK, DiPalma JA. Review article: colon cleansing preparation for gastrointestinal procedures. Aliment Pharmacol Ther 2001;15:605-11. 4. Rex DK, Imperiale TF, Latinovich DR, Bratcher LL. Impact of bowel preparation efficiency and cost of colonoscopy. Am J Gastroenterol 2002;97: 1696-700. 5. ASGE technology status evaluation report. Colonoscopy preparations. Gastrointest Endosc 2001;54:829-32. 6. Leaper M, Johnston MJ, Barclay M, Dobbs BR, Frizelle FA. Reasons for failure to diagnose colorectal carcinoma at colonoscopy. Endoscopy 2004;36:499-503. 7. Laine L, Stein C, Sharma V. A prospective outcome study of patients with clot in an ulcer and the effect of irrigation. Gastrointest Endosc 1996;43:107-10. 8. Chang KJ, Erickson RA, Schandler S, Coye T, Moody C. Per-rectal pulsed irrigation versus per-oral colonic lavage for colonoscopy preparation: a randomized controlled trial. Gastrointest Endosc 1991;37:444-8.
Received March 2, 2005. Accepted May 12, 2005. Current affiliations: Department of Endoscopy, St Mary’s Hospital; Department of Medical Physics, University College, London, United Kingdom. This work was presented, in part, during Digestive Diseases Week, May 15-20, 2004, New Orleans, Louisiana (Gastrointest Endosc 2004;59:AB126). K. Ikeda received a research grant to study abroad from Jikei University, Tokyo, Japan. Reprint requests: Paul Swain, MD, Department of Surgical Oncology and Technology, St Mary’s Hospital, 41 Willow Rd, London NW3 1TN, UK.
Volume 63, No. 1 : 2006 GASTROINTESTINAL ENDOSCOPY 143
Background: Poor colon cleaning frequently impairs colonoscopy. The aim of the study was to develop a method of cleaning the colon during colonoscopy. Methods: A soft-tipped catheter with a water jet spray at its tip was designed to break up and propel stool contents in the direction of the anus. Stool contents were collected in a container attached to an endoscopy trolley. Observations: In bench tests, colon models filled with porridge were rapidly cleaned. Unprepared colons (n Z 15) of anesthetized pigs were cleared in a few minutes by using this device at colonoscopy, by advancing the catheter under direct vision into concretions, which were rapidly broken down. There was minimal trauma to mucosa in these survival studies. Conclusions: A colon cleaning method for use at colonoscopy was highly effective in cleaning colon models and in unprepared pig colon. This device may have a role in cleaning the colon in unprepared or poorly prepared patients.
Copyright ª 2006 by the American Society for Gastrointestinal Endoscopy 0016-5107/$32.00 doi:10.1016/j.gie.2005.05.023
Warm water (w30 C) was pumped from a reservoir with a volumetric pump, i.e., a pump that uses a piston to deliver a constant flow rate with an overpressure cutout. This was chosen so that if the attached catheter burst, the flow would not increase. This pump is likely to be safer than a pump that delivers a constant pressure. The disposable catheters, made of flexible nylon, were 240-cm long and, at the tip, had 4 radial nozzles through which the water was pumped. The catheter tip had a rounded nosepiece made from silicon rubber to minimize trauma to the mucosa. Technical details of catheter design and function are given in Table 1. A metal-tipped catheter used in the first two animals was found to produce linear red streaks on the mucosa and, consequently, the tip was modified. The nozzle diameter and flow rate were selected for animal testing after a series of bench tests, where a stoolfilled colon was simulated by a thin-walled, collapsible nylon tube filled with porridge to which was added 2.5% cooking oil. Once the stool was broken up and diluted, it was removed from the bowel by allowing about 200 mL to accumulate and then gently withdrawing the colonoscope with the water still flowing. This produced a cascade of water and fecal matter out of the anus. This was collected by using a polyethylene bag. A suction connector was designed to fit onto the accessory channel port with a switch to allow suction through the channel, bypassing the valve and the umbilicus of the colonoscope.
www.giejournal.org
Volume 63, No. 1 : 2006 GASTROINTESTINAL ENDOSCOPY 141
Unlike upper-GI endoscopy, colonoscopy requires a bowel preparation to allow visualization of the colonic mucosa. Unfortunately, incomplete bowel preparation is reported in up to 20% of patients, resulting in aborted procedures in 6%.1-6 Moreover, inadequate bowel preparation has been shown to increase costs of colonoscopy by 12% to 22%4 and contributes to missed pathology and procedure-related complications. Therefore, it would be beneficial if a method were available to complete the bowel preparation safely and efficiently in those patients for whom bowel preparation is unsatisfactory or is difficult to achieve. The aim of the study was to design and to test a method for cleaning the poorly prepared colon during colonoscopy.
MATERIAL AND METHODS The device consists of an external pump that is connected to a catheter via a handle with a trigger (Fig. 1), which activates the water flow. The tip of the catheter (Fig. 2) can be advanced, under direct vision, through the accessory channel of the endoscope into the feces so that when water is pumped through, even impacted stool can be broken up into slurry. The water and the broken-up stool are flushed or suctioned out of the colon into a collection system.
Colon cleaning during colonoscopy
Fritscher-Ravens et al
Capsule Summary What is already known on this topic d
Poor preparation for colonoscopy is reported in up to 20% of patients, resulting in aborted procedures in 6%, missed abnormalities, and repeat procedures.
What this study adds to our knowledge d
Figure 1. A view of the hand control for the colon cleaning device.
A colon-cleaning method that sprays water through a catheter at colonoscopy was highly effective in cleaning colon models and unprepared pig colon.
TABLE 1. Catheter specifications
Catheter Catheter Nozzle size length diameter 7F/10F
240 cm
Flow rate
0.5 mm 14 mL/s
Pressure Pressure drop drop across across nozzle catheter 4 bar
11 bar
water pump was started by using the trigger, and the stool was broken up. The resultant slurry was propelled to the rectum where it tended to collect before passing out of the anus. Pulling the colonoscope backward while pumping water through the catheter was an effective cleaning maneuver. It also was found helpful to hold the anus open to allow passage of stool and water into a disposable plastic bag, designed for this purpose, in a container made in our laboratory, which was attached to the examination bed. Figure 2. The tip of the catheter spraying water.
For experimental colon cleaning for colonoscopy, 15 domestic pigs (25-45 kg) were used. These studies were approved by the ethical review board of the Royal Veterinary College and by the Home Office (government review board). The pigs were fasted overnight before the colonoscopy. They had no oral purgative medication or enemas before colon cleaning. The cleaning catheter was passed through a 165-cm long Olympus videocolonoscope (CF 140 L; Olympus Optical Co Ltd, Tokyo, Japan). During colon cleaning, the flow rates were measured, and, after the cleaning, the mucosa of the pigs was inspected for any mucosal damage, which was recorded on videotape. The time to clean the colon was documented, as well as the efficacy of cleaning, which was measured by using a visual analogue scale of 0 to 10, from bad to very good. Ten pigs had a repeat colonoscopy 1 to 2 weeks later to identify possible lesions caused by the first examination. The catheter was advanced by 2 cm or more beyond the tip of the colonoscope into stool collections. The 142 GASTROINTESTINAL ENDOSCOPY Volume 63, No. 1 : 2006
RESULTS The device was tested in unprepared pig colons in 15 animals. The colons were cleared in a few minutes (a median of 12 minutes, range 9-20 minutes), by advancing the catheter under colonoscopic vision into concretions, which were rapidly broken down. It required a mean of 6 insertions (range 2-10) of the colonoscope into the colon, with subsequent washing when using the colon cleaning device to clear the unprepared pig colon to 120 cm, measured once redundant loops had been straightened. All animals had a rectum filled with feces that caused a dark colonoscopic image once the anus was crossed. The stool content was assessed as soft in 8, fibrous but firm in 12, and constipated in 4. The stool appeared to form a continuous column in all but one of the animals, which only had a few lumps of stool to clear. Filling the colon with water was observed to induce a propulsive contraction, which tended to push feces www.giejournal.org
Fritscher-Ravens et al
toward the anus. Gentle abdominal pressure sometimes helped evacuation. The retrograde direction of the water jet tended to break up stool ahead of the endoscope under direct vision and to propel the material coaxial to the endoscope, which allowed the colonoscope to image the way ahead. The water jet spray sometimes reduced the quality of the endoscopic image for a few seconds. The colonoscope channels did not become blocked in the course of the cleaning studies. Visual analog scores assessed the quality of the preparation as a median of 9/10 (range 7-10). Most of the preparations were totally atraumatic. It was possible to identify red streaks on the mucosa in the first 2/15 preparations when pulling or pushing a metal catheter tip across the mucosal surface with an early prototype catheter. This trauma was reduced by designing a softer tip for the catheter, which was used in subsequent studies. The washing process itself was not observed to produce visible trauma or to raise blebs or to cause submucosal edema. One pig had self-limited diarrhea for 12 hours after the procedure. All other pigs were well after the examination, and, in particular, there were no perforations, delayed bleeding, or deaths. The mucosa of the colon was always normal at repeat examination at 7 of 14 days after colon cleaning.
DISCUSSION A simple method for cleaning the colon is presented. It was used in pig studies and allowed successful colonoscopy. The pig colon is nearly twice as long as the human colon and includes a spiral loop that is fixed in a fibrous sheath. We found that the progress of conventional colonoscopes was limited by the tightening spiral at 120 cm. It was possible to clean a few centimeters beyond this distance by advancing the catheter beyond the colonoscope. It seems unlikely that differences between pig and human colonic anatomy should influence cleaning efficacy and safety. Further studies are needed to demonstrate the usefulness of this technique during colonoscopy in patients with poor preparation. Washing and flushing devices have been used to clear blood, especially in the upper-GI tract,7 but have been little studied for bowel cleaning during colonoscopy. Per-anal catheters have been used to assist bowel preparation.8 Possible limitations to this method might include mucosal trauma, bleeding, perforation, clogging of the colonoscope channels, and electrolyte imbalance. Randomized, blinded studies may yield lower scores assessing efficacy of colon cleaning.
www.giejournal.org
Colon cleaning during colonoscopy
This newly developed cleaning procedure may offer some advantages to current practice. It could be used selectively in the endoscopy unit during colonoscopy and might reduce the number of procedures that require to be repeated because the preparation is poor. It is not likely to prolong the procedure by more than a few minutes. Patient compliance and normal colonic motility is not needed, and the cleaning procedure itself is not difficult to do. DISCLOSURE This study also was supported by an educational grant from Ethicon Endosurgery, Cincinnati, Ohio, USA. A provisional patent application has been filed by the authors.
REFERENCES 1. Neidich RL, Zuckermann GR. Patient preparation. In: Raskin JB, Nord HJ, editors. Colonoscopy: principles and techniques. New York: Igaku Shoin; 1995. p. 53-83. 2. DiPalma J. Preparation for colonoscopy. In: Waye JD, Rex DK, Williams CB, editors. Colonoscopy: principles and practice. Oxford: Blackwell; 2003. p. 210-20. 3. Toledo TK, DiPalma JA. Review article: colon cleansing preparation for gastrointestinal procedures. Aliment Pharmacol Ther 2001;15:605-11. 4. Rex DK, Imperiale TF, Latinovich DR, Bratcher LL. Impact of bowel preparation efficiency and cost of colonoscopy. Am J Gastroenterol 2002;97: 1696-700. 5. ASGE technology status evaluation report. Colonoscopy preparations. Gastrointest Endosc 2001;54:829-32. 6. Leaper M, Johnston MJ, Barclay M, Dobbs BR, Frizelle FA. Reasons for failure to diagnose colorectal carcinoma at colonoscopy. Endoscopy 2004;36:499-503. 7. Laine L, Stein C, Sharma V. A prospective outcome study of patients with clot in an ulcer and the effect of irrigation. Gastrointest Endosc 1996;43:107-10. 8. Chang KJ, Erickson RA, Schandler S, Coye T, Moody C. Per-rectal pulsed irrigation versus per-oral colonic lavage for colonoscopy preparation: a randomized controlled trial. Gastrointest Endosc 1991;37:444-8.
Received March 2, 2005. Accepted May 12, 2005. Current affiliations: Department of Endoscopy, St Mary’s Hospital; Department of Medical Physics, University College, London, United Kingdom. This work was presented, in part, during Digestive Diseases Week, May 15-20, 2004, New Orleans, Louisiana (Gastrointest Endosc 2004;59:AB126). K. Ikeda received a research grant to study abroad from Jikei University, Tokyo, Japan. Reprint requests: Paul Swain, MD, Department of Surgical Oncology and Technology, St Mary’s Hospital, 41 Willow Rd, London NW3 1TN, UK.
Volume 63, No. 1 : 2006 GASTROINTESTINAL ENDOSCOPY 143