Sunday, January 27, 2013

Bad Colon Prep Can Be Hazardous To Your Heath

Exploding bowels!
This sounds like a topic more suited to the Weekly World News than an evidence-based blog on inflammatory bowel disease, but unfortunately it is a real phenomenon.  From 1952 to 2006, twenty cases of intestines exploding during GI exams occurred.  As you can well imagine, having your intestines go nuclear and breach the barrier of the abdomen creates an immediate, life-threatening emergency.  While not common, it does highlight the need for good colon preparation before the frequent colonoscopy/sigmoidoscopy sessions needed by those with Crohn's disease and Ulcerative Colitis. (1)

How exactly does the bowel explode?  There are three items necessary for a bowel explosion.  Remove any one of the three, and things can’t go boom:
·         Fuel.  In this case, the explosive is either methane or hydrogen gas.  Both are produced naturally as byproducts of bacteria in the intestine (or archea, for those tri-domain pedants out there).  In the normal, unevacuated bowel, they can reach concentrations of 40% or higher.  If a proper preparation is performed, they should be present in only minimal amounts.  It only takes a 5% concentration of methane or 4% of hydrogen to reach the critical point for explosion.
·         An oxidizer.  Things don’t burn without oxygen, which means good old O2 is necessary for explosions as well.  The atmosphere has approximately 21% oxygen, and only 5% or so is needed to cause the methane/hydrogen to go boom.*
·         An ignition source.  Generally, this is either an electrical spark or a heat source.  Electricity (or the capacity for a spark) is present through any electronics associate with the scope.  The heat source comes from the cauterization tip used in cauterization after polyp removal or biopsy.

In general, the third factor is outside the control of both the doctor and the patient.  The other two factors are well within their control, though.  First is preparation.  During a colon prep, the patient needs to fully evacuate their bowels – lowering the gas content of the bowels to subcritical levels (and making it viable to visualize the colon walls).  In the 1980s, substances like mannitol and sorbitol were used as more tolerable bowel preparation tools (these, along with xylitol, are sugar alcohols now most likely to be found in chewing gum).  They worked by drawing water into the colon, but had the side effect of fermenting into less favorable gaseous byproducts.  As such, they are no longer used.(2)

Current bowel preps don’t have the issue of generating dangerous gas byproducts – as long as they are followed!  Approximately 22% of colonoscopies find inadequate preparation.  Of these, 18% of patients reported they did not follow preparation protocols (because this is self-reporting, the actual number is likely a bit higher).  While the preparation isn’t fun, it is an easy way to ensure you don’t go out with a bang.  The added benefits include shorter colonoscopy times and better imaging results.  As with the sorbitol and mannitol above, patients should follow their doctor’s instructions as to what they can mix and not mix with their prep – mixing drinks with the wrong artificial sweetener can cause the unwanted fermentation.  (3)

The other factor is the presence of oxygen.  While this is not up to the patient, the doctor can take certain precautions.  First, performing appropriate suction during the procedure will reduce the presence of unwanted gases and solids.  Second, insufflation (blowing air into the intestines) can be done using CO2 instead of air (remember the 21% O2 concentration noted above).  CO2 is inert and has the side benefit of reducing bloating and discomfort during and after the procedure.(4)

Bottom Line

·         Follow colonoscopy preparation guidelines carefully.  If you can’t complete the prep, be honest with your doctor.  Though very rare, bad complications can occur.
·         Doctors should consider CO2 insufflation where available instead of air insufflation.

* Technically, many explosives have bound oxygen as part of their chemical makeup, so gaseous O2 isn’t really needed.  As for nuclear reactions – don’t even go there.  This is a blog on medicine, and if there is a fusion and/or fission reaction as a result of your colonoscopy, you have bigger problems than bowel prep.
1.       Spiros D Ladas, George Karamanolis, Emmanuel Ben-Soussan.  Colonic gas explosion during therapeutic colonoscopy with electrocautery.  World Journal of Gastroenterology.  2007.
2.       A Avgerinos, N Kalantzis, G Rekoumis, G Pallikaris, G Arapakis, and T Kanaghinis.  Bowel preparation and the risk of explosion during colonoscopic polypectomy.  Gut. 1984.
3.       Reid M Ness MD, MPH, Raj Manam B, Helena Hoen M and Naga Chalasani MD.  Predictors of inadequate bowel preparation for colonoscopy.  American Journal of Gastroenterology. 2001.
4.       Wu J, Hu B. The role of carbon dioxide insufflation in colonoscopy: a systematic review and meta-analysis.  Endoscopy.  2012.

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