The use of sterile water at colonoscopy—is it money down the drain?

At a time of protracted economic difficulty, hospital trusts are being forced to focus on cost saving measures across the network. This has involved reduction in bed numbers, job cuts, and a restriction on finite resources. With financial constraints ever present in a clinician’s mind, we consider the use of sterile water at colonoscopy and whether this is a necessary expenditure or an unnecessary luxury we can ill afford.

In our NHS trust, there were 2424 colonoscopies performed during the year 2010-11. Each of these procedures used sterile water to irrigate the colonoscope and clean the lens for a clear view. Sterile water bottles are 53 pence per litre, and one litre is used for approximately five patients. Therefore, our unit used approximately 485 bottles per year for colonoscopy alone, at a cost of £257 (€328; $424) per annum. This can be extrapolated for the number of other endoscopic procedures that also use this resource.

There are currently 513 Joint Advisory Group (JAG)-accredited units performing endoscopic procedures nationwide. If our unit was deemed representative in numbers of colonoscopies performed, then the cost saving to the NHS would be £131 841 per annum by switching to tap water for colonoscopies alone, and higher still if all endoscopic procedures were included.

The sterile water currently used is not deionised, and thus there are no concerns regarding damaging the colonoscopes. The primary concern when this cost cutting measure was initially considered was the infection risk it may pose. Two studies have previously addressed this issue. In 1996,1 the prevalence of water bottle contamination was compared between sterile water and tap water. It was concluded that bacterial growth was infrequent and yielded no increased clinical complications, as most commonly non-pathogenic organisms were found. These findings were reiterated in 1997.2

Given the cost savings we could be making, this leads us to ask, if it is good enough for the nation to drink, can’t we also use tap water when examining their colons?