Learning and teaching the water method (with videos)

Abstract

The water method is an insertion technique for colonoscopy which has recently become popular owing to its demonstrated ability to decrease patient pain and sedation requirements. This review focuses on learning and teaching the water method. Data from the United States and Asia suggests that trainees at all levels of experience can safely learn and utilize the water method. Demonstrated benefits in some of the reviewed studies include lessened sedation requirements, less pain for patients and increased cecal intubation rates in minimally sedated patients. These benefits are realized without compromising safety, adenoma detection rates, or procedure times.

Data reported by investigators at Veterans Affairs facilities in the US indicate the water method (water infusion in lieu of air insufflation, suction removal of all residual air and water exchange to clear the luminal view)¹ to aid insertion of the colonoscope has the following significant effects: (1) Cecal intubation can be achieved in fully sedated veterans and in veterans given ½ usual dose of sedation medication²; (2) When veterans accepted sedation on demand 52%³ to 78%⁴ could complete colonoscopy without any sedation; (3) Increases cecal intubation rate from 76% (air method)^5,6 to 96%⁵ and 98% (water method)⁶ in veterans undergoing scheduled unsedated colonoscopy.

This presentation will be focused on learning and teaching the water method, specifically about application of the water method in training colonoscopists. There are benefits at all levels of training. The examination is less painful for the patient.^7–9 The cecal intubation rate can be higher. If less experienced fellows are participants like we did in our study at the Palo Alto VA and the protocol does not call for sedating the patient deeper and deeper as the loops build up, then a difference in cecal intubation rate can be observed with the water method being better.⁸ But if very experienced trainees who are already reaching the cecum 95% of the time with air or water are involved then a difference may not be observed.⁹ In some studies, the water method is also faster for trainees.⁸ From a supervisor's point of view if the trainee is unsuccessful a patient with a colon that has some water in it is less challenging than a very distended air-filled patient when it is necessary for the supervisor to complete the procedure.

For teaching and learning the water method the trainer and the trainee need a bit of patience. With air the colonoscopist pushes the button, the lumen quickly expands widely and the scope can be advanced. With water, the water comes out more slowly, the whole lumen need not be full- just enough to clearly see where to go. In fact, the optimal technique¹ is to turn off the air button to avoid accidental air insufflation during insertion, infuse only as much water as is necessary to visualize the path forward, and also to suction any air pockets that are encountered. The next issue is recognition. It's important to recognize diverticula, colonic anastomoses and the appendiceal orifice underwater. Finally, a good bowel preparation is needed. Although the water method does result in cleansing of the colon from small amounts of residue, it cannot replace the bowel preparation. As the focus on adenoma detection rates (ADR) and missed lesions is here to stay, we're all recognizing that we really can't get the job done properly with stool-filled colons and poor bowel preparations. When the water method works really well, you don't even notice how far you've come until you see the appendiceal orifice under water (Video 1). Video 2 shows a patient with an anastomosis. This can be a bit of a scary sight if you're supervising a trainee and perhaps a full history wasn't obtained and they reach a point where there's no obvious place to advance. Hopefully they're not tempted to think the lumen is way up at 12 o'clock where you can't quite see it and try to push! Anyway, this is an issue with both water and air- you need to see where you're going, and it is important to recognize when you've reached the end- whether it's the site of the appendiceal orifice underwater (Video 1), the blind end of an end-to-side anastomosis (Video 2), or the ileum in a patient who has undergone a partial colectomy. Video 3 shows some examples of diverticula. Remember that water immersion was originally described many years ago as a way to advance through severe diverticulosis. And that's true, it's quite good in these patients- but of course you do need to be very careful. And finally, here is an example of suctioning air pockets and suctioning dirty water while simultaneously infusing more water via the water jet to get a nice clean lumen (Video 4).

We performed a study comparing water method to standard air in a randomized study of colonoscopy with minimal sedation at the Palo Alto VA.⁸ The focus of this review is on the results for the subset of patients that had a procedure done by a fellow in training. We only enrolled male patients. Everyone got 2 mg midazolam IV before the procedure. They were then randomized to water vs. air. During the procedure, the nurse administering sedation monitored the patient and if their pain level was 4 or higher for 10 seconds or longer then more sedation was given and the procedure was considered unsuccessful based on intent-to-treat analysis. Also, when the procedure was being done by a trainee, if they couldn't reach the cecum then again the procedure was considered unsuccessful.

What we found was that for trainees the success rate in reaching the cecum without needing to give more sedation beyond the initial 2 mg of midazolam was about twice as high in the water group as in the air group. They also reached the cecum faster with water and even with all the water that they suctioned on the way out the overall procedure time was shorter with water. So the water method was very useful in this setting, for fellows doing colonoscopy with minimal sedation. And this fits with our clinical impression observing them and we can speculate on the exact mechanism whether it's by preventing the trainees from overinflating the patients with air, or because the water tends to straighten out the sharp turns in the colon, or some lubricating effect of the fluid, or a combination of factors.¹⁰ It's clear that the trainees are doing well with water, and that the patient is having less pain and requiring less sedation. In addition, there were no complications and for trainees there was a trend towards higher ADR with water.

Colleagues at the Sacramento VA reported a comparable study.⁹ The fellows were very experienced, in their 2^nd and 3^rd year of training with over 400 prior colonoscopies each. There were 62 patients, nearly all men with a mean age of 61. This was a randomized study comparing the water method with standard air insufflation. All of the patients received 50 mg diphenhydramine (benadryl), 1 mg midazolam and 25 µg fentanyl before starting the procedure. The idea was that the sedation nurse would keep track of the patients, assess their pain, and give additional sedation on demand to keep them comfortable. The additional medicine would be given in incremental units, alternating fentanyl and midazolam, and the question was whether the water method was in fact less painful, whether the water group would end up requesting less medication.

And this was in fact true- the water group did end up with less medication. Fewer incremental doses of fentanyl and midazolam were needed for the water group, 2.5 vs. 3.4, where each increment is either 25 µg fentanyl or 1 mg midazolam, which were alternated. As far as pain levels, there was a difference in the ascending colon, less pain in the water group, 3.1 vs. 4.8, but in the cecum there was no difference in pain levels between the two groups. At the time of discharge, patients in the water group had a bit less pain, 0.4, compared to 1.1 for the air group. It's always difficult in these studies when you're looking at pain while giving variable doses of sedation, because if you sedate well, then you won't have much difference in the pain level between the groups, but if you don't sedate well then you'll see a difference in the pain but maybe not in the sedative dose. So it's hard to achieve dramatically less pain and less sedation in one group- but here again you do see both an element of less sedation and an element of less pain and this is a sign that the water method is beneficial.

The other measured variables in this study include cecal intubation rate, time to cecum, total colonoscopy time and adenoma detection rate. They are all excellent in both the water and air groups. These are clearly very proficient fellows, with a cecal intubation rate in the mid 90%, and short times to the cecum and total colonoscopy times. Similar findings were observed at the Palo Alto VA when we compared attendings to fellows. There are certain trends that are much more dramatic in less experienced operators. So it's hard to demonstrate a higher cecal intubation rate for experienced staff when they're getting there basically almost 100% of the time and the occasional failure requires a double balloon scope or anesthesia. With relatively inexperienced fellows participating in the Palo Alto VA study, water helps them both get to the cecum and get there faster. In contrast, with experienced fellows like the ones that participated in the Sacramento VA study (over 400 prior colonoscopies each), they're getting to the cecum very quickly and effectively with air or water. As far as the ADR, the Sacramento VA ADR for trainees was the same with water or air.

One Japanese experience¹¹ describes quite a different operation. They had 6 trainees who had experience only in EGD. There was no control group in this study. A cap is placed on the end of the scope in this institution; it can improve visualization. The patients were “unsedated”, although they did get spasmolytics. The trainee was allowed up to 10 min to reach the cecum (unless the patient experienced significant pain). The trainee was given one chance per week, with one patient, to learn colonoscopy and the results they had was that on average a trainee was able to reach the cecum on week #3.3. The weakness of these types of studies is that there's no control group. The trainees had no prior colonoscopy experience, but we don't really know how experienced they were in doing EGDs, and this measure of how many cases it takes to reach the cecum for the first time is not a commonly used measure.

The next study to be discussed is also from Japan.¹² This was a randomized trial of water vs. air. This was actually a precursor to the water method that we commonly used now where they gave the water group patients water enemas up to 1000 cc or as much as the patient could tolerate if they couldn't reach the full 1000 cc. The trainees then proceeded with unsedated colonoscopy. For the water group, water was suctioned while inserting the scope. In this study the trainees, who had less than 200 prior colonoscopies on their resumes, were actually very successful in both groups (95% vs. 96%), but the cecum was reached faster in the water group (11 vs. 16 min) and fewer patients complained of pain in the water group (17% vs. 33%). The common theme here is less pain. In some populations and study designs, particularly unsedated protocols^5,6 or minimally sedated protocols⁸, less pain often gives higher cecum intubation rates and in others like this study¹² we see less pain but the success rate is nearly 100% in both air and water.

The last study involving trainees to be discussed is from Korea.¹³ They had a water group, an air group, and a third group where they infused oil to lubricate the colon. Oil has been tried in several studies, but results haven't been as reproducible as with water. In this case the oil was actually not successful on any of the parameters they measured, so this oil group will not be mentioned any further. For the water group what they did was infuse 200 cc of warm (body temperature) water when the scope reached the rectosigmoid and then proceeded with the rest of the colonoscopy. The air group was done conventionally. The trainees were alotted 15 min to reach the cecum, and they were quite successful in both water and air (95% and 90%; the study wasn't powered for such a small difference however). There was also a trend towards a faster time to cecum in the water group (494 vs. 425 seconds, but the p value was only 0.2). The pain levels were essentially the same (1.3 vs. 1.2). This is a relatively disappointing result in that they were not able to conclusively demonstrate superiority of water over air (they did demonstrate inferiority of the oil method, but that's not so interesting). We could argue about some of the details such as putting in such a small amount (200 cc) of water, so perhaps the results would have been better with a more rigorous application of the water method. Also, the statistics could have perhaps worked out better with a larger sample size. But even in the hands of Korean trainees we can be encouraged that there are some trends that favor water, so even in the least favorable study out of all the trainee studies there is non-inferiority along with some indications that the water may give some benefit during insertion.

A colonoscopist experienced in the air method can undertake self-training in learning the water method with results confirmatory of the beneficial effects of the water method in published literature.¹⁴

So what can we say in summarizing all of this data? There are multiple studies involving trainees from the US and from Asia. The protocols are very different, and there are some differences in results, but all of the studies suggest that there is something with the water method in terms of lessening pain and/or sedation requirements for the patient. We can also conclude that trainees at all levels of training do well with water, that it can be done safely, that it doesn't compromise other aspects of the procedure such as adenoma detection, that in many situations it can actually speed up the procedure. It is also important to note that the water technique has undergone some refinements through these multiple studies and some of the best results have been achieved with strict avoidance of air insufflation and suctioning of all air pockets during insertion,

We can conclude that (1) The water method is useful for trainee education; (2) The method is straightforward to teach, even to trainees who have little or no colonoscopy experience; (3) It improves the procedure and can help trainees reach the cecum while minimizing pain for the patient; and (4) For the supervising physician, in those cases where the trainee cannot reach the cecum, it's really very nice not to inherit a patient who is massively distended with 20 minutes worth of air insufflation from the attempted colonoscopy because that can turn a routine colonoscopy into a real challenge.

Abbreviations

ADR

adenoma detection rates