Adenoma detection rate – is it all about adding water?

Detecting adenomatous polyps is the main task of screening colonoscopy. The discovery of the adenoma – carcinoma sequence some decades ago marked the basis for current endoscopic prevention strategies. Since the establishment of screening colonoscopy programs in many countries, both the incidence and the mortality derived from colorectal cancer have declined [1] [2]; the latter fact suggests effectiveness of this preventive approach.

“It will be interesting to see whether water exchange colonoscopy will gain importance in future clinical practice.”

Against this background, the adenoma detection rate (ADR) has become one of the most important quality measures in diagnostic colonoscopy [3]. Recently, new quality guidelines have been published by the European Society of Gastrointestinal Endoscopy, which recommend that endoscopists achieve a 25 % ADR in screening colonoscopies [4].

The use of water instead of air insufflation was first published in 1984 as a coping strategy for difficult sigmoid circumstances due to diverticulosis [5]. In principle, the method is based on the injection of water during the insertion phase of colonoscopy in order to distend the colonic wall. In 2002, Church published a study on the use of heated water (to body temperature), which was injected via the accessory channel of the colonoscope [6]. The objective was to show that water injection was capable of reducing spasms of the colonic wall [6]. Since then, a number of trials have been published in this field.

It is important to identify the exact nature of the procedure “using water” for insertion because this differs widely among clinical trials. Water infusion in some cases was restricted to a specific location, for example, the sigmoid colon, where water was injected to overcome difficulties in advancing the scope. Other trials used water injection only as “an adjunct” to air insufflation, thus generating rather “hybrid procedures” and making a clear distinction difficult [7]. Over recent years “water injection colonoscopy” has emerged as a method that exclusively uses water for distention of the colonic wall during insertion [7]. The majority of trials investigating this approach have shown beneficial effects derived from the “water method.” One major point in this context is the reduction of pain and discomfort during the insertion phase [8] [9]. The latter fact might also explain why, in an on-demand sedation setting, patients undergoing water colonoscopy rarely required sedatives compared with patients undergoing common air insufflation procedures [8] [9].

Within the past decade, a considerable amount of data has reported higher ADRs in water colonoscopy procedures compared with traditional air insufflation practice. However, the respective data often resulted from secondary outcome analyses, as the majority of trials focused on reducing pain and/or sedative use. In addition, owing to data inconsistencies in some trials, it has been difficult to specify which intervention played the decisive role in this aspect. As mentioned above, a number of practical approaches have been used in clinical trials, all of them being summarized under the term of “water injection colonoscopy.” It has to be pointed out that different methods have been used to remove the water after injection. The so-called water immersion method involves water being removed by suction during withdrawal of the endoscope. In contrast, in the water exchange colonoscopy method, the water is immediately removed by suction to prevent any fecal remnants from obscuring the endoscopic view. The latter procedure naturally leads to an enhanced cleansing effect of the mucosa during insertion. Until now, comparative studies have been unable to distinguish between the effects of different water injection and removal methods on adenoma detection in the colon. This uncertainty of the value of the different approaches might have resulted in a relatively low usage of water colonoscopy in European countries.

In the current issue of Endoscopy, Cadoni et al. present a randomized trial comparing air insufflation, water immersion, and water exchange colonoscopy in a large screening cohort of patients being admitted for colonoscopy following a positive fecal occult blood tests [10]. The major strength of this study was the blinding procedure, which enabled patients as well as the participating colonoscopists to be unaware of the insertion method used. After reaching the cecum, withdrawal was performed by a different endoscopist who was blinded to the respective method used in the first part of the investigation. The risk of biased results due to an unblinded endoscopist advancing the scope using either water injection or air insufflation and investigating the colon afterwards was therefore eliminated. The present study allows reliable conclusions to be drawn about how water injection should be used in terms of enhancing the detection of adenomas. Water exchange was superior to air insufflation in terms of ADR, but water immersion colonoscopy was not. As mentioned above, the water exchange method naturally enhances cleanliness of the colon mucosa by injecting and suctioning water repeatedly. Thus, it is not surprising that significant differences were obtained between the three study groups regarding colon cleanliness. In particular, the best cleanliness scores were obtained in patients receiving water exchange colonoscopy procedures.

The effect of bowel cleansing on successful adenoma detection is well known from many clinical trials. In line with this knowledge, most practical guidelines recommend adequate colon cleansing as a prerequisite for the conduction of high quality colonoscopy procedures [11] [12]. The cleansing effect might be of even greater importance in light of technical developments that have resulted in brilliant video pictures. New technologies enable us to become increasingly capable of detecting minimal alterations of the mucosa, provided that even small fecal remnants have been removed. The results from the Cadoni study presented here might therefore raise the question of whether successful adenoma detection in the main could be improved simply by adding water. However, the results also show that choosing the correct method of adding water is crucial in terms of outcome.

The Cadoni study therefore adds useful information to current clinical knowledge regarding the detection of neoplastic lesions of the colorectum. Until now, water exchange colonoscopy has not been used routinely in Europe. Using water during insertion is time-consuming compared with the air insufflation method. Another reason for a limited usage might be that the technique requires a flushing pump, which might not be available in every endoscopy unit, especially in the outpatient sector. However, as successful adenoma detection represents an important quality criterion in screening colonoscopy, approaches that increase ADR should be welcomed. Therefore, it will be interesting to see whether water exchange colonoscopy will gain importance in future clinical practice.

• References

• 1 Ryerson AB, Eheman CR, Altekruse SF. et al. Annual Report to the Nation on the Status of Cancer, 1975–2012, featuring the increasing incidence of liver cancer. Cancer 2016; 122: 1312-1337
• 2 Brenner H, Schrotz-King P, Holleczek B. et al. Declining bowel cancer incidence and mortality in Germany. Dtsch Arztebl Int 2016; 113: 101-106
• 3 Rex DK, Schoenfeld PS, Cohen J. et al. Quality indicators for colonoscopy. Gastrointest Endosc 2015; 81: 31-53
• 4 Kaminski MF, Thomas-Gibson S, Bugaiski M. et al. Performance measures for lower gastrointestinal endoscopy: a European Society of Gastrointestinal Endoscopy (ESGE) Quality Improvement Initiative. Endoscopy 2017; 49 DOI: 10.1055/s-0043-103411.
• 5 Falchuk ZM, Griffin PH. A technique to facilitate colonoscopy in areas of severe diverticular disease. N Engl J Med 1984; 310: 598
• 6 Church JM. Warm water irrigation for dealing with spasm during colonoscopy: simple, inexpensive, and effective. Gastrointest Endosc 2002; 56: 672-674
• 7 Hafner S, Zolk K, Radaelli F. et al. Water infusion versus air insufflation for colonoscopy. Cochrane Database Syst Rev 26.05.2015; 5: CD009863
• 8 Cadoni S, Gallittu P, Sanna S. et al. A two-center randomized controlled trial of water-aided colonoscopy versus air insufflation colonoscopy. Endoscopy 2014; 46: 212-218
• 9 Pohl J, Messer I, Behrens A. et al. Water infusion for cecal intubation increases patient tolerance, but does not improve intubation of unsedated colonoscopies. Clin Gastroenterol Hepatol 2011; 9: 1039-1043 .e1
• 10 Cadoni S, Falt P, Rondonotti E. et al. Water exchange for screening colonoscopy increases adenoma detection rate: a multicenter, double-blinded, randomized controlled trial. Endoscopy 2017; 49: 456-467
• 11 Hassan C, Bretthauer M, Kaminski MF. et al. European Society of Gastrointestinal Endoscopy (ESGE) guideline. Endoscopy 2013; 45: 142-150
• 12 Johnson DA, Barkun AN, Cohen LB. et al. Optimizing adequacy of bowel cleansing for colonoscopy: recommendations from the U.S. multi-society task force on colorectal cancer. Gastrointest Endosc 2014; 80: 543-562