More adenomas seen with water insufflation

Water infusion during the insertion phase of colonoscopy improved overall and proximalcolon  adenoma detection rates by 11% over standard air insufflation in a prospective randomized trial involving 368 patients.

After controlling for age, body mass index, smoking, alcohol consumption, withdrawal time, and the quality of bowel preparation, researchers found 81 %higher odds of detecting an adenoma using the water-method group than in the air-method patients (odds ratio 1.81).

A prospective randomized trial in 82 veterans reported last year as a proof of principle of water insufflation in unsedated colonoscopy demonstrated improved patient comfort and cecal intubation with that method.

The use of water to aid colonoscope insertion avoids colon elongation, minimizes angulations, helps identify the lumen, and provides a clear view of the colon, explained the Veterans Affairs Greater Los Angeles Healthcare System in North Hills, California.

Water had been used before in colonoscopy, but the method proved cumbersome because multiple syringes were required to deliver the liquid. In the current study, doctors delivered room temperature water via pedal pump and a tube connected to the base of the colonoscope, with its air feature turned off. Roughly 100 cc of water were used of the bowel was fairly clean, and 1-1.5 liters if fairly dirty.

In the other group, air insufflation was performed as usual. Doctors used air during the withdrawal of colonoscopes from the patients in both groups. All procedures were performed using high-definition adult colonoscopes.

The overall adenoma detection rate was 46% among the patients that were treated with air insertion and 57% among patients treated with water, a significant difference (P= .04), according to the University of Arizona, Phoenix.

Patients in whom colonoscopy detected at least one proximal adenoma were more likely to be in the water than the air group (46% vs. 35% P= .03). This advantage held for adenomas less than 10 mm in size (42% vs. 31% P= .04) but not for those 10 mm or larger (9% vs. 10%).

The mean time to the cecum was longer during colonoscopy initiated with water than with air, but only by 1.6 minutes (6.9 minutes vs. 5.3 minutes, P < .0001).

Colonoscopy was accomplished in the water group with lower mean doses of fentanyl (68.8 mcg vs. 76.5 mcg, P = .0006) and midazolam (2 .8 mg vs. 3.1 mg, P = .0007), and fewer patients in the water group received additional sedation (17.5% vs. 27%, P = .03).

The use of external pressure was also lower with water vs. air (12% vs. 28% P < .0001).

Limitations of the study include a mostly male population (96%) and that a single endoscopist with a relatively high baseline adenoma detection rate (46%) performed the procedures.

Good and excellent bowel preparation was reported in 79% of the 191 air-method patients and in 84% of the 177 water-method patients. Cecal intubation rates were similar at 100% in the air group and 92% in the water group. One adverse event was reported in each group.

The next randomized trial should compare the use of water for insertion and carbon dioxide for withdrawal – with polypectomy allowed at physician discretion – vs. a traditional air technique. He speculated that the water-carbon dioxide method would reduce pain during and after colonoscopy, salvage the procedure in patients with suboptimal bowel prep, and perhaps increase adenoma detection.

As for how often American clinicians are using water during colonoscopies, it is estimated that only 10% of colonoscopists use water throughout a procedure.

Use of water has steadily increased and that hybrid technique incorporates large amounts of water during insertion, then switches to a combination of air and water when the colonoscope approaches the transverse and ascending colon.

Cautioned during his presentation, that switching from water to air during a procedure can simplify the identification of the lumen but leave behind dirty water that can impair the view during withdrawal.