The water method of colonoscopy: Few risks, many rewards
Colonoscopy is traditionally performed using air insufflation to open the lumen and advance the colonoscope into the cecum. But certain factors make cecal intubation more challenging, including diverticulosis, angulations at the splenic and hepatic flexures, and areas of fixation due to prior abdominal or pelvic surgery. Air insufflation compounds the difficulty by lengthening the colon and exaggerating angulations. It also increases distension, leading to more pain and increased sedation.
Francisco C. Ramirez, M.D., of Mayo Clinic in Arizona, says water immersion — using water instead of air to distend the colon during insertion — helps overcome these problems. It also reduces pain and can significantly increase cecal intubation and adenoma detection rates (ADRs).
"Water distends the lumen and facilitates advancement of the scope, even in segments with substantial diverticulosis," he explains. "Water also has a sinking effect, weighing down the left colon and straightening the sigmoid segment. By keeping the colon minimally distended with air, water reduces angulation at the flexures."
More comfort, less sedation
The water method of colonoscopy was originally adopted to minimize discomfort in patients receiving little or no sedation.
"Using water instead of air significantly decreases the need for sedation drugs, external pressure or position change and increases the completion rate in patients with prior difficult colonoscopies," Dr. Ramirez says.
It also allows patients to recover faster, increases the efficiency of the endoscopy lab and greatly improves a patient's experience.
"When patients aren't heavily sedated, they become engaged in watching the screen and actually find the procedure fascinating," Dr. Ramirez says. "They enjoy participating in the process. I always ask if they are having too much discomfort, and I'm always surprised at how positively they respond to the experience."
Dr. Ramirez admits he was a reluctant convert to water colonoscopy. But after witnessing significant improvements in patient comfort and adenoma detection, it is now the insertion technique he uses most. As to why the method has not been more widely adopted, he suggests that colonoscopists accustomed to air insufflation may consider water immersion too complex or time-consuming to learn.
To better understand the learning phase of the water method and its effect on procedural outcomes, Dr. Ramirez examined four consecutive groups of 25 patients using water immersion only. Outcomes were compared to a historical cohort examined using air insufflation.
Results showed that the intent-to-treat (ITT) cecal intubation rate increased from 76 percent in the first quartile to 96 percent in the fourth. Cecal intubation time in the first two quartiles was considerably longer than in the historical cohort but comparable in the second two quartiles. Overall adenoma detection rates were higher for the water group than for the historical cohort — 55 and 46 percent respectively, echoing a number of other studies that have found a similar improvement in the ADR.
Dr. Ramirez stresses that the water method is easily learned by an experienced colonoscopist — he attained proficiency after 50 procedures — and recommends training the next generation of specialists in it from the beginning.
Pitfalls and solutions
The major challenge in using the water method is recognizing when the tip of the scope has reached the cecum. Finding landmarks such as the appendix and ileocecal valve can be more difficult when the colon is underwater, Dr. Ramirez says, but suction marks on the cecal wall and distance traveled in centimeters can help confirm cecal intubation.
Another problem, premature air insufflation, usually disappears with experience. The tendency to overload the colon with water, causing distension and discomfort, also can be controlled, especially when using a novel hybrid approach called water exchange.
Unlike water immersion, in which the infused water is mainly removed during the withdrawal phase, water exchange allows for the infusion of clean water and the simultaneous suction of dirty water during insertion.
Dr. Ramirez notes, "The constant exchange of dirty water for fresh water cleanses the mucosa, making it easier to find small lesions, especially in people with suboptimal bowel preparation."
Water makes economic sense
Between 2003 and 2009, the use of general anesthesia for gastroenterological procedures, including colonoscopy, more than doubled. During the same period, payments for anesthesia doubled for Medicare patients and quadrupled for those with private insurance. This led some insurers to propose restricting coverage of anesthesiology for certain GI procedures.
Although such measures have not been implemented, the drive to trim costly and unnecessary procedures will only increase. Because the water method reduces or eliminates the need for sedation and extra staff, it is a cost-effective approach to both screening and surveillance colonoscopy.
Dr. Ramirez points out that water exchange requires a slightly longer intubation time — about one-and-a-half minutes longer than air — but he says, "The beauty is that the patient is much more comfortable, requires less sedation and is more likely to complete with no sedation. As important, we can perhaps find more polyps — the final goal of colonoscopy."