Total underwater colonoscopy can surmount challenges with insertion, simplify endoscopic mucosal resection, and lessen pain and the need for sedation, according to a “Here and Now: Clinical Practice” article published in Clinical Gastroenterology and Hepatology.
At the same time, total underwater colonoscopy has not been shown to significantly affect adenoma miss rates, requires a longer insertion and overall procedure time, and cannot be performed without adequate bowel preparation, wrote Joseph C. Anderson, MD, of the Department of Veterans Affairs Medical Center in White River Junction, Vt., and the Geisel School of Medicine at Dartmouth, Hanover, N.H.
He noted that total underwater colonoscopy is not the same as water immersion or water exchange, both of which involve infusing water while inserting the colonoscope and then distending the colon with carbon dioxide to visualize the mucosa during withdrawal. During total underwater colonoscopy, insertion, examination, and resection all are carried out with the lumen filled with water. Air is suctioned out, and the air valve is kept off.
This approach can surmount problems with insertion stemming from either severe angulation (often of the sigmoid colon), or redundant colon (excessive looping) that does not respond to abdominal pressure, colonoscope stiffening, or a change in position, Dr. Anderson noted. He explained that, unlike air, water does not maximally distend the lumen and therefore does not exacerbate angulation. “When I am in the ascending colon and cannot reach the cecum, I turn off the air valve, aspirate all gas, infuse water, and complete the insertion underwater,” he said. “Another advantage of water in patients with angulated sigmoid colons is that its use could prevent [the] excessive use of air and potential barotrauma of the cecum, even when using carbon dioxide.”
The use of water can aid endoscopic mucosal resection (EMR) because polyps tend to float into view (including from hard-to-visualize areas, such as folds) and into the snare, he said. “Because water has a magnifying property, underwater EMR may allow for easier delineation of the polyp’s border, also facilitating complete removal.”
Nonetheless, it remains unclear whether the use of total underwater colonoscopy significantly affects adenoma detection rates. In a recent study, Dr. Anderson and his coinvestiators randomly assigned 121 patients to undergo either colonoscopy with carbon dioxide insufflation, followed by total underwater colonoscopy, or the same examinations in the reverse sequence (Anderson KC et al. Gastrointest Endosc. 2019;89:591-8). Adenoma miss rates were statistically similar between groups. Although water decreases green mucus and residual stool and suspends “unsuctionable” particles (e.g. seeds) into the cecal lumen, where colonoscopists can better see past them, water also increases the production of white mucus, which can be difficult to remove during withdrawal, Dr. Anderson said.
He cited meta-analyses in which colonoscopies performed with water, without sedation or with minimal sedation, were associated with less pain and a higher likelihood of performing a complete examination than when only air was used. “I find this [approach] particularly useful in older, thinner patients, especially women,” Dr. Anderson said. “In addition, in patients with multiple comorbidities, cecal intubation often can be achieved safely with minimal sedation.”
Dr. Anderson reported having no relevant conflicts of interest.
SOURCE: Anderson JC. Clin Gastroenterol Hepatol. 2020 Feb 25. doi: 10.1016/j.cgh.2020.02.042.