Does Inspection During Insertion Improve Adenoma Yields During Colonoscopy?
Background: Colonoscopy is not a perfect test. It misses a substantial number of
neoplastic lesions and has some risk of missing cancer. Nearly all work on detection during
colonoscopy has focused on the withdrawal phase of the examination. Thus, colonoscopy is
typically performed by rapidly passing the instrument through the loops and bends of the
colon in order to reach the tip of the cecum, and then performing a slow withdrawal in which
the tip of the instrument is systematically deflected, and the mucosa is careful cleaned and
suctioned, to expose all of the colonic mucosa for viewing.
Many experienced colonoscopists recognize that small polyps seen incidentally but not
removed during insertion are sometimes quite difficult to find during withdrawal. The
reason for this observation is probably because the colon is in a very different anatomical
conformation during endoscope insertion and withdrawal. During insertion, the colon is in
its natural conformation in which the sigmoid and transverse colon has several sharp bends
or flexures, and the overall length has not yet been shortened. In this phase, the colon is
often significantly stretched because of the formation of loops and bends in the
colonoscope. This greatly affects the conformation of the colonic wall visualized proximal
to the instrument tip. During withdrawal, the colon is shortened and pleated over the
colonoscope, with successive regions of the colon being inspected as they slip off the end
of the instrument. Thus, segments of visualized colon are often much straighter during
withdrawal than during insertion. The insertion and withdrawal phases, therefore, expose
somewhat different sections of the mucosal surface to the colonoscope and inspection on
insertion and withdrawal are, quite possibly, complementary.
Aims: This randomized, controlled trial will compare the additional effect on the rate of
adenoma detection of mucosal inspection during colonoscope insertion, with inspection during
instrument withdrawal, in patients undergoing colonoscopy for colorectal cancer screening or
Study procedure: In this study, we plan to investigate whether a specified interval of
inspection during insertion can increase overall adenoma detection. We will conduct a
randomized controlled trial, in which patients will be randomized to have all of the
inspection performed during the withdrawal phase (as is usual care) versus having several
minutes of examination specifically devoted to inspection during insertion.
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Open Label, Primary Purpose: Diagnostic
Adenoma detection rate
Douglas K Rex, M.D.
Indiana University School of Medicine
United States: Institutional Review Board
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