Practical Gastrointestinal Endoscopy

COLONOSCOPY AND FLEXIBLE SIGMOIDOSCOPY 121
to suction off excess air until the colon outline starts to wrinkle
and collapse, making it shorter and also easier to manipulate. In
contrast, after having evacuated fluid from the rectum, only aspirate
fluid during the rest of the insertion phase when absolutely
necessary to keep a view, and only do so when there is enough
air present and a good enough view to suction accurately (sucking
blind when already immersed is usually rather ineffectual).
During insertion there will be numerous local ‘sumps’ or pools
of residual fluid; aspirating each one wastes a lot of time, loses
the view and requires reinflation. It is usually possible to inflate
a little and steer in over the fluid level rather than plunging into it
and having to suction. Even solid stool can often be successfully
passed, deliberately angling the tip to slide along the mucosa for
a few centimeters rather than impacting against a bolus, which
can coat the lens irrevocably. Any residue can easily be suctioned
or removed from view by changes of patient position on the way
back when a perfect view is important.
•–Insufflate as little as possible. A distended colon is less manageable
and more uncomfortable. Gentle insufflation is needed
throughout the examination to keep a view. However, the policy
is ‘as much as necessary, as little as possible’; it is essential to see,
but counterproductive to overinflate. Remember that bubbles are
caused by insufflating under water (Fig. 6.14), which can usually
be avoided by the simple means of angling above it. If fluid
preparation and bile salts do result in excessive bubbles, these
can be dispersed instantly by injecting an antifoam preparation
solution containing particulate silicone down the instrument
channel.
•–Use all visual clues. A perfect view is not needed for progress;
but the correct direction or axis of the colonic lumen should be
ascertained before pushing in. The lumen when deflated or in
spasm is at the center of converging folds (Fig. 6.29). With only a
partial or close-up view of the mucosal surface, there are usually
sufficient clues to detect the luminal direction. Aim toward the
darkest (worst illuminated) area because it is furthest from the
instrument and nearest the lumen (Fig. 6.30). The convex arcs
formed by visible wrinkling of the circular muscles, or the haustral
folds or the highlights reflected from the mucosa over them,
indicate the center of the arc as the correct direction in which to
angle (Fig. 6.31). The slight bulge of the underlying longitudinal
muscle bundles (teniae coli) is another, occasionally useful, clue.
The expert can make his steering decisions on evidence that
would be inadequate for the beginner. On the other hand, each
time the expert is ‘lost’ for more than 5–10 seconds he pulls back
quickly to regain the view and reorientate, whereas the beginner
can flounder around blindly for a minute or more in each
difficult spot and is surprised that the overall examination takes
so long.
Fig. 6.29–Aim at the convergence
of folds.
Fig. 6.30–Aim at the darkest
area.