Practical Gastrointestinal Endoscopy

COLONOSCOPY AND FLEXIBLE SIGMOIDOSCOPY 135
point of the examination for most colonoscopists. The sigmoid–
descending junction conventionally appears as an acute bend at
approximately 40–70·cm. It can be so acute as to appear at first
to be a blind ending. In a capacious colon there may be a longitudinal
fold pointing toward the correct direction of the lumen,
caused by the muscle bulk of a tenia coli (Fig. 6.51); follow the
longitudinal fold closely to pass the bend.
At the sigmoid–descending colon junction the tip may reach a
fixed (retroperitoneal) point, with the chance of the endoscopist
getting control of the mobile sigmoid. As the tip reaches the junction
it is worth trying a ‘pull-back-and-shortening’ move. ‘Direct
passage’ to the descending colon is the ideal, trying to wriggle
the tip around the junction without forcing up the sigmoid loop.
Experts occasionally, and inexperienced endoscopists frequently,
have trouble in achieving this. Typically an overenthusiastic
endoscopist, having rounded the sigmoid with panache, will
have stretched up a large (iatrogenic) sigmoid spiral N-loop (Fig.
6.52) and created an acute ‘hairpin’ bend (and extra difficulty)
as a result. Being more careful, using less air and frequent withdrawals,
should be rewarded by a straighter, even direct, passage
from the sigmoid to descending colon (Fig. 6.53).
As soon as the tip is even partially into or around the sigmoid–descending
junction try following these steps:
1–Pull back the shaft to reduce the loop, which creates a more
favorable angle of approach to the junction and also optimizes
the instrument mechanics.
2–Apply abdominal pressure, the assistant pushing on the left
lower abdomen so as to compress the loop or reduce the abdominal
space within which it can form.
3–Deflate the colon (without losing the view) to shorten it and
make it as pliable as possible and help to relax the flaplike inner
angle of the sigmoid–descending bend.
4–‘Pre-steer’ into the bend, the tip being steered at the mucosa just
before the inner angle (Fig. 6.54), so that on pushing in the pre-
Fig. 6.51–At acute bends a longitudinal
bulge (tenia coli) shows
the axis to follow.
Fig. 6.52–An N-loop stretching
up the sigmoid colon.
(a)
(b)
Fig. 6.53–(a) Pull back and deflate to keep the sigmoid short …
(b)… which may allow direct passage to the descending colon.
Fig. 6.54–‘Pre-steer’ before
pushing into an acute bend.