Practical Gastrointestinal Endoscopy

COLONOSCOPY AND FLEXIBLE SIGMOIDOSCOPY 151
possible to be overoptimistic and get hopelessly lost. The clue to
this is often that the hepatic flexure (in left lateral position) is dry
or air-filled, whereas the splenic is likely to be fluid-filled.
ASCENDING COLON AND ILEO-CECAL REGION
Endoscopic anatomy
The ascending colon is posteriorly placed at its origin from the
hepatic flexure, but then runs anteriorly so that where it joins
the cecum it is just under the anterior abdominal wall and usually
accessible to finger palpation or transillumination. In 90%
of subjects, the ascending colon and cecum are predictably fixed
retroperitoneally, but the remainder may be mobile on a persistent
mesocolon, with correspondingly variable positions.
At the pole of the cecum the three teniae coli may fuse around the
appendix (crow’s-foot or ‘Mercedes Benz’ sign) (Fig. 6.82), but
the anatomy is somewhat variable. Between the teniae coli and
the marked cecal haustra there can be cavernous out-pouchings,
which are difficult to examine. The appendix orifice is normally
an unimpressive slit, which is often crescentic because the appendix
is folded around the cecum. The appendix is characteristically
flexed around toward the center of the abdomen, thereby
giving guidance as to the likely site of entry of the ileum (see
‘Finding the ileo-cecal valve’, below). Only rarely is the appendix
orifice seen straight-on as a tube, probably when the cecum is
fully mobile. The appendix may sometimes be less than obvious
in a local whirl of mucosal folds. The operated appendix usually
looks no different unless it has been invaginated into a stump,
when it can sometimes resemble a polyp (take care—perhaps
take a biopsy but do not attempt polypectomy!).
The ileo-cecal valve is on the prominent ileo-cecal fold encircling
the cecum about 5·cm back from its pole. Unfortunately for
the endoscopist, the orifice of the valve is often a slit on the invisible
upstream or ‘cecal’ aspect of the ileo-cecal fold. The most the
endoscopist normally sees is the slight bulge of the upper lip. It
is therefore rare to see the orifice directly without specific closeup
maneuvers.
Reaching the cecum
On seeing the ascending colon the temptation is to push in, but
this usually results in the transverse loop re-forming and the
tip sliding back. The secret is to deflate; the resulting collapse of
the capacious hepatic flexure and ascending colon will drop the
tip downward toward the cecum (see Fig. 6.81c); it also lowers
the position of the hepatic flexure relative to the splenic flexure
and with this mechanical advantage, pushing inward should
Fig. 6.82–Appendix orifice.