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4 Endoscopy
Ultrasound transducers designed for transanal use allow
for 360° circumferential assessment of the anal canal and
distal rectum. Probes are available for two-dimensional
imaging, which is generally used for evaluation of the anal
sphincter, or three-dimensional imaging, which is typically
used for rectal cancer staging. Transducer frequencies for
transanal use range from 3 to 20MHz. The use of higher
frequencies produces a higher-resolution image but cannot
penetrate deeper tissues, while lower frequencies allow for a
greater depth of penetration, though the resulting image
may not have the ne detail of one produced at higher
frequencies.
The procedure is generally well tolerated, does not require
sedation, and can easily be performed in an ofce or outpatient
setting. An enema should be administered prior to the procedure to clear the rectum of residual waste. The patient is positioned in the left lateral decubitus position, and, after DRE is
performed, the well-lubricated ultrasound probe is gently
advanced to the desired depth of insertion, then withdrawn to
image the distal rectum and anus. Newer transducers are held
stationary while the crystal moves within the transducer housing via an automated program for image acquisition.
Highly reective tissues with higher water content will
appear hyperechoic (light) on ultrasonographic imaging,
while poorly reective tissues with less water content will
appear hypoechoic (dark). When performing EAUS, the anal
canal is divided into three levels based on anatomic landmarks. In the distal anal canal, only the hyperechoic external
anal sphincter is visible (Fig. 4.4). In the mid-anal canal,
55
Fig. 4.5 Two-dimensional endoanal ultrasonographic appearance of
the mid-anal canal, highlighting the external anal sphincter (large
arrow) and the internal anal sphincter (small arrow)
Fig. 4.4 Two-dimensional endoanal ultrasonographic appearance of
the lower anal canal, highlighting the external anal sphincter (arrow)
Fig. 4.6 Two-dimensional endoanal ultrasonographic appearance of
the upper anal canal, highlighting the U-shaped puborectalis (arrows)
both the hyperechoic external anal sphincter and the
hypoechoic internal anal sphincter are present (Fig.4.5). The
upper anal canal is characterized by the U-shaped puborectalis muscle wrapping around the anal canal (Fig.4.6).
56
M. D. Zelhart and B. R. Kann
On ERUS, ve distinct layers of the rectal wall can typically be seen. The innermost hyperechoic layer is the interface
between the ultrasound probe and the mucosa. The next layer
moving outward is the hypoechoic mucosal layer. The middle
layer is the hyperechoic submucosa, followed by the
hypoechoic muscularis propria. The nal layer is the hyperechoic interface between the rectal wall and the perirectal fat.
When a neoplasm is present, its relationship to the submucosal
layer determines the ultrasonographic T-stage (uTx). A uT1
lesion invades the submucosa, whereas a uT2 lesion extends
into but not through the muscularis propria. uT3 lesions extend
through the muscularis propria into the perirectal fat, producing a characteristic “scalloped” appearance. uT4 lesions
directly invade adjacent organs, such as the bladder or vagina.
Relative contraindications to EAUS/ERUS include anal
stenosis and painful anorectal conditions. Complications are
rare and usually a result of minor trauma to the anorectal
mucosa or anoderm. The major advantages of EAUS/ERUS
are that it is fast and easy to perform, relatively inexpensive
(aside from the cost of acquiring the equipment), does not
require sedation, and does not involve exposure to ionizing
radiation exposure. The major disadvantage is that it is operator dependent, which raises concerns regarding reliability,
reproducibility, and accuracy.
and the tip of the scope moves away from the lumen, the
endoscopist should return the tip to the center of the bowel
lumen, manipulating the inner and outer directional control
knobs with the left hand. Ideally, the endoscopist should be
able to control and use both control knobs with only the
thumb and index nger of the left hand. The goal should be
to keep the right hand on the shaft of the scope and the left
hand on the scope controls throughout the entire scope
insertion.
Dithering/Jiggle
Rapid up-and-down, side-to-side, and to-and-fro movements
of the shaft of the scope are often referred to as “dithering”
or “jiggle.” The objective of these maneuvers is to pleat or
“accordion” the colon onto the shaft of the scope in order to
shorten the length of the colon and keep the scope straight.
This technique is especially useful when combined with
rapid torqueing and rapid in-and-out movements of the
scope.
Air Aspiration
Flexible Endoscopy Techniques
A multitude of technical maneuvers are required to successfully perform exible endoscopy. Like any invasive procedure,
endoscopic technique is best “learned by doing” under the
careful supervision of an experienced endoscopist. Mastery of
the insertion techniques described below, used for both exible sigmoidoscopy (FS) and colonoscopy, is essential in order
to perform an efcient endoscopic examination while keeping
patient discomfort and risk of harm to a minimum.
Torque
The twisting motion applied to the shaft of the scope by the
endoscopist’s right hand is called torque, an essential technique that allows for stiffening of the scope, changing the
direction in which the angulation control knobs orient the tip
of the scope. Torque can also increase the resistance of the
scope to avoid formation of troublesome loops. “Gentle”
torque can be used to keep the scope straight during scope
advancement, and more “forceful” torque is used when
removing or pushing through a loop.
Tip Deection
Every effort should be made to keep the tip of the scope in
the middle of the bowel lumen. As the scope is advanced
As insufated air accumulates in the colon during the procedure, the colon becomes distended and elongates, essentially
pushing the “nishing line” further away. Judicious use of air
insufation is important during the procedure, but calculated
aspiration/suction of air can be an important adjunct insertion technique. Aspiration of air can “pull” the tip of the
scope around a turn of exure without needing to push the
scope forward and form a loop. Once the tip of the scope has
passed the turn, advancement should be much easier due to
the straightness of the colon.
Slide-By
The slide-by technique involves pushing blindly into a turn
or bend with maximum tip deection and without full visualization of the colon lumen, allowing the curvature of the
bowel wall to guide the scope past the turn. This is a controversial maneuver due to the potential risk of bowel wall
injury/perforation and should never be performed by unsupervised trainees or novice endoscopists. If signicant resistance to forward advancement is experienced or the mucosa
becomes blanched at the tip of the scope, the maneuver
should be terminated immediately. In the non-sedated/minimally sedated patient, the slide-by maneuver can be very
painful due to tension on the bowel mesentery. Once the
slide-by maneuver has successfully passed an area of sharp
angulation, the scope should be immediately straightened
and any loops reduced.
4 Endoscopy
57
Flexible Sigmoidoscopy
The use of exible sigmoidoscopy (FS) allows for a greater
length of the distal colon and rectum to be evaluated in the
ofce setting and has become more popular due to its ease of
use, improved magnication and optics, better patient tolerance, and higher yield of ndings over conventional rigid
proctoscopy [6]. Depending on the manufacturer, the length
of the scope ranges from 60 to 71cm and the outer diameter
ranges from 12 to 14. When performed properly by an experienced endoscopist, FS has been shown to have an average
depth of insertion of 40–50 cm, reaching the descending
colon in 80% of examinations [7, 8], and is capable of detecting 65–75% of polyps and 50–65% of colorectal cancer [9–
11]. It should be noted that FS is not an adequate substitute
for screening colonoscopy, as it will not detect colonic polyps and/or neoplasms proximal to the distal transverse colon/
splenic exure.
While the exible sigmoidoscope is easier to handle than
a colonoscope and the technique is easier to learn than colonoscopy, it should only be performed by a properly trained
endoscopist or a closely supervised trainee. Given that the
patient is not sedated, often anxious, and bowel preparation
can be suboptimal, the procedure can occasionally be challenging to perform in the ofce setting. The indications for
FS in the ofce setting are numerous. FS can be used to evaluate rectal bleeding not explained by ndings on anoscopy
or to evaluate for suspected proctitis. It can be used to identify the level of a rectal or rectosigmoid tumor, though this is
somewhat less reliable than rigid proctoscopy. FS is also an
excellent tool in the evaluation of the response to neoadjuvant chemoradiation in patients with rectal cancer.
Additionally, postoperative evaluation of distal anastomoses
can rapidly be performed to evaluate for stricture or cancer
recurrence. FS is also a useful means of monitoring for recurrence after local excision of a rectal neoplasm or in patients
with a complete response to neoadjuvant chemoradiation
who are in a “watch and wait” protocol.
It is advisable to give the patient one to two enemas prior
to the procedure. Sedation is typically not needed, and the
patient is best positioned in the left lateral decubitus position. After a proper DRE, the well-lubricated scope is gently
inserted, and air should be gently insufated to distend the
rectum. As the scope is advanced, it is navigated around the
valves of Houston to the rectosigmoid junction. The scope is
then advanced into sigmoid colon, which sometimes requires
torqueing of the scope either clockwise or counterclockwise.
Care should be taken to clearly visualize the lumen of the
bowel before advancing the scope. Blind “slide-by” maneuvers should be avoided in the non-sedated patient to minimize discomfort, and care should be taken to insufate just
enough air to distend the bowel enough for adequate visualization and safe advancement. The scope is then advanced
under direct visualization as far as possible, generally to the
level of the splenic exure. Limitations to the depth of scope
insertion include the volume of residual stool, patient discomfort, and signicant sigmoid diverticular disease. Once
the scope has been advanced to its fullest extent, it is then
withdrawn carefully and deliberately to evaluate the entire
mucosal surface. Any lesions that are identied can be biopsied. Small polyps can be removed with biopsy forceps,
though removal of larger polyps may best be done during a
subsequent colonoscopy when the patient has performed a
full bowel preparation. Identication of polyps in the distal
colon during FS should prompt the patient to undergo a full
colonoscopy in order to assess for additional polyps in the
proximal colon.
The most common complication after FS is abdominal
pain and bloating due to overdistention and air trapping.
Bleeding may occur after a biopsy or polypectomy.
Fortunately, serious complications are exceedingly rare with
FS.The perforation rate has been reported to be as low as
0.002% [12]. When perforation does occur, it is typically at
the level of the distal sigmoid where it angulates from the
xed rectum at the sacral promontory.
Colonoscopy
Colonoscopy is essential in screening for colorectal cancer,
surveillance of patients with history of colorectal neoplasia,
and evaluation and management of patients with intestinal
complaints. A well-performed colonoscopy allows the physician to evaluate the mucosa of the terminal ileum, colon,
and rectum, with biopsy and photodocumentation of abnormal ndings, as well as other therapeutic interventions.
Asurvey of American Society of Colon and Rectal Surgeons
(ASCRS) members found that more than 90% reported performing colonoscopy as part of their clinical practices, completing an average of 41 procedures per month [13]. The
ability to perform a thorough colonoscopy is an essential
skill for colorectal surgeons to possess, and training in colonoscopy remains an essential core component of colon and
rectal surgery residency programs. The indications for colonoscopy are numerous and covered in the appropriate chapters elsewhere in this book.
Bowel Preparation
The necessity of an adequate bowel preparation prior to
colonoscopy cannot be emphasized enough. Removal of all
debris from the colonic lumen in order to thoroughly examine the mucosal surface remains a challenge for both the physician and the patient. Most patients describe the bowel prep
prior to colonoscopy as the most unpleasant part of the pro-
58
M. D. Zelhart and B. R. Kann
cedure. The ideal bowel prep is one that is safe, highly effective and reliable, convenient, and tolerable enough that
patients are not deterred from completing the prep or undergoing future procedures. Unfortunately, this has not yet been
developed [14]. In spite of the development of “better tolerated” bowel preps, approximately one-quarter of colonoscopies performed in the United States and Western Europe are
considered to have an inadequate quality preparation [15,
16]. Inadequate bowel preparations lead to lower adenoma
detection rates (ADRs), longer colonoscopy times, repeated
procedures, shorter surveillance intervals, increased cost of
colorectal cancer prevention, and decreased patient satisfaction [17].
A number of commercially available bowel preparations
are currently available (Table4.1), and the choice of which
agent is used is often practitioner dependent or directed by
which agent a patient’s health insurance will cover at the
lowest cost. Currently available bowel preps fall into one of
three categories: iso-osmotic, hypo-osmotic, and hyperosmotic agents.
Polyethylene glycol (PEG), an inert polymer of ethylene
oxide that passes through the gastrointestinal tract without
net absorption or secretion, is typically combined with electrolyte solutions to create iso-osmotic preparations. The use
of such PEG-electrolyte lavage solutions (PEG-ELS) is one
of the most common formulations for precolonoscopy bowel
preparation and is the “gold standard” against which other
bowel prep formulations are compared. Unfortunately, the
large volume required to be ingested (4 L) and poor palatability limit patient compliance; up to 15% of patients are
unable to complete the preparation fully [18]. A sulfate-free
formulation of PEG-ELS has been developed in an attempt
to improve the taste and smell, with similar efcacy and
safety when compared with standard PEG-ELS [19].
Additionally, an FDA-approved low-volume (2 L) PEG-ELS
prep combined with ascorbic acid has also been shown to
have similar efcacy to the standard 4 L PEG-ELS with
improved tolerance [20]. The “low-volume” nature of this
preparation is misleading, however, as the patient is required
to drink an additional 1L of clear liquids in addition to the
2L of prep.
The use of PEG-3350 (MiraLax®, Bayer, Whippany, NJ)
combined with a commercially available electrolyte solution
in the form of a sports drink (PEG-3350-SD) has been widely
adopted due to its low cost and better tolerance, though it is
not FDA approved for colonoscopy preparation. PEG3350- SD, often combined with a stimulant laxative such as
bisacodyl, results in intestinal catharsis through a hypoosmotic effect. Studies comparing it with a standard 4 L
PEG-ELS prep have shown conicting results in terms of
adenoma detection rates and quality of bowel prep [21–23].
One should also keep in mind that, unlike the electrolyte
solutions used for prescription bowel preps, commercially
available sports drinks are typically not osmotically balanced, and there have been reports of severe hyponatremia
associated with the use of PEG-3350-SD as a bowel prep
prior to colonoscopy.
Hyperosmotic agents, such as magnesium citrate,
sodium sulfate, and sodium phosphate, are also used as
components of oral bowel preparation prior to colonoscopy. Magnesium citrate is not FDA approved as a colonoscopy prep, as data regarding its effectiveness are limited,
and there is signicant potential for toxicity, especially in
the elderly and those with kidney disease. Oral sodium sulfate has been shown to be equivalent to low-volume (2 L)
PEG-ELS [24] and superior to 4L sulfate-free PEG-ELS
[25]. A major advantage of oral sodium sulfate is the lack
of signicant uid and electrolyte shifts. Sodium phosphate
preparations had previously been used widely and were
very popular due to the smaller volume of uid required.
However, concern regarding electrolyte disturbance and
acute renal failure in certain populations has limited its use.
The aqueous formulation of sodium phosphate has been
voluntarily withdrawn from the market. A tablet formulation of sodium phosphate is available by prescription, but
this requires the patient to take 32 tablets with 2L of water,
which limits its attractiveness. An FDA box warning
advises against its use in elderly patients and in those with
gastrointestinal motility disorders, renal or liver disease, or
congestive heart failure. Sodium phosphate has also been
reported to cause mucosal inammation and ulceration that
can mimic the appearance of inammatory bowel disease,
so its use is not recommended in this patient population
[26, 27]. Sodium picosulfate combined with magnesium
citrate has more recently become a popular alternative as a
low-volume bowel prep, combining both osmotic effects
and laxative effects to cleanse the colon.
Regardless of the specic bowel preparation chosen, there
is overwhelming evidence that a split-dose regimen, administering a portion (usually half) of the prep the day/evening
prior to the procedure and the remaining portion of the prep
the day of the procedure, results in a higher-quality prep
[28–36]. A split-dose prep has also been shown to improve
adenoma detection rates [37] as well as patient tolerance
[32]. The second dose should be given 3–8hours prior to the
planned start of the procedure, but must be completed at least
2 hours prior to administering sedation to avoid potential
aspiration, as recommended by the American Society of
Anesthesiologists guidelines [38]. While 4 L PEG-ELS is
FDA approved to be used in a single-dose fashion but not in
a split-dose fashion, there is sufcient evidence to suggest
that split-dose 4 L PEG-ELS produces the highest-quality
preparations [39], and, per the Standards of Practice
Committee of the American Society for Gastrointestinal
Endoscopy (ASGE), is considered the current standard colonoscopy prep [39, 40].
4 Endoscopy
Magnesium
citrate Sodium phosphate tablets
Sodium picosulfate/
magnesium oxide/
anhydrous citric acid
(Raleigh, NC)
Sodium phosphate
OTC Salix Pharmaceuticals
Ferring Pharmaceuticals
Inc. (Parsippany, NJ)
Magnesium
citrate
Sodium picosulfate,
magnesium sulfate,
anhydrous citric acid
32 tablets;
2L water
20–30oz;
2L water
10oz;
2L water
Split dose: 20 tablets
day before and 12
tablets day of procedure
Split dose:
1–1.5 10-oz
bottles day
before and
1–1.5 10-oz
bottles day
of procedure
Split dose: 5oz Prepopik
+ 40oz clear liquids day
before and 5oz Prepopik
day before + 24oz clear
liquids day of procedure;
Single dose: 5oz
Prepopik + 40oz clear
Avoid in patients with
heart or liver failure,
renal insufciency or
Avoid in
patients with
renal
liquids the afternoon or
early evening before the
procedure and 5oz
Prepopik + 24oz clear
liquid 6hours later
Less volume; well
tolerated; expensive;
avoid in patients with
risk factors for acute
phosphate nephropathy,
volume depletion, and
patients taking ACEi or
NSAIDs; not
insufciency
and elderly;
not FDA
approved as
bowel prep
renal insufciency
recommended for
routine use
59
Low-volume
PEG-3350-SD Oral sodium sulfate
Low-volume
PEG-ELS with
ascorbic acid
PEG-ELS SF-PEG-ELS
Braintree
Laboratories
(Braintree, MA)
Bayer
(Whippany, NJ)
PEG-3350 Sodium sulfate,
Salix
Pharmaceuticals
(Raleigh, NC)
PEG-3350, sodium
Braintree
Laboratories
(Braintree, MA)
PEG, sodium
Laboratories
(Braintree, MA)
potassium sulfate,
magnesium sulfate
sulfate, sodium
chloride, ascorbic
acid
bicarbonate,
sodium
chloride,
potassium
chloride
sulfate, sodium
bicarbonate,
sodium chloride,
potassium
chloride
12oz;
2.5L water
238g
PEG-3350in
2L SD
2L;
1L clear uid
4L;
None
4L;
None
Split dose: 6oz
OSS with 10oz
water + 32oz water
day before and 6oz
OSS with 10oz
Split dose:
1Lday before
and 1Lday of
procedure;
Single dose:
Split dose: 1Lday
before and 1Lday
of procedure;
Single dose:
2Lday before
Split dose:
2–3Lday
before and
1–2Lday of
procedure;
Split dose:
2–3Lday before
and 1–2Lday of
procedure;
Single dose:
water + 32oz water
day of procedure
2Lday before
procedure
procedure
Single dose:
4Lday before
procedure
4Lday before
procedure
Pleasant taste; less
volume; well
tolerated;
expensive; avoid in
patients with heart
failure, renal
Well tolerated;
available OTC;
not FDA
approved as
bowel prep;
unbalanced
Poor taste;
expensive; avoid in
patients with
glucose-6-
phosphate
dehydrogenase
More palatable
than PEG-ELS
volume; poorly
tolerated;
split-dose not
FDA approved
but considered
insufciency,
end-stage liver
disease, and
electrolyte
abnormalities
ELS–electrolyte
shifts may
occur
deciency
criterion standard
Table 4.1 Partial list of commercially available bowel preparations
Brand name GoLTYELY® NuLYTELY® Moviprep® Miralax® Suprep® Prepopik® Generic Osmoprep®
Company Braintree
Composition PEG, sodium
Volume;
recommended
minimum
additional uid
a
Dosing
regimens
Comments Poor taste; large
When utilizing split-dose regimen, second dose must be completed at least 2hours prior to procedure
a
Adapted from Saltzman etal. [40] and Harrison and Hjelkrem [14]
PEG-ELS polyethylene glycol electrolyte solution, SF sulfate-free, SD sports drink, OTC over the counter, OSS oral sodium sulfate, FDA US Food & Drug Administration, ACEi Angiotensin-
converting enzyme inhibitor, NSAIDs nonsteroidal anti-inammatory drugs
60
M. D. Zelhart and B. R. Kann
Special Considerations
Poor/Dicult Prep
It is not uncommon for patients to have a history of poor
prior bowel preps for colonoscopy. Patients with a previous
experience of inadequate preps or a history of chronic constipation are at particular risk for having a prep insufcient to
undergo a thorough colonoscopy. It has been demonstrated
that a low-quality bowel prep, dened as the inability to
detect lesions <0.5cm, should be followed up with an early
repeat colonoscopy due to the risk of missed lesions [41]. In
one study, split-dosage prep was superior to non-split prep in
terms of completeness of prep and adenoma detection rates,
while there was no difference between the patient having
ingested a clear liquid diet and a low-residue diet prior to the
prep [42].
Unfortunately, there is a paucity of literature prospectively addressing patients with a history of poor prep, leaving
clinicians to individualize their practices based on clinical
judgment. Many will start the prep and a clear liquid diet
2days before the procedure. If the patient does not achieve
clear bowel movements with this, then an additional osmotic
or cathartic prep can still be administered the day before or
the morning of the procedure. Patients with chronic constipation may also have coexisting gastroparesis or intestinal
dysmotility, making it difcult to complete the bowel prep;
the addition of an antiemetic agent can sometimes be helpful
for this subset of patients. As a last resort, the patient can be
admitted the day before the procedure to administer the prep
through a nasogastric tube or endoscope.
Need forAntibiotics
Outside of scattered case reports, there is little data endorsing the need for routine prophylactic antibiotics in patients
undergoing a colonoscopy. The updated 2015 ASGE guidelines recommend against the routine administration of antibiotic prophylaxis solely for prevention of infective
endocarditis, as well as before GI endoscopic procedures for
patients with synthetic vascular grafts, other nonvalvular cardiovascular devices, or orthopedic prosthesis. The guidelines
do make the recommendation, based on low-level evidence,
that patients with high-risk cardiac conditions and an established GI tract infection in which enterococci may be part of
the infecting bacterial ora should receive antibiotic coverage [43].
Peritonitis in patients undergoing continuous ambulatory
peritoneal dialysis can result from translocation across the
bowel wall during GI endoscopic procedures. A retrospective study found that the risk of peritonitis after colonoscopy
without antibiotic prophylaxis was 6.3% [44]. The ASGE
guidelines suggest administration of antibiotic prophylaxis
before endoscopy of the lower GI tract in patients undergoing continuous ambulatory peritoneal dialysis, though this is
based on very low-level evidence [43]. The International
Society for Peritoneal Dialysis (ISPD) recommends ampicillin (1 g) plus a single dose of an aminoglycoside, with or
without metronidazole, given intravenously immediately
before GI endoscopic procedures to lower the risk of peritonitis [45].
Anticoagulated Patient
The potential risk vs benet of anticoagulation in a patient
undergoing endoscopy can present a challenging situation
for the clinician, and clinical decisions should be made in
conjunction with the physician managing the anticoagulation. While procedure-related bleeding can be a tangible and
often immediate event, therapeutic maneuvers can be utilized to mitigate the risk and manage post-colonoscopy
bleeding. Conversely, thromboembolic events can have devastating and irreversible effects. Balancing the risks of bleeding and a thromboembolic event can be difcult.
A screening colonoscopy, even with a biopsy, is considered a low-risk procedure for bleeding and almost all anticoagulant agents can be continued. However, if a polypectomy
needs to be performed, the procedure now becomes high
risk. Unfortunately, this information is usually not known in
advance. The ASGE recommends that for patients receiving
anticoagulant therapy, the procedure should be postponed
until the patient no longer has a need for anticoagulation, if it
can be done safely [46].
Most guidelines do not suggest mandatory discontinuation of aspirin or nonsteroidal anti-inammatory drugs
(NSAIDs) prior to diagnostic or therapeutic endoscopy,
especially in patients at high risk for cardiovascular disease.
If these agents are to be held, they should be discontinued at
least 7days before the procedure. Thienopyridines, such as
clopidogrel, should be stopped 5–7days before the procedure. Consideration can be given to continuing aspirin for
patients on dual platelet therapy [47].
Warfarin should be discontinued 5days prior to the procedure, and low-molecular-weight heparin should be discontinued 12 hours prior to the procedure. Factor Xa
inhibitors and direct thrombin inhibitors should be discontinued 1–5days prior to the procedure, depending on the
half-life of the individual medication. When holding anticoagulant therapy, “bridging” with low-molecular-weight
heparin is sometimes practiced, though one double-blinded
trial demonstrated that forgoing bridging was noninferior
to bridging with low- molecular- weight heparin for prevention of arterial thromboembolism, while bridging inferred a
risk of major bleeding events three times that of not bridging [48].
4 Endoscopy
61
Sedation
While there is ample literature demonstrating that colonoscopy can be performed safely and adequately in non-sedated
patients [49–51], most patients who undergo colonoscopy in
the Unites States are administered some form of sedation.
Sedation is utilized for multiple reasons—patients prefer a
favorable experience, endoscopists prefer reasonable technical conditions under which to work, and both prefer optimal
patient safety and procedural outcomes [52]. Sedation can be
administered by either the endoscopy team or by an anesthesia specialist, though one must keep in mind that adding
anesthesia services adds substantially to the cost of these
procedures. Historically, most patients received endoscopistdirected moderate sedation. However, a 2017 study using a
combination of Medicare and commercial billing data demonstrated a steady increase in the utilization of anesthesia
services for gastrointestinal endoscopy, rising from one-third
of all patients in 2009 to about one-half of all patients in
2013 [53]. The authors estimated that this may cost as much
as $1.5 billion annually in the United States. The main driver
of this shift in sedation care is due to the use of propofol deep
sedation.
Endoscopist-directed moderate sedation most commonly
employs a combination of a benzodiazepine and an opiate.
The main disadvantages of this regimen include the length of
time needed to achieve adequate sedation, procedural recall,
poor intra-procedural sedation, prolonged recovery, and
post-procedural emesis. One study evaluating the actual
depth of sedation in patients undergoing endoscopic procedures with a targeted moderate level of sedation found that
45% actually were at a level of deep sedation at least once
during the procedure [54]. This demonstrates that moderate
sedation is inadequate for some patients who are at risk for
having a suboptimal experience or receive excessive sedation, leading to the potential for increased adverse effects.
When employing moderate sedation, it is essential to have
reversal agents readily available—naloxone for opioid reversal and umazenil for benzodiazepine reversal.
Propofol is a hypnotic alkylphenol derivative that facilitates inhibitory neurotransmission mediated by gammaaminobutyric acid (GABA), resulting in sedation, amnesia,
and hypnosis. The use of propofol has proven to be more
advantageous than moderate sedation in a number of variables, including rapid onset, rapid recovery, minimal postprocedural adverse effects, procedural amnesia, good
procedural operating conditions, and excellent patient and
provider satisfaction [55]. Propofol is traditionally reserved
for use by trained anesthesia professionals for a number of
reasons. It easily results in deep sedation, and patients often
achieve a level of general anesthesia, dened as a lack of
response to painful stimulation and frequent need for airway
intervention.
Due to the increased cost associated with the requirement
of an anesthesia provider to administer propofol, alternative
delivery methods have been investigated. A meta-analysis
published in 2015 found that the safety of non-anesthesia
provider-administered propofol sedation for advanced endoscopic procedures compared favorably with anesthesia
provider- administered propofol sedation, though it came at
the cost of decreased patient and endoscopist satisfaction
[56]. There is rapidly accumulating data to suggest that
administration of propofol by registered nurses supervised
by endoscopists can be performed safely [57], and there is a
substantial evidence base to support the safety of
endoscopist- delivered propofol protocols, demonstrating its
cost- effectiveness compared with administration of propofol by anesthesia specialists. Although these protocols have
been implemented successfully in some European countries, their use in the United States has been limited by
nancial considerations, medical–legal risk concerns, and
what some feel to be nonevidence-based policies of governing organizations [58].
Instrumentation
Depending on the specic manufacturer and product specications, colonoscopes vary in length from 133 to 170 cm
(Fig. 4.7). The typical outer diameter of a standard adult
colonoscope is 12.8–13.2 mm, though smaller-diameter
pediatric (11.6–11.7mm) and neonatal (9.7–9.8mm) colonoscopes are also available. The basic colonoscope houses a
suction channel, an air/water insufation channel, beroptic
bundles for light transmission, a biopsy port/working channel connected to the suction channel, and cables attached to
the angulation control knobs (also called “wheels” or “dials”)
used to deect the tip of the colonoscope for direction
change. There are specic models of colonoscopes with a
Fig. 4.7 Colonoscope
62
second working channel, which can be helpful for more
advanced therapeutic procedures. Most modern colonoscopes also have a variable stiffness control that allows the
endoscopist to vary the rigidity of the scope.
Colonoscopy Technique
Colonoscopy can be an extremely challenging skill to learn,
requiring appropriate training, practice, patience, and attention to detail. A redundant/tortuous colon, angulation created
by postoperative or inammatory adhesions, and altered
postoperative anatomy can create technical challenges in
navigating the entire length of the colon for even the most
experienced of endoscopists.
Once the patient has provided informed consent for the
procedure (and separate consent for sedation if anesthesia
services are being utilized) and appropriate cardiopulmonary
monitoring has been instituted, he or she is positioned in the
left lateral decubitus position. The colonoscope is brought
from the procedure cart to the bed/stretcher, ensuring that
there are no loops or twists in the scope, which will add additional tension to the inner cables. After an appropriate level of
sedation is achieved, visual inspection of the anal margin/anal
verge is performed, followed by DRE.The well- lubricated
colonoscope is then advanced into the anus. It is helpful to
double-glove the right hand, removing the outer glove after
performing DRE and inserting the colonoscope, in order to
avoid getting lubricant on the control body and angulation
control knobs, which can make them difcult to maneuver.
Air is gently insufated to distend the bowel lumen as the
colonoscope is advanced into the rectum. There is a tendency
for residual liquid to pool in the distal rectum. This should be
suctioned prior to advancing the colonoscope to prevent
forceful expulsion of the residual bowel contents should the
patient begin coughing at any point in the procedure due to
airway irritation. One should keep in mind that the suction
port is located at the 5:00 position on the tip of the colonoscope. The colonoscope should be rotated so that the uid
being suctioned is located at the inferior aspect of the eld of
view, and the tip of the scope should be placed just above the
air–uid interface prior to suctioning. The force of suction is
dependent upon how far the suction button is depressed. In
order to prevent the mucosa from being drawn into the suction port and obstructing it, one should avoid full depression
of the suction button for prolonged periods. Instead, repeated
short periods of partial depression of the suction button followed by releasing it allows for re-distention of the lumen,
preventing luminal collapse around the scope. Simultaneous
air insufation and suction can accomplish the same result.
The colonoscope is then advanced through the rectum,
navigating around the valves of Houston (Fig.4.8) to reach
the rectosigmoid junction. Advancing the colonoscope past
this point can be one of the more challenging areas of the
M. D. Zelhart and B. R. Kann
Fig. 4.8 Endoscopic appearance of the rectum, noting the three valves
of Houston
colonoscopy. There is often an acute angle at this junction,
especially if the sigmoid colon is redundant. If the patient
has undergone prior pelvic surgery, especially hysterectomy,
the sigmoid may become xed, making negotiation of this
angle even more difcult and often painful. As the colonoscope is advanced, it should be kept as straight as possible. A
combination of short advancements/withdrawals with slight
clockwise torque and appropriate tip deection can help
advance the scope into the sigmoid colon. Slide-by maneuvers should be avoided, if at all possible, as this is one of the
most frequent sites of colonoscopic perforation.
Once the colonoscope is advanced into the sigmoid colon,
any loops should be reduced, using tip deection and torque.
If loop reduction is not possible, the scope can be carefully
inserted farther into the sigmoid, “pushing through the loop,”
as long as there is minimal resistance and it does not cause
the patient excessive discomfort. Keep in mind that this may
elicit a vasovagal response with bradycardia—if this occurs,
the colonoscope should be withdrawn to reduce the loop.
The sigmoid colon is the most tortuous segment of the
colon and is associated with high muscular tone, frequent
spasm, and a higher incidence of diverticulosis (Fig.4.9).
The sigmoid colon lacks xation and can be quite redundant
and elongated. A number of techniques can be required to
successfully navigate this portion of the colon, including
insertion/pull back, jiggle, and torque (usually clockwise),
allowing for the sigmoid colon to “accordion” over the
scope, advancement of the scope, and prevention of further
loop formation.
Large diverticula, when present, can be mistaken for the
true bowel lumen. Careful advancement of the colonoscope
through a sigmoid colon riddled with diverticula requires
patient, frequent use of pull-back techniques to gain a better
appreciation of the true colonic lumen. As the scope is
4 Endoscopy
Fig. 4.9 Endoscopic appearance the sigmoid colon, noting diverticulum (arrow)
63
be a complex series of turns and twists in multiple planes,
requiring tip deection, torque, and push/pull techniques.
Once the colonoscope traverses the splenic exure, the
lumen of the transverse colon takes on a characteristic triangular appearance formed by the taenia coli (Fig.4.11). The
transverse colon can also be quite redundant, and the midpoint may descend down into the pelvis where it can become
xed by adhesions, especially following pelvic surgery.
Loops are commonly created during this part of the exam,
and external pressure on the abdominal wall assists
advancement.
As the transverse colon is traversed, the hepatic exure
can be recognized by visualizing the blue shadow from the
liver, especially in thinner patients (Fig. 4.12), as well as
pooling of liquid. If the hepatic exure is especially acute,
Fig. 4.10 Endoscopic appearance of the spleen (arrow) visible through
the colonic wall at the splenic exure
advanced, one should strive to keep it as straight as possible
to prevent loop formation.
Passage of the colonoscope from the sigmoid colon into
the descending colon is usually evident, as the descending
colon is typically much straighter and less muscular than the
sigmoid colon. Once the descending colon is reached, any
remaining loops should be reduced with withdrawal and
torqueing maneuvers. If there are no loops present, the colonoscope should be easily advanced from this point to the
splenic exure, which can sometimes be identied by the
blue shadow of the spleen seen through the wall of the colon
(Fig.4.10) and/or pooling of uid. Negotiating the splenic
exure is often a simple maneuver, requiring minimal tip
deection and torque. Other times, the splenic exure may
Fig. 4.11 Endoscopic appearance of the transverse colon, noting the
triangular lumen
Fig. 4.12 Endoscopic appearance of the liver visible through the
colonic wall at the hepatic exure
64
abc
M. D. Zelhart and B. R. Kann
the novice endoscopist often mistakes this “fool’s cecum”
for the true cecum. One should use tip deection to negotiate
this area of particularly sharp angulation. Occasionally, it is
necessary to gently push through a loop to advance the colonoscope into the ascending colon and then reduce the loop, at
which point withdrawing the scope often will result in paradoxical advancement of the tip of the colonoscope toward
the cecum. Another maneuver is to use intermittent suction
to draw the tip of the scope down toward the cecum once the
colonoscope has made the initial turn around the hepatic
exure. Transitioning the patient from the lateral decubitus
position to supine position and the use of external abdominal
pressure can also be useful adjuncts in getting the colonoscope to advance to the cecum.
The ileocecal valve marks the junction between the
ascending colon and the cecum. The appearance of the valve
can be highly variable—it may be visible simply as a fold at
the base of the ascending colon, as a polypoid-like yellowish
mass with a lipomatous appearance, as a visible lumen opening into the terminal ileum, or it may be completely hidden
(Fig.4.13a–c). When the valve is not easily identied, the
presence of gas bubbles or enteric contents owing from it
can assist with its identication.
A complete colonoscopic examination is ensured only
when the cecum has been clearly and indisputably cannulated. This base of the cecum is characterized by a “crow’s
foot” appearance, caused by the muscular arrangement of the
colonic wall coalescing around the appendiceal orice
(Fig. 4.14). Identication and photodocumentation of the
ileocecal valve and appendiceal orice (and terminal ileum if
intubated) is mandatory for quality assurance of a complete
examination. Trans-illumination of the scope through the
right-lower-quadrant abdominal wall or endoscopic visualization of external pressure on the right-lower-quadrant
abdominal wall is not a reliable indicator that the cecum has
been cannulated and should never be used as a substitute for
clear visualization of anatomic landmarks. Detailed evaluation of the entire cecum is essential, including the recess
behind the ileocecal valve, where it is easy to miss small, at
lesions.
While intubation of the ileocecal valve to visualize the
terminal ileum is an essential component of a colonoscopy in
patients with inammatory bowel disease or in a search for
obscure gastrointestinal bleeding, the exact role of routine
visualization of the terminal ileum during all colonoscopies
is not clear. One study in which routine terminal ileal intubation was attempted in over 1300 consecutive patients found
that it was successfully performed in 90.2% of cases, but
clinically signicant ndings in asymptomatic patients were
found in only 3.3% of cases [59]. Another retrospective
study of over 6400 patients who had terminal ileal intubation
performed at the time of screening colonoscopy found gross
endoscopic abnormalities in 1% and pathologic abnormalities in 0.3%, calling into question the need for routine terminal ileal intubation [60]. Others have argued that, because
asymptomatic small bowel lesions with potential for signicant consequences such as terminal ileal carcinoid tumors
can be identied, routine ileoscopy should be performed
with all colonoscopies [61].
While the routine performance of routine ileocecal valve
cannulation is somewhat controversial, it is a skill that all
endoscopists must possess, and the ability to expertly per-
Fig. 4.14 Endoscopic appearance of the appendiceal orice (arrow)
Fig. 4.13 (a–c) Varied endoscopic appearances of the ileocecal valve