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CHAPTER 25 Training the Gastroenterologist for NOTES
https://t.me/med1917
(a) (b)
Figure 25.2 EndoSAMURAI (a) controls and (b) effector arms. (From Shaikh SN [1], with permission from Baishideng Publishing Group Co.)
instrument channels have lifting devices to allow simultaneous vertical lifting and horizontal dissection; this allows a
small degree of triangulation.
The EndoSAMURAI (Olympus) comprises a steerable,
lockable overtube and two short independent effector arms
that are controlled via remote workstation (EVIS EXERA II
Universal Platform, Olympus) [1] (see Figure 25.2). The
lockable overtube adds stiffness and stability. The effector
arms remain parallel to the endoscope shaft but have fi ve
degrees of freedom when in position, eliminating parallelism
and allowing triangulation to provide tissue traction and tie
sutures. There are three instrument channels, and forceps
germane to NOTES are available, including insulated -tip
electrosurgical knife, triangle -tip electrode, and needle
grasper [7]. The EndoSAMURAI has been compared with a
DCE in a bimanual coordination task (dropping a pin into a
hole covered by a coin) and benchtop suturing [8]. Twelve
subjects (students, trainees, and attendings) with varying
laparoscopic and endoscopic experience were found to complete the coordination task more quickly with EndoSAMURAI than DCE (304 ± 125 s versus 867 ± 312 s, p < 0.001)
and with fewer pin drops (0.4 versus 1.8, p < 0.01). All
participants were able to create a reliable suture with
EndoSAMURAI, but none could do so with DCE. An ex vivo
porcine model has been used to compare EndoSAMURAI
with DCE for full -thickness resection of a 10 mm pseudolesion with an electrosurgical knife [7]. The mean procedure
time was shorter using EndoSAMURAI than DCE (13 min
25 s versus 23 min 28 s, p = 0.002). Accuracy of resection,
inversely related to the difference between minimum and
maximum resected margin, was higher using EndoSAMURAI than DCE (7.8 mm versus 15.3 mm, p = 0.028). Effectiveness of counter -traction, inversely related to the
difference between serosal and mucosal margin, was 3.6 mm
using EndoSAMURAI versus 7.6 mm using DCE ( p = 0.025).
Effi ciency was assessed using duty ratio, which is percentage
of time spent for main purposes compared with total procedure time; this was 36.2% using EndoSAMURAI versus
24.8% using DCE ( p = 0.047). Although EndoSAMURAI is
an advancement toward the ideal NOTES platform, it was
found to be diffi cult to maneuver in the gastrointestinal tract
with effector arms extended; also, time lag in the effector
arms made smooth movement diffi cult [7].
The Direct Drive Endoscopic System (DDES, Boston Scientifi c, Natick, MA, USA) is based on a 55 cm steerable and
lockable guide sheath with three 4 mm lumens; a variety of
cautery devices, needle drivers, graspers, and scissors are
available [1] (see Figure 25.3). The device has seven degrees
of freedom, and a 4.9 mm endoscope (GIFN180, Olympus)
is used for visualization independent of the effectors. Triangulation is achieved, but irrigation and suction are dependent on the N -scope. The DDES has been shown to be capable
of grasping, suturing, and knot -tying.
The Incisionless Operating Platform (IOP, USGI Medical,
San Capistrano, CA, USA) is based on a steerable 110 cm
shaft with four channels (7 mm, 6 mm, 4 mm, 4 mm) and
use of an independently rotatable 4.9 mm endoscope
(GIFN180, Olympus) for visualization [1] (see Figure 25.4).
It is controlled by navigational dials. The device is capable
of triangulation, but is susceptible to parallelism (which may
be overcome by modifying the instruments). A variety of
NOTES-appropriate instruments are available, including a
jaw capable of tissue plication; the channels can be used for
high-fl ow carbon dioxide insuffl ation [9].
Guidance systems
Guidance systems can be used to overcome the challenges
of spatial orientation, organ identifi cation, and navigation
outside the gastrointestinal lumen.
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(a) (b)
Figure 25.3 (a) Direct Drive Endoscopic System and (b) effectors. (From Shaikh SN [1], with permission from Baishideng Publishing Group Co.)
versus 636 s, p = 0.04). Rate of complications (hemorrhage,
liver laceration, abdominal wall tear) trended toward lower
in the image -registration group (13.3% versus 40.0%,
p = ns). Kinematic evaluation revealed that image -registered
NOTES procedures were performed with signifi cantly
improved smoothness of motion and velocity than unguided
procedures. This suggests that real -time visualization of
endoscope position may facilitate comprehension of orientation and navigation during training [11].
Figure 25.4 Incisionless Operating Platform and 4 -lumen distal tip.
(From Shaikh SN [1], with permission from Baishideng Publishing
Group Co.)
The Shape Tool (Northern Digital, Waterloo, Canada)
is a catheter with embedded electromagnetic sensors that
fi ts within a standard endoscope instrument channel;
it is paired with an electromagnetic tracker (Aurora
System, Northern Digital) (see Figure 25.5). A study in
pigs using transgastric entrance into the peritoneum to identify the spleen, gallbladder, bladder, and fallopian tube
reported mean time to identify all targets was 75.1 ± 42.7
seconds versus 100.2 ± 60.7 seconds without the device
(p < 0.001) [10].
Image-registered instrument guidance uses three dimensional models of the patient generated from pre procedure cross -sectional imaging combined with sensors
placed on the patient and the endoscope to provide a real time display of the endoscope position in the body (see
Figure 25.6). A system using CT imaging and electromagnetic sensors has been tested versus unguided NOTES in
peritoneoscopy in 30 pigs via transrectal, transgastric anterior, and transgastric posterior access points. Time to perform
the incision and reach the peritoneal cavity via transgastric
access was lower in the image -registration group (454 s
Endoscopic ultrasound
Although endoscopic ultrasound (EUS) has a long learning
curve, facility with EUS provides the gastroenterologist with
valuable expertise that is widely applicable in the performance of NOTES procedures. Most importantly, it bestows the
gastroenterologist with the adaptability to perform procedures developed in the future.
EUS has utility in locating optimal points for translumenal
access while protecting adjacent vascular and visceral structures from injury. This has been demonstrated in a porcine
study comparing the rate of complications in EUS -guided
and unguided access via the gastric antrum, posterior gastric
wall, and rectum [12]. Access points were deemed safe if
no identifi able organs or vascular structures were present
in the intended trajectory of puncture; unsafe access points
were adjacent to extralumenal structures such as the liver,
gallbladder, pancreas, or kidney. All fi ve safe access procedures in the gastric antrum were used without complication;
all six unsafe procedures resulted in injury, including
liver and splenic laceration and gallbladder puncture. All
fi ve safe access procedures through the posterior gastric
wall resulted in access near the pancreas without signifi cant
complication; all six unsafe procedures resulted in injury,
including pancreatic laceration and kidney puncture. Three
of six transrectal safe access procedures resulted in injury:
small bowel perforation, puncture through the left
mesosalpinx without bleeding, and puncture through the
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CHAPTER 25 Training the Gastroenterologist for NOTES
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Figure 25.5 Shape Tool and corresponding digital image. (Reproduced from Fowler et al. [10], with permission from Elsevier.)
registered guidance is used [13]. EUS has been used to avoid
injury during endoscopic full -thickness resection (described
below) [14].
Once in the peritoneal cavity, EUS can be used for staging
of tumors; emerging technologies, such as contrast and
sonoelastography, can augment its accuracy in real -time
diagnosis (discussed below) [15,16]. EUS -guided transgastric
lymphadenectomy using a thread -tag system and needle has
been described [17]. At certain centers, EUS is routinely
used for pancreatic pseudocyst drainage and necrosectomy
(discussed below) [18]. Celiac plexus block has also become
a routine translumenal procedure [19]. EUS guidance has
been used in the creation of anastomoses between viscera
(discussed below) [20]. EUS -guided cholecystoenterostomy
with stent placement has been used for treatment of acute
cholecystitis in patients who are poor candidates for chole-
Figure 25.6 Image registration guidance using 3D reconstruction of
endoscope tip and abdomen. (From Shaikh SN [1], with permission from
Baishideng Publishing Group Co.)
cystectomy [21].
As the pancreas is easily accessible via EUS, echoendoscopists are experienced in pancreatic imaging and are
uniquely positioned to perform future translumenal pancre-
lateral pelvic wall muscle without bleeding. All six unsafe
procedures resulted in injury, including bladder puncture
and iliac artery injury. As vascular structures change position
after insuffl ation of air into the gastrointestinal tract, EUS
retains its utility during translumenal access even if image -
atic interventions. Emerging EUS -guided pancreatic cancer
therapies include radiofrequency ablation, photodynamic
therapy, brachytherapy, and mixed lymphocyte culture
(cytoimplant) [22–26]. EUS -guided diathermy may eventually be used to enucleate small pancreatic tumors [27].
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Training
Training gastroenterologists for NOTES is a multifaceted task
ideally comprising didactic teaching, experience in skills
trainers and simulators and/or animal models, preceptored
experience, and verifi cation of skills and satisfactory patient
outcomes.
Didactic teaching should familiarize the gastroenterologist
with the requisite indications, objectives, anatomy, instruments, techniques, and complications pertinent to a NOTES
procedure. Motor skill acquisition then begins with the
erratic cognitive stage [28]. Box trainers are useful in this
stage, training psychomotor skills for specifi c tasks rather
than entire procedures [29]. Graded levels of expertise can
be determined for these tasks, and trainees can practice until
they reach target levels of performance. A task -specifi c box
trainer for NOTES procedures would be of value.
Simulation has been shown to improve endoscopic and
surgical performance [30]. Its value becomes apparent when
the human consequences of inexperienced practice are considered: the Southern Surgeons Club found that 90% of
common bile duct (CBD) injuries during laparoscopic cholecystectomy occurred during the fi rst 30 such procedures
performed by a surgeon; the 1.7% probability of CBD injury
during the fi rst laparoscopic cholecystectomy fell to 0.17%
by the 50th procedure [31,32]. In fact, malpractice insurers
have incentivized trainees to pass certifi cation on the validated Fundamentals of Laparoscopic Surgery system [33].
To be of value, training devices and simulators must have
certain characteristics: internal consistency, reliability, and
validity; if these are achieved, the simulator can also be used
to assess trainee progress. Internal consistency requires that
each component of the simulator measure some aspect of
the NOTES procedure. Reliability requires that the resulting
scores are precise and consistent, yielding stable results for
the same trainee if the evaluators change (inter -rater reliability) or the test is repeated (test -retest reliability); this will
ensure that change in score only refl ects change in the
trainee’s skill [34]. Validity has several components that
imply that the simulator accurately assesses ability. Construct validity allows a simulator to differentiate between
experts and novices [35]. Face validity refl ects expert opinion
that the test measures what it intends to; content validity
refl ects expert opinion that the test comprehensively measures all aspects of the skill. External validity requires that
the test results achieved from the sample can be generalized
to different populations or situations. Criterion validity
requires that simulator performance refl ects actual performance (concurrent) and predicts future performance (predictive). Determination of predictive validity requires
comparison with a valid measure of actual procedure performance; this will require development of NOTES -specifi c
performance metrics [33].
Simulators should have established profi ciency targets
and should provide trainees with immediate and targeted
feedback, so that practice can be focused on weaknesses
until targets are reached. Compliance with simulation -based
training improves when objective goals are established and
improvement can be demonstrated with repeated practice
[36]. Profi ciency targets for NOTES simulators should be
defi ned by measuring experts ’ scores at their plateau. Immediate feedback throughout the training process was proven
useful during enrollment for a sentinel lymph node biopsy
trial, in which surgeons were evaluated on fi ve cases. The
fi rst group submitted fi ve cases for evaluation, and 48% met
criteria for participation in the trial; the second group
received feedback after each case, and 80% met approval
criteria [37].
Virtual reality simulators are versatile: they can integrate
presentation of a didactic curriculum, assess knowledge and
skills, and train either an array of basic skills such as orientation or entire operative procedures from start to completion
[4]. Fidelity can be enhanced by high -quality imaging, use
of force feedback to provide realistic tactile responses, and
use of anatomic models based on actual patients. The ProMIS
simulator, for example, uses virtual reality simulation with
animal or synthetic tissue inside the simulator to provide
actual tissue feel.
Simulators developed specifi cally for NOTES should allow
familiarization with instruments, transmural access, orientation, navigation, dissection, tissue mobilization with opportunity for vascular and visceral injury, and access closure.
Hence, they should include multiple access points, a realistic
spatial environment including obstructions that will defl ect
the endoscope tip during movement, and independent internal motion that realistically refl ects physiologic processes
such as pulsation and respiration [38]. For a more detailed
discussion of simulation in NOTES, the reader is referred to
Chapter 27.
Several laparoscopic and endoscopic trainers and simulators have been validated for their respective indications. The
Fundamentals of Laparoscopic Surgery (FLS) trainer uses a
camera and two trocars to test peg transfer, precision cutting,
placement of a ligating loop, and suturing with extracorporeal and intracorporeal knot tying; effi ciency and precision
are scored (see Figure 25.7). The score predicts intraoperative laparoscopic performance independent of surgeon experience [33]. The Endoscopic -Laparoscopic Interdisciplinary
Training Entity (ELITE) trainer (MITI, Klinikum Rechts der
Isar, Germany and Coburger Lehrmittelanstalt, Coburg,
Germany) is a humanoid model with a realistic airtight
abdominal cavity. It has a fi xed and modulated retroperitoneum; complete gastrointestinal tract with mesentery and
omentum, liver, gallbladder, and spleen have been made for
inclusion. The model was validated by having 8 gastroenterology and 22 surgery trainees (15 endoscopy novices and 15
experts) use a standard endoscope to enter the peritoneum
278
Figure 25.7 Fundamentals of Laparoscopic Surgery trainer box (Venture
https://t.me/med1917
Technologies, North Billerica, MA, USA) and monitor. (Reproduced from
Vassiliou et al. [33], with permission from Elsevier.)
via preformed trans -sigmoidal access and then endoscopically remove markers from all four abdominal quadrants.
This was performed fi ve times in succession. Twenty
randomly chosen subjects then used the same scope and
access point to perform cholecystectomy by clipping and
excising the cystic duct and then excising the gallbladder
and removing it from its bed. Construct validity was shown
as experts were signifi cantly faster at peritoneoscopy
(p = 0.041), and gastroenterologists signifi cantly faster than
surgeons; procedure time between the fi rst and fi fth trial
was signifi cantly reduced ( p = 0.02). Face validation was
achieved by survey [35].
Simulators do have limitations. They may be technically
easier than the actual procedure and often do not present
the trainee with the unpredictable complexities, external
distractions, and stresses that are inherent in clinical practice
[33]. Furthermore, simulators are no substitute for preceptorship – this was demonstrated during a study of FLS in
Botswana [39]. After only 2/20 trainees passed the cognitive
and manual certifi cation, a group of surgeons were proctored weekly from Toronto via telesimulation; a control
group of surgeons was left only with access to FLS equipment and videos. The telesimulation group universally
passed manual certifi cation (versus 38% of controls) with
scores nearly double that of the unpreceptored group.
Reaching target benchmarks even on validated trainers and
simulators does not imply that a trainee has become competent; it only validates acquisition of the knowledge and
technical skills needed to perform a procedure so that the
trainee is free to focus on acquiring the clinical and operative
judgment that can only be acquired during actual procedures [33].
CHAPTER 25 Training the Gastroenterologist for NOTES
Assessment
Assessment is essential in determination of training effectiveness, in identifi cation of trainee weaknesses to direct
remediation, and in assessment of trainee progress. Currently, many training institutions use subjective assessments
that are summative (evaluative, at the end of training)
rather than formative (diagnostic, frequently throughout
training). These assessments are subject to errors in recall,
with particularly good or adverse events coloring recall of
prior performance; errors of distribution (the tendency to be
overly lenient or severe); errors of central tendency (failure
to use the range of the scale); and “halo effects, ” in which
trainees with a good work ethic or pleasant personality are
perceived as having better performance in unrelated areas,
such as technical skill [40,41]. All of these deprive the
trainee of valuable guidance toward areas that need improvement. Objective measures of procedural aptitude should be
developed for NOTES in order to validate simulator effectiveness, evaluate trainee progress, and identify areas for
improvement, and eventually to aid in credentialing professionals for NOTES.
The selection of accurate metrics is important; case
number, operative time, and complication rates have been
used as surrogates for competence, but these are easily adulterated. For example, endoscopists may undertake more
challenging cases as experience increases, resulting in longer
procedure times and higher complication rates. Performing
procedures more quickly may result in higher complication
rates [42].
Such an evaluation system, the Global Operative Assessment of Laparoscopic Skills (GOALS), has been developed
for laparoscopic surgery; it evaluates performance in fi ve
categories with a grade of one to fi ve [40]. Depth perception
assesses motor performance in a three -dimensional environment while viewing a two -dimensional monitor. Bimanual
dexterity assesses whether the surgeon uses both hands
optimally rather than ignoring the non -dominant hand.
Effi ciency assesses procedural fl uidity – does the surgeon
make progress in one area before proceeding to the
next? Tissue handling assesses appropriate instrument use
and gauges whether tissues are handled with appropriate
care. Autonomy evaluates independence by measuring
how much guidance the surgeon needs to safely complete
the task.
A NOTES -specifi c global assessment tool, Formative Intraoperative Tool for NOTES Evaluation of Surgical Skills
(FITNESS), has been developed [43]. It comprises six areas:
access (A), navigation and orientation (NO), visualization
and stabilization (VS), instrument manipulation and targeting (IMT), closure (C), and application of surgical principles
(SP). It has been tested for reliability and construct validity
on eight participants, four novice and four experienced, in
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a live porcine model. The subjects performed transgastric
access, peritoneoscopy, liver biopsy and hemostasis, targeted
peritoneal biopsy, and gastrotomy closure with the Tissue
Apposition System (TAS, Ethicon EndoSurgery, Cincinnati,
OH, USA). Internal consistency of the items was 0.96. The
mean total score for novices was 17.3 ± 3.8 versus 28.8 ± 1.3
for experienced operators ( p = 0.03). Inter -rater reliability
for the total score between observers (two endoscopists and
NOTES surgeons) was 0.95 (95% CI 0.80 –0.99); between
subjects and observers, it was 0.92 (0.76 –0.98).
Procedures
Given the disparate skills required for the broad range of
NOTES procedures, procedure -specifi c training may be the
optimal way to safely and effectively integrate NOTES
techniques into advanced endoscopic training. The following procedures fall within the realm of procedural
gastroenterology.
Cystogastrostomy
Pancreatic pseudocysts are fl uid collections that develop as
a complication of acute or chronic pancreatitis [44]. General
indications for drainage include presence of infection, size
>5 cm, and symptoms such as abdominal pain, gastric outlet
obstruction, or obstructive jaundice. Morbidity rates of 10 –
30% and mortality rates of 1 –5% have been reported with
surgical management [45–47]. Percutaneous aspiration
alone is associated with recurrence rate up to 71%; usage of
indwelling catheter is associated with bleeding, infection,
and fi stula formation [48]. Hence, endoscopic creation of a
fi stulous tract between the cyst and gastric lumen (cystogastrostomy) or duodenal lumen (cystoduodenostomy) has
become widely accepted [49].
The tract is created by locating the contact area between
the cyst and gastrointestinal lumen; EUS guidance is essential when there is no bulging of the gastric or duodenal
wall [48]. EUS with Doppler also increases procedural safety
by demonstrating vasculature in the puncture trajectory
[44]. Once the tract is created, stents or a nasocystic
drain can be inserted to maintain patency [48]. Common
complications include infection (5%), bleeding (1%), and
perforation (1%); stent occlusion or dislodgement may
occur later [49,50]. Nevertheless, endoscopic therapy has
shown to be of value and can be safely performed by the
gastroenterologist.
Endoscopic necrosectomy
Walled -off pancreatic necrosis (WOPN) develops after acute
necrosis evolves into a well -defi ned, partially encapsulated
collection [51]. When the patient has persistent pain, food
intolerance, failure to thrive, gastric outlet or biliary obstruction, or concern for infected necrosis, intervention is indi-
cated [52]. The mortality rate in patients with infected
necrosis has been shown to be over 70% without debridement or necrosectomy [53]. Surgical necrosectomy has early
and late complications – a study reported a 93% rate of
postoperative complications, largely multiple -organ failure
(50%) or thrombotic and cardiovascular complications
(31%), and a 28% mortality rate [54].
An endoscopic alternative to surgical and percutaneous
approaches is creation of cystoduodenostomy or cystogastrostomy followed by entry into the cavity with direct endoscopic necrosectomy [51,55]. The endoscopic approach
avoids the morbidity of open necrosectomy and is not complicated by development of external fi stulae [52]. Collections with internal septations can be better addressed via
endoscopic debridement than drainage alone [56]. The
endoscopic approach is ideal when the necrosis is accessible
via the posterior gastric wall (pancreatic body and tail) or
via the medial duodenal wall (pancreatic head and proximal
body) [52,53]. EUS can be used to determine the thickness
of the gastric wall ( <10 mm preferred), avoid blood vessels
in the puncture route, and locate the cyst if extrinsic compression of the gastric wall is not apparent. Additionally, if
there is communication between the cyst and the main
pancreatic duct or ductal disruption, the gastroenterologist
can concurrently place a pancreatic duct stent across the
disruption to avoid eventual duct disconnection [53]. When
compared with standard transmural drainage and stent
placement, direct endoscopic necrosectomy has been shown
to reduce need for eventual operative drainage (30% versus
4%, p < 0.04) or percutaneous drainage (20% versus 0%,
p < 0.04) [51].
Direct endoscopic necrosectomy may not be optimal
initial management in cases of necrosis not reachable
through the posterior gastric or medial duodenal wall,
extensive extrapancreatic necrosis (especially extension into
the paracolonic gutters), or multiple pockets that are not
organized [52]. Furthermore, gastroenterologists who
undertake the procedure should be comfortable with management of common complications – especially bleeding,
which has often been treated endoscopically in reported
series [54,55]. Other reported complications include cyst
perforation, fi stula formation, and air embolism [54]. These
procedures are best performed under anesthesia and using
CO
insuffl ation.
2
Endoscopic myotomy
Myotomy is considered the most effective therapy for achalasia [57]. Laparoscopic myotomy is an improvement over
open surgery, but still incurs risk of injury to collateral structures and stimulates formation of adhesions, resulting in
subsequent open surgery in the event of treatment failure
[58,59]. While gastroenterologists perform pneumatic dilation to treat achalasia, it is not as effective as myotomy in
reduction of lower esophageal sphincter (LES) pressure or
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relief of symptoms; hence, endoscopic myotomy techniques
have been developed. The fi rst was reported in 1980.
Pasricha et al. have performed endoscopic myotomy
through a submucosal tunnel in a porcine model [57]. Submucosal saline injection was used to create mucosal lift 5 cm
proximal to the gastroesophageal junction. A unipolar
needle-knife was used to nick the mucosa and insert a controlled radial expansion balloon (10 –11–12 mm; Boston Scientifi c, Natick, MA, USA). The scope was advanced over the
balloon catheter into the submucosal space between the
mucosa and circular muscle. When the gastroesophageal
junction was reached, a needle -knife (Boston Scientifi c) or
insulated-tip knife (Olympus) was used to incise the circular
layer of muscle distally to proximally. The scope was withdrawn into the lumen and the mucosal defect was closed
with clips (Resolution; Boston Scientifi c). Average procedure time was 15 min. LES pressures fell from an average
16.4 mmHg before myotomy to an average of 6.7 mmHg
afterwards ( p = 0.03). Necropsy showed that the esophageal
mucosa healed in all cases, and there was no evidence of
mediastinitis or peritonitis.
Per -oral endoscopic myotomy (POEM) in 17 patients was
reported by Inoue et al. [60]. This uses an endoscopic submucosal dissection technique to create a submucosal tunnel
from the esophagus into the proximal stomach. Triangle knife (KD -640L; Olympus) was used to dissect the circular
muscle layer from approximately 7 cm proximal to 2 cm
distal to the gastroesophageal junction under endoscopic
visualization. Coagulating forceps was used for hemostasis.
Closure of mucosal entry was done with hemostatic clips
(HX-110QR; Olympus). The procedure was successful in all
17 patients. The submucosal tunnel was 12.4 cm long on
average, and the length of the myotomy was 8.1 cm on
average (6.1 cm in esophagus, 2.0 cm in stomach). Operating
time ranged from 100 to 180 min. Dysphagia symptom score
fell from 10 before POEM to 1.3 afterwards ( p = 0.0003);
resting LES pressure decreased from a mean of 52.4 mmHg
to 19.8 mmHg ( p = 0.0001). No patient had recurrent dys-
phagia on follow -up. There were no signifi cant POEM related complications; cardiac mucosa was penetrated in two
cases, mediastinal tissue was exposed in four cases, and
pneumoperitoneum occurred in one patient. The less invasive nature of this technique and ability to approach
longer segments of the circular muscle layer may allow this
technique to have broader applications, and a possible role
in other esophageal motility disorders.
tip
Endoscopic full-thickness resection
Endoscopic mucosal resection and endoscopic submucosal
dissection are increasingly used for en bloc resection of early
cancers; however, excision of tumors penetrating deeper
than the submucosal layer presents risk of perforation.
Endoscopic full -thickness resection (EFTR) presents an
intermediate step between these techniques and surgical
resection [7]. EFTR has potential applications in the esophagus, stomach, and colon.
Many methods of tissue isolation, excision, and closure
have been demonstrated using standard fl exible endoscopes
and new NOTES platforms. Notably, the use of an endoloop
to secure the base of the EFTR site prior to resection can
prevent lumenal collapse, which makes closure more diffi cult [61]. Excision has been demonstrated with snares and
electrosurgical cutting tools [7,61–67]. Closure has been performed using tissue anchors with integrated suture, hemostatic clips, over -the-scope clips, and a variety of novel
purpose-specifi c devices. Early human trials have demonstrated varying complication rates; a small head -to-head
comparison of gastric stromal tumor resection versus laparoscopic surgery found signifi cantly higher overall complication rates [66]. Safety can be increased by use of EUS to
avoid resection in proximity to large mural vessels; injection
of sclerosants or epinephrine into peritumoral tissue may
provide further protection from hemorrhage [62]. Risk of
incomplete resection can be reduced by performing multiple
biopsies around the tumor to determine appropriate resection margin. Although full -thickness resection currently lies
within the reach of procedural gastroenterology, further
technique/device development and verifi cation of safety is
needed before this procedure fi nds broad acceptance.
Endoscopic anastomosis creation
NOTES has been used in a porcine model to create anastomoses between both the stomach and small intestine and
the stomach and gallbladder. Fritscher -Ravens et al. used
ultrasonic guidance to insert a needle, metal tag, and suture
into the target organ [20]. Two 7F catheter segments were
pushed into the target organ over a guidewire and formed
into a cross shape. This was compressed against a fl at plate
in the accessible lumen. Within 7 days, a 3 –9 mm anastomosis had formed. This minimally invasive technique can be
applied even when only one lumen is accessible via fl exible
endoscopy. The Swain group has developed other devices
for endoscopic creation of anastomoses [68]. Ryou and
Thompson demonstrated gastrojejunostomy creation using
endoscopically delivered self -assembling magnets (SAMSEN)
in a porcine model [69] (see Figure 25.8). A gastroscope was
advanced into the peritoneal cavity via gastrotomy; an overtube with two graspers was advanced over it and used to
secure the small intestine for enterotomy creation with a
needle-knife. The overtube was inserted into the small
bowel over guidewires and the fi rst magnet was inserted
into the small bowel. The overtube was retracted into the
stomach and a second magnet was deployed over the
guidewire attached to the small bowel magnet. Using a
contrast-fi lled balloon collar, the second magnet was
advanced to mate with the fi rst under fl uoroscopic guidance.
The needle -knife was used to create a gastrojejunostomy
within the magnets ’ center. This process was also completed
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(a) (b)
(c) (d)
Figure 25.8 Delivery of SAMSEN magnets: (a) NOTES gastrotomy, small bowel mobilization, an enterotomy using custom grasping overtube.
(b) Insertion of small bowel magnet. (c) Opening of small bowel magnet and then insertion of gastric magnet. (d) Mating of magnets and
gastrojejunostomy creation. (Reproduced from Ryou and Thompson [69], with permission from Elsevier.)
in a human cadaver. Endoscopic anastomosis creation has
the potential to supplant surgical management of bowel or
biliary obstruction as well as obesity.
Endoscopic peritoneoscopy
Endoscopic cancer staging can be performed after translumenal entry into the peritoneum. The ostensible benefi ts of
NOTES over laparoscopy, including faster postoperative
recovery and decreased suppression of immune response,
may allow quicker use of chemotherapy or radiation [70,71].
Increased magnifi cation of view as well as access to the lesser
sac and suprahepatic/infradiaphragmatic spaces may eventually result in increased sensitivity [1]. Adjunct use of technologies such as EUS with contrast and optical confocal
microscopy (discussed below) will further enhance the effectiveness of cancer staging via NOTES.
Hazey et al. have compared transgastric endoscopic peritoneoscopy with diagnostic laparoscopy to evaluate for
distant metastatic disease in 20 patients with radiographic
diagnosis of resectable pancreatic head mass [72]. Endoscopic visualization of the liver, omentum, and four quadrants of the abdomen was achieved in a mean 21 minutes.
In 14/20 cases, endoscopy and laparoscopy were consistent
in localization of pathology; surgical decision making based
on fi ndings was consistent in 19/20 cases. Four inconsistencies were small lesions in the right upper quadrant and right
lobe of the liver; one benign abdominal wall implant was
missed. One lesion was removed by laparoscopy prior to
endoscopy.
Porcine models have been created with beads implanted
into the peritoneum, diaphragm, and liver [73,74]. Laparoscopy detected 95% of beads; transcolonic peritoneoscopy
using standard endoscopic instruments found 76%, with
only 53% of beads at the inferior liver surface found. Transgastric peritoneoscopy demonstrated a yield of 64%; while
92% of beads on the abdominal and diaphragmatic peritoneum were seen, only 38% of beads on the liver were found
[74]. A similar cadaver model found diagnostic yield of 97%
in laparoscopy, 76% with transgastric access, and 85% with
transcolonic access [75]. Again, most of the missed beads
were located at the inferior liver surface; transgastric peritoneoscopy missed 67% and transcolonic peritoneoscopy
missed 44%. Continued advancements in instrument capability will allow better tissue traction and triangulation for
examination of the liver, as well as intraprocedural tissue
evaluation.
Lymph node mapping and sentinel node biopsy
Besides staging, NOTES procedures can be used to evaluate
intraperitoneal lymph nodes in patients with a variety of
malignancies. With the proliferation of screening, patients
are increasingly undergoing endoscopic resection of early
282
stage cancer; minimally invasive lymph node evaluation can
https://t.me/med1917
be especially useful in these cases to determine operative
extent, need for adjuvant therapy, and prognosis.
Submucosal injection of dye followed by endoscopic excisional node biopsy has been used to demonstrate feasibility
of NOTES lymph node mapping and sentinel node biopsy
for gastric, pancreatic, biliary, and colonic tumors [76–79].
NOTES lymphadenectomy has also been studied for gynecologic malignancies [80].
Liver biopsy
Liver biopsy has wide application in gastroenterology. The
complication rate, including pain, bleeding, bile peritonitis,
and pneumothorax, is approximately 3% [81,82]. NOTES
liver biopsies have been performed safely in humans with
endoscopic biopsy forceps and electrocautery for hemostasis
if needed [83–85]. When advanced technologies (below)
allow real -time in vivo evaluation of tissue, instruments
allow better retraction of tissue, and reliable access closures
are developed, NOTES will arm the gastroenterologist with
safer, more versatile methods of liver biopsy. The reader is
referred to an in -depth discussion of mini -laparoscopy and
liver biopsy in Chapter 7.
Intraprocedural tissue evaluation
Advanced technologies can be used to enhance the capability and accuracy of NOTES staging, lymph node evaluation,
and liver biopsy. Many of these technologies already have
applications in gastroenterology, such as diagnosis of Barrett’s esophagus.
EUS contrast agents in conjunction with Doppler imaging
can accurately assist in differentiation of benign and malignant tumors using characteristics of vasculature; they can
also assist in monitoring of response to antiangiogenic treatment [16]. Real -time sonoelastography (RTSE) presents
visualization of tissue strain, allowing virtual palpation to
highlight probable malignant nodes and to guide tissue sampling during staging and mapping [86]. Optical coherence
tomography (OCT) uses echo time -delay, much like ultrasound, of near -infrared light to provide a cross -sectional
image of 2 –3mm depth in opaque tissue [87] (see Figure
25.9). Injection of a probe into the node could provide
deeper 360 ° views. Imaging is real -time, and resolution
approaches that of standard histology; there is potential to
detect micrometastases without excisional biopsy [87,88].
Confocal laser microscopy (CLM) uses laser illumination to
image up to 0.25 mm deep (up to the subcapsular sinus of
a lymph node), potentially reaching up to 75% of nodal
metastases [88]. It is also useful in liver biopsy [89]. Tumor specifi c dyes may enhance its sensitivity in the future. The
CLM probe fi ts through the instrument channel of a gastroscope. Elastic scattering spectroscopy (ESS) measures intensity of photon backscatter, using statistical analysis of changes
in subcellular structure to recognize patterns and provide
CHAPTER 25 Training the Gastroenterologist for NOTES
Figure 25.9 Optical coherence tomography (OCT) examination of
sigmoid mesentery lymph node in vivo via transgastric NOTES approach;
inset: OCT view of lymph capsule, subcapsular space, and superfi cial
nodal parenchyma. (Reproduced from Cahill RA [88], with permission
from Elsevier.)
likelihood of tumor presence in tissue up to 1 mm deep
[88,90].
Conclusion
Gastroenterologists have tremendous potential to apply
NOTES principles widely to the diagnosis and therapy of
gastrointestinal diseases. As technology continues to enhance
instrumentation, training of gastroenterologists to perform
NOTES procedures will become increasingly important.
Structured teaching programs comprising didactic teaching,
trainers, simulators, preceptorship, assessment, and credentialing should be incorporated into advanced endoscopic
training. Effective integration of NOTES into the training of
gastroenterologists has the potential to change the face of
practice in gastroenterology.
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