Introduction
Interventional endoscopic ultrasound (EUS)-guided procedures have rapidly evolved
over the past two decades. A variety of procedures have shown promise with level I
evidence in certain procedures like EUS-guided biliary drainage (EUS-BD), EUS-guided
pancreatic fluid collection drainage, and EUS-guided celiac plexus block [1]
[2]. The evolution of these procedures is also being facilitated by a parallel evolution
in technology. Availability of EUS-specific stents, especially lumen apposing metal
stent (LAMS) and bi-flanged metal stents, has helped increase the ease of procedures.
While these procedures continue to evolve, an important lacuna is the lack of training
opportunities for them. Fellowship programs typically may not provide adequate training
in advanced interventional EUS procedures, as most of advanced centers have a limited
number of such procedures. In addition, the higher incidence of adverse events reported
with some of these procedures makes it prudent to for perform initial learning of
basic techniques on models. Models are available for some individual technique, such
as EUS-guided fine-needle biopsy (EUS-FNB), EUS-guided pseudocyst drainage (EUS-PSD),
and EUS-BD. However, there is no one model that allows training in all these procedures.
We have been attempting to create an interventional EUS model for the last several
years. Our first attempt was creation of a 3D-printed model for BD [3]. This was followed by a hybrid model for EUS-BD [4]. One of our aims has always been to explore the possibility of a model that allows
training in most if not all interventional EUS procedures. This study evaluated a
novel all-in-one model with the possibility of multiple procedures in a single model
(EUS magic box). The aims of this study were: 1) creation of a model for multiple
interventional EUS procedures such as EUS-guided fine-needle biopsy, EUS-guided hepaticogastrostomy
(EUS-HGS), EUS-guided rendezvous biliary drainage (EUS-RV-BD), EUS-guided rendezvous
pancreatic duct drainage (EUS-RV-PD), EUS-PSD, and EUS-guided gastroenterostomy (EUS-GE);
and 2) assessment of the efficacy of this model (EUS magic box) during training sessions,
and associated problems if any.
Material and methods
Creation of EUS magic box
Based on our experiences with our previous models [3]
[4], we realized that our previous models needed X-ray, and hence, could be used only
in endoscopy theater with X-ray protection. Therefore, we planned to create a model
that could be used both with or without X-ray, making it suitable for workshops and
conferences.
As mentioned previously in an earlier article, we found it difficult to obtain a suitable
artificial material for the stomach, as needle puncture and cautery use through any
synthetic material created problems with unsatisfactory end results. Hence, we decided
to use a pig stomach and a synthetic duodenum and pancreato-biliary tree ([Fig. 1]). For the stomach, we utilized disinfected terminal esophagus (distal 5 cm) and
pig stomach. The esophagus was used to attach the stomach to the relevant inlet in
the magic box through a trocar. The distal end of the stomach was closed with sutures
and attached to the side of the EUS magic box. The duodenum with C loop was created
using medical grade silicone. Thus, two separate inlets were provided in the magic
box, one for the stomach, and one for the duodenum ([Fig. 1]). The need for separate openings for the stomach and duodenum arose from the fact
that the papilla in pig duodenum is very high and the bile duct (BD) and the PD configurations
are different from humans. Also, our final aim was to create an entirely synthetic
model without any pig parts. Because of lack of a suitable material, we created a
hybrid model, part synthetic and part porcine. The dimensions of the duodenum were
kept slightly larger than normal (4-cm diameter), for ease of procedure during training.
A papilla was created on the medial wall of the second part of the duodenum, with
separate openings for the BD and PD ([Fig. 2]). The duodenum was provided with openings on the anterior wall for visualization
of the guidewire, when X-ray was not being used ([Fig. 1]). The design of the duodenum was such that the C loop of the duodenum ended just
underneath the stomach making it possible to do EUS -GE. We intentionally created
a markedly dilated biliary and pancreatic ductal system for trainees to learn easily.
The BD measured 2 cm, the left intra hepatic bile duct 1 cm, and the PD 1 cm. The
right intrahepatic biliary system was kept non-dilated, with the purpose of teaching
guidewire manipulation. The BD and PD separately joined the papillary orifice with
the help of a narrow plastic valve, thus simulating a stricture.
Fig. 1 a EUS Magic box exterior. Note two separate opening for
(A) stomach and (B) duodenum and (C) external control for camera on the roof. b The inner view of the roof showing the internal camera (A) with light. c The Interior of the model after removing the roof. The pig stomach (A) is sutured
to the side of the box with thread. The ultrasound gel medium bathes the organs. The
duodenum (B) is attached to a separate inlet, and has holes (D) to see guide wire
movement, when X-ray is not being used. The bile duct (C) and pancreatic duct are
underneath the pig stomach, and can be seen converging toward the papilla. The electrocautery
pad is seen submerged in the gel medium(E). d Interior of model after pulling the stomach away. Note pig liver tissue (A) for biopsy
and pancreatic pseudocyst (B) made up of pig urinary bladder. The dilated bile duct
(C) and pancreatic duct (D), can be seen joining at the papilla. The third part of
the duodenum is submerged in the medium. It can be filled with water, and used as
enteral loop (E) for EUS-GE.
Fig. 2 The Silicone duodenum. a interior of duodenum with folds. b Duodenum showing papillary orifice. c Sphincterotome entering the bile duct at papilla. d Sphincterotome entering in pancreatic duct at papilla.
Multiple pieces of liver tissue were embedded in gelatin, to be used for EUS-guided
fine-needle biopsy (EUS-FNB). For pseudocyst we used pig urinary bladder filled with
gelatin. The size of the pseudocyst was kept at 6 cm. The pseudocyst and liver tissue
were fixed with help of a plastic anchor to the base of model. The positioning of
the biopsy target ([Fig. 1]) and pseudocyst is shown in ([Fig. 1]).
The outer box was made up of fine acrylic (5 mm) and measured 37 cm × 29 cm × 32 cm
([Fig. 1]). It had a detachable roof fitted with a camera (standard-definition camera with
2.8-mm lens) with light (DC-12V LED) and external controls ([Fig. 1]). A 12V DC power adapter was used. This allowed projection of the interior of the
model on to a TV screen, thus obviating the need for X-ray. However, if the procedure
had to be learned under fluoroscopic control, the roof of the model along with the
camera could be removed. Electrocautery application was made possible, the cautery
pad being kept on the pig stomach or on the gel interface ([Fig. 1]) We used the gel used for electrocardiography/ultrasound (neutralized copolymer
of maleic anhydride and a C 1 -C five alkyl vinyl ether), as it is cheap, non-degradable
and offers excellent acoustic views and electrocautery usage with no problem. The
box was filled with gel in such a way that the gel remained just below the level of
the inlet ports. This allowed placement of the stomach on the surface of the gel while
the biliary system, the PD, the biopsy targets and the pseudocyst were submerged within
the gel. The duodenum second part was kept on the surface of the gel, while the third
part was submerged in the gel. The position of the left intrahepatic bile duct, biopsy
targets and pseudocyst in relation to the stomach is shown in [Fig. 1].
Evaluation of the model
We conducted an observational study on this model during two train-the-trainers courses
held in September 2019 and January 2020. Thirty-six trainees were chosen from a group
of applicants. The criteria for choosing the candidates were: 1) at least 3 years’
experience in gastroscopy and colonoscopy with certification; 2) at least 2 years’
experience in diagnostic EUS; and 3) availability of linear echo-endoscope at the
candidate’s institute. The institutional ethics committee approved the study.
A therapeutic linear echo-endoscope (Olympus TGF140, Olympus Inc, Tokyo) was used.
A 19-gauge fine-needle aspiration cytology needle (Cook Inc. Bloomington, Indiana,
United States) was used for puncture, a 260 cm 0.032″ or a 450 cm 0.035″ guidewire
(Terumo, Radifocus, Japan, and Hydra Jag wire, Boston Scientific, Massachusetts, United
States) was used for negotiation within ducts or pseudocyst. Tract dilation was done
with a 6F cystotome. An Acquire 22-gauge needle (Boston Scientific, Massachusetts,
United States) was used to train in EUS-guided biopsy ([Fig. 3a], [Fig. 3b]). For pseudocyst drainage and gastroenterostomy, an Axios LAMS (Boston Scientific;
Massachusetts, United States) stent was used. For pancreatic and bile duct interventions,
plastic stents were used.
Fig. 3 a EUS image showing target lesion (arrow). b EUS-guided fine-needle biopsy with 22-gauge needle (arrow). EUS-guided hepaticogastrostomy.
c Needle puncture in left hepatic duct (arrow). d Guidewire passage. Note the guidewire seen within the bile duct (arrow) without need
for fluoroscopy. e Tract dilation with cystotome (arrow). f Plastic stent deployed in stomach.
Multiple therapeutic EUS procedures (EUS-FNB, EUS-RV-BD, EUS-HGS, EUS- RV-PD, EUS-PSD,
EUS-GE,) were taught during the course. No humans or live animals were used. Training
was imparted over 3 days in two batches. The first batch (September 2019) had 16 trainees
and the second batch (January 2020) had 20 trainees. The training consisted of lectures,
demonstration of live cases of various procedures, and finally training on the model.
Stepwise training
The trainees were exposed to technical aspects of various EUS procedures by didactic
lectures and live procedures. The hands-on training was divided into three parts over
3 days. On the first day, EUS-FNB ([Fig. 3], [Video 1]) and EUS-PSD were taught ([Fig. 5], [Video 4]). The trainees performed predefined tasks such as needle puncture and LAMS insertion
in the pseudocyst cavity. On the second day, the trainees performed EUS-RV-BD and
EUS-HGS on the model ([Fig. 3], [Video 2]). They were taught the following steps: 1) appropriate scope position for each procedure;
2) puncture with a 19-gauge needle; 3) guidewire manipulation; 4) tract dilation with
6F cystotome; and 5) stent placement including steps for LAMS placement. On the third
day, they were taught EUS-RV-PD ([Fig. 4], [Video 3]) and EUS-GE ([Fig. 6], [Video 5]).
Fig. 4 EUS rendezvous (EUS-RV) of pancreatic duct. a Needle puncture in the pancreatic duct (arrow). b Snare grasping the guidewire at the papilla. c Wire is seen in the gastric and duodenal ports. d Fluoroscopic image of ERCP scope with sphincterotome entering into bile duct (arrow).
Fig. 5 a EUS evaluation of pseudocyst cavity. b The hot device entering the cyst cavity guided pancreatic pseudocyst drainage. c Distal flange of Axios stent being deployed. d Deployment of proximal flange of Axios stent within the stomach.
Fig. 6 EUS-guided gastroenterostomy with Axios stent. a Note the nasobiliary drain in the duodenum to fill water mixed with methylene blue.
b Measurement of adequate diameter of the duodenum before stent placement. c Deployment of distal flange within the duodenum. d Final deployment of proximal flange. See the methylene blue mixed water indicating
a successful anastomosis.
Video 1 US-guided fine-needle biopsy.
Video 2 EUS-guided hepaticogastrostomy.
Video 3 EUS-guided rendezvous pancreatic duct drainage.
Video 4 EUS-guided pseudocyst drainage.
Video 5 EUS-guided gastroenterostomy.
For EUS-RV-PD, the PD was accessed through the trans-gastric route on the hybrid model.
They were taught scope position, needle puncture, and guidewire manipulation across
the papilla into the duodenum. The echo-endoscope was then removed, leaving the wire
in place. A duodenoscope was then inserted through the other port into the duodenum.
They were taught to catch the wire at the papilla with the snare and pull it up into
the duodenoscope channel.
For EUS-PSD and EUS-GE, the technique of Hot Axios placement was taught. In addition,
for EUS-GE, a nasobiliary drain was placed in the duodenum and water mixed with methylene
blue was instilled. A free-hand technique was used for EUS-GE.
A brief description of the individual techniques is as follows.
For EUS-FNB, the echo-endoscope was placed in the stomach and lesions were identified.
A 22-gauze EUS-guided biopsy needle was then fixed into the biopsy channel of the
echo-endoscope, needle trajectory was assessed and puncture was done through the stomach
wall, once in the lesion fanning technique was applied to sample multiple areas within
the lesion. A slow pull was applied on the stylet to generate gentle negative pressure.
The needle was then removed and sample was expressed in a pastry dish filled with
saline.
For US-HGS, trainees were taught needle puncture with 19-gauge needle, appropriate
scope position, wire manipulation to coil and keep the wire at the liver hilum, track
dilation with 6F cystotome, and finally placement of single pigtail plastic stent
in left hepatic duct. About 3 cm of stent was left in the stomach.
For the antegrade procedure, trainees were taught appropriate scope position, puncture
of the left intrahepatic bile duct with a 19-gauge needle, manipulation of guidewire
across the hilum into the duodenum, tract dilation with a 6F cystotome and placement
of single pigtail plastic stent in the bile duct and the distal end coming out of
the papilla into the duodenum.
For the rendezvous procedure, with both biliary and pancreatic rendezvous, the trainees
were taught appropriate scope position (left intrahepatic duct for biliary rendezvous
and pancreatic duct in the tail of pancreas for pancreatic rendezvous), guide wire
was then manipulated downstream across the papilla into the duodenum. The echo-endoscope
was then removed leaving the guide wire in position. The duodenoscope was then introduced
through the inlet of the duodenum and guide wire was seen exiting from papilla. The
guidewire was caught with a snare and gently pulled into the biopsy channel of the
duodenoscope. Once enough guide wire was available at the biopsy port of duodenoscope
a 5F sphincterotome was threaded over it and pancreatic duct or bile duct was cannulated.
Once selective cannulation was achieved, the original guidewire was removed and fresh
guidewire passed through the sphincterotome into the BD or PD. Finally, a plastic
stent was placed over the guidewire.
For EUS-guided pseudocyst drainage, the pseudocyst in relation to posterior wall was
identified and measured. A Hot Axios stent was utilized and the stent was deployed
in a single step.
For EUS-GE, a nasoduodenal tube was placed in the third part of duodenum which was
filled with water mixed with methylene blue. The echo-endoscope was positioned in
the stomach to visualize the third or fourth part of the duodenum. Once the position
was achieved, a Hot Axios stent was deployed and influx of methylene blue water into
the stomach confirmed the successful anastomosis.
Assessment
The experts graded the various aspects of the model as follows: Grade 1 – average,
Grade 2 – good, Grade 3 – very good, and Grade 4 – excellent. Objective assessment
of the trainee performance was done. The trainees were assisted in all procedures
by an expert who identified their mistakes and corrected them. Assessment parameters
were correct scope position, needle puncture and visibility under ultrasound, guidewire
manipulation and avoidance of shearing, grasping the guidewire in the duodenum, pulling
the guidewire into duodenoscope biopsy channel, plastic stent deployment and LAMS
insertion techniques. Deficiencies for each trainee were noted and corrected.
Results
Details of trainee prior experience are shown in [Table 1]. The expert assessment of the model for various interventional EUS procedures is
shown in [Table 2]. All the trainees were able to complete the requisite steps for all the procedures
under supervision. The results of the assessments are shown in [Table 3]. The success rate in EUS-FNB was high and the trainees also were quick to learn
pseudocyst drainage and EUS-GE with LAMS; the success in BD and pancreatic duct drainage
(PD) was relatively less. Time taken to complete the requisites step of EUS-FNB, EUS-PSD,
EUS-GE was significantly less than for EUS-BD, EUS-RV-PD (mean time 10.5 minutes;
range 3.5 to 22 vs 28 minutes; range 17 to 40; P < 0.001). A total of 107 technical difficulties ([Table 4]) were noted while doing interventional procedures on the model: wrong scope position
55, incorrect duct puncture 27, guidewire-related problems 25 (wrong direction 13;
shearing 10; slippage during retrieval 2). EUS-FNB and LAMS insertion for pseudocyst
and gastroenterostomy showed fewer technical difficulties than bile duct and PD (35
vs 75; P < 0.001). On subjective assessment, 30 trainees (83 %) graded the model as good or
excellent. Six trainees had 10 minor suggestions for improvement (smaller size of
papillary orifice 4, thinner wall of the duodenum for easy EUS-GE 4, and use of EUS-specific
stents for training in EUS-BD 2).
Table 1
Details of trainees.
|
Total no. trainees (n)
|
36
|
|
|
24
|
|
|
12
|
|
Time since gastroenterology degree/ fellowship
|
|
|
30
|
|
|
6
|
|
Current affiliation
|
|
|
8
|
|
|
28
|
|
ERCP experience (performed ERCP independently)
|
|
|
36
|
|
|
0
|
|
Prior EUS experience
|
|
|
28
|
|
|
8
|
|
Duration
|
|
|
27
|
|
|
9
|
ERCP, endoscopic retrograde cholangiopancreatography; EUS, endoscopic ultrasound.
Table 2
Objective assessment of the model by experts.
|
Score
|
EUS-RV-BD
|
EUS-HGS
|
EUS-PSD
|
EUS-GE
|
EUS-RV-PD
|
EUS-biopsy
|
|
Expert 1
|
Expert 2
|
Average score
|
Expert 1
|
Expert 2
|
Average score
|
Expert 1
|
Expert 2
|
Average score
|
Expert 1
|
Expert 2
|
Average score
|
Expert 1
|
Expert 2
|
Average score
|
Expert 1
|
Expert 2
|
Average score
|
|
Scope position
|
3
|
3
|
3
|
3
|
4
|
3.5
|
4
|
3.5
|
3.75
|
3
|
3
|
3
|
3
|
3
|
3
|
3
|
4
|
3.5
|
|
Needle visibility (EUS)
|
4
|
4
|
4
|
3.5
|
4
|
3.75
|
NA
|
NA
|
NA
|
NA
|
NA
|
NA
|
3
|
3
|
3
|
4
|
3.5
|
3.75
|
|
Duct visibility
(EUS)
|
4
|
4
|
4
|
3
|
4
|
3.5
|
4[1]
|
4[1]
|
4
|
4[2]
|
4[2]
|
4
|
3
|
3.5
|
3.25
|
NA
|
NA
|
NA
|
|
Duct visibility
(X-ray/
external camera)
|
4
|
4
|
4
|
4
|
4
|
4
|
NA
|
NA
|
NA
|
NA
|
NA
|
NA
|
3.5
|
4
|
3.75
|
NA
|
NA
|
NA
|
|
Guidewire manipulation
|
3
|
3.5
|
3.25
|
3
|
3
|
3
|
NA
|
NA
|
NA
|
NA
|
NA
|
NA
|
3
|
3
|
3
|
NA
|
NA
|
NA
|
|
Guidewire retrieval (RV)
|
3
|
4
|
3.5
|
NA
|
NA
|
NA
|
NA
|
NA
|
NA
|
NA
|
NA
|
NA
|
3
|
3.5
|
3.25
|
NA
|
NA
|
NA
|
|
Cautery usage
|
4
|
3
|
3.5
|
4
|
3
|
3.5
|
NA
|
NA
|
4
|
3
|
3.5
|
3.25
|
4
|
3
|
3.5
|
NA
|
NA
|
NA
|
|
Stent placement
|
4
|
4
|
4
|
3
|
4
|
3.5
|
4
|
4
|
4
|
3
|
4
|
3.5
|
3
|
4
|
3.5
|
NA
|
NA
|
NA
|
Score: Grade 1 – average, Grade 2 – good, Grade 3 – very good, and Grade 4 – excellent
EUS-RV-BD, EUS-guided rendezvous biliary drainage; EUS-HGS, EUS-guided hepaticogastrostomy;
EUS-PSD, EUS-guide pseudocyst drainage; EUS-GE, EUS-guided gastroenterostomy; EUS-RV-PD,
EUS-guided rendezvous pancreatic duct drainage.
1 Cyst and contents visibility
2 Enteral loop visibility
Table 3
Trainee performance on various procedures.[1]
|
Total no. 36
|
EUS-RV-BD
no. (%)
|
EUS-HGS
no. (%)
|
EUS-PSD
no. (%)
|
EUS-GE
no. (%)
|
EUS-RV-PD
no. (%)
|
EUS-biopsy
no. (%)
|
|
Appropriate scope position
|
25 (69.4)
|
27 (75)
|
30 (83.3)
|
22 (61.1)
|
24 (66.6)
|
33 (91.6)
|
|
Needle puncture
|
30 (83.3)
|
31 (86.1)
|
NA
|
NA
|
29 (80.5)
|
34 (94.4)
|
|
Wire manipulation
|
26 (72.2)
|
27 (75)
|
NA
|
NA
|
30 (83.3)
|
NA
|
|
Tract dilation
|
35 (97.2)
|
34 (94.4)
|
NA
|
NA
|
35 (97.2)
|
NA
|
|
Stent placement
|
32 (88.8)
|
34 (94.4)
|
36 (100)
|
36 (100)
|
34 (94.4)
|
NA
|
EUS-RV-BD, EUS-guided rendezvous biliary drainage; EUS-HGS, EUS-guided hepaticogastrostomy;
EUS-PSD, EUS-guided pseudocyst drainage; EUS-GE, EUS-guided gastroenterostomy; EUS-RV-PD,
EUS-guided rendezvous pancreatic duct drainage.
1 Number of trainees who could successfully perform the step without assistance
Table 4
Technical difficulties during trainee performance.
|
EUS-RV-BD
no. (%)
|
EUS- HGS
no. (%)
|
EUS-PSD
no. (%)
|
EUS- GE
no. (%)
|
EUS-RV-PD
no. (%)
|
EUS-FNB
no. (%)
|
|
Wrong scope position
|
11 (10)
|
9 (8.4)
|
6 (5.6)
|
14 (13)
|
12 (11)
|
3 (3)
|
|
Incorrect puncture
|
6 (5.6)
|
5 (4.6)
|
2 (1.8)
|
5 (4.6)
|
7 (6.5)
|
2 (1.8)
|
|
Guidewire passage in wrong direction
|
6 (5.6)
|
5 (4.6)
|
NA
|
NA
|
2 (1.8)
|
NA
|
|
Guidewire shearing
|
3 (2.8)
|
4 (3.7)
|
NA
|
NA
|
3 (2.8)
|
NA
|
|
Guidewire slippage during retrieval
|
1 (1)
|
NA
|
NA
|
NA
|
1 (1)
|
NA
|
|
Total
|
27 (25)
|
23 (21)
|
8 (7.5)
|
19 (18)
|
25 (23)
|
5 (5)
|
EUS-RV-BD, EUS-guided rendezvous biliary drainage; EUS-HGS, EUS-guided hepaticogastrostomy;
EUS-PSD, EUS-guided pseudocyst drainage; EUS-GE, EUS-guided gastroenterostomy; EUS-RV-PD,
EUS-guided rendezvous pancreatic duct drainage; EUS-FNB, EUS-guided fine-needle biopsy.
EUS-guided fine-needle biopsy
Thirty-three of 36 students (92 %) were able to achieve appropriate scope position.
Thirty-four of 36 were successful with needle puncture. Core obtained from biopsy
was adequate. Mean time taken by trainees to complete the procedure was 5.4 minutes
(range 3.5 to 10 minutes) ([Fig. 3], [Video 1]).
EUS-guided rendezvous biliary drainage
Appropriate scope position was attained by two-thirds of trainees (n = 25, 69 %) in
the first attempt. Needle puncture was successful by 30 trainees (83 %). Twenty-six
trainees (72 %) and 35 trainees (97 %) did successful wire manipulation and tract
dilation, respectively. Successful stent placement was done by 32 trainees (89 %)
on the first attempt. Initially 11 had the wrong scope position, which was corrected
by experts. Guidewire shearing was encountered by three trainees. One trainee had
guidewire slippage during retrieval. Mean time taken by trainees to complete the procedure
was 29.05 minutes (range 24 to 32 minutes).
EUS-guided hepaticogastrostomy
In first attempt, appropriate scope position was attained by 27 trainees (75 %). The
needle puncture was successful by 31 trainees (86 %). Twenty-seven (75 %) and 34 (94 %)
did successful wire manipulation and tract dilation, respectively. Successful stent
placement was done by 34 trainees (94 %) on the first attempt. Five had incorrect
needle puncture and guidewire passage in the wrong direction. Four had guidewire shearing
during retrieval. Mean time taken by trainees to complete the procedure was 20.6 minutes
(range, 17 to 24 minutes) ([Fig. 3], [Video 2]).
EUS-guided rendezvous PD
In first attempt, appropriate scope position was difficult and attained by only 24
trainees (67 %). The needle puncture was successful by 29 trainees (80.5 %). Thirty
trainees (83 %) and 35 trainees (97 %) did successful wire manipulation and tract
dilation, respectively. Successful stent placement was done by 34 trainees (94 %)
on the first attempt. Seven had an incorrect puncture, two had guidewire passage in
the wrong position. Three had guidewire shearing and one had slippage. Mean time taken
by trainees to complete the procedure was 34.4 minutes (range, 31 to 40 minutes) ([Fig. 4], [Video 3]).
EUS-guided pancreatic pseudocyst drainage
In 30 trainees (83 %), scope position was appropriate on the first attempt to identify
pseudocyst and drain it under EUS guidance. All 36 trainees (100 %) deployed a LAMS
stent successfully. Mean time taken by trainees to complete the procedure was 10.5
minutes (range, 8 to 12 minutes) ([Fig. 5], [Video 4]).
EUS-guided gastroenterostomy
Twenty-two trainees (61 %) were able to identify jejunum with appropriate scope position.
All trainees (100 %) deployed a LAMS stent successfully, free flow of fluid from enteral
loop to stomach was noted through the stent. Fourteen trainees had the wrong scope
position and five had an incorrect puncture. Mean time taken by trainees to complete
the procedure was 15.8 minutes (12– 22minute) ([Fig. 6], [Video 5]).
Durability of the model
We used the model for two train-the-trainer sessions involving 36 trainees. Our experience
indicates that the model is durable even after self-expanding metal stent placement.
It can be reused by changing the position of the puncture for at least 25 times. In
addition, we also created separate duodenum and bile ducts, which could replace the
damaged parts if necessary.
Discussion
This is the first report of an all-in-one model with the possibility of performing
multiple EUS-guided interventional procedures in a single compact model, which can
be utilized in conference as well as institutional settings, with or without X-ray.
EUS-guided therapeutic interventions are complex, each having its own unique technical
challenges. They are currently indicated in a small but growing number of patients,
and the case volume remains low even at advanced endoscopy centers, with the probable
exception of pancreatic fluid collections [5]
[6]. Models for training in EUS-guided interventions are evolving gradually. Separate
models have been described for individual procedures like EUS-FNB, EUS-PSD and EUS-BD.
[3]
[4]
[7]
[8]
[9]
[10]
[11]
[12] We are not aware of any model for EUS-GE. We have previously published our experience
with a 3D-printed BD model, which appears suitable for teaching the essential basics
of EUS-BD [3]. Our subsequent hybrid model for EUS-BD was an improved version with possibilities
of cautery as well as two different entry points to facilitate the rendezvous procedure
[3]
[4]. However, that model was only limited to EUS-BD, needed X-ray, and did not have
the possibility of performing other procedures like EUS-FNB, EUS-PSD, and EUS-GE.
Our current model is a further improvement, with the addition of multiple procedures
in the same model, while also removing the constraints of X-ray.
An ideal synthetic material for the duodenum and pancreato-biliary system is not yet
available. The existing materials tend to be harder, or too soft, thus creating difficulties
in puncture or retention of shape. For the past models, we utilized polycarbonate
material, which did not allow a good puncture and restricted the movement of the echo-endoscope.
For the current model, we settled for thin silicone, as it allows needle puncture,
retains its shape, and has good acoustic windows ([Fig. 1]). We also made the use of fluoroscopy optional by utilizing an internal camera with
external control. This along with the compact size of the model allows transportability
for use in a conference setting. However, X-ray could still be used for training if
needed, by removing the top cover.
The magic box was graded well on most of the parameters by experts as well as the
trainees. Our trainees were selected carefully as a part of a train-the-trainer program.
Thus, they were well versed with diagnostic EUS and scope maneuvers. This explains
the very good success rate in almost all the interventional procedures. However, they
did have difficulties, primarily in two broad areas. First, they found it difficult
to get a good scope position to puncture. They also found it difficult to hold this
position during the procedure. Second, they had difficulties in manipulating the guidewire
across a stricture.
Difficulties encountered by trainees did not differ significantly from our earlier
studies. Trainees found it relatively easy to learn LAMS insertion and perform EUS-FNB.
Time taken and technical difficulties for these two procedures were significantly
less as compared to that for EUS-BD and EUS-RV-PD procedures. This could partially
be due to the fact that LAMS placement is a single-step procedure and does not require
multiple instruments. The BD and PD interventions proved more difficult primarily
due to difficulty in maintaining scope position and guidewire manipulation. Trainees
found EUS-GE to be relatively easy because of the fixed easily identifiable silicone
enteral loop. In real-life situations, locating and fixing the jejunum endosonographically
can be challenging. We did try to replicate the technique by placing a nasojejunal
tube in the duodenum, and filling the duodenum with water mixed with methylene blue.
There were limitations to this study. The model, although comprehensive, is designed
for easy procedures, as evidenced by very dilated common BD and PD, and easily identifiable
duodenum for EUS-GE. Thus, the trainees are not exposed to some of the complexities
of these procedures. However, this can easily be rectified by creating narrower ducts
with strictures, multiple jejunal loops, and complex cysts in future versions. It
is also possible to create blood vessels in the vicinity of the ducts or cysts, to
make the procedure more challenging. Further, the duodenum and stomach are entered
through separate ports. While this distorts the anatomy, it did not preclude the demonstration
and performance of the various procedures. Our search for a perfect synthetic material
still continues, and while this model is a significant improvement, we realize that
we need a better material that simulates the human tissue. There are few interventional
EUS procedures that are not included in this hybrid model, such as EUS-guided gall
bladder drainage and vascular therapy. These can be added easily with no likely additional
technical problems.
