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 Table of Contents  
Year : 2014  |  Volume : 3  |  Issue : 4  |  Page : 226-231

Endoscopic ultrasound-assisted direct peritoneal visualization with a small-caliber scope: A proof of concept study in a swine model

1 Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Texas, USA; Department of Gastroenterology and Rheumatology, Fukushima Medical University School of Medicine, Fukushima, Japan
2 Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Texas, USA
3 Department of Neurosurgery, The University of Texas Medical School at Houston, Texas, USA
4 Department of Gastroenterology, Fukushima Medical University Aizu Medical Center, Aizuwakamatsu, Fukushima, Japan
5 Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Texas, USA
6 Department of Bioengineering, Rice University, Houston, Texas, USA
7 Department of Gastroenterology and Rheumatology, Fukushima Medical University School of Medicine, Fukushima, Japan

Date of Submission14-Apr-2014
Date of Acceptance13-Jul-2014
Date of Web Publication12-Nov-2014

Correspondence Address:
Manoop S Bhutani
Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Texas
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Source of Support: Dr. Bhutani is supported by Boston Scientifi c Investigator Sponsored Research Program. Dr. Suzuki is supported by a research grant from the Japanese Foundation for Research and Promotion of Endoscopy. Dr. Richards-Kortum is supported by NCI Cancer Center Support Grant (CA016672) and NIH grant 5R01 EB007594 and holds minority ownership of Remicalm, LLC as a scientifi c advisor. The endoscopic equipment was provided by Olympus Corporation of the America to MD Anderson Cancer Center for endoscopic research by any investigator., Conflict of Interest: None

DOI: 10.4103/2303-9027.144535

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Background: Laparoscopic and natural orifice transluminal endoscopic surgery techniques can diagnose peritoneal findings that suggest tumor cell dissemination. However, they have not been incorporated into routine practice, mainly owing to their complexity. To develop a minimally invasive endoscopic technique for the diagnosis of peritoneal findings, we conducted feasibility study using an acute swine model. Materials and Methods: This study involved six domestic pigs. Trans-gastric access to the peritoneal cavity was performed utilizing an endoscopic ultrasound fine needle aspiration (EUS-FNA) technique. After dilation of the needle hole with a biliary dilatation catheter and balloon, a small-caliber scope was inserted into the peritoneal cavity. Peritoneal images were obtained with the scope and a high-resolution microendoscope (HRME). Main outcome measurements were technical feasibility and time needed to access the peritoneal cavity. Results: Direct visualization of the peritoneum was successful in all six pigs and gained access to the gross appearance of the peritoneal cavity. HRME imaging with topical contrast agent also obtained reasonable quality images representing nuclei of the peritoneal mesothelium. Average operation time from the initiation of EUS-FNA to acquiring peritoneal images was 26.5 min (range 15-40 min). Autopsy found no damage to the adjacent organs, and stomach wall defects were tightly closed with hemostasis clips. Conclusion: EUS-assisted direct peritoneal visualization with small-caliber scope is technically feasible. HRME may assist in the diagnosis of findings on the peritoneum.

Keywords: Cancer staging, endoscopic ultrasound-guided fine needle aspiration, natural orifice transluminal endoscopic surgery, peritoneoscopy, tumor implant

How to cite this article:
Suzuki R, Bhutani MS, Shin D, Irisawa A, Fleming JB, Richards-Kortum R, Ohira H. Endoscopic ultrasound-assisted direct peritoneal visualization with a small-caliber scope: A proof of concept study in a swine model. Endosc Ultrasound 2014;3:226-31

How to cite this URL:
Suzuki R, Bhutani MS, Shin D, Irisawa A, Fleming JB, Richards-Kortum R, Ohira H. Endoscopic ultrasound-assisted direct peritoneal visualization with a small-caliber scope: A proof of concept study in a swine model. Endosc Ultrasound [serial online] 2014 [cited 2021 Sep 19];3:226-31. Available from: http://www.eusjournal.com/text.asp?2014/3/4/226/144535

  Introduction Top

Accurate preoperative staging is essential to determine the appropriate treatment strategy in cancer patients. Cross sectional imaging studies, such as computed tomography, and endoscopic ultrasound (EUS) have been widely accepted in clinical practice as a method for pre-operative staging. [1],[2] However, it remains difficult to detect small metastatic tumor implants on the peritoneum or liver surface even with these state-of-art imaging modalities. Preoperative laparoscopy has been utilized in the staging of various types of cancers and proven to be more accurate for decisions of resectability than other cross-sectional imaging studies and EUS. However, it has not been widely accepted owing to a lack of validated studies and its complexity for this purpose (e.g., requirements for general anesthesia and operating room). [3],[4],[5],[6],[7]

To overcome the limitations of existing laparoscopic techniques, natural orifice transluminal endoscopic surgery (NOTES) has been recently developed. This new endoscopic technique utilizes natural orifices (e.g., stomach, colon) as access routes to the peritoneal cavity and enables diagnostic and therapeutic procedures with less physiological insult. [8],[9],[10] Recently, several studies have used a standard endoscope in animal models as well as humans to demonstrate this technique for peritoneal exploration (NOTES-peritoneoscopy). [11],[12],[13] The results suggest that this novel technique has diagnostic ability to detect minute peritoneal findings equal to that of laparoscopy and has potential application outside the operating room. Although these results are promising, various issues remain to be resolved before there can be widespread application in the daily clinical setting.

One of the most pressing issues in NOTES-peritoneoscopy is the need for reliable transluminal defect closure in order to prevent peritoneal bacterial contamination and severe infection. [14],[15] To date, various attempts have been made with specially designed devices or special techniques. [16],[17],[18],[19] We hypothesize that there will be less technical difficulty and chance of bacterial contamination using NOTES-peritoneoscopy with smaller transluminal defects than with conventional NOTES techniques.

In this current study, we demonstrate the technical feasibility of direct peritoneal visualization with a commercially available 10 Fr small-caliber scope under EUS guidance. Using this method, transluminal defects can be <1 cm in size and readily closed with hemostatic clips. We also utilized high-resolution microendoscopy (HRME) as a potential auxiliary diagnostic tool for peritoneal findings.

  Materials and methods Top

The study was conducted at the animal facility of The University of Texas MD Anderson Cancer Center after approval was obtained from the Animal Care and Use Committee. Six male domestic pigs weighing between 40 and 50 kg were used. Pigs were deprived of food for 24 h before the procedure. Pre-anesthesia medications consisted of intra-muscular injection of ketamine (22-33 mg/kg) and acepromazine (0.22-1.1 mg/kg). General anesthesia was achieved with isoflurane (1-3% to up to effective dose) and propofol (12 mg/kg/h). All procedures were performed with swine in the left lateral position. Pulse oximetry and electrocardiography findings were monitored continuously during the procedures.

Endoscopic devices

All procedures were performed with a commercially available upper endoscope (GIF-160; Olympus, Center Valley, PA) and an EUS (GF-UC140P-AL5; Olympus). An optic fiber with a 10 Fr access and delivery catheter (SpyGlass Direct Visualization System and SpyScope; Boston Scientific, Natick, MA) was utilized to obtain the peritoneal cavity images.

High-resolution microendoscopy system

A recently developed HRME system was also utilized to obtain images of cellular morphology and tissue architecture in situ and in real time. [20],[21] Detailed information regarding system assembly and techniques in imaging acquisition has been described previously. Briefly, a fluorescent contrast agent (Proflavine, Sigma-Aldrich, St. Louis, MO) was applied topically to the targeted tissue to stain nuclei and then a probe placed in contact with the tissue. The HRME used here has 4.4-μm spatial resolution and a 720 μm diameter field of view and displays images at 12 frames/s in real time. Use of a probe with a 330 μm field of view allows passage through a 19-gauge aspiration needle (Expect, Boston Scientific).

Endoscopic techniques

The entire stomach contents were removed with the upper endoscope during observation. In the next step, EUS was utilized to visualize adjacent organs as well as blood vessels to avoid damage during the procedure. Subsequently, stomach wall puncture was performed with the same method using EUS-guided fine needle aspiration (EUS-FNA) with a 19-gauge EUS-FNA needle [Figure 1]a.
Figure 1. Endoscopic techniques. (a) A stomach defect was created with an endoscopic ultrasound-guide fi ne needle aspiration technique. (c-d) The defect was dilated with biliary catheter and balloon under fluoroscopic guidance. (e) A small-caliber scope was inserted into the peritoneal cavity. (f) The peritoneum was visualized

Click here to view

A 0.035-inch flexible tip guidewire was then inserted into the peritoneal cavity through the EUS-FNA needle lumen with or without fluoroscopic guidance. Along the guidewire, the stomach wall defect was enlarged with a biliary catheter and then a 4-8 mm biliary dilatation balloon [Figure 1]b-d. After EUS scope withdrawal, the SpyGlass system deployed within the SpyScope was introduced into the peritoneal cavity over the guidewire under upper endoscope observation [Figure 1]e and f.

The peritoneal cavity was examined with SpyGlass and HRME through the working channel of the SpyScope. To provide a sufficient space for observation in the peritoneal cavity, sterile saline was infused through the irrigation channels of Spyscope. The biopsy specimen was obtained from the peritoneum with a biopsy forceps (SpyBite, Boston Scientific). At the end of the procedure, SpyGlass was withdrawn and the stomach wall defect was closed with 1 or 2 hemostatic clips (Resolution Clip, Boston Scientific).

In the first three pigs, fluoroscopy was used with a contrast agent to confirm that the needle tip was positioned in the peritoneal cavity. For the latter three pigs, we performed the entire procedure without fluoroscopic guidance to simulate whether this technique can be performed in a standard endoscopic room without fluoroscopy. Instead of fluoroscopic guidance, successful access to the peritoneal cavity was confirmed with EUS. All six pigs were euthanized immediately after the procedures.


We aimed to evaluate the technical feasibility of EUS-assisted direct peritoneal visualization utilizing the SpyGlass. As an outcome measure, procedure times between the initiation of EUS-FNA to create the stomach wall hole and acquisition of the peritoneal cavity images were measured in all experiments. Additionally, the efficacy of stomach defect closure was also evaluated at autopsy. Adverse effects and any damage to vascular structures or adjacent organs were also evaluated at autopsy.

  Results Top

We successfully performed EUS-assisted trans-gastric direct peritoneal visualization with a 10 Fr small-caliber scope in all six pigs. No significant acute adverse events occurred during any of the procedures, including creating a stomach wall defect with EUS-FNA needle, dilatation of the hole with dilatation catheter and balloon, SpyScope insertion into the peritoneal cavity, and visualization of the peritoneum even without fluoroscopic guidance.

SpyGlass could obtain gross appearance of the peritoneum with reasonable quality image. HRME imaging following topical contrast agent application also could obtain images representing the nuclei of the peritoneal cells covering the small intestine [Figure 2]. Additionally, small biopsy forceps could selectively obtain a specimen from the peritoneum at the same point where HRME obtained its image [Figure 3]. After withdrawal of the SpyScope from the peritoneal cavity, one or two hemostasis clips were deployed to close the stomach wall defect [Figure 4]a. Autopsy revealed that the defect was closed tightly enough to prevent air leakage from inflated stomach on gross inspection [Figure 4]b. Average operation time between the initiation of EUS-FNA and acquiring peritoneal images was 26.5 min (range 15-40 min). Consistent with a rapid learning curve, the average operation time was shorter in the latter three pigs without fluoroscopic guidance (19.6 min) than in the first three pigs with fluoroscopic guidance (33.3 min). Autopsy identified no bleeding or damage to the adjacent organs.
Figure 2. High-resolution microendoscopy imaging of the peritoneum. White dots represent nuclei of the peritoneal mesothelium which are
stained with the fl uorescent contrast agent

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Figure 3. Biopsy specimen obtained from the peritoneum (×100)

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Figure 4. The stomach defect closure. (a) A hemostatic clip was deployed to close the defect with upperendoscope. (b) Autopsy revealed that the defect was closed tightly enough to prevent any leakage (arrow)

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  Discussion Top

Our pilot study demonstrates the technical feasibility of EUS-assisted direct peritoneal visualization with a 10 Fr small-caliber scope in a swine model. As we hypothesized, the <1 cm stomach wall defect can be closed tightly with commercially available hemostasis clips without any special techniques. Additionally, HRME allowed us to obtain reasonable quality images of the peritoneum that can assist in the diagnosis of peritoneal findings.

There are several ways to diagnose peritoneal findings, which can change treatment strategy regarding resectablity of disease in cancer patients. Cross-sectional imaging modalities (e.g., computed tomography, magnetic resonance imaging, and positron emission topography) can detect lesions on the peritoneum. However, it has been consistently reported that these state-of-art cross-sectional imaging modalities are falsely negative in up to one third of patients. [5] On the other hand, several invasive procedures (e.g., open laparotomy, laparoscopy and NOTES-peritoneoscopy) can explore within the peritoneal cavity and may have the ability to detect and obtain specimens from small metastatic tumor implants. Compared with conventional open laparotomy, laparoscopic techniques utilizing specially designed devices make a smaller incision on the external body surface and require less invasive manipulation. These techniques have various benefits for patients, including less pain and a shorter hospital stay.

Natural orifice transluminal endoscopic surgery is an endoscopic technique that requires no external incision and which can potentially perform diagnostic and therapeutic procedures that have previously required laparoscopy. [9],[10] Currently, NOTES procedures utilize a conventional upper endoscope or a two-channel scope 10 mm in diameter or more. Consequently, this procedure usually requires a transluminal defect that may be up to 20 mm in some cases and has a chance of bacterial contamination via luminal organs (e.g., colon, stomach). [13],[15],[22] To date, how to close the NOTES transluminal defect lying in the deep part of the body in a secure, reliable, and safe manner is still under debate. We believe that our concept, direct peritoneal visualization with a smaller caliber scope, may offer an advance in NOTES-peritoneoscopy because our results show the defect can be readily closed with standard devices and technique. In addition, we surmise that this procedure can be performed along with other endoscopic procedures for cancer diagnosis or staging, because the additional procedural time to access the peritoneal cavity can be <20 min.

Several limitations in study design and device specifications should be addressed in the further studies that are necessary to refine this approach. Animal survival studies should be conducted to verify long-term safety. Evaluation of the orientational ability of this procedure in detecting certain points of interest in comparison with a standard technique (e.g., laparoscopy) is needed. Given the design of the SpyGlass system for pancreatico-biliary diseases, its specifications are not sufficient to perform peritoneoscopy at this time. Further developments are required especially in its pixilation to obtain clearer images, and scope stiffness and adequate angulation of the scope tip which can enable us to manipulate the catheter smoothly within in the peritoneal cavity.

The HRME has been developed quite recently and its potential to aid in the diagnosis of gastrointestinal neoplasms has been explored. [20],[21],[23],[24] Although histopathological diagnosis is the standard method for definite diagnosis, the ability of this device to visualize cellular morphology and tissue architecture in real time may help us to diagnose target lesions in cases in which biopsy sampling is difficult to obtain or hard to interpret. Considering the small size of the specimens obtained in this study, this technique may be ancillary to other diagnostic methods. We believe that this low-cost portable system (<$3,500 to build) can be a reasonable choice for this purpose. Further study is required to evaluate characteristics of normal, benign, and malignant lesions of the peritoneum using the HRME.

  Conclusion Top

Endoscopic ultrasound-assisted trans-gastric direct peritoneal visualization with a small-caliber scope is technically feasible. Furthermore, HRME imaging with topical contrast agent application may assist in the histological diagnosis of the peritoneal findings. Survival studies with control groups and more improvement in devices are needed to demonstrate the true value of this technique.

  Acknowledgement Top

We are grateful to Dr. Agatha Borne, DVM, PhD and the staff of Veterinary Medicine and Surgery as well as the John S. Dunn Center for Radiological Sciences for their help and support of this project.

  References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

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