Medical Grand Rounds: An Introduction to Third Space Endoscopy Featuring Dr. Rob Bechara
Cassie Brand, MSc Candidate (Translational Medicine)
At last week’s Medical Grand Rounds, we had the pleasure of hearing from Dr. Rob Bechara on the emerging field of third space endoscopy. Third space endoscopy refers to a group of endoscopic proceedures that take advantage of accessing the submucosal space of the body for therapeutic intervention1. The development of these relatively new proceedures offers a less invasive and less painful alternative to traditional surgical techniques for the treatment of gastrointestinal neoplasms and motility disorders2.
Dr. Bechara started off his presentation with an introduction to endoscopic submucosal dissection (ESD), a technique that bridges the gap between traditional endoscopic mucosal resections (EMR) and surgery. Here it was highlighted that while ESD does not replace traditional proceedures, it allows for otherwise challenging en blocresections and offers the highest chance of avoiding unnecessary surgery3. This technique has laid the foundation for the development of a new chain of endoscopic therapeutics2.
In 2008, the first peroral endoscopy myotomy (POEM) proceedure was performed4. POEM is commonly used to treat achalasia and has more recently been expanded to other spastic esophageal and foregut conditions5. In addition to being less invasive, POEM can be performed after previous therapeutic interventions such as Laparoscopic Heller Myotomies, botulinum injections and previous POEM6. The POEM proceedure relies on five core steps: 1) submucosal injection to expand the third space 2) mucosal incision 3) creation of a submucosal tunnel 4) myotomy 5) closure of the incisions with clips5. Meta analyses have shown POEM to have a technical success rate of 97% and a clinical efficacy of 93%, highlighting the value of this proceedure7. Furthermore, POEM is a safe proceedure with a low rate of adverse events, most of which are non-severe and can easily be managed without affecting the overall post operative state of the patient. As a result, POEM has become the standard therapy for achalasia4.
Dr. Bechara proceeded to introduce peroral endoscopy tumor resection (POET), which came into practice shortly after the development of POEM. POET is a technique used to resect benign submucosal gastrointestinal tumors with low lymph node metastatic potential8. However, POET is limited to tumors less than 4 cm in size to allow for oral resection. Similar to POEM, a submucosal injection is made above the lesion allowing for an incision to be made. The tumor is then dissected and removed orally8. This offers a less painful and shorter alternative to traditional resection techniques whilst being effective (92%) and safe (adverse events are rare and easily treated)9. POEM and POET have similar contraindications including conditions preventing the use of anesthetics, pathologies precluding submucosal tunnel formation, cirrhosis with portal hypertension and severe coagulopathies.
The principles of POEM have recently been expanded to address new therapeutic avenues for the treatment of other gastrointestinal pathologies. Gastric peroral endoscopy myotomy (G-POEM) is a variation of POEM that targets the pyloric sphincter to treat gastroparesis10. While this technique is still somewhat experimental, there is evidence of an 81.3% long term clinical improvement G-POEM11. In addition to the traditional contraindications of POEM, the use of G-POEM is further limited by unmanaged psychiatric conditions and uncontrolled diabetes. Zenker’s peroral endoscopy myotomy (Z-POEM) is another variation in which submucosal tunnels are created improving septal visualization and allowing for a complete cricopharyngeal myotomy to be performed12. Although closure for this technique is generally quite challenging, preliminary results have indicated a high clinical success rate (95.8% ). While both proceedures have evidence supporting their efficacy, better physiological studies and larger prospective trials are required to refine these proceedures and identify the population of patients best suited to benefit from them.
Following Grand Rounds, the Translational Medicine (TMED) students were fortunate to continue the discussion of third space endoscopy with Dr. Bechara. A common theme of the discussion revolved around challenges associated with the implementation of these new techniques to benefit patients. Dr. Bechara highlighted that while these are highly effective treatments that avoid unnecessary surgeries, implementation in Canada is limited by funding and justification. Even with appropriate funding, Dr. Bechara predicts that these proceedures would only be available at tertiary hospitals due to the expertise required. We ended off the discussion by talking about Dr. Bechara’s challenging but rewarding international medical training in Japan and were very excited to hear about the introduction of a new third space endoscopy fellowship program starting up at Queen’s University this fall.
On behalf of the TMED students, I would like to thank Dr. Bechara for his time and contributions to increasing the practice of endoscopic procedures in Canada.
Nabi Z, Reddy DN, Ramchandani M. Recent advances in third-space endoscopy. Gastroenterology & Hepatology. 2018;14(4):224.
Shanbhag AB, Thota PN, Sanaka MR. Recent advances in third space or intramural endoscopy. World Journal of Gastrointestinal Endoscopy. 2020;12(12):521.
Asano M. Endoscopic submucosal dissection and surgical treatment for gastrointestinal cancer. World journal of gastrointestinal endoscopy. 2012;4(10):438.
Ahmed Y, Othman MO. Peroral endoscopic myotomy (POEM) for achalasia. Journal of Thoracic Disease. 2019;11(Suppl 12):S1618.
Kumbhari V, Khashab MA. Peroral endoscopic myotomy. World journal of gastrointestinal endoscopy. 2015;7(5):496.
Kolb JM, Jonas D, Funari MP, Hammad H, Menard-Katcher P, Wagh MS. Efficacy and safety of peroral endoscopic myotomy after prior sleeve gastrectomy and gastric bypass surgery. World Journal of Gastrointestinal Endoscopy. 2020;12(12):532.
Barbieri LA, Hassan C, Rosati R, Romario UF, Correale L, Repici A. Systematic review and meta-analysis: efficacy and safety of POEM for achalasia. United European gastroenterology journal. 2015;3(4):325-34.
Chiu PWY, Yip HC, Teoh AYB, Wong VWY, Chan SM, Wong SKH, et al. Per oral endoscopic tumor (POET) resection for treatment of upper gastrointestinal subepithelial tumors. Surgical Endoscopy. 2019;33(4):1326-33.
Onimaru M, Inoue H, Bechara R, Tanabe M, Abad MRA, Ueno A, et al. Clinical outcomes of per‐oral endoscopic tumor resection for submucosal tumors in the esophagus and gastric cardia. Digestive Endoscopy. 2020;32(3):328-36.
Mohan BP, Chandan S, Jha LK, Khan SR, Kotagiri R, Kassab LL, et al. Clinical efficacy of gastric per-oral endoscopic myotomy (G-POEM) in the treatment of refractory gastroparesis and predictors of outcomes: a systematic review and meta-analysis using surgical pyloroplasty as a comparator group. Surgical endoscopy. 2020;34(8):3352-67.