Anterior versus posterior peroral endoscopic myotomy: a prospective randomized controlled trial from a Thai tertiary center

Tharathorn Suwatthanarak; Siwaree Maneesoi; Chatbadin Thongchuam; Thawatchai Akaraviputh; Vitoon Chinswangwatanakul; Somchai Leelakusolvong; Chainarong Phalanusitthepa

doi:10.5946/ce.2025.407

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Original Article Anterior versus posterior peroral endoscopic myotomy: a prospective randomized controlled trial from a Thai tertiary center: Tharathorn Suwatthanarak^1,2, Siwaree Maneesoi¹, Chatbadin Thongchuam¹, Thawatchai Akaraviputh¹, Vitoon Chinswangwatanakul¹, Somchai Leelakusolvong³, Chainarong Phalanusitthepa¹; DOI: https://doi.org/10.5946/ce.2025.407
Published online: August 13, 2026

¹Minimally Invasive Surgery Unit, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand

²Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan

³Division of Gastroenterology, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand

Correspondence: Chainarong Phalanusitthepa Department of Surgery, Faculty of Medicine Siriraj Hospital, 12th Floor, Siamindra Building, Wang Lang Road, Bangkok Noi, Bangkok 10700, Thailand E-mail: chainarong.pha@mahidol.ac.th

• Received: October 31, 2025 • Revised: February 4, 2026 • Accepted: February 9, 2026

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Abstract
Graphical abstract
INTRODUCTION
METHODS
ETHICAL STATEMENT
RESULTS
DISCUSSION
NOTES
REFERENCES

Abstract

Background/Aims
Achalasia is an esophageal motility disorder. Peroral endoscopic myotomy is widely used for all subtypes; however, randomized head-to-head evidence comparing the anterior and posterior approaches remains limited. We compared efficacy, safety, and reflux outcomes.
Methods
We conducted a single-center, single-blind, prospective randomized controlled trial from February 2023 to August 2024. Twenty-eight patients with achalasia types I–III were randomized to anterior or posterior peroral endoscopic myotomy. The primary outcomes were esophageal acid exposure at 3 months (24-hour pH monitoring) and clinical success (Eckardt score ≤3). The secondary outcomes were procedural parameters, complications, timed barium esophagography, manometry, and reflux esophagitis.
Results
Baseline characteristics were comparable between the groups. Procedural metrics and complication rates were similar and mild, with no severe adverse events. At 12 months, both groups showed significant symptom relief, reduced Eckardt scores, and decreased lower esophageal sphincter pressure. Posterior myotomy yielded a higher proportion of abnormal DeMeester scores (57.1% vs. 28.6%, p=0.14), although reflux esophagitis remained mild and comparable between the groups.
Conclusions
Posterior peroral endoscopic myotomy demonstrated comparable efficacy, safety, and reflux outcomes. The anterior approach improved clearance on timed barium esophagography; however, both approaches achieved durable symptom control with acceptable safety profiles, supporting posterior myotomy as a valid alternative.
Keywords: Esophageal achalasia; Esophageal sphincter, lower; Esophagitis; Manometry; Myotomy

Graphical abstract

INTRODUCTION

Achalasia is a neurodegenerative esophageal motility disorder characterized by impaired lower esophageal sphincter relaxation and absent esophageal peristalsis. Management options include nonsurgical therapies, such as botulinum toxin injection and medications; pneumatic balloon dilatation; laparoscopic Heller myotomy; and peroral endoscopic myotomy (POEM). Currently, pneumatic balloon dilatation and laparoscopic Heller myotomy with partial fundoplication are regarded as first-line therapies with comparable efficacy.¹ POEM, a minimally invasive endoscopic procedure performed without external incisions, has emerged as an alternative to laparoscopic Heller myotomy.² It demonstrates equivalent therapeutic efficacy, along with safety advantages and shorter hospital stays.³^-⁶ Instrumentation and technical refinements have further improved feasibility and safety.⁶

However, POEM techniques remain heterogeneous.⁴ The procedure entails selective division of the esophageal inner circular muscle, performed either anteriorly at the 2 o’clock position or posteriorly at the 5 o’clock position. Approach selection depends on operator expertise and preference. Comparative studies exist, but randomized controlled trials are scarce, particularly in Thailand.⁷^-¹⁰ Consequently, reported outcomes for postoperative swallowing function, gastroesophageal reflux, and complications remain inconsistent.¹¹

Therefore, we conducted a randomized controlled trial to compare anterior and posterior POEM and to provide evidence to guide procedural selection and optimize achalasia management.

METHODS

Study design

This single-blind, randomized, prospective clinical trial was conducted in Thailand from February 2023 to August 2024. Eligible participants were adults (age ≥18 years) with achalasia types I–III diagnosed using timed barium esophagography (TBE) and high-resolution manometry. The exclusion criteria were current or prior esophageal or gastric perforation, prior esophageal or gastric surgery, active esophagitis, esophageal malignancy, and inability to tolerate sedated upper endoscopy. Reasons for intolerance included cardiopulmonary instability, severe pulmonary disease, or other contraindications. We also excluded patients with cirrhosis with portal hypertension, varices and/or ascites, other causes of portal hypertension, pregnancy or breastfeeding, and active gastrointestinal bleeding. Uncorrectable coagulopathy was defined as an international normalized ratio >1.5 or a platelet count <50×10⁹/L.

Sample size calculation

Sample size estimation was based on prior 24-hour pH monitoring at 3 months postoperatively. Previous data showed greater esophageal acid exposure with the posterior approach than with the anterior approach (13.99%±14.48% vs. 2.98%±4.24%; p<0.01).⁷ Using the formula for comparing two independent means, we calculated that 14 patients per group were required to detect a significant difference in esophageal acid exposure. To account for an anticipated dropout rate of approximately 20%, the target enrollment was increased to 34 patients. This increase was prespecified to ensure that the final analyzable cohort met the required sample size.

Randomization

Patients were randomized in a 1:1 ratio to undergo POEM via the anterior or posterior approach using a computer-generated sequence, with allocation concealed in sequentially numbered, sealed envelopes. All participants provided written informed consent before enrollment. On the day of the procedure, the assigned envelope was opened in the endoscopy room immediately before initiation of the intervention. Participants were blinded to group assignment, whereas endoscopists were not blinded.

Technique

The procedures were performed with patients in the supine position under general anesthesia following complete endoscopic inspection. A mixture of 0.3% indigo carmine and normal saline was injected using an endoscopic needle to create a submucosal cushion for mucosal entry. A 2-cm vertical mucosal incision was created at the 2 o’clock position for the anterior approach or at the 5 o’clock position for the posterior approach using a triangular-tip knife (Olympus) (Fig. 1). After entry into the submucosa, a straight tunnel encompassing approximately one-third of the esophageal circumference was created using spray coagulation with a non-touch technique. The tunnel crossed the esophagogastric junction and extended 3 cm into the proximal stomach. Selective circular myotomy began 2 cm distal to the mucosal entry point and extended ≥8 cm proximally and ≥2 cm distally beyond the esophagogastric junction. For type III achalasia, the myotomy length was tailored according to preoperative manometric findings. The mucosal entry was closed using hemostatic clips.⁴

Postprocedural care

Patients were monitored overnight and advanced from a liquid diet on postoperative day 1 to a soft diet on day 2 and a regular diet on day 3.

Follow-up

TBE was performed at 3 weeks to assess esophageal clearance.¹²^-¹⁴ Clinical status was evaluated using the Eckardt score at 1, 3, 6, and 12 months. Ambulatory 24-hour pH monitoring was performed at 3 months, with proton pump inhibitors routinely discontinued 2 weeks beforehand in accordance with institutional protocols. High-resolution manometry was performed at 6 months, and esophagogastroduodenoscopy was scheduled at 12 months or earlier if reflux symptoms occurred.

Endpoints

The primary outcomes were esophageal acid exposure at 3 months, measured by 24-hour pH monitoring, and clinical success, defined as an Eckardt score ≤3 during follow-up.¹⁵^-¹⁷ Secondary outcomes included intraoperative and postoperative complications. Physiological outcomes included lower esophageal sphincter pressure measured by high-resolution manometry and gastroesophageal reflux disease assessed by esophagogastroduodenoscopy.¹⁷^-¹⁹ Procedural parameters included myotomy length, mucosal incision length, and operative time.

Statistical analysis

Continuous variables are summarized as means with standard deviations or medians with interquartile ranges, according to distribution. Between-group comparisons were performed using the Mann-Whitney U-test. Categorical variables are reported as frequencies and percentages and were compared using chi-square or Fisher’s exact tests, as appropriate. A p-value <0.05 was considered statistically significant. Statistical analyses were performed using IBM SPSS Statistics ver. 26.0 (IBM Corp.).

ETHICAL STATEMENT

Statement of human and animal rights and informed consent

The study was conducted in accordance with the Declaration of Helsinki and relevant ethical guidelines. Patient confidentiality was strictly maintained, and no identifying information was disclosed. This study was approved by the Institutional Review Board of the Faculty of Medicine Siriraj Hospital, Mahidol University (COA No. Si 153/2023). Written informed consent to participate was obtained from all patients. The study was registered with the Thai Clinical Trials Registry (Identification number: TCTR20260112002).

RESULTS

Baseline characteristics

A total of 34 patients were enrolled and randomized to either the anterior or posterior approach. Twenty-eight patients completed the intervention and follow-up according to the study protocol and were included in the final analysis (Fig. 2). None of the patients had received prior treatment for achalasia, including pneumatic dilatation, botulinum toxin injection, or surgical myotomy. The two groups were comparable in terms of age, sex, comorbidities, symptom duration, and preoperative Eckardt scores. Integrated relaxation pressure was similar between the groups (32.67 vs. 30.51 mmHg, p=0.55). The achalasia subtype distribution according to the Chicago classification did not differ significantly; type II was predominant. Preoperative TBE parameters were comparable between the groups (Table 1).

Procedural outcomes

The mucosal entry, tunnel, and myotomy lengths were equivalent between the groups. Operative times were similar (32.5 vs. 30 minutes, p=0.60). Postoperative pain scores on days 0–2 did not differ significantly between the groups. Intraoperative complications were infrequent: four events occurred in the anterior group (one mucosal injury, two cases of pneumoperitoneum, and one case of subcutaneous emphysema), whereas two patients in the posterior group developed subcutaneous emphysema. All events were mild and resolved with conservative management. No severe or fatal complications were observed (Table 2).

Postoperative complications

Minor complications occurred in both groups. In the anterior group, one patient developed lung atelectasis and a urinary tract infection; additional events included subcutaneous emphysema and pneumoperitoneum. All events were mild and resolved without sequelae (Table 2).

Functional outcomes

TBE showed a significant improvement in esophageal emptying at 1 month after POEM in both groups, with no early differences. Between 1 and 12 months, the anterior myotomy group maintained superior clearance at 1 and 2 minutes, whereas the posterior myotomy group showed a relative decline, with statistically significant differences. At the 5-minute assessment, no significant differences were noted between the groups. High-resolution manometry at 6 months confirmed similar reductions in integrated relaxation pressure between the groups (Fig. 3).

Symptom outcomes

Symptom outcomes paralleled these findings. Median Eckardt scores decreased markedly from baseline and remained ≤1 across all follow-up intervals, with no significant differences between the approaches. Rates of symptomatic improvement were comparable, although anterior myotomy showed a nonsignificant trend toward greater improvement at intermediate time points. Both approaches achieved excellent and durable symptom control. Although TBE suggested a functional advantage of the anterior approach in esophageal clearance at longer follow-up, this did not translate into clinically meaningful differences in symptom burden (Fig. 4).

Reflux outcomes

At 3 months, DeMeester scores were comparable between the approaches. However, abnormal esophageal acid exposure (DeMeester score >14.7) occurred more often after posterior myotomy than after anterior myotomy (57.1% vs. 28.6%, p=0.12), although the difference was not statistically significant. At 12 months, endoscopy revealed mild reflux esophagitis in both groups (Los Angeles grade A or B) without severe disease (grade C or D, Table 3).

DISCUSSION

This randomized, prospective trial compared anterior and posterior POEM in achalasia. Both techniques were safe and effective and achieved symptom relief, functional improvement, and low complication rates. The posterior approach had comparable primary outcomes, although subtle differences in esophageal clearance and reflux may inform procedural selection.

Efficacy outcomes

Both approaches produced marked, durable symptom improvement, with sustained reductions in Eckardt scores over 12 months and no symptomatic recurrence. Lower esophageal sphincter pressure decreased comparably between the groups, confirming an effective myotomy in both orientations. These findings are consistent with those of multiple randomized controlled trials and a meta-analysis showing no significant differences in efficacy between the two approaches.⁷^-⁹^,²⁰ TBE height improved significantly at 1 month in both groups. From 1 to 12 months, the anterior myotomy group maintained superior clearance at 1 and 2 minutes, whereas the posterior myotomy group showed a relative decline, resulting in significant between-group differences. At 5 minutes, clearance did not differ between the groups. These data suggest a functional advantage of anterior POEM in terms of faster bolus transit. This may be clinically relevant, as discordance between TBE improvement and symptom relief predicts recurrence. Suwatthanarak et al.¹² reported that patients with persistently poor clearance despite Eckardt score improvement had nearly a sixfold higher recurrence risk at 12 months. Thus, the enhanced clearance after anterior myotomy in our cohort may have prognostic significance, although longer follow-up is required to determine whether it improves durability.

Safety and complications

The two approaches were equally safe, with low intraoperative and postoperative complication rates. Intraoperative events were minor and included mucosal injury, pneumoperitoneum, and subcutaneous emphysema, all of which were managed endoscopically. No severe adverse events, mucosal perforations, or deaths occurred. This safety profile mirrors that of previous randomized controlled trials, which reported similarly low complication rates and confirmed the technical feasibility of both orientations.⁷^-¹⁰^,²⁰

The anterior approach required slightly more clips, consistent with reports of greater bleeding risk near branches of the left gastric artery.⁹ Conversely, some series have associated the posterior approach with shorter procedure times and fewer mucosal heat injuries, although these differences were not clinically significant.¹⁰ Our findings confirm that both techniques can be performed safely with comparable outcomes.

Technical refinements beyond myotomy orientation have also been evaluated. A recent randomized trial comparing transverse and longitudinal mucosal incisions found no differences in entry or closure times, complication rates, or long-term efficacy, further emphasizing the robustness of POEM across technical variations.²¹

Reflux outcomes

Postoperative gastroesophageal reflux disease is a major concern after POEM. In our trial, the posterior approach tended to result in a higher rate of abnormal esophageal acid exposure, although the difference was not statistically significant. Given the small sample size, the study may have been underpowered to detect clinically meaningful differences, and a type II error cannot be excluded. Therefore, the absence of statistical significance should not be interpreted as equivalence in reflux outcomes. Endoscopy at 12 months showed predominantly mild esophagitis (Los Angeles grades A–B), with no severe cases. These findings parallel those of Ramchandani et al.,⁷ who reported higher acid exposure after posterior than after anterior myotomy. The mechanism may involve disruption of gastric sling fibers during posterior myotomy, which form part of the anti-reflux barrier.²³ Anterior myotomy may spare sling fibers and preserve the angle of His, potentially lowering the reflux risk. Sling-preserving POEM has been proposed to mitigate reflux. Shiwaku et al.²⁴ demonstrated a significant reduction in severe erosive esophagitis with this technique compared with conventional posterior POEM. We routinely preserved sling fibers, which may explain the absence of severe reflux esophagitis. Prior studies have indicated that reflux after POEM, although frequent, is generally less severe than that after laparoscopic Heller myotomy with fundoplication, likely due to preservation of the phrenoesophageal ligament and avoidance of external dissection.²³

Clinical implications

Posterior POEM achieved clinical success, safety, and reflux outcomes comparable to those of anterior POEM. Although the anterior orientation yielded slightly better esophageal clearance and a trend toward less reflux, these differences were neither statistically significant nor clinically meaningful within 12 months. Therefore, posterior POEM remains a dependable option, particularly when operator experience, patient anatomy, or procedural logistics favor a posterior tunnel. Routine postoperative TBE is important because it may identify patients at risk of recurrence despite symptomatic improvement. For posterior procedures, sling-preserving POEM may further reduce reflux risk. Our randomized design with 12 months of follow-up extends the literature, which is often limited to 6 months. However, generalizability is limited by the small sample size and single-center setting. Multicenter trials with larger cohorts and longer follow-up periods are needed to determine whether the modest functional advantages of the anterior approach yield durable clinical benefits. Incorporating nutritional status, quality-of-life measures, and long-term gastroesophageal reflux disease outcomes may refine our understanding of how orientation influences patient outcomes.

Limitations

This study has some limitations. The small sample size may have limited generalizability and statistical power, particularly for reflux-related outcomes, and the risk of type II error cannot be excluded. In addition, prospective trial registration prior to patient enrollment was lacking. This study was conducted as an exploratory randomized comparison. Throughout the study, we adhered strictly to ethical research principles and conducted the trial in accordance with the approved protocol. Accordingly, the findings should be viewed as hypothesis-generating rather than confirmatory.

In conclusion, posterior POEM was comparable to the anterior approach in terms of clinical efficacy, safety, and reflux outcomes. Although the anterior orientation showed a trend toward better esophageal clearance and lower reflux, the posterior approach achieved equivalent symptomatic and functional success without clinically meaningful disadvantages. These findings support the posterior approach as a valid alternative; however, the anterior approach remains the preferred approach at our institution. Larger multicenter trials with longer follow-up periods are required to determine whether these physiological differences yield durable clinical benefits.

Conflicts of Interest

The authors have no potential conflicts of interest.

Funding

None.

Acknowledgments

We thank Dr. Saowalak Hunnangkul for statistical consultation and Mr. David Park for assistance with editing the English version of this manuscript.

Author Contributions

Conceptualization: TS, SM, CT, CP; Data curation: TS, SM, CT; Formal analysis: SM, CT; Methodology: SM, CT; Project administration: SM, CT, CP; Resources: SM, CT, TA, VC, SL, CP; Supervision: SM, CT, TS, TA, CP; Validation: SM, CT, CP; Visualization: TS, SM, CT, CP; Writing–original draft: SM, CT; Writing–review & editing: all authors.

Fig. 1.

Anterior vs. posterior peroral endoscopic myotomy (POEM): schematic of tunnel and myotomy orientation. The mucosal entry is created at the 2 o’clock (anterior) or 5 o’clock (posterior) position. A submucosal tunnel traverses the esophagogastric junction (EGJ), followed by selective circular myotomy extending proximally and distally beyond the EGJ. A sling-fiber–preserving technique may be used to mitigate reflux risk. The illustrate was created by Chatbadin Thongchuam.

Fig. 2.

Patient flow diagram through the prospective randomized comparative study (CONSORT-style diagram). Participants were screened, randomized in a 1:1 ratio to the anterior vs. posterior peroral endoscopic myotomy groups, and followed through predefined assessments (timed barium esophagography, high-resolution manometry, 24-hour pH, and esophagogastroduodenoscopy) for 12 months. Numbers reflect enrollment, allocation, follow-up, and analysis of 28 patients. STER, submucosal tunneling endoscopic resection.

Fig. 3.

Improvement in timed barium esophagography (TBE) heights after anterior vs. posterior peroral endoscopic myotomy (POEM) over 12 months. Esophageal column heights at 1, 2, and 5 minutes improved after POEM. The anterior approach showed better early clearance at 1 and 2 minutes during follow-up, whereas 5-minute values were similar between the groups.

Fig. 4.

Eckardt symptom score trajectories over 12 months after the anterior vs. posterior approach. Median Eckardt scores decreased from baseline and remained low across all intervals, with no significant between-group differences. Values reflect durable symptom control after either approach. IQR, interquartile; POEM, peroral endoscopic myotomy.

Table 1.

Baseline characteristics of randomized patients by myotomy orientation

Characteristic	Anterior approach (n=14)	Posterior approach (n=14)	p-value
Age (yr)	52.00±22.74	52.21±14.33	0.10
Sex (female)	7 (50.0)	10 (71.4)	0.25
Underlying disease			0.22
Diabetes mellitus	1	1	1.00
Hypertension	3	5	0.68
Dyslipidemia	3	5	0.68
Cerebrovascular disease	0	1	1.00
Other	2^a)	4^b)	0.52
Symptom duration (mo)	12 (6, 27)	12 (12, 27)	0.63
Preoperative Eckardt score
Weight loss			0.33
0	2 (14.3)	4 (28.6)
1	3 (21.4)	4 (28.6)
2	4 (28.6)	2 (14.3)
3	5 (35.7)	4 (28.6)
Dysphagia			0.44
0	0 (0)	0 (0)
1	1 (7.1)	3 (21.4)
2	2 (14.3)	1 (7.1)
3	11 (78.6)	10 (71.4)
Chest pain			0.45
0	7 (50.0)	6 (42.9)
1	5 (35.7)	4 (28.6)
2	1 (7.1)	2 (14.3)
3	1 (7.1)	2 (14.3)
Regurgitation			0.10
0	3 (21.4)	0 (0)
1	5 (35.7)	8 (57.1)
2	6 (42.9)	1 (7.1)
3	0 (0)	5 (35.7)
Total score	6 (5, 8)	5 (4, 9)	0.79
Preoperative IRP (mmHg)	32.67±12.50	30.51±9.71	0.55
Chicago classification			0.47
Type 1	4 (28.6)	2 (14.3)
Type 2	9 (64.3)	11 (78.6)
Type 3	1 (7.1)	1 (7.1)
Preoperative TBE Height (cm)
1 min	13.56±5.00	9.23±3.68	0.06
2 min	13.19±5.44	9.38±3.83	0.48
5 min	11.60±4.26	9.53±3.83	0.74

Values are presented as number (%) for categorical variables, mean±standard deviation for normally distributed data, and median (P25, P75) for non-normally distributed data. IRP was measured using high-resolution manometry. The TBE heights were recorded at 1, 2, and 5 minutes.

IRP, integrated relaxation pressure; TBE, timed barium esophagography.

^a)Other underlying diseases in the anterior approach included asthma and hepatitis C virus infection.

^b)Other underlying diseases in the posterior approach included atrial fibrillation, benign prostatic hypertrophy, chronic kidney disease, and hepatitis C virus infection.

Table 2.

Procedural parameters and complications after anterior vs posterior peroral endoscopic myotomy

	Anterior approach (n=14)	Posterior approach (n=14)	p-value
Mucosal entry length (cm)	2 (2, 2)	2 (2, 2.25)	0.57
Tunnel length (cm)	12 (12, 12)	12 (9.75, 12.25)	0.60
Myotomy length (cm)	10 (9.75, 10)	10 (7.75, 10)	0.51
Operative time (min)	32.5 (30, 77.25)	30 (30, 61.25)	0.60
Pain score^a)
0	6 (4.75, 7.25)	5 (4, 6)	0.39
1	4 (3, 5)	3.5 (3, 4)	0.29
2	2.5 (2, 3.25)	2 (2, 3)	0.35
Intraoperative complications			0.53
None	10 (71.4)	12 (83.3)
Esophageal mucosal injury	1 (7.2)	0 (0)
Pneumoperitoneum	2 (14.2)	0 (0)
Subcutaneous emphysema	1 (7.2)	2 (16.7)
Further intervention after intraoperative complications			0.20
None	2 (50.0)	2 (100.0)
Endoscopic management	2 (50.0)	0 (0)
Severity of complications^b)			N/A
Mild	4 (100.0)	2 (100.0)
Moderate	0 (0)	0 (0)
Severe	0 (0)	0 (0)
Fatal	0 (0)	0 (0)
Postoperative complication			0.37
None	4 (28.6)	6 (42.9)
Subcutaneous emphysema	1 (7.1)	8 (57.1)
Pneumoperitoneum	8 (57.1)	0 (0)
Other	1^c) (7.2)	0 (0)

Values are presented as number (%) for categorical variables and median (P25, P75) for non-normally distributed data.

^a)Day after surgery.

^b)Intraoperative events and management. American Society for Gastrointestinal Endoscopy complications were graded as mild, moderate, severe, or fatal.

^c)Other postoperative complications of the anterior approach included lung atelectasis and urinary tract infection.

Table 3.

Postoperative reflux and manometry outcomes

	Anterior approach (n=14)	Posterior approach (n=14)	p-value
DeMeester score^a)	15.55±22.03	18.91±15.47	0.41
Esophageal acid exposure^b)	4 (28.6)	8 (57.1)	0.14
Reflux esophagitis^c)			0.81
Normal	6 (42.9)	5 (35.7)
Grade A	4 (28.6)	7 (50.0)
Grade B	4 (28.6)	2 (14.3)
Grade C	0 (0)	0 (0)
Grade D	0 (0)	0 (0)
Postoperative IRP (mmHg)^d)	10.26±3.01	11.66±5.36	0.40

Values are presented as mean±standard deviation or number (%).

IRP, integrated relaxation pressure.

^a)DeMeester scores reflect 24-hour pH monitoring at 3 months.

^b)Abnormal esophageal acid exposure is defined as DeMeester score >14.7.

^c)Reflux esophagitis grades were assessed at the 12-month postoperative follow-up and graded according to the Los Angeles classification system.

^d)Postoperative IRP was measured by high-resolution manometry.

REFERENCES

1. Rohof WO, Salvador R, Annese V, et al. Outcomes of treatment for achalasia depend on manometric subtype. Gastroenterology 2013;144:718–725.Article PubMed
2. Calabrese EC, Kindel T, Slater BJ, et al. 2024 Update to SAGES guidelines for the use of peroral endoscopic myotomy (POEM) in the treatment of achalasia. Surg Endosc 2025;39:4027–4037.Article PubMed PDF
3. Hungness ES, Teitelbaum EN, Santos BF, et al. Comparison of perioperative outcomes between peroral esophageal myotomy (POEM) and laparoscopic Heller myotomy. J Gastrointest Surg 2013;17:228–235.Article PubMed PDF
4. Phalanusitthepha C, Inoue H, Ikeda H, et al. Peroral endoscopic myotomy for esophageal achalasia. Ann Transl Med 2014;2:31.Article PubMed PMC
5. Inoue H, Shiwaku H, Iwakiri K, et al. Clinical practice guidelines for peroral endoscopic myotomy. Dig Endosc 2018;30:563–579.Article PubMed PDF
6. Inoue H, Sato H, Ikeda H, et al. Per-oral endoscopic myotomy: a series of 500 patients. J Am Coll Surg 2015;221:256–264.Article PubMed
7. Ramchandani M, Nabi Z, Reddy DN, et al. Outcomes of anterior myotomy versus posterior myotomy during POEM: a randomized pilot study. Endosc Int Open 2018;6:E190–E198.Article PubMed PMC
8. Tan Y, Lv L, Wang X, et al. Efficacy of anterior versus posterior per-oral endoscopic myotomy for treating achalasia: a randomized, prospective study. Gastrointest Endosc 2018;88:46–54.Article
9. Khashab MA, Sanaei O, Rivory J, et al. Peroral endoscopic myotomy: anterior versus posterior approach: a randomized single-blinded clinical trial. Gastrointest Endosc 2020;91:288–297.Article PubMed
10. Stavropoulos SN, Modayil RJ, Zhang X, et al. 841 Is there a difference in outcomes between anterior and posterior peroral endoscopic myotomy (POEM)? a randomized study from an experienced high-volume operator. Gastrointest Endosc 2018;87:AB121–AB122.Article
11. Stavropoulos SN, Modayil RJ, Friedel D, et al. The International Per Oral Endoscopic Myotomy Survey (IPOEMS): a snapshot of the global POEM experience. Surg Endosc 2013;27:3322–3338.Article PDF
12. Suwatthanarak T, Phalanusitthepa C, Thongchuam C, et al. Timed barium esophagography to predict recurrent achalasia after peroral endoscopic myotomy: a retrospective study in Thailand. Clin Endosc 2024;57:610–619.Article PubMed PMC PDF
13. DeWitt JM, Siwiec RM, Perkins A, et al. Evaluation of timed barium esophagram after per-oral endoscopic myotomy to predict clinical response. Endosc Int Open 2021;9:E1692–E1701.Article PubMed PMC
14. Neyaz Z, Gupta M, Ghoshal UC. How to perform and interpret timed barium esophagogram. J Neurogastroenterol Motil 2013;19:251–256.Article PubMed PMC
15. Vaiciunaite D, Eriksson SE, Sarici IS, et al. The utility of Symptom Association Probability (SAP) in predicting outcome after laparoscopic fundoplication in patients with abnormal esophageal acid exposure. J Gastrointest Surg 2023;27:2014–2022.Article PubMed PMC PDF
16. Vaezi MF, Pandolfino JE, Yadlapati RH, et al. ACG clinical guidelines: diagnosis and management of achalasia. Am J Gastroenterol 2020;115:1393–1411.Article PubMed PMC
17. Khashab MA, Vela MF, Thosani N, et al. ASGE guideline on the management of achalasia. Gastrointest Endosc 2020;91:213–227.Article PubMed
18. Jung HK, Hong SJ, Lee OY, et al. 2019 Seoul consensus on esophageal achalasia guidelines. J Neurogastroenterol Motil 2020;26:180–203.Article PubMed PMC
19. Oude Nijhuis RAB, Zaninotto G, Roman S, et al. European guidelines on achalasia: United European Gastroenterology and European Society of Neurogastroenterology and Motility recommendations. United European Gastroenterol J 2020;8:13–33.Article PubMed PMC PDF
20. Mohan BP, Ofosu A, Chandan S, et al. Anterior versus posterior approach in peroral endoscopic myotomy (POEM): a systematic review and meta-analysis. Endoscopy 2020;52:251–258.Article
21. Shukla J, Mandavdhare HS, Shah J, et al. Transverse versus longitudinal mucosal incision during POEM for esophageal motility disorders: a randomized trial. Surg Endosc 2024;38:5053–5059.Article PDF
22. Teh JL, Tham HY, Soh AYS, et al. Gastro-esophageal reflux disease (GERD) after peroral endoscopic myotomy (POEM). Surg Endosc 2022;36:3308–3316.Article PubMed PDF
23. Inoue H, Minami H, Kobayashi Y, et al. Peroral endoscopic myotomy (POEM) for esophageal achalasia. Endoscopy 2010;42:265–271.Article PubMed
24. Shiwaku H, Inoue H, Shiwaku A, et al. Safety and effectiveness of sling fiber preservation POEM to reduce severe post-procedural erosive esophagitis. Surg Endosc 2022;36:4255–4264.Article PubMed PDF

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Anterior versus posterior peroral endoscopic myotomy: a prospective randomized controlled trial from a Thai tertiary center

DOI: https://doi.org/10.5946/ce.2025.407

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Anterior versus posterior peroral endoscopic myotomy: a prospective randomized controlled trial from a Thai tertiary center

Fig. 1. Anterior vs. posterior peroral endoscopic myotomy (POEM): schematic of tunnel and myotomy orientation. The mucosal entry is created at the 2 o’clock (anterior) or 5 o’clock (posterior) position. A submucosal tunnel traverses the esophagogastric junction (EGJ), followed by selective circular myotomy extending proximally and distally beyond the EGJ. A sling-fiber–preserving technique may be used to mitigate reflux risk. The illustrate was created by Chatbadin Thongchuam.

Fig. 2. Patient flow diagram through the prospective randomized comparative study (CONSORT-style diagram). Participants were screened, randomized in a 1:1 ratio to the anterior vs. posterior peroral endoscopic myotomy groups, and followed through predefined assessments (timed barium esophagography, high-resolution manometry, 24-hour pH, and esophagogastroduodenoscopy) for 12 months. Numbers reflect enrollment, allocation, follow-up, and analysis of 28 patients. STER, submucosal tunneling endoscopic resection.

Fig. 3. Improvement in timed barium esophagography (TBE) heights after anterior vs. posterior peroral endoscopic myotomy (POEM) over 12 months. Esophageal column heights at 1, 2, and 5 minutes improved after POEM. The anterior approach showed better early clearance at 1 and 2 minutes during follow-up, whereas 5-minute values were similar between the groups.

Fig. 4. Eckardt symptom score trajectories over 12 months after the anterior vs. posterior approach. Median Eckardt scores decreased from baseline and remained low across all intervals, with no significant between-group differences. Values reflect durable symptom control after either approach. IQR, interquartile; POEM, peroral endoscopic myotomy.

Graphical abstract

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

Graphical abstract

Anterior versus posterior peroral endoscopic myotomy: a prospective randomized controlled trial from a Thai tertiary center

Characteristic	Anterior approach (n=14)	Posterior approach (n=14)	p-value
Age (yr)	52.00±22.74	52.21±14.33	0.10
Sex (female)	7 (50.0)	10 (71.4)	0.25
Underlying disease			0.22
Diabetes mellitus	1	1	1.00
Hypertension	3	5	0.68
Dyslipidemia	3	5	0.68
Cerebrovascular disease	0	1	1.00
Other	2^a)	4^b)	0.52
Symptom duration (mo)	12 (6, 27)	12 (12, 27)	0.63
Preoperative Eckardt score
Weight loss			0.33
0	2 (14.3)	4 (28.6)
1	3 (21.4)	4 (28.6)
2	4 (28.6)	2 (14.3)
3	5 (35.7)	4 (28.6)
Dysphagia			0.44
0	0 (0)	0 (0)
1	1 (7.1)	3 (21.4)
2	2 (14.3)	1 (7.1)
3	11 (78.6)	10 (71.4)
Chest pain			0.45
0	7 (50.0)	6 (42.9)
1	5 (35.7)	4 (28.6)
2	1 (7.1)	2 (14.3)
3	1 (7.1)	2 (14.3)
Regurgitation			0.10
0	3 (21.4)	0 (0)
1	5 (35.7)	8 (57.1)
2	6 (42.9)	1 (7.1)
3	0 (0)	5 (35.7)
Total score	6 (5, 8)	5 (4, 9)	0.79
Preoperative IRP (mmHg)	32.67±12.50	30.51±9.71	0.55
Chicago classification			0.47
Type 1	4 (28.6)	2 (14.3)
Type 2	9 (64.3)	11 (78.6)
Type 3	1 (7.1)	1 (7.1)
Preoperative TBE Height (cm)
1 min	13.56±5.00	9.23±3.68	0.06
2 min	13.19±5.44	9.38±3.83	0.48
5 min	11.60±4.26	9.53±3.83	0.74

	Anterior approach (n=14)	Posterior approach (n=14)	p-value
Mucosal entry length (cm)	2 (2, 2)	2 (2, 2.25)	0.57
Tunnel length (cm)	12 (12, 12)	12 (9.75, 12.25)	0.60
Myotomy length (cm)	10 (9.75, 10)	10 (7.75, 10)	0.51
Operative time (min)	32.5 (30, 77.25)	30 (30, 61.25)	0.60
Pain score^a)
0	6 (4.75, 7.25)	5 (4, 6)	0.39
1	4 (3, 5)	3.5 (3, 4)	0.29
2	2.5 (2, 3.25)	2 (2, 3)	0.35
Intraoperative complications			0.53
None	10 (71.4)	12 (83.3)
Esophageal mucosal injury	1 (7.2)	0 (0)
Pneumoperitoneum	2 (14.2)	0 (0)
Subcutaneous emphysema	1 (7.2)	2 (16.7)
Further intervention after intraoperative complications			0.20
None	2 (50.0)	2 (100.0)
Endoscopic management	2 (50.0)	0 (0)
Severity of complications^b)			N/A
Mild	4 (100.0)	2 (100.0)
Moderate	0 (0)	0 (0)
Severe	0 (0)	0 (0)
Fatal	0 (0)	0 (0)
Postoperative complication			0.37
None	4 (28.6)	6 (42.9)
Subcutaneous emphysema	1 (7.1)	8 (57.1)
Pneumoperitoneum	8 (57.1)	0 (0)
Other	1^c) (7.2)	0 (0)

	Anterior approach (n=14)	Posterior approach (n=14)	p-value
DeMeester score^a)	15.55±22.03	18.91±15.47	0.41
Esophageal acid exposure^b)	4 (28.6)	8 (57.1)	0.14
Reflux esophagitis^c)			0.81
Normal	6 (42.9)	5 (35.7)
Grade A	4 (28.6)	7 (50.0)
Grade B	4 (28.6)	2 (14.3)
Grade C	0 (0)	0 (0)
Grade D	0 (0)	0 (0)
Postoperative IRP (mmHg)^d)	10.26±3.01	11.66±5.36	0.40

Table 1. Baseline characteristics of randomized patients by myotomy orientation

IRP, integrated relaxation pressure; TBE, timed barium esophagography.

Other underlying diseases in the anterior approach included asthma and hepatitis C virus infection.

Other underlying diseases in the posterior approach included atrial fibrillation, benign prostatic hypertrophy, chronic kidney disease, and hepatitis C virus infection.

Table 2. Procedural parameters and complications after anterior vs posterior peroral endoscopic myotomy

Values are presented as number (%) for categorical variables and median (P25, P75) for non-normally distributed data.

Day after surgery.

Intraoperative events and management. American Society for Gastrointestinal Endoscopy complications were graded as mild, moderate, severe, or fatal.

Other postoperative complications of the anterior approach included lung atelectasis and urinary tract infection.

Table 3. Postoperative reflux and manometry outcomes

Values are presented as mean±standard deviation or number (%).

IRP, integrated relaxation pressure.

DeMeester scores reflect 24-hour pH monitoring at 3 months.

Abnormal esophageal acid exposure is defined as DeMeester score >14.7.

Reflux esophagitis grades were assessed at the 12-month postoperative follow-up and graded according to the Los Angeles classification system.

Postoperative IRP was measured by high-resolution manometry.