Abstract Objectives: Endoscopic ultrasound-guided transmural drainage (EUS-TD) is widely performed to treat postoperative peripancreatic fluid collection (POPFC). Recent reports on EUS-TD lack a consensus on stent selection. This study aimed to assess the efficacy of EUS-TD for POPFC using an external drainage-first approach. Methods: We retrospectively examined the medical records of patients with POPFC treated with EUS-TD using external drainage between October 2016 and July 2024. Technical success was defined as successful placement of the external drainage. Clinical success was defined as the disappearance of fluid collection on follow-up computed tomography without additional intervention. Results: This study included 14 patients. The median duration from surgery to endoscopic treatment was 13 (range: 11–26) days. The median procedural time was 26 (range: 13–35) min. The technical success rate was 100%, and 6 Fr endoscopic nasocystic drainage was performed in all patients. The clinical success rate was 64.3%, and no adverse events were observed. In 35.7% (5/14) of the patients, additional endoscopic internal drainage was required; the POPFC was successfully controlled in all patients. The reasons for conversion to internal drainage were prolonged inflammation in one patient, remaining fluid collection in one patient, and requests from surgeons in three patients. Conclusions: EUS-TD for POPFC with external drainage proved to be safe and effective, with a short procedure time. However, in certain patients, additional internal drainage is required.

The authors have declared no competing interest.

The author(s) received no specific funding for this work.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This retrospective study was reviewed and approved by the Ethics Committee of Showa University (approval no. 21-061-A).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All relevant data are within the manuscript and its Supporting Information files.