Extraperitoneal tunneling reduces intraperitoneal drain displacement in rectal cancer surgery: a single-center before-and-after comparative study

Mi Jeong Choi; Min Hyeong Jo; Kyong Min Kang; Hong-Min Ahn; Heung-Kwon Oh; Duck-Woo Kim; Sung-Bum Kang

doi:10.3393/ac.2025.01536.0219

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Original Article Complications Extraperitoneal tunneling reduces intraperitoneal drain displacement in rectal cancer surgery: a single-center before-and-after comparative study: Mi Jeong Choi , Min Hyeong Jo , Kyong Min Kang , Hong-Min Ahn , Heung-Kwon Oh , Duck-Woo Kim , Sung-Bum Kang; Annals of Coloproctology 2026;42(4):446-453.
DOI: https://doi.org/10.3393/ac.2025.01536.0219
Published online: August 26, 2026

Department of Surgery, Seoul National University Bundang Hospital, Seongnam, Korea

Correspondence to: Sung-Bum Kang, MD, PhD Department of Surgery, Seoul National University Bundang Hospital, 82 Gumi-ro 173beon-gil, Bundang-gu, Seongnam 13620, Korea Email: kangsb@snubh.org

• Received: December 13, 2025 • Revised: May 13, 2026 • Accepted: May 20, 2026

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://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
INTRODUCTION
METHODS
RESULTS
DISCUSSION
ARTICLE INFORMATION
Supplementary materials
REFERENCES

Abstract

Purpose
Anastomotic leakage (AL) is a serious complication of rectal cancer surgery, and a properly positioned pelvic drain may aid early detection and conservative management; however, intraperitoneal drains frequently migrate. We evaluated whether extraperitoneal tunneling (EPT) of the pelvic drain reduces drain displacement compared with conventional intraperitoneal placement.
Methods
This single-center before-and-after comparative study enrolled adults with rectal cancer located within 15 cm of the anal verge who underwent elective radical resection between August 2021 and July 2024. Patients operated between August 2021 and December 2022 received conventional intraperitoneal drains (non-EPT group) and those operated between January 2023 and July 2024 received EPT drains (EPT group). The primary outcome was drain displacement (>3 cm from the anastomotic staple line) on postoperative day 2 plain radiograph. Secondary outcomes were AL, EPT-related complications, and the need for additional intervention. Multivariate logistic regression, propensity score matching (PSM), and inverse probability of treatment weighting (IPTW) were performed.
Results
Of 228 patients, 111 received EPT and 117 received conventional drains. Drain displacement occurred in 5 of 111 EPT patients (4.5%) versus 55 of 117 non-EPT patients (47.0%; P<0.001). After multivariate adjustment, EPT was an independent protective factor (adjusted odds ratio [OR], 0.05; 95% confidence interval [CI], 0.02–0.13; P<0.001). The protective association was robust across PSM (matched OR, 0.07; 95% CI, 0.02–0.18) and IPTW (OR, 0.05–0.06; both P<0.001). AL occurred in 6 patients (2.6%) without a significant between-group difference (EPT, 1.8% vs. non-EPT, 3.4%; Fisher exact, P=0.681). Operative time, overall complications, and EPT-related complications did not differ between groups.
Conclusion
In this single-center before-and-after series, EPT was associated with a substantially lower rate of postoperative day 2 drain displacement after rectal cancer surgery.
Keywords: Rectal neoplasms; Anastomotic leak; Drainage; Comparative study; Propensity score

INTRODUCTION

Surgeons traditionally place intraperitoneal drains after colorectal or pelvic surgery to enable early detection of anastomotic leakage (AL) and to provide a therapeutic drainage effect [1, 2]. However, intraperitoneal drains frequently migrate within the peritoneal cavity and lose functional efficacy once displaced. Although surgeons commonly suture the drain to the peritoneum or surrounding tissues, most drains nevertheless become displaced within the first few postoperative days [1, 2].

Recent meta-analyses and randomized trials have not shown a clear benefit of routine prophylactic drains in colorectal surgery, even after anterior resection, and Enhanced Recovery After Surgery (ERAS) pathways further encourage early drain removal when drains are used [3–8]. A key limitation of these studies, however, is the minimal documentation of drain displacement despite short typical in situ durations (often 1–3 days) [1–3]. Lee et al. [2] reported that more than 40% of drains had displaced by postoperative day 3. Because AL is most often recognized around postoperative day 7, many affected patients may have no functional drain at the time of diagnosis, implying that some “drain versus no drain” comparisons were effectively “no drain versus no functional drain” [1–3].

Radiologic intervention (image-guided percutaneous drainage) has become a standard first-line treatment for AL or pelvic sepsis because radiology enables precise and stable drain placement [7, 9]. If a surgically placed drain could be maintained in its intended position and remain functional, its effect might be comparable to that of a radiologically placed drain.

Recently, extraperitoneal tunneling (EPT) has been proposed as a way to maintain drain position by directing the tube through the extraperitoneal fat plane, a route less affected by abdominal movement or bowel peristalsis, analogous to that used for an extraperitoneal colostomy [10]. In an introductory technical note, Kang et al. [10] reported that EPT was associated with reduced drain migration and reoperation rates. A subsequent comparative cohort study by the same group, using the same 3-cm radiologic cutoff, reported drain displacement of 2.8% with EPT versus 40.1% with conventional placement among 334 anterior or low anterior resections [11]. Given that the available evidence is limited to a single surgical group and a relatively small body of work, independent evaluation in a different institution—with a different surgeon, larger cohort, and more rigorous statistical adjustment—is warranted.

Accordingly, we compared EPT with conventional intraperitoneal drain insertion at our institution to assess differences in drain displacement, and we additionally tracked the clinical course of all AL cases. Our study contributes the following to the existing literature: (1) providing independent validation by a different surgical team; (2) using a larger single-center cohort (n=228); (3) adding multivariate risk-factor analysis with prespecified covariates that satisfy events-per-variable recommendations; (4) addressing the inherent time-period confounding of the before-and-after design through propensity score matching (PSM) and inverse probability of treatment weighting (IPTW); and (5) tracking the clinical course of all AL cases.

METHODS

Ethics statement

This study was approved by the Institutional Review Board of Seoul National University Bundang Hospital (No. B-2510-1000-114). The requirement for written informed consent was waived due to the use of deidentified data and the retrospective nature of the study. All procedures were conducted in accordance with the principles of the Declaration of Helsinki.

Study design and patients

This single-center retrospective before-and-after comparative study was conducted at Seoul National University Bundang Hospital and included consecutive adult patients who underwent elective radical resection with total mesorectal excision (TME) for histologically confirmed rectal adenocarcinoma located within 15 cm of the anal verge between August 2021 and July 2024. Patients were excluded if they underwent emergency surgery, abdominoperineal resection, or had synchronous double primary cancers. Regarding the level of anastomosis, ultralow anterior resection (uLAR) was defined by a distance of 5 cm or less from the anal verge, whereas cases with an anastomosis height between 5 cm and 15 cm were classified as low anterior resection (LAR). All operations were performed by a single colorectal surgeon (SBK). Patients were grouped according to the time period during which surgery was performed. The non-EPT group included patients who received conventional transabdominal drain insertion between August 2021 and December 2022, and the EPT group included those who received EPT drain insertion between January 2023 and July 2024. EPT was performed using a newly developed device (Drain-TG, JSR Medical). This time-based grouping yielded a historical-control before-and-after design.

Operative drain placement and EPT procedure

A closed-suction silicone Jackson-Pratt drain was used in all patients. The perforated drainage segment of the device is approximately 10 cm in length and was positioned with its midpoint at the anastomotic staple line. With this configuration, the active drainage zone is centered on the anastomosis (Fig. 1). In the non-EPT group, the drain was introduced through a lateral abdominal port site and advanced into the pelvic cavity, with the tube lying posterior to the anastomosis and the tip placed adjacent to the anastomotic staple line. In the EPT group, the drain was tunneled through the extraperitoneal fat plane: from the lateral abdominal port site, the tube was guided posteriorly along the extraperitoneal soft tissue, traversed the pelvic side wall, and entered the pelvic cavity adjacent to the posterior aspect of the anastomosis. The perioperative drain management protocol was identical for both groups. Drain output was monitored daily, and removal was considered following dietary advancement when the following criteria were met: a decreasing trend in output volume, clear or serous fluid characteristics, and the absence of clinical signs of infection (e.g., fever, elevation of inflammatory markers, or changes in drain color). For patients with a low anastomosis or those with suspected AL, drain removal was deferred until the outpatient follow-up visit at 1 to 2 weeks after discharge.

Drain displacement assessment

Intra-abdominal drain position was evaluated on postoperative day 2 using routine plain abdominal radiographs in both erect and supine (flat) positions, in accordance with our institutional postoperative protocol. Each radiograph was reviewed jointly by 2 colorectal surgeons; discordant cases were resolved by consensus. Drain displacement was defined as the drain tip located >3 cm away from the anastomotic staple line or pelvic dissection bed as measured by the shortest distance on radiograph (Fig. 2). The approximately 10-cm perforated segment of the drain is positioned directly inferior to the anastomosis. Therefore, we reasoned that an upward displacement of more than 3 cm above the anastomosis would compromise the drain's ability to effectively cover and drain the surrounding target area. The same 3-cm cutoff has been applied in the most directly comparable study by Kang and Kim [11]—a recent comparative cohort of EPT versus conventional drain insertion in patients undergoing anterior resection or LAR.

Definitions and outcomes

The primary outcome was the drain displacement rate. Secondary outcomes were the incidence of AL, risk factors for drain displacement, EPT-related complications, and the need for additional intervention (image-guided percutaneous drainage or reoperation). AL was defined as a clinically apparent or radiologically confirmed leak corresponding to International Study Group of Rectal Cancer (ISREC) grade B or C [12]. The clinical course of every AL case was traced from the electronic medical record. AL was managed according to a standard protocol: conservative management with the existing Jackson-Pratt drain alone for clinically stable grade B leaks; image-guided percutaneous drainage when an undrained pelvic fluid collection persisted; and reoperation for diffuse peritonitis or failed drainage. The protocol was applied identically to both groups.

Statistical analysis

Categorical variables were compared using chi-square or Fisher exact test as appropriate (Fisher exact when any expected cell count was <5). Continuous variables were compared using Student t-test or the Mann-Whitney U-test, depending on distribution. Independent predictors of drain displacement were identified by multivariate logistic regression. The multivariate model included 5 clinically relevant covariates that showed a P-value of <0.2 in the univariate analysis: EPT, tumor height ≥5 cm from the anal verge, anastomosis height ≥5 cm, presence of a diverting stoma, and operative method. Given the 60 displacement events recorded, this specification yields an events-per-variable of 12 [13].

To address the potential time-period confounding inherent to the before-and-after design, we additionally performed propensity score (PS) analyses. The PS was estimated by logistic regression of EPT on the 4 baseline covariates (tumor height, anastomosis height, diverting stoma, and operative method). We performed 1:1 nearest-neighbor PSM without replacement, with a caliper of 0.2×standard deviation (SD) of the logit of the PS, restricted to the region of common support [14]. Both dichotomized and continuous covariate specifications were tested. As a sensitivity analysis, we also estimated the EPT effect using IPTW with the same PS model.

All analyses were performed using Stata ver. 18 (StataCorp). All tests were 2-sided, and P<0.05 was considered statistically significant.

RESULTS

Baseline characteristics

Of 228 patients included, 111 received EPT and 117 received conventional drains. The groups were similar in age, sex, body mass index, clinical T and N categories, tumor height, neoadjuvant chemoradiotherapy, anastomosis method, anastomosis height, and tumor size, but differed in operative method (more robotic procedures in the EPT group, 12.6% vs. 1.7%; P<0.001), operative procedure (more uLAR in the EPT group, 80.2% vs. 62.4%; P=0.003), and histology distribution (more poorly differentiated tumors in the EPT group, 8.1% vs. 1.7%; P=0.017) (Table 1, Supplementary Tables 1, 2). Mean operative time was similar between groups (233.0±74.9 minutes vs. 238.2±99.3 minutes, P=0.663), as were overall postoperative complication rates (22.5% vs. 16.2%, P=0.240).

Drain displacement

Drain displacement on the postoperative day 2 radiograph occurred in 5 of 111 EPT patients (4.5%) versus 55 of 117 non-EPT patients (47.0%; P<0.001). In univariate analysis, both lower tumor height and conventional (non-EPT) drain placement were significantly associated with displacement. After multivariate adjustment with the prespecified 5-variable model, EPT was an independent protective factor against drain displacement (adjusted odds ratio [OR], 0.05; 95% confidence interval [CI], 0.02–0.13; P<0.001). No other covariate (tumor height ≥5 cm, anastomosis height ≥5 cm, diverting stoma, or operative method) reached statistical significance after adjustment (Table 2).

Robustness to time-period confounding (PSM and IPTW)

After 1:1 nearest-neighbor PSM with a caliper of 0.2×SD of the logit PS, EPT remained the dominant protective factor for drain displacement (matched OR, 0.07 [95% CI, 0.02–0.18] with dichotomized covariates, n=198; matched OR, 0.03 [95% CI, 0.01–0.10] with continuous covariates, n=192; both P<0.001) (Table 2). IPTW analyses yielded essentially identical estimates (OR, 0.05–0.06; both P<0.001). The consistency of the EPT effect across unadjusted, multivariate, propensity-matched, and IPTW analyses suggests that the observed reduction in displacement is unlikely to be attributable to time-period confounding alone.

AL and clinical course

AL occurred in 6 patients (2.6%), with no statistically significant between-group difference (EPT, 2 of 111 [1.8%] vs. non-EPT, 4 of 117 [3.4%]; Fisher exact, P=0.681). Of these 6 cases, 4 were associated with drain displacement: in 3 the displaced drain was removed and a new percutaneous catheter was placed at the appropriate site under image guidance (without reoperation), and 1 (non-EPT, uLAR) underwent reoperation. The remaining 2 cases occurred without drain displacement: 1 (EPT, uLAR) was managed by image-guided replacement of the existing drain (without reoperation), while the other (non-EPT, LAR) underwent reoperation. Although the number of events (n=6) is negligible for formal inferential testing, the descriptive reoperation rate was 0% (0 of 2) in the EPT group and 50% (2 of 4) in the non-EPT group. No EPT-related complications were observed. Hospital stay was similar between groups (EPT, 6.1±1.4 days vs. non-EPT, 6.5±2.8 days; P=0.067).

DISCUSSION

In this single-center before-and-after comparative study of 228 consecutive rectal cancer patients, EPT was associated with substantially lower postoperative day 2 drain displacement than conventional intraperitoneal drain placement (4.5% vs. 47.0%). The association was robust across multivariate adjustment, PSM with both dichotomized and continuous covariate specifications, and IPTW: across all 6 specifications the EPT OR remained between 0.03 and 0.07 with P<0.001.

Conventional drain placement through a laparoscopic or robotic port leaves most of the drain lying intraperitoneally, where its position is influenced by tube flexibility, peristalsis, respiration, and patient position [1]. EPT directs the drain through the extraperitoneal fat plane, shielding it from these forces and, plausibly, reducing displacement [10, 11]. A nondisplaced drain may provide earlier detection of pelvic complications and more effective drainage of fluid collections, and may reduce dead-space in the narrow post-TME pelvis [15–17]. We did not, however, formally test these clinical endpoints, and our findings should be interpreted as an observation about a surrogate (radiographic drain position) rather than a definitive demonstration of clinical benefit. Despite extensive debate on prophylactic drains, the fate of the drain, particularly displacement, has rarely been quantified. Gilbert et al. [1] reported 19.8% drain migration within 5 days after gastrointestinal surgery on computed tomography. Lee et al. [2] reported drain displacement in 37.5% (93 of 248) of patients after proctectomy; among these 93 displaced drains, 34.4% had displaced by postoperative day 2 and 74.2% by day 4 (cumulative). Kang and Kim [11] recently reported day-3 displacement of 40.1% with conventional placement versus 2.8% with EPT, and noted that AL cases without displacement were less likely to require reoperation. Differences in reported rates likely reflect varying displacement definitions and imaging modalities across studies [1, 2, 11].

Our study is distinct from the technical introduction of EPT by Kang et al. [10] and from the subsequent EPT comparative cohort by Kang and Kim [11] in several ways. First, the surgeries were performed by a different colorectal surgeon at a different institution, providing independent technical validation. Second, our cohort provides an independent series of comparable size to the previously reported cohort, assembled under a different surgical team and institution. Third, we traced the clinical course of every AL case rather than reporting an aggregate AL rate. Fourth, we explicitly framed drain displacement as a surrogate outcome whose clinical relevance must eventually be tested in prospective comparative studies with patient-centered endpoints.

Multiple meta-analyses and randomized trials have challenged the routine use of pelvic drains in colorectal surgery, including within ERAS pathways [3–9, 18, 19]. The latest ERAS update explicitly downgrades the recommendation against routine drainage in rectal resection to “weak” with low-to-moderate quality of evidence, in contrast to the strong recommendation for colonic resection [20]. A meta-analysis specifically of extraperitoneal anastomosis showed that pelvic drainage was associated with lower AL (OR, 0.51) and reoperation (OR, 0.29) rates [3]. Within this context, our institutional practice of selective drainage in low rectal cancer is defensible. Importantly, drains that are removed early or displaced by the time AL typically manifests (around day 7) cannot serve their intended diagnostic or therapeutic role; many published “drain versus no drain” comparisons may have partly contrasted no drain with no functional drain, which could attenuate the apparent effect of drains in trials that did not control for displacement [1–3, 9, 17]. By maintaining drain position, EPT offers a biologically plausible way to preserve both the diagnostic and therapeutic functions of a pelvic drain. A stable, nondisplaced drain may aid both early detection and conservative management of AL, a hypothesis that requires prospective confirmation.

Several limitations should be acknowledged. First, this is a single-center, single-surgeon, retrospective before-and-after study; despite PS adjustment, residual confounding by unmeasured time-varying factors, such as evolving perioperative care, surgeon learning, or unrecorded selection, cannot be excluded. Second, the primary outcome is a surrogate endpoint based on plain radiographs taken on postoperative day 2 to align with our historical pre-EPT practice; plain radiography does not provide 3D information, and computed tomography rereading was not feasible because of efforts to minimize radiation exposure. Third, 2 colorectal surgeons jointly assessed each radiograph and the assessors were not blinded to the time period (and therefore potentially to drain technique); although joint reading mitigates individual reader bias, formal interobserver agreement (κ) could not be computed because discordant readings were not preserved—an explicit observer-bias acknowledgement. Fourth, the study was not powered to detect differences in AL or reoperation; the AL course is reported descriptively only. Fifth, we did not have continuous, per-patient data on drain dwell time and could not formally examine displacement-by-duration trade-offs. Sixth, the low overall AL rate may reflect single-surgeon consistency, exclusion of emergency and double-primary cases, frequent diverting ileostomy, and the exclusion of asymptomatic ISREC grade A leaks [15, 16, 21]. Findings from this single-center series should therefore be confirmed in multicenter prospective comparative studies before broader practice change.

In this single-center before-and-after comparative study, EPT drain insertion was associated with significantly lower drain displacement on postoperative day 2 after rectal cancer surgery.

ARTICLE INFORMATION

Conflict of interest

Hong-Min Ahn is an editorial board member of this journal, but was not involved in the peer reviewer selection, evaluation, or decision process of this article. No other potential conflict of interest relevant to this article was reported.

Funding

None.

Author contributions

Conceptualization: SBK; Data curation: MJC; Formal analysis: MJC; Investigation: SBK, MHJ, KMK, HMA; Methodology: SBK; Project administration: SBK; Supervision: SBK; Validation: SBK, HKO, DWK; Visualization: MJC; Writing–original draft: MJC; Writing–review & editing: all authors. All authors read and approved the final manuscript.

Supplementary materials

Supplementary Table 1.

Baseline characteristics of the covariates included in the propensity score model before and after PSM

ac-2025-01536-0219-Supplementary-Table-1.pdf

Supplementary Table 2.

Baseline characteristics of the other variables before and after PSM

ac-2025-01536-0219-Supplementary-Table-2.pdf

Supplementary materials are available from https://doi.org/10.3393/ac.2025.01536.0219.

Fig. 1.

Schematic illustration of the extraperitoneal tunneling (EPT) drain route. The red line represents the EPT method, and the yellow line indicates the non-EPT method. The drain is introduced through a lateral abdominal port site, tunneled through the extraperitoneal soft tissue posterior to the anastomosis, traverses the pelvic side wall, and enters the pelvic cavity adjacent to the posterior aspect of the anastomosis.

Fig. 2.

Postoperative day 2 plain abdominal radiograph illustrating drain displacement. The yellow line indicates the position of the drain, while the red arrows mark the site of the anastomosis. The distance between these 2 indicators represents the radiological displacement measured in this study. Displacement was defined as a distance exceeding 3 cm between the drain tip and the staple line. A displaced drain tip, being far from the anastomosis, has a limited capacity to detect or drain pelvic leaks. (A) An x-ray of a patient with a tumor height of 4 cm from the anal verge who underwent ultralow anterior resection, demonstrating no drain displacement. (B) An x-ray of a patient with a tumor height of 3 cm from the anal verge who underwent ultralow anterior resection, serving as an example of drain displacement.

Table 1.

Baseline characteristics (n=228)

Characteristic	EPT (n=111)	Non-EPT (n=117)	P-value
Age (yr)	61.5±12.2	61.4±12.7	0.969
Female sex	39 (35.1)	48 (41.0)	0.361
Body mass index (kg/m²)	24.4±3.4	24.2±3.7	0.643
Clinical T category			0.310
cTx	1 (0.9)	5 (4.3)
cT1	3 (2.7)	3 (2.6)
cT2	22 (19.8)	13 (11.1)
cT3	59 (53.2)	71 (60.7)
cT4a	17 (15.3)	16 (13.7)
cT4b	9 (8.1)	9 (7.7)
Clinical N category			0.417
cN0	43 (38.7)	52 (44.4)
cN1	68 (61.3)	65 (55.6)
Tumor height from AV (cm)			0.382
<5	26 (23.4)	32 (27.4)
5–10	58 (52.3)	50 (42.7)
10–15	27 (24.3)	35 (29.9)
Neoadjuvant CCRT	62 (55.9)	59 (50.4)	0.434
Operative method			<0.001
Open	1 (0.9)	1 (0.9)
Laparoscopy	95 (85.6)	110 (94.0)
Robot	14 (12.6)	2 (1.7)
Conversion to open	1 (0.9)	4 (3.4)
Operative procedure			0.003
LAR	22 (19.8)	44 (37.6)
uLAR	89 (80.2)	73 (62.4)
Operative time (min)	233.0±74.9	238.2±99.3	0.663
Anastomosis method			0.668
Hand-sewn	13 (11.7)	11 (9.4)
Double-stapled	98 (88.3)	106 (90.6)
Anastomosis height from AV (cm)	4.11±2.45	4.43±2.69	0.560
<5	70 (63.1)	66 (56.4)	0.211
5–10	38 (34.2)	42 (35.9)
10–15	3 (2.7)	9 (7.7)
Histology			0.017
Well differentiated	4 (3.6)	10 (8.5)
Moderately differentiated	97 (87.4)	105 (89.7)
Poorly differentiated	9 (8.1)	2 (1.7)
Undifferentiated	1 (0.9)	0 (0)
Tumor size (cm)	3.65±2.26	3.52±2.42	0.686
Diverting stoma	69 (62.2)	81 (69.2)	0.273
Postoperative complication	25 (22.5)	19 (16.2)	0.240
Wound	3 (2.7)	5 (4.3)
Ileus	12 (10.8)	9 (7.7)
Anastomotic leakage	2 (1.8)	4 (3.4)
Other	8 (7.2)	1 (0.9)

Values are presented as mean±standard deviation or number (%). Group comparisons used Student t-test for continuous variables and chi-square or Fisher exact tests for categorical variables.

EPT, extraperitoneal tunneling; AV, anal verge; CCRT, concurrent chemoradiotherapy; LAR, low anterior resection; uLAR, ultralow anterior resection.

Table 2.

Risk factors for drain displacement (univariate, multivariate, and PSM-matched logistic regression)

Predictor	No. of patients		Univariate analysis		Multivariate analysis		PSM-matched analysis
Predictor	Displaced (n=60)	Nondisplaced (n=168)	OR (95% CI)	P-value	aOR (95% CI)	P-value	OR (95% CI)	P-value
Drain type
Non-EPT	55	62	1 (Reference)		1 (Reference)		1 (Reference)
EPT	5	106	0.05 (0.02–0.14)	<0.001	0.05 (0.02–0.13)	<0.001	0.07 (0.02–0.18)	<0.001
Age
≤70 yr	46	125	1 (Reference)
>70 yr	14	43	0.89 (0.45–1.76)	0.742
Sex
Male	34	107	1 (Reference)
Female	26	61	1.34 (0.74–2.43)	0.338
Body mass index
≤25 kg/m²	39	100	1 (Reference)
>25 kg/m²	21	68	0.79 (0.43–1.46)	0.460
Clinical T category
cT1–cT2	12	29	1 (Reference)
cT3–cT4	46	135	0.82 (0.39–1.75)	0.612
Clinical N category
cN0	26	69	1 (Reference)
cN1	34	99	0.91 (0.51–1.64)	0.763
Tumor height (from AV)
<5 cm	22	36	1 (Reference)		1 (Reference)
≥5 cm	38	132	0.47 (0.25–0.89)	0.020	0.60 (0.25–1.45)	0.251
Neoadjuvant CCRT
No	25	82	1 (Reference)
Yes	35	86	1.33 (0.74–2.42)	0.342
Operative method
Open or converted	4	3	1 (Reference)		1 (Reference)
Laparoscopy or robot	56	165	0.25 (0.06–1.16)	0.081	0.36 (0.01–14.40)	0.589
Anastomosis height (from AV)
<5 cm	41	95	1 (Reference)		1 (Reference)
≥5 cm	19	73	0.60 (0.32–1.13)	0.133	0.52 (0.21–1.31)	0.170
Anastomosis method
Hand-sewn	6	18	1 (Reference)
Double-stapled	54	150	1.08 (0.41–2.85)	0.884
Tumor size
<3.5 cm	36	90	1 (Reference)
≥3.5 cm	24	78	0.77 (0.43–1.39)	0.450
Diverting stoma
No	15	63	1 (Reference)		1 (Reference)
Yes	45	105	1.80 (0.93–3.49)	0.081	0.94 (0.37–2.37)	0.900

Univariate ORs were estimated by univariate logistic regression. The multivariate model is a parsimonious, prespecified specification with 5 predictors (EPT, tumor height ≥5 cm, anastomosis height ≥5 cm, diverting stoma, operative method).

PSM, propensity score matching; OR, odds ratio; CI, confidence interval; aOR, adjusted odds ratio; EPT, extraperitoneal tunneling; AV, anal verge; CCRT, concurrent chemoradiotherapy.

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Extraperitoneal tunneling reduces intraperitoneal drain displacement in rectal cancer surgery: a single-center before-and-after comparative study

Ann Coloproctol. 2026;42(4):446-453. Published online August 26, 2026

DOI: https://doi.org/10.3393/ac.2025.01536.0219

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Figure

Extraperitoneal tunneling reduces intraperitoneal drain displacement in rectal cancer surgery: a single-center before-and-after comparative study

Fig. 1. Schematic illustration of the extraperitoneal tunneling (EPT) drain route. The red line represents the EPT method, and the yellow line indicates the non-EPT method. The drain is introduced through a lateral abdominal port site, tunneled through the extraperitoneal soft tissue posterior to the anastomosis, traverses the pelvic side wall, and enters the pelvic cavity adjacent to the posterior aspect of the anastomosis.

Fig. 2. Postoperative day 2 plain abdominal radiograph illustrating drain displacement. The yellow line indicates the position of the drain, while the red arrows mark the site of the anastomosis. The distance between these 2 indicators represents the radiological displacement measured in this study. Displacement was defined as a distance exceeding 3 cm between the drain tip and the staple line. A displaced drain tip, being far from the anastomosis, has a limited capacity to detect or drain pelvic leaks. (A) An x-ray of a patient with a tumor height of 4 cm from the anal verge who underwent ultralow anterior resection, demonstrating no drain displacement. (B) An x-ray of a patient with a tumor height of 3 cm from the anal verge who underwent ultralow anterior resection, serving as an example of drain displacement.

Fig. 1.

Fig. 2.

Extraperitoneal tunneling reduces intraperitoneal drain displacement in rectal cancer surgery: a single-center before-and-after comparative study

Characteristic	EPT (n=111)	Non-EPT (n=117)	P-value
Age (yr)	61.5±12.2	61.4±12.7	0.969
Female sex	39 (35.1)	48 (41.0)	0.361
Body mass index (kg/m²)	24.4±3.4	24.2±3.7	0.643
Clinical T category			0.310
cTx	1 (0.9)	5 (4.3)
cT1	3 (2.7)	3 (2.6)
cT2	22 (19.8)	13 (11.1)
cT3	59 (53.2)	71 (60.7)
cT4a	17 (15.3)	16 (13.7)
cT4b	9 (8.1)	9 (7.7)
Clinical N category			0.417
cN0	43 (38.7)	52 (44.4)
cN1	68 (61.3)	65 (55.6)
Tumor height from AV (cm)			0.382
<5	26 (23.4)	32 (27.4)
5–10	58 (52.3)	50 (42.7)
10–15	27 (24.3)	35 (29.9)
Neoadjuvant CCRT	62 (55.9)	59 (50.4)	0.434
Operative method			<0.001
Open	1 (0.9)	1 (0.9)
Laparoscopy	95 (85.6)	110 (94.0)
Robot	14 (12.6)	2 (1.7)
Conversion to open	1 (0.9)	4 (3.4)
Operative procedure			0.003
LAR	22 (19.8)	44 (37.6)
uLAR	89 (80.2)	73 (62.4)
Operative time (min)	233.0±74.9	238.2±99.3	0.663
Anastomosis method			0.668
Hand-sewn	13 (11.7)	11 (9.4)
Double-stapled	98 (88.3)	106 (90.6)
Anastomosis height from AV (cm)	4.11±2.45	4.43±2.69	0.560
<5	70 (63.1)	66 (56.4)	0.211
5–10	38 (34.2)	42 (35.9)
10–15	3 (2.7)	9 (7.7)
Histology			0.017
Well differentiated	4 (3.6)	10 (8.5)
Moderately differentiated	97 (87.4)	105 (89.7)
Poorly differentiated	9 (8.1)	2 (1.7)
Undifferentiated	1 (0.9)	0 (0)
Tumor size (cm)	3.65±2.26	3.52±2.42	0.686
Diverting stoma	69 (62.2)	81 (69.2)	0.273
Postoperative complication	25 (22.5)	19 (16.2)	0.240
Wound	3 (2.7)	5 (4.3)
Ileus	12 (10.8)	9 (7.7)
Anastomotic leakage	2 (1.8)	4 (3.4)
Other	8 (7.2)	1 (0.9)

Predictor	No. of patients		Univariate analysis		Multivariate analysis		PSM-matched analysis
Predictor	Displaced (n=60)	Nondisplaced (n=168)	OR (95% CI)	P-value	aOR (95% CI)	P-value	OR (95% CI)	P-value
Drain type
Non-EPT	55	62	1 (Reference)		1 (Reference)		1 (Reference)
EPT	5	106	0.05 (0.02–0.14)	<0.001	0.05 (0.02–0.13)	<0.001	0.07 (0.02–0.18)	<0.001
Age
≤70 yr	46	125	1 (Reference)
>70 yr	14	43	0.89 (0.45–1.76)	0.742
Sex
Male	34	107	1 (Reference)
Female	26	61	1.34 (0.74–2.43)	0.338
Body mass index
≤25 kg/m²	39	100	1 (Reference)
>25 kg/m²	21	68	0.79 (0.43–1.46)	0.460
Clinical T category
cT1–cT2	12	29	1 (Reference)
cT3–cT4	46	135	0.82 (0.39–1.75)	0.612
Clinical N category
cN0	26	69	1 (Reference)
cN1	34	99	0.91 (0.51–1.64)	0.763
Tumor height (from AV)
<5 cm	22	36	1 (Reference)		1 (Reference)
≥5 cm	38	132	0.47 (0.25–0.89)	0.020	0.60 (0.25–1.45)	0.251
Neoadjuvant CCRT
No	25	82	1 (Reference)
Yes	35	86	1.33 (0.74–2.42)	0.342
Operative method
Open or converted	4	3	1 (Reference)		1 (Reference)
Laparoscopy or robot	56	165	0.25 (0.06–1.16)	0.081	0.36 (0.01–14.40)	0.589
Anastomosis height (from AV)
<5 cm	41	95	1 (Reference)		1 (Reference)
≥5 cm	19	73	0.60 (0.32–1.13)	0.133	0.52 (0.21–1.31)	0.170
Anastomosis method
Hand-sewn	6	18	1 (Reference)
Double-stapled	54	150	1.08 (0.41–2.85)	0.884
Tumor size
<3.5 cm	36	90	1 (Reference)
≥3.5 cm	24	78	0.77 (0.43–1.39)	0.450
Diverting stoma
No	15	63	1 (Reference)		1 (Reference)
Yes	45	105	1.80 (0.93–3.49)	0.081	0.94 (0.37–2.37)	0.900

Table 1. Baseline characteristics (n=228)

Values are presented as mean±standard deviation or number (%). Group comparisons used Student t-test for continuous variables and chi-square or Fisher exact tests for categorical variables.

EPT, extraperitoneal tunneling; AV, anal verge; CCRT, concurrent chemoradiotherapy; LAR, low anterior resection; uLAR, ultralow anterior resection.

Table 2. Risk factors for drain displacement (univariate, multivariate, and PSM-matched logistic regression)

PSM, propensity score matching; OR, odds ratio; CI, confidence interval; aOR, adjusted odds ratio; EPT, extraperitoneal tunneling; AV, anal verge; CCRT, concurrent chemoradiotherapy.