ABSTRACT
Background
Single‐incision laparoscopic surgery (SILS) is an evolving minimally invasive technique for Crohn's disease (CD). However, evidence regarding conversion risk, specifically in SILS, is limited. This study aimed to identify independent predictors of conversion to open surgery.
Methods
We retrospectively analyzed patients with CD who underwent intestinal resection using an SILS‐first strategy between April 2018 and October 2025. The patients were classified into conversion and non‐conversion groups. Logistic regression analyses were performed to analyze risk factors for conversion to open surgery. The model's performance was evaluated using receiver operating characteristic (ROC) analysis.
Results
Of 289 patients, 34 (11.8%) required conversion to open surgery. Additional ports were required in 30 (10.4%) patients; 22 of these were completed laparoscopically. Multivariate analysis identified fistula (odds ratio [OR]: 7.53, 95% confidence interval [CI]: 3.28–17.6), colon resection (OR: 4.26, 95% CI: 1.87–9.91), and smoking history (OR: 2.49, 95% CI: 1.09–5.77) as independent risk factors. The predictive model demonstrated good discrimination (area under the curve [AUC] = 0.81). Conversion was associated with a longer operative time and greater blood loss, whereas postoperative complications and length of hospital stay were similar between the groups.
Conclusion
The SILS‐first strategy achieved a low conversion rate, while maintaining operative safety. Risk factors for conversion were consistent with those reported in multi‐port laparoscopy, supporting a flexible and staged port‐escalation approach in CD.
In this retrospective study of 289 patients with Crohn's disease undergoing a single‐incision laparoscopy‐first (SILS‐first) strategy, conversion to open surgery was required in only 11.8% of cases. Fistula formation, colon resection, and smoking history were identified as independent risk factors for conversion, while postoperative complications and hospital stay were comparable between groups. These findings support a flexible SILS‐first approach with staged port escalation according to disease complexity.
1. Introduction
Crohn's disease (CD), a chronic inflammatory bowel disease, is characterized by recurrent flare‐ups, with many patients potentially requiring multiple intestinal resections over the course of their lives [1]. Therefore, minimally invasive surgery (MIS), particularly laparoscopic surgery, has been introduced to reduce postoperative complications, shorten hospital stays, and improve wound scarring [2]. Laparoscopic surgery for CD offers advantages of faster recovery and fewer adhesions while demonstrating safety and efficacy equivalent to open surgery [3, 4]. In addition, a meta‐analysis comparing laparoscopic and open surgery further supports the advantages of laparoscopic approaches in terms of postoperative outcomes and recovery [5, 6]. These are especially beneficial for patients who may require reoperation in the future. MIS has evolved over the past decade. Single‐port laparoscopic surgery (SILS) and robot‐assisted surgery are now widely used for CD, offering enhanced maneuverability, reduced surgeon burden, and additional minimally invasive benefits [7, 8].
However, conversion from laparoscopic to open surgery remains a significant issue, with previous reports documenting conversion rates of approximately 20%–40% in CD [9, 10, 11]. This conversion rate tends to be higher than the 7%–25% in general colon surgery [12, 13, 14]. Conversion might be associated with poorer short‐term outcomes, including higher rates of stoma creation, longer hospital stays, and postoperative complications [15, 16]. Risk factors for conversion to open surgery are primarily due to technical challenges, such as difficulty in anatomical assessment due to inflammatory masses or adhesions, and the severity of the disease, such as the presence of fistulas or colonic disease type [9]. Nevertheless, reports on the conversion of SILS to open surgery in patients with CD are lacking.
Therefore, we aimed to retrospectively investigate the clinical characteristics and risk factors for conversion surgery in patients with CD who underwent laparoscopic intestinal resection via SILS.
2. Methods
2.1. Patient Selection
Patients with CD who underwent intestinal resection at Hyogo Medical University between April 2018 and October 2025 were included in this study. Laparoscopic surgery was indicated for cases without severe peritoneal contamination due to perforation, and eligibility was determined based on the following criteria: Cases in which a fistula was suspected only on computed tomography (CT) but not clearly demonstrated by endoscopy or contrast studies, or cases with abscess formation where inflammation resolved with conservative treatment (fasting and antibiotics) were considered eligible for laparoscopic surgery. Patients who had previously undergone anastomotic resection or had clear fistula formation involving the urinary tract were excluded. Patients undergoing rectal resection were also excluded, as the SILS‐first strategy was not applied in cases requiring rectal mobilization. Patients without histological confirmation of CD were excluded from the study. Pediatric patients were excluded because of the possibility of different postoperative outcomes.
The following data were retrospectively collected from the clinical records: Sex, age at onset, age at initial surgery, duration of disease, Montreal classification for CD, blood parameters, body mass index, current smoking habits, American Society of Anesthesiologists (ASA) score, Charlson comorbidity index, total administered prednisolone (PSL) dose, immunomodulator (thiopurines, including azathioprine and 6‐mercaptopurine) administration, Janus kinase inhibitor (tofacitinib) administration, biologic (infliximab, adalimumab, golimumab, and vedolizumab) administration, surgical indication (cancer/dysplasia and refractory disease), emergent or elective surgery, surgical procedures (small bowel resection/ileocecal resection, colon resection including partial colon resection, right and left hemicolectomy, and total colectomy), operative time, amount of blood loss, intraoperative blood transfusion, return to the operating room within 30 days. Blood parameters, including serum albumin (Alb), C‐reactive protein, white blood cell, lymphocyte counts, and hemoglobin levels before surgery, were retrospectively obtained from the patients' clinical records. Disease behavior (B1–B3) was classified preoperatively according to the Montreal classification. Fistula was recorded as a separate preoperative variable when a fistula or suspected fistula was identified based on clinical findings and/or contrast imaging. The number of prior intestinal surgeries was recorded for each patient. In patients with multiple prior surgeries, all procedures were documented. Patients who received immunomodulators, calcineurin inhibitors, or Janus kinase inhibitors within 72 h before surgery, regardless of the dosage, were included. All infusions administered within 12 weeks before surgery were considered biologically administered.
2.2. Laparoscopic Surgery
The SILS‐first strategy was not used in cases where rectal mobilization or multiple surgeries were performed. A 30–40 mm longitudinal incision was made at the umbilicus, through which a Lap Protector and EZ Access (Hakko Medical, Nagano, Japan) were inserted (Figure 1) [17]. The procedure was performed using two 5 mm ports and one 12 mm camera port (Figure 2). Only bowel removal was performed laparoscopically, whereas other procedures, such as resection or anastomosis, were performed via a small laparotomy through the umbilical incision. The affected bowel segment was extruded through a small incision, and resection was performed with bowel preservation. Because the mesentery of the resected specimen was often thickened, the colic artery and vein were ligated and divided to confirm blood flow and prevent stump bleeding, and the mesenteric stump was sutured closed. Intestinal anastomoses were performed using the Albert‐Lembert suture technique, and the mesenteric defect was sutured closed. An umbilical incision of 30–40 mm was made, which allowed safe exteriorization of the entire small bowel in most cases. When difficulty was encountered, limited fascial extension, gentle mobilization, and adhesiolysis were performed as needed.
FIGURE 1.
Postoperative incision site created by single‐incision laparoscopic surgery.
FIGURE 2.
Using a Lap Protector and EZ Access (Hakko Medical, Nagano, Japan), two 5‐mm ports and one 12‐mm camera port were inserted.
2.3. Definition of Outcomes
Conversion to open surgery was defined a priori as any unplanned extension of the incision to ≥ 6 cm during laparoscopic surgery, irrespective of its purpose, including specimen extraction and/or extracorporeal anastomosis. This definition was adopted to provide an objective and reproducible criterion and to avoid subjective judgment regarding the reason for incision extension. Cases where an assistant port (5 mm) was added as an adjunct when securing the surgical field was difficult were classified as multi‐port laparoscopic surgery.
The patients were classified into the conversion surgery group or the non‐conversion surgery group. Possible risk factors for conversion surgery were analyzed to identify the significant predictors. Significant risk factors for conversion surgery identified in the univariate analysis were included in the multivariate analysis. We analyzed the areas under the curve (AUCs) for factors in the multivariate analysis model.
An exploratory subgroup analysis was conducted in patients from our institution with available follow‐up data to compare long‐term outcomes between the SILS and multi‐port approaches.
2.4. Postoperative Course and Complications
We recorded the length of hospital stay, postoperative day (POD) of initiation of liquid intake, POD of initiation of diet, POD of first flatus, POD of first defecation, and postoperative complications. Postoperative complications were defined as unexpected medical events that occurred between the end of surgery and hospital discharge. The presence of postoperative bleeding, surgical site infection (SSI), anastomotic leakage, obstruction, ileus, and pneumonia was included. Postoperative bleeding included intra‐abdominal and gastrointestinal bleeding, such as gastric/duodenal/small intestinal ulcers and anastomotic bleeding. SSIs were diagnosed and recorded based on the location after surgery. Generally, incisional SSIs include wound infections, whereas organ or space SSIs include abdominal and pelvic abscesses. Incisional SSIs were detected based on the presence of erythema, induration, purulent drainage, or dehiscence at the wound site, and the grade at which the wound infections were opened at the bedside or in ambulatory practice was included. Organ/space SSIs and anastomotic leakage were detected using gastrografin enema, abdominal echo, or CT scans. SSIs were diagnosed by designated staff on our infection control team, trained in applying surveillance methods and identifying SSIs based on definitions provided in the guidelines issued by the NNIS system of the Centers for Disease Control and Prevention [18]. Obstruction, ileus, and pneumonia were detected on plain radiography or CT scans, and the grade requiring pharmacological treatment was included.
2.5. Statistical Analysis
Categorical variables were compared using the chi‐square test or Fisher's exact test. Continuous variables were expressed as medians and ranges and were compared using the Mann–Whitney U test or ANOVA. The level of statistical significance was set at p < 0.05. Univariate logistic regression analysis was performed to evaluate factors associated with conversion to open surgery, and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Variables with p < 0.10 in univariate analysis and those considered clinically relevant were selected as candidates for multivariate logistic regression analysis. Because B3 behavior and fistula both represent penetrating disease, collinearity between these two binary variables was assessed using the phi coefficient. To avoid redundancy and maintain interpretability of the model, these variables were not included simultaneously in the final multivariate model, and fistula was selected as the representative variable. The discriminative ability of the final multivariate model was evaluated using receiver operating characteristic (ROC) curve analysis, and the area under the curve (AUC) was calculated. Statistical analyses were performed using JMP version 18 (SAS Institute Inc., Cary, NC, USA).
3. Results
3.1. Patient Flow and Study Cohort
In total, 339 patients underwent intestinal resection for CD using a single‐incision laparoscopic approach during the study period. Twelve pediatric patients (aged < 18 years), 19 patients who had previously undergone anastomotic resection (including three with bladder fistula), and 19 patients who had undergone rectal resection were excluded. Finally, 289 patients were included in the final analysis (Figure 3). Among them, 34 (11.8%) required conversion to open surgery. The procedure was completed for the remaining 255 (88.2%) patients without conversion; of these, 22 (8.6%) patients required the addition of extra ports to avoid conversion. Conversely, among the 34 conversion cases, eight required multi‐port conversion but ultimately underwent open surgery. The most frequent causes included difficulty with laparoscopic dissection owing to fistula or abscess formation, inability to exteriorize an inflammatory mass in which the diseased bowel was densely conglomerated, along with marked mesenteric thickening or dense inflammatory adhesions that prevented safe mobilization from the retroperitoneum. A total of 19 patients had a history of prior intestinal surgery. A total of 21 prior procedures were recorded, as two patients had undergone two previous intestinal resections. The types of previous procedures included partial ileal resection (n = 12), ileocecal resection (n = 3), right hemicolectomy (n = 3), sigmoid colectomy (n = 2), and transverse colostomy (n = 1). Prior intestinal surgery was observed in 3 of 34 patients (8.8%) in the conversion group and in 16 of 255 patients (6.2%) in the non‐conversion group, with no significant difference between the groups (p = 0.47).
FIGURE 3.
Flow chart of enrollment of patients with Crohn's disease (CD).
3.2. Patient Characteristics
The baseline characteristics of the patients are summarized in Table 1. Patients in the conversion group tended to be older at the time of surgery than those in the non‐conversion group, although this difference was not statistically significant (41.1 ± 13.0 vs. 36.4 ± 14.5 years, p = 0.07). With regard to disease phenotype, the proportion of patients with colonic disease (L2) was significantly higher in the conversion group (14.7% vs. 6.6%, p = 0.04). Penetrating disease behavior (B3) was also more frequently observed among patients who required conversion (50.0% vs. 26.6%, p = 0.01). The presence of fistulas was markedly higher in the conversion group than in the non‐conversion group (47.0% vs. 12.1%, p < 0.01). Smoking history was significantly more common in the conversion group (47.0% vs. 28.2%, p = 0.03). Colon resection was performed significantly more frequently in the conversion group than in the non‐conversion group (47.0% vs. 21.5%, p < 0.01). Emergency surgery, operator experience, and preoperative interventions did not differ significantly between the two groups.
TABLE 1.
Baseline characteristics of patients with CD.
| Factors | Overall (n = 289) | Conversion group (n = 34) | Non‐conversion group (n = 255) | p |
|---|---|---|---|---|
| Male sex, n (%) | 222 (76.8) | 29 (85.3) | 193 (75.7) | 0.28 |
| Height, cm, average ± SD | 167.4 ± 8.5 | 169.4 ± 7.1 | 167.2 ± 8.7 | 0.15 |
| Weight, kg, median [range] | 55.5 [34.2–123] | 55.8 [37.9–89.4] | 55.5 [34.2–123.0] | 0.54 |
| BMI, median [range] | 19.7 [13.9–39.4] | 19.7 [14.6–28.5] | 19.6 [13.9–39.4] | 0.82 |
| Age at onset, years, average ± SD | 29.2 ± 13.16 | 32.1 ± 12.9 | 28.8 ± 13.2 | 0.18 |
| Duration of disease, months, median [range] | 54.8 [0.3–582.9] | 64.4 [1.1–582.9] | 53.2 [0.3–542.3] | 0.36 |
| Age at surgery years, average ± SD | 37.0 ± 14.4 | 41.2 ± 13.0 | 36.4 ± 14.5 | 0.07 |
| Age at diagnosis, n (%) | 0.35 | |||
| A1 (≤ 16) | 25 (8.7) | 2 (5.9) | 23 (9.0) | |
| A2 (17–40) | 219 (75.8) | 24 (70.6) | 195 (76.5) | |
| A3 (> 40) | 45 (15.6) | 8 (23.5) | 37 (14.5) | |
| Location of diagnosis, n (%) | 0.04* | |||
| L1 (ileum) | 89 (30.8) | 5 (14.7) | 84 (32.9) | |
| L2 (colon) | 22 (7.6) | 5 (14.7) | 17 (6.7) | |
| L3 (ileocolonic) | 178 (61.6) | 24 (70.6) | 154 (60.4) | |
| Anoperineal disease, n (%) | 97 (33.6) | 14 (41.2) | 83 (32.5) | 0.33 |
| Behavior, n (%) | 0.01* | |||
| B1 (inflammatory) | 11 (3.8) | 2 (5.9) | 9 (3.5) | |
| B2 (stricturing) | 193 (66.8) | 15 (44.1) | 178 (69.8) | |
| B3 (penetrating) | 85 (29.4) | 17 (50.0) | 68 (26.7) | |
| Fistula, n (%) | 47 (16.3) | 16 (47.1) | 31 (12.2) | < 0.01* |
| Smoking history, n (%) | 88 (30.4) | 16 (47.1) | 72 (28.2) | 0.03* |
| ASA‐PS ≥ 3, n (%) | 38 (13.1) | 7 (20.6) | 31 (12.2) | 0.17 |
| Charlson index ≥ 3, n (%) | 3 (1.0) | 0 (0) | 3 (1.2) | 1.00 |
| PSL administration, mg, median [range] | 0 [0–25 000] | 0 [0–10 000] | 0 [0–25 000] | 0.97 |
| Immunomodulator administration, n (%) | 60 (20.8) | 5 (14.7) | 55 (21.6) | 0.49 |
| Biologic administration, n (%) | 138 (47.8) | 19 (55.9) | 119 (46.7) | 0.31 |
| JAK inhibitor, n (%) | 0 (0) | 0 (0) | 0 (0) | 0.00 |
| Preoperative long intestinal tube, n (%) | 15 (5.2) | 2 (5.9) | 13 (5.1) | 0.69 |
| Preoperative endoscopic dilation, n (%) | 17 (5.9) | 0 (0) | 17 (6.7) | 0.23 |
| Preoperative drainage | 7 (2.4) | 1 (2.9) | 6 (2.4) | 0.58 |
| Number of intestinal surgeries, median [range] | 0 [0–2] | 0 [0–2] | 0 [0–2] | 0.59 |
| Prior intestinal surgery, n (%) | 19 (6.6) | 3 (8.8) | 16 (6.3) | 0.47 |
| Surgical procedure, n (%) | < 0.01* | |||
| (1) small/ileocecal resection | 218 (75.4) | 18 (52.9) | 200 (78.4) | |
| (2) colon resection | 71 (24.6) | 16 (47.1) | 55 (21.6) | |
| Emergency surgery, n (%) | 11 (3.8) | 1 (2.9) | 10 (3.9) | 1.00 |
| Operator (n ≥ 50), n (%) | 181 (62.6) | 20 (58.8) | 161 (63.1) | 0.62 |
| Alb, g/dL median [range] | 3.7 [0.6–4.9] | 3.5 [2.1–4.3] | 3.7 [0.6–4.9] | 0.15 |
| CRP, mg/dL median [range] | 0.2 [0–29.3] | 0.2 [0–12.4] | 0.2 [0–29.3] | 0.95 |
| WBC, 102/μL median [range] | 56.0 [16.9–293.5] | 58.7 [21.4–119.7] | 55.6 [16.9–293.5] | 0.60 |
| Lymph, /μL median [range] | 1122.7 [61.8–3810.7] | 960.4 [256.8–3075.9] | 1132.5 [61.8–3810.7] | 0.11 |
| Hb, g/dL median [range] | 12.5 [6.6–19.5] | 12.0 [7.3–19.5] | 12.5 [6.6–17.6] | 0.85 |
Note: The Mann–Whitney U test was performed for continuous variables. The chi‐square test or Fisher's exact test was used for categorical variables.
Abbreviations: Alb = Albumin, ASA = American Society of Anesthesiologists, BMI = Body mass index, CD = Crohn's disease, CRP = C‐reactive protein, Hb = Hemoglobin, JAK = Janus kinase, PSL = Prednisolone, SD = Standard deviation, WBC = White blood cell.
p < 0.05 (indicates a significant difference).
3.3. Risk Factors for Conversion to Open Surgery
Univariate and multivariate logistic regression analyses were performed to identify the factors associated with conversion to open surgery (Table 2). In univariate analysis, penetrating disease behavior, fistula presence, smoking history, and colon resection were significantly associated with conversion. Variables with p < 0.10 in univariate analysis and those considered clinically relevant were entered into the multivariate model, considering potential multicollinearity. In the multivariate analysis, fistula presence emerged as the strongest independent risk factor for conversion (OR: 7.53, 95% CI: 3.28–17.60, p < 0.01). Colon resection was also independently associated with an increased risk of conversion (OR: 4.26, 95% CI: 1.87–9.91, p < 0.01). Smoking history remained a significant predictor (OR: 2.49, 95% CI: 1.09–5.77, p = 0.03). Age at surgery showed a borderline association with conversion (OR: 1.02 per year, 95% CI: 0.99–1.05, p = 0.08) and was retained in the model as an adjustment factor. The discriminative ability of the multivariate model was evaluated using ROC curve analysis, showing an AUC of 0.81 (Figure 4). Univariate analysis showed that both B3 behavior and fistula were significantly associated with conversion. The correlation between B3 behavior and fistula was moderate (r = 0.42).
TABLE 2.
Logistic regression analysis of the risk factors for conversion surgery.
| Factors | Univariate Analysis (95% CI) | p | Multivariate Analysis (95% CI) | p |
|---|---|---|---|---|
| Male sex | 0.53 (0.19–1.44) | 0.28 | ||
| Height, cm | 1.03 (0.98–1.07) | 0.14 | ||
| Weight, kg | 2.18 (0.14–25.6) | 0.55 | ||
| BMI | 0.98 (0.88–1.08) | 0.82 | ||
| Age at onset, per 1 year | 1.01 (0.99–1.04) | 0.19 | ||
| Duration of disease, per 1 month | 1.00 (0.99–1.00) | 0.38 | ||
| Age at surgery, per 1 year | 1.02 (0.99–1.04) | 0.07 | 1.02 (0.99–1.05) | 0.08 |
| Age at diagnosis, A3 (> 40) | 1.81 (0.72–4.16) | 0.17 | ||
| Location of diagnosis, L2 (colon) | 2.41 (0.82–7.03) | 0.15 | ||
| Anoperineal disease | 1.45 (0.69–3.01) | 0.33 | ||
| Behavior, B3 (penetrating) | 2.75 (1.32–5.69) | < 0.01* | ||
| Fistula | 7.53 (3.28–17.67) | < 0.01* | 7.53 (3.28–17.6) | < 0.01* |
| Smoking history | 2.25 (1.09–4.67) | 0.03* | 2.49 (1.09–5.77) | 0.03* |
| ASA‐PS ≥ 3 | 1.87 (0.75–4.66) | 0.17 | ||
| Charlson index ≥ 3 | 0 | 1.00 | ||
| PSL administration, per 1 mg | 1.00 (0.99–1.00) | 0.97 | ||
| Immunomodulator administration | 0.62 (0.23–1.69) | 0.49 | ||
| Biologic administration | 1.44 (0.70–2.97) | 0.36 | ||
| JAK inhibitor | 0 | 0 | ||
| Preoperative long intestinal tube | 1.16 (0.25–5.39) | 0.69 | ||
| Preoperative endoscopic dilation | 0 | 0 | ||
| Preoperative drainage | 1.25 (0.14–10.7) | 0.58 | ||
| Number of abdominal surgeries | 1.31 (0.40–3.22) | 0.60 | ||
| Surgical procedure, colon resection | 3.23 (1.54–6.75) | < 0.01* | 4.26 (1.87–9.91) | < 0.01* |
| Emergency surgery | 0.74 (0.09–5.98) | 1.00 | ||
| Operator (n ≥ 50) | 0.83 (0.40–1.72) | 0.62 | ||
| Alb | 0.67 (0.39–1.16) | 0.15 | ||
| CRP | 0.99 (0.87–1.08) | 0.95 | ||
| WBC | 0.99 (0.98–1.00) | 0.60 | ||
| Lymphocyte count | 0.99 (0.99–1.00) | 0.11 | ||
| Hb | 0.98 (0.82–1.17) | 0.85 |
Note: The Mann–Whitney U test was performed for continuous variables. The chi‐square test or Fisher's exact test was used for categorical variables.
Abbreviations: Alb = Albumin, ASA = American Society of Anesthesiologists, BMI = Body mass index, CD = Crohn's disease, CRP = C‐reactive protein, Hb = Hemoglobin, JAK = Janus kinase, PSL = Prednisolone, WBC = White blood cell.
p < 0.05 (indicates a significant difference).
FIGURE 4.
The discriminative ability of the multivariable model of risk factors for conversion surgery was evaluated using ROC analysis, yielding an AUC of 0.81.
Sensitivity analysis restricting the cohort to patients who underwent small bowel resection/ileocecal resection (n = 230) demonstrated that fistula (OR: 17.51, 95% CI: 5.98–57.46, p < 0.01) and smoking history (OR: 3.33, 95% CI: 1.11–10.56, p = 0.03) remained independently associated with conversion to open surgery (Table S1). An exploratory analysis of resected small bowel length showed a weak association with conversion (OR per cm: 0.98, p = 0.048); however, data were missing in seven cases.
3.4. Surgical Outcomes and Postoperative Course
Intraoperative and postoperative outcomes are shown in Table 3. Operative time was significantly longer in the conversion group than in the non‐conversion group (median 228 vs. 163 min, p < 0.01), and blood loss was significantly greater (median 132.5 vs. 30 mL, p < 0.01). Stoma creation was more frequently performed in the conversion group (14.7% vs. 3.9%, p = 0.02). No significant differences were observed between the groups in terms of postoperative bleeding, SSI, anastomotic leakage, or pneumonia. Postoperative bowel obstruction tended to be more common in the conversion group, although the difference was not significant (17.6% vs. 7.4%, p = 0.09). There were no significant differences between the conversion and non‐conversion groups with respect to postoperative recovery or length of hospital stay.
TABLE 3.
Comparison of surgical factors and postoperative complications for CD patients.
| Factors | Overall (n = 289) | Conversion group (n = 34) | Non‐conversion group (n = 255) | p |
|---|---|---|---|---|
| Operative time, min, median [range] | 167 [79–640] | 228 [124–336] | 163 [79–640] | < 0.01* |
| Blood loss, ml, median [range] | 30 [0–1 660] | 132.5 [5–1 060] | 30 [0–1 660] | < 0.01* |
| Blood transfusion, (%) | 4 (1.4) | 2 (5.9) | 2 (0.8) | 0.06 |
| Incision length, cm, median [range] | 4 [2.5–12] | 6 [6–12] | 4 [2.5–10] | < 0.01* |
| Stricture plasty, (%) | 36 (12.5) | 2 (5.9) | 34 (13.3) | 0.21 |
| Stricture plasty numbers, median [range] | 0 [0–8] | 0 [0–2] | 0 [0–8] | 0.20 |
| Stoma creation, (%) | 15 (5.2) | 5 (14.7) | 10 (3.9) | 0.02* |
| Residual lesions, (%) | 44 (15.2) | 3 (8.8) | 41 (16.1) | 0.44 |
| Postoperative bleeding, (%) | 7 (2.4) | 0 (0) | 7 (2.7) | 1.00 |
| Postoperative obstruction/ileus, (%) | 25 (8.7) | 6 (17.6) | 19 (7.5) | 0.09 |
| Incisional SSI, (%) | 8 (2.8) | 1 (2.9) | 7 (2.7) | 1.00 |
| Organ/space SSI, (%) | 6 (2.1) | 2 (5.9) | 4 (1.6) | 0.14 |
| Anastomotic leakage, (%) | 1 (0.3) | 0 (0) | 1 (0.4) | 1.00 |
| Pneumonia, (%) | 1 (0.3) | 0 (0) | 1 (0.4) | 1.00 |
| Hospital stay, days, median [range] | 20 [3–385] | 23 [14–126] | 19 [3–385] | 0.41 |
| Initiation of liquid intake, POD, median [range] | 1 [1–8] | 1 [1–5] | 1 [1–8] | 0.90 |
| Initiation of diet, POD, median [range] | 8 [5–69] | 8 [7–54] | 8 [5–69] | 0.32 |
| First flatus, POD, median [range] | 3 [1–50] | 3 [1–50] | 3 [1–12] | 0.11 |
| First defecation, POD, median [range] | 3 [1–50] | 4 [1–50] | 3 [1–12] | 0.09 |
Note: The Mann–Whitney U test was performed for continuous variables. The chi‐square test or Fisher's exact test was used for categorical variables.
Abbreviations: CD = Crohn's disease, POD = Post‐operative day, SSI = Surgical site infection.
p < 0.05 (indicates a significant difference).
In the cohort (n = 199) from our hospital, long‐term adhesion‐related events were infrequent (median follow‐up: 44 months), with small bowel obstruction recorded in 4 patients (2.0%), balloon dilation procedures in 5 (2.5%), and reoperation in 3 (1.5%). In an exploratory subgroup analysis (multi‐port: n = 18), no significant differences were observed between the SILS and multi‐port groups: Small bowel obstruction (0/18 vs. 4/181, p = 0.38), balloon dilation (0/18 vs. 5/181, p = 0.33), and reoperation (1/18 vs. 2/181, p = 0.24).
4. Discussion
In this study, we analyzed the risk factors for conversion surgery in patients with CD who underwent laparoscopic intestinal resection via SILS. The SILS‐first strategy could be safely initiated in most patients with CD, with 88.2% of cases completed laparoscopically and 80.6% completed by SILS alone without additional ports. Multivariate analysis identified the presence of fistula, smoking history, and colon resection as independent predictors of conversion surgery.
Laparoscopic surgery for CD is associated with increased surgical difficulty due to disease‐specific factors, such as intra‐abdominal adhesions, degree of inflammation, fistula formation, and high reoperation rates. CD status is an independent predictor of conversion [15]. The risk factors for conversion to open surgery in CD include a history of prior ileocecal resection, presence of abscesses or fistulas, severity of inflammation, poor nutritional status, emergency surgery, and prolonged operative time [9, 10]. In particular, previous surgeries involving the same operative field are associated with a high incidence of adhesions, and surgical procedures may be technically demanding due to tissue fragility and anatomical changes caused by scar formation. Therefore, we excluded patients who had undergone previous anastomotic resection. Regarding the risk factors for open conversion in SILS for CD, most reports involve only a small number of cases, and no specific risk factors have been reported [19]. Our findings are consistent with previous reports indicating that laparoscopic surgery for CD is complicated by lesion type and fistula formation, with comparable conversion rates in this study [9, 11]. Fistulas reflect advanced full‐thickness inflammation, robust adhesions, and anatomical distortion, suggesting that colon resection is important in the removal from the retroperitoneum and the extent of intestinal resection. Both B3 behavior and fistula were associated with conversion in univariate analysis, underscoring the impact of penetrating disease. While B3 represents a broad disease category, fistula reflects a more specific structural abnormality. Given their conceptual overlap, fistula was selected for the multivariate model as a more direct indicator of surgical complexity. A history of smoking was associated with more aggressive disease behavior and impaired tissue healing in CD, which is consistent with previous reports [20]. Age at surgery may reflect cumulative disease burden and past inflammatory damage; incorporating this allowed for a more robust estimation of the independent effects of major risk factors. Importantly, a sensitivity analysis restricted to standard ileal and ileocecal resections yielded consistent results, with fistulas and smoking history remaining principal determinants of conversion.
SILS offers superior cosmetic results compared with multi‐port approaches [21]. Furthermore, a key strength of this study was its ability to evaluate outcomes across the entire treatment process using the SILS‐first strategy. Although a certain number of cases required transition to an additional port for safe dissection, most cases did not require an additional port; no substantial operative time penalty was observed, and the complication rate was low. These findings support the use of a SILS‐first strategy as a reasonable initial approach while allowing for additional port placement when technically required. Furthermore, among approximately 10% of cases requiring conversion to multi‐port laparoscopy, less than 30% ultimately required open surgery. These results support the practical approach of gradually adjusting port access according to disease complexity rather than uniformly restricting surgical technique selection in CD and confirm that the SILS‐first strategy is a valid option. Recent systematic reviews and meta‐analyses reported no statistically significant differences in conversion rates or postoperative complications between SILS for general colorectal resection and conventional multi‐port laparoscopy [22]. Regarding CD, SILS was also associated with reduced postoperative pain, but showed no effect on postoperative complications or the length of hospital stay [23]. Evidence regarding the long‐term impact of SILS in Crohn's disease remains limited. In this exploratory analysis, SILS was not associated with an increased risk of long‐term outcomes such as small bowel obstruction or reoperation.
This study has some limitations. First, this was a retrospective analysis performed at a single institution, which may have been subject to selection bias, and caution is required when generalizing the results to other contexts. Although SILS was the initial choice, in principle, during the study period, the decision to add ports or convert to open surgery may have been influenced by the surgeon's experience and preoperative assessment of lesion severity. However, no significant differences were observed in the surgeon experience variables in this study. This finding cannot be generalized to all institutions, as our facility maintains a system in which at least one expert surgeon is involved in the procedure. Second, critical factors during surgery, such as the degree of mesenteric thickening or adhesions, were difficult to evaluate quantitatively and may have influenced the results. Third, postoperative outcomes, other than conversion to open surgery, particularly long‐term recurrence, were limited. These results must be interpreted considering these limitations. Future prospective studies comparing SILS‐first and multi‐port‐first strategies across multiple centers and surgeons may clarify the patient population that maximally benefits from SILS.
5. Conclusions
Fistula formation, smoking history, and colon resection were identified as independent predictors of conversion surgery in patients undergoing a SILS‐first strategy for CD. These factors are consistent with previously reported risk factors for conversion. Notably, the overall conversion rate in the present study was lower than that reported in earlier series. The majority of procedures were completed without the need for additional ports. Even in technically demanding cases, sequential addition of ports enabled safe completion of the operation. Taken together, these findings suggest that a flexible SILS‐first approach, in which port access is gradually adjusted according to disease complexity, may represent a safe and practical minimally invasive surgical strategy when applied to appropriately selected patients with CD.
Author Contributions
Motoi Uchino: conceptualization, project administration. Masataka Ikeda: supervision, conceptualization. Yuki Horio: writing – original draft, investigation, validation, conceptualization, methodology, visualization. Ryuichi Kuwahara: investigation, data curation. Yusuke Tomoo: investigation, data curation. Kei Kimura: investigation. Hiroki Ikeuchi: supervision, conceptualization. Kozo Kataoka: data curation, investigation. Kentaro Nagano: investigation, data curation. Kurando Kusunoki: data curation, investigation.
Funding
The authors have nothing to report.
Ethics Statement
The institutional review board at Hyogo Medical University approved the study protocols (Approval No. 5255).
Consent
Written informed consent was obtained via the opt‐out method, and an opt‐out informed consent protocol was used for the use of participant data for research purposes.
Conflicts of Interest
The authors declare no conflicts of interest.
Supporting information
Table S1: Logistic regression analysis of the risk factors for conversion surgery.
Acknowledgments
The authors have nothing to report.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Table S1: Logistic regression analysis of the risk factors for conversion surgery.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.