Single-incision versus multi-port laparoscopic ileocolic resections for Crohn’s disease: Systematic review and meta-analysis

Abstract

Introduction:

The aim of this systematic review and meta-analysis is to compare the outcomes of single-incision laparoscopic surgery (SILS) versus multi-port laparoscopy for ileocolic resection in patients with Crohn’s disease (CD).

Patients and Methods:

A systematic search of multiple electronic databases was conducted. The peri- and post-operative outcomes were evaluated between Crohn’s patients undergoing SILS versus multi-port laparoscopy for ileocolic resection. The primary outcomes included operative time, anastomotic leak rate, post-operative wound infections and length of hospital stay. Analysed secondary outcomes were conversion rates, ileus occurrence, intra-abdominal abscess formation, return to theatre and re-admissions. Revman 5.3 was used to perform the statistical analysis.

Results:

Five observational studies with 521 patients (SILS: 211; multi-port: 310) were included in the data synthesis. Patients undergoing SILS had a reduced total operative time compared to multi-port laparoscopy (mean difference [MD]: −16.14, 95% confidence interval: [CI] −27.23 − 5.05, P = 0.004). Post-operative hospital stay was also found to be significantly less in the SILS group (MD: −0.57, 95% CI: −0.73–−0.42, P < 0.0001). No significant difference was seen in the anastomotic leak rate (MD: −16.14, 95% CI: 0.18–1.71, P = 0.004) or post-operative wound infections (odds ratio: 0.78, 95% CI: 0.24 − 2.47, P = 0.67) between the two groups. Moreover, all the measured secondary outcomes were comparable.

Conclusion:

SILS seems to be a feasible alternative to multi-port laparoscopic surgery for ileocolic resection in patients with CD. Improved outcomes in terms of total operative time and length of hospital stay were observed in patients undergoing SILS surgery. Adopting this procedure into routine clinical practice constitutes the next step in the development of minimally invasive surgery.

INTRODUCTION

The exact aetiology of Crohn’s disease (CD) remains unclear and in the UK prevalence rates of 396/100,000 of the population have been reported.[1] The disease is often characterised by ‘skip’ lesions, with the terminal ileum/caecum being the most commonly affected sites.[2] This chronic, relapsing-remitting, non-infectious gastrointestinal disorder can lead to long-term complications, including fibrotic strictures, bowel obstruction/perforation, enteric fistulae, perianal sepsis and increased risk of intestinal neoplasia.[3]

Disease management aims to induce and maintain remission and options include drug therapy, addressing lifestyle/dietary factors and surgery.[4] An estimated 50%–80% of patients eventually require surgery for Crohn’s complications or failure of medical therapy.[4,5]

Given the risk of multiple surgical interventions in patients with CD, laparoscopy offers an acceptable and viable alternative to open resections. These patients benefit from reduced scar and adhesion formation, quicker return to bowel function, reduced rates of wound infection and shorter length of hospital stay.[6]

With advances in surgical techniques and technologies, an emphasis on improving the quality of life parameters in addition to clinical outcomes, the role of laparoscopy is also evolving. Single-incision laparoscopic surgery (SILS) has been shown to be a feasible approach with the added benefits of reduced scar formation (and incisional hernia risk) and decreased analgesia requirement postoperatively.[6]

However, a recent prospective, double-blind trial of patients undergoing laparoscopic colonic resections for benign or malignant disease showed that other than cosmesis, single-port colectomy did not confer any additional benefit compared to multi-port surgery.[7] We assessed the available literature by conducting a systematic review and meta-analysis, specifically investigating the role of SILS compared with multi-port laparoscopy in ileocolic resections for CD.

PATIENTS AND METHODS

This systematic review was designed, performed and reported as per the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions and the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.[8,9]

Data sources and search strategy

An online systematic search was conducted on 01/12/2021 using PubMed, Embase, Scopus, Cochrane Database of Systematic Reviews (CENTRAL), clinical trials.gov, ScienceDirect and VHL (virtual health library). Two independent reviewers performed the search. The keywords used were as follows: ‘inflammatory bowel disease’, ‘IBD’, ‘Crohn’s disease’, ‘Crohns disease’, ‘ileitis’, ‘terminal ileitis’, ‘ileo-colitis’, ‘ileocolitis’ AND ‘ileocecal resection’, ‘right colectomy’, ‘right hemicolectomy’ AND ‘laparoscopic’, ‘laparoscopy’, ‘single incision’, ‘single-incision’, ‘single port’, ‘single-port’, ‘SILS’, ‘multi-port’, ‘multiport’.

In addition, reference lists in previous studies were manually searched for relevant articles.

Design and study selection

Two independent authors screened titles, abstracts or full texts of the selected articles to identify potentially eligible studies. All studies comparing single-port versus multi-port laparoscopy for ileo-caecal resection in patients with CD were considered. All single-arm studies, case series, case reports, letters to the editor and review articles were excluded. Studies with duplicate patient cohorts were also excluded. Any disagreement between the authors on inclusion and exclusion criteria was resolved through discussion and consensus.

Data extraction and collection

Two authors independently performed data extraction from the selected studies. Information extracted included: First author name, year of study publication, study design and size, patient characteristics and outcomes. A pre-generated standard Microsoft ® Excel (Microsoft Corporation, Redmond, Washington, USA) file was pilot-tested, adjusted accordingly, and used to enter extracted data. Any disagreement during this process was resolved by discussion and consensus. An independent third author was consulted if no agreement could be reached.

Outcome measures

Peri- and post-operative outcomes (total operative time, anastomotic leak rate, wound infection post-operatively and length of hospital stay) were the measured primary parameters. Secondary outcomes included conversion rate, ileus occurrence, intra-abdominal abscess/sepsis, rates of re-admission and re-intervention.

Assessment of bias

The Newcastle–Ottawa Scale (NOS) was used to assess the risk of bias for observational studies.[10] Studies were considered low, medium or high-risk of bias if the NOS was 9, 7/8, or <6, respectively. Disagreement was resolved through discussion and consulting a third reviewer where required.

Statistical analysis

Odds ratio (OR) was used as the statistical measure for dichotomous outcomes using the Mantel–Haenszel method. For continuous outcomes, the mean difference (MD) with 95% confidence interval (CI) was estimated. When mean values were not available for continuous outcomes, data on median and interquartile range were extracted and subsequently converted to mean and standard deviation using the well-practised equation described by Hozo et al.[11] P < 0.05 was considered statistically significant for all analyses, a 95% CI was used in this study and random-effects modelling was applied to all outcome analysis.

Furthermore, between-study heterogeneity was assessed using the I² and χ² statistic. High values of I² and the χ² statistic signify increasing levels of heterogeneity, with P < 0.05 or an I² value exceeding 50% indicating significant heterogeneity.

To check the possible causes of heterogeneity and evaluate the robustness of the results, sensitivity analysis was performed by calculating risk ratio or RD for dichotomous variables. Moreover, leave one out analysis was conducted to assess the effect of each study individually. All statistical analysis was performed using Review Manager 5.3 (The Cochrane Collaboration, Copenhagen, Denmark).

RESULTS

A total of 967 studies were identified after the systematic search of the above-mentioned databases. Following review of the titles, abstracts and exclusion of any duplicates, 754 studies were excluded. Full manuscripts of the remaining 213 articles were reviewed and assessed for eligibility criteria. This process identified five relevant studies[12-16] that were then included in our final analysis. PRISMA flow chart is shown in Figure 1.

Figure 1.

PRISMA flow chart. PRISMA: Preferred reporting items for systematic reviews and meta-analyses

All five studies in our data synthesis were observational and included a total of 521 patients; 211 underwent a SILS procedure and 310 multi-port laparoscopy operations. Characteristics of the included studies are shown in Tables 1 and 2.

Table 1.

Study characteristics

Author/year	Journal	Country	Study design	Size of population (n)	SILS	MLS	Inclusion criteria	Exclusion criteria
Rijcken et al., 2012[16]	Dis colon rectum	Germany	Retrospective matched cohort	40	20	20	Ileocolic resection for terminal ileal stenosis in medically refractory CD	NR
Maeda et al., 2012[15]	Asian J Endosc Surg	Japan	Retrospective cohort	45	11	34	Stricture type of disease at the ileocecal region or small bowel	Severe abscesses, haemorrhage, perforation, penetration to other organs or prior abdominal surgery emergency surgery
Gardenbroek et al., 2013[13]	J Crohn’s colitis	Netherlands	Retrospective-prospective	63	21	42	Ileocaecal resection for CD	NR
Carvello et al., 2018[12]	Colorectal disease	Italy/Netherlands/Belgium	Retrospective cohort	257	101	156	Adult CD patients Stricture/abscess/refractory to medical therapy Elective and emergency operations	NR
Celentano et al., 2020[14]	Int J colorectal disease	UK/Italy/Spain	Retrospective cohort	116	58	58	>16 years undergoing primary iloecaecal or redo ileocolic resection for CD	Proctocolectomy, proctectomy, segmental colectomy Hand assisted surgery

SILS: Single incision laparoscopic surgery, MLS: Multi-port laparoscopic surgery, CD: Crohn’s disease, NR: Not reported

Table 2.

Baseline characteristics of the included population

Study	Age (years)	Sex (male: female)	BMI	ASA grade (I/II/III)	Smoking (yes/no)	Previous surgery	Immunosuppressive therapy	Anastomosis (stapled/total)	Duration of disease (years)	Stoma construction
Rijcken, 2012	SILS: 31.6±10.8 MLS: 31.7±10.7	SILS: 6:14 MLS: 6:14	SILS: 21.5±2.6 MLS: 21.5±2.5	SILS: 7/12/1 MLS: 4/15/1	SILS: 5:15 MLS: 4:16	SILS: 6/20 MLS: 7/20	SILS: 17/20 MLS: 17/20	SILS: 18/20 MLS: 14/20	SILS: 9.4±9.7 MLS: 8.9±8.2	SILS: 0/20 MLS: 0/20
Maeda, 2012	SILS: 31.5±9.2 MLS: 31±6.9	SILS: 10:1 MLS: 25:9	SILS: 21.02±2.6 MLS: 21.2±2.7	SILS: 1.2 (mean) MLS: 1.3 (mean)	NR	NR	NR	NR	NR	SILS: 0/11 MLS: 0/34
Gardenbroek, 2013	SILS: 28.4±5.4 MLS: 27.6±3.6	SILS: 7:14 MLS: 11:31	SILS: 21.3±1.3 MLS: 21.7±1.2	NR	SILS: 15/21 MLS: 24/42	SILS: 1/21 MLS: 4/42	SILS: 15/21 MLS: 24/42	SILS: 21/21 MLS: 6/42	SILS: 5.8±2.8 MLS: 2.1±1.1	SILS: 0/21 MLS: 0/42
Carvello, 2018	SILS: 30.5±6.4 MLS: 30.75±4.9	SILS: 37:64 MLS: 61:95	SILS: 22±1.2 MLS: 22.25±1.5	NR	SILS: 28/101 MLS: 56/156	NR	SILS: 83/101 MLS: 137/156	SILS: 88/101 MLS: 144/156	SILS: 4.4±1.8 MLS: 4.4±1.9	SILS: 4/101 MLS: 5/156
Celentano, 2020	SILS: 45.6±16.5 MLS: 46.6±16.9	NR	SILS: 23.1±4.4 MLS: 23±4.6	NR	NR	SILS: 18/58 MLS: 18/58	SILS: 19/58 MLS: 19/58	NR	NR	SILS: 8/58 MLS: 4/58

Continuous variable expressed as mean±SD unless otherwise mentioned in the table. SILS: Single incision laparoscopic surgery, MLS: Multiport laparoscopic surgery, BMI: Body mass index (kg/m²), ASA: American Society of Anaesthesiology, SD: Standard deviation, NR: Not reported

Risk of bias assessment

Table 3 highlights the outcomes of methodological quality assessment based on the NOS for observational studies.

Table 3.

Methodological quality of the observational studies assessed with the Newcastle-Ottawa Scale

Study	Representativeness of the exposed cohort	Selection of the non-exposed cohort	Ascertainment of exposure	Demonstration that outcome of interest was not present at start of study	Comparability of cohorts on the basis of the design or analysis controlled for confounders	Assessment of outcome	Was follow-up long enough for outcomes to occur	Adequacy of follow-up of cohorts	Total
Rijcken, 2012	*	*	*	*	*	*	*	*	8
Maeda, 2012	*	*	*	*		*	*	*	7
Gardenbroek, 2013	*	*	*	*	*	*	*	*	8
Carvello, 2018	*	*	*	*		*	*	*	7
Celentano, 2020	*	*	*	*	*	*	*	*	8

*One star awarded. Stars represent awarded for a particular question. A maximum of one star is awarded for each numbered item within the selection and exposure categories. A maximum of two stars can be given for comparability category. NR: Not reported

Outcomes

Figure 2 illustrates the forest plots of outcomes measured.

Figure 2.

Forest plots of outcomes

Primary outcomes

The measured primary outcomes were total operative time (minutes), anastomotic leak rate, wound infection postoperatively and length of hospital stay (LOS).

Total operative time (minutes)

Total operative time was reported in four studies and included a total number of 405 patients. Operative time was found to be significantly less in the SILS group compared to the multi-port group (MD: −16.14; 95% CI: −27.23–−5.05, P = 0.004). The between-study heterogeneity was significant (I^2: 87%, P = 0.001).

Anastomotic leak rate

Anastomotic leak rate was reported in all five of our included studies (n = 521). This was 1.4% in the SILS group and 3.9% in the multi-port group, respectively. However, no statistically significant difference was detected between the two groups (OR: 0.56; 95% CI: 0.18–1.71, P = 0.31). The between-study heterogeneity was low (I^2: 0%, P = 0.98).

Wound infection

Five studies, comprising 521 patients, were included in the analysis of wound infection. The pooled incidence was 2.4% (SILS group) and 3.9% (multi-port group). No significant difference in wound infection rate was observed between the two groups (OR: 0.78; 95% CI: 0.24 − 2.47, P = 0.67). No significant heterogeneity was detected between the included studies (I^2: 0%, P = 0.68).

Length of stay

This outcome was reported in all five studies. There was significant difference in LOS favouring the SILS group (MD: −0.57; 95% CI: −0.73–−0.42, P < 0.0001). A moderate level of heterogeneity existed between the studies (I^2: 0%, P = 0.71).

Secondary outcomes

The analysed secondary outcomes were conversion rate, post-operative ileus, intra-abdominal abscess/sepsis and rates of re-admission and re-intervention.

Conversion (to open surgery) rate

Five studies reported conversion rate was as follows: 4.7% SILS group versus 2.9% in the multi-port laparoscopy group. No statistically significant difference was observed between the two groups (OR: 0.66; 95% CI: 0.30–1.47, P = 0.31). The between-study heterogeneity was low (I^2: 0%, P = 0.93).

Post-operative ileus

Four studies (n = 405) patients reported on the incidence of post-operative ileus. This occurred in 3.9% in the SILS group and 3.2% in the multi-port group. No significant difference was noted between the two groups (OR: 1.32; 95% CI: 0.47–3.72, P = 0.6). A low level of heterogeneity was observed between the studies (I^2: 0%, P = 0.82).

Post-operative intra-abdominal abscess/sepsis

Intra-abdominal abscess formation postoperatively was reported in four studies (n = 476). The pooled incidence in the SILS group was 4% compared to 1.8% in the multi-port group. No significant difference was noted between the groups (OR: 1.83; 95% CI: 0.59–5.79, P = 0.3]). A low level of heterogeneity was noted in the included studies (I^2: 0%, P = 0.5).

Re-admission rate

Three studies with a total of 436 patients reported on re-admission rates. The SILS group had a 4.5% pooled re-admission rate compared to the multi-port laparoscopic surgery group of 3.1%, respectively. However, this difference was not statistically significant (OR: 1.73; 95% CI: 0.62–4.79, P = 0.29) and the heterogeneity between studies was low (I^2: 0%, P = 0.77).

Re-intervention rate

Re-intervention rate was reported in all five studies. In the SILS group re-intervention was reported in 2.8% versus 4.8% in the multi-port group. No significant difference was observed between the two groups (OR: 0.75; 95% CI: 0.31–1.82, P = 0.53). The heterogeneity between studies was low (I^2: 0%, P = 0.80).

DISCUSSION

To our knowledge, this is the first systematic review and meta-analysis specifically focusing on comparative outcomes between SILS and multi-port laparoscopic surgery for ileocolic resection in patients with CD. We included five observational studies[12-16] with a total of 521 patients (211 underwent a SILS procedure; 310 multi-port laparoscopy).

No significant differences were observed between the two groups in terms of wound infection rate postoperatively, the occurrence of ileus or intra-abdominal abscess/sepsis post-procedure. Moreover, anastomotic leak, re-intervention and readmission rates were also comparable.

Perhaps, surprisingly, total operative time in SILS was found to be significantly less compared to multi-port surgery (mean difference of 16 min). However, this finding should be interpreted with caution as there was no clear definition of what constituted ‘operative time’ in each study. Moreover, although most studies following bowel mobilisation and exteriorisation performed an extracorporeal anastomosis there was variation in terms of performing a stapled or hand-sewn anastomosis undoubtedly impacting on operative times. In the study by Gardenbroek et al.[13] all patients (n = 21) in the SILS group underwent a stapled anastomosis. In the multiport laparoscopy group only 6 patients (out of 42) had their anastomosis fashioned through a stapling device and the remainder underwent a hand-sewn technique. Consequently, the median operating time in the SILS and multi-port group were 103 (94–121) min and 123.5 (100–157) min, respectively.

SILS is technically more challenging due to a lack of triangulation with a steep ‘learning curve’. ‘In-line viewing’ with a compromised operative field compared to conventional laparoscopy may actually increase total operative time.[17] Moreover, primary operator and assistant frustration/fatigue may stem from restricted movements, poorer ergonomics[18] and increase the likelihood of inadvertent injury.

Conversely certain factors could account for the observed differences in operative times between the two techniques. SILS has been practiced for over a decade and the ‘learning curve’ might have been faster in high volume centres. Moreover, in comparison to the leap between open surgery and laparoscopy, SILS represents a modification of laparoscopic surgery. As such, surgical instruments and theatre set-up would be more familiar to the operating surgeon. An improvement in laparoscopic skills generally since its inception could additionally account for this finding.

Heterogeneity in our included studies introduced through intra-or extracorporeal division of the mesentery and in performing further procedures along with the primary operation such as fistula repair, bowel resection, bladder repair and strictureplasty may also contribute to observed differences in operating time between the two groups. This is further compounded by stoma creation in certain cases and the lack of standardisation of wound and skin closure techniques. Other factors including surgical expertise, operating surgeon experience, elective and emergency resections and indication for surgery (stricture formation, abscess, inflammatory mass) all add further technical challenges and make direct comparisons between the techniques difficult. Therefore, robust randomised trials are needed for a more accurate reflection on operating time between SILS and multi-port laparoscopy.

Length of hospital stay (LOS) was also noted to be shorter in the single incision group. Observed differences may be accounted for by post-operative pain and analgesia requirements between the two groups. Moreover, analgesia protocols and utilisation of enhanced recovery pathways (ERAS) will also lead to the differences in LOS. Gardenbroek et al.[13] enrolled all patients onto the ERAS programme in the single incision group compared to only 7.1% in the multi-port group. However, none of the other selected studies have mentioned using ERAS protocol in their post-operative management. Further, well-designed studies are needed to resolve these questions.

Unfortunately, we were unable to analyse post-operative pain/analgesia requirements in the present study. These parameters were recorded in three[12,13,16] of the five studies, but due to variability in reporting, data synthesis was not possible. The large multicentre study by Carvello et al.[12] found that SILS was associated with less pain and a reduction in analgesia compared with multi-port ileocolic resection. This was significantly lower on postoperative days 1 and 2 and better on day 3.

However, Gardenbroek et al.[13] reported no difference in median post-operative day 1 pain score between the groups. Although pain scores on the Visual Analogue Scale (VAS) were improved on the post-operative days 2 and 3 in the single incision group compared with the multi-port incision, this did not reach statistical significance. Patients in the SILS group required significantly less morphine on the first post-operative day (median 12.5 mg vs. 28 mg; P = 0.012) and hospital stay was significantly shorter. Table 4 illustrates the reported pain outcomes from the selected studies.

Table 4.

Reported pain outcomes

Author/year	Peridural anaesthesia use (days)	Median PCA use (days)	POD1 VAS score	POD2 VAS score	POD3 VAS score	POD 7 VAS score	Day 1 morphine use (mg)
Rijcken et al., 2012	SILS: 3.5±1.7	SILS: 4	SILS: 4.5±2.3	SILS: 2.8±1.8	SILS: 2.8±2	SILS: 2.3±2.1	NR
	MLS: 3.8±2	MLS: 4	MLS: 3.6±2.3	MLS: 4±2.3	MLS: 3±2	MLS: 1.5±1.2
Maeda et al., 2012	NR	NR	NR	NR	NR	NR	NR
Gardenbroek et al., 2013	NR	NR	SILS: 4 (median)	SILS: 2.5 (median)	SILS: 2 (median)	NR	SILS: 15.8±8.1
			MLS: 4 (median) P=0.57	MLS: 4 (median) P=0.34	MLS: 3 (median) P=0.14		MLS: 30.3±10.1
Carvello et al., 2018	NR	NR	Lower in SILS (P=0.016)	NR	NR	NR	NR
Celentano et al., 2020	NR	NR	NR	NR	NR	NR	NR

Values represented as mean±SD unless specified. SILS: Single incision laparoscopic surgery, MLS: Multiport laparoscopic surgery, POD: Post-operative day, VAS: Visual analogue scale, SD: Standard deviation, PCA: Patient controlled analgesia, NR: Not reported

Rijcken et al.[16] conducted a retrospective matched-pair control study. They also found no differences in daily post-operative pain scores (VAS) over 7 days and the length of peridural anaesthesia between both groups was similar. The mean hospital stay in this study was similar in both groups.

The VAS has been validated and shown to be sensitive to changes in a patient’s pain experience. It is quick and relatively easy to use for most patients, avoiding descriptive words and allowing a more meaningful comparison of measurements over time. However, there are drawbacks, including assigning a single value to a multidimensional, complex experience. Due to this value placed on the patient’s pain intensity, healthcare providers may assume that this represents a specific ‘amount’ of pain and thereby make treatment decisions accordingly.

In summary, in the present study, the results of the above outcomes (namely total operative time and LOS) should be interpreted with caution due to numerous confounding factors and risk of bias. Rigorous, well-designed trials will help in addressing these outstanding issues.

No significant differences were observed in the anastomotic leak rate between the two groups. Four of the five studies[12,13,15,16] provided details on surgical technique and all performed an extra-corporeal anastomosis. However, as mentioned, there was a combination of stapled and hand-sewn anastomosis. Previous literature suggests no significant difference on leak rate between intra- and extracorporeal anastomosis performed laparoscopically.[19] A more recent retrospective review of 89 patients undergoing robotic ileocolonic resections for CD found no anastomotic leak in patients undergoing intra- or extracorporeal anastomosis.[20]

The evidence on technique in ileocaecal resection/right hemicolectomy relating to anastomotic leak is variable but seems to show comparable outcomes between intra- and extracorporeal anastomosis.[21,22]

Wound infection rates postoperatively did not differ significantly between the SILS and multi-port laparoscopy groups. Surgical site infections can double the length of hospital stay and thereby increase the costs of healthcare.[23] Risk factors include advanced age, obesity, smoking, diabetes, site, duration and complexity of the procedure.[23,24]

Due to technical challenges with the SILS procedure compared with the multiport technique, obesity may be considered a relative contraindication. However, a study on single-incision cholecystectomies found that a high BMI (≥30 kg/m²) did not adversely impact post-operative outcomes.[25]

SILS seems to be a safe and feasible approach for the obese patient.[25] However, due to a lack of robust randomised studies with long-term follow-up means, the implication of SILS in the development of incisional hernias remains unclear.

A further advantage of single-incision surgery over conventional laparoscopy seems to be less abdominal wall trauma and improved cosmesis.[26]

We acknowledge that there are several limitations with performing a meta-analysis on observational studies, but this does not necessarily negate its relevance in generating a higher level of clinical evidence.

First, although the synthesis of randomised controlled trials (RCTs) is generally considered the highest level of clinical evidence, there are several concerns regarding the potential of meta-analysing observational studies to provide reliable results. Some of the concern relates to the high risk for within-study and across-study biases, as well as the increased risk of heterogeneity, which is the case in our study to some degree.

Second, observational evidence has limited internal validity as it is subject to both bias and confounding factors, which naturally translate into the meta-analysis process.

Third, by and large, observational study designs are not the most appropriate to assess the causal relationship between an intervention and an outcome, as several characteristics might differ or might change over time between the different intervention groups. Hence, the inclusion of observational studies in a meta-analysis might introduce bias in the summary effect. To mitigate the risk of confounding factors and to make more comparable the different study groups, investigators usually adjust the relative effects for several characteristics that may be related to the outcome and/or to the intervention by using propensity scoring system (the probability of treatment assignment conditional on observed baseline characteristics) are now also being used frequently in the analysis of observational studies as they likely allow reduction of confounding and selection bias. This was used in an observational study that was included in this meta-analysis. Although propensity scoring helps in reducing biased results, during meta-analysis, they increase the methodological heterogeneity as often different studies use different analysis methods or different adjustment factors and the comparability of their results may be questionable.

Fourth, apart from methodological heterogeneity, clinical heterogeneity is also expected to be much higher than in meta-analyses of RCTs since observational studies are based on less stringent inclusion criteria, which is the case in this current study. Assessing for the risk of bias both within and across studies is often very challenging, perhaps because preregistration and protocol preparation are not mandatory for observational studies, and as a result, unpublished studies or partly unpublished results cannot be identified. This leads to an increased risk of publication bias and other reporting biases, such as selective outcome reporting. Recently, a draft Cochrane risk of bias tool for non-randomised studies was also developed that considers each observational study as an attempt to mimic a hypothetical pragmatic randomised trial.[27] However, this tool has not been validated yet.

Fifth, despite all the above issues, observational data not only offer a valuable source of supplementary information to RCTs but also, for some clinical questions, provide the most reliable data (e.g. the safety of interventions and long-term outcomes) and could serve as hypothesis-generating studies, which could inform the need for the design of a more comprehensive RCT, just as in this study. In addition, results from meta-analysed observational studies might be more directly applicable to the general population as they are designed under a more real-life setting.

Finally, the more obvious limitation of this study, which will inherently limit the reliability and degree of its clinical applicability in general, includes inconsistency on post-operative pain documentation, lack of long-term follow-up which meant that information on cosmesis and development of incisional hernia were not available from the original observational studies.

CONCLUSION

The debate surrounding SILS and its future remains. Technical advances such as the introduction of multi-lumen ports, articulating instruments and adjustments in laparoscopes will help to facilitate this technique further, allowing its adoption into routine clinical practice. However, at present, there is a lack of high-level evidence and long-term follow-up in single incision surgery. Satisfaction post-procedure with cosmesis is an established advantage but reduced pain, although also considered an advantage has not been consistently demonstrated in the literature.[26]

Careful patient selection is the key to the successful completion of a procedure with single-incision surgery. Patient safety must never be compromised and where a view is inadequate, a low threshold for additional ports or conversion to open surgery must be considered.

On-going exposure and experience to SILS will help to overcome the ‘learning curve’, as with the introduction of laparoscopy. This will translate into shorter operative times and provide all the benefits of SILS, and multi-port laparoscopic surgery combined. However, large, well-designed, multi-centre RCTs are needed to assess the efficacy and safety of SILS, but this study does show that SILS is an acceptable alternative to multiport laparoscopic surgery for ileocaecal resection in CD.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.