Comparison of Midline and Off-midline specimen extraction following laparoscopic left-sided colorectal resections: A systematic review and meta-analysis : Journal of Minimal Access Surgery

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Comparison of Midline and Off-midline specimen extraction following laparoscopic left-sided colorectal resections: A systematic review and meta-analysis

Bhattacharya, Pratik1,; Hussain, Mohammad Iqbal2; Zaman, Shafquat1; Mohamedahmed, Ali Yasen3; Faiz, Nameer1; Mashar, Ruchir1; Sarma, Diwakar Ryali1; Peravali, Rajeev1

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Journal of Minimal Access Surgery 19(2):p 183-192, Apr–Jun 2023. | DOI: 10.4103/jmas.jmas_309_22
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Laparoscopic surgery is well-established in the field of colorectal cancer resections. Since its advent, it has shown to have significant improvement in important post-operative outcomes. Compared to open surgery, the minimally invasive approach is associated with reduced length of hospital stay (LOS), better cosmesis, reduced surgical complications, bleeding and post-operative pain. In addition, mortality rates are better, and laparoscopy is seen as an oncologically acceptable alternative to the traditional open approach.[1]

However, laparoscopic surgery and particularly left-sided colonic resections can be anatomically challenging, and this is often exacerbated by the effects of neoadjuvant therapy.[2,3]

Continued refinement and development of the laparoscopic technique have been made to further enhance and improve patient outcomes, including the introduction of single-incision laparoscopic surgery. In addition, studies have also attempted to evaluate the optimal specimen extraction site.[4–9] These have included the transumbilical or midline incision, the low transverse or Pfannenstiel incision and the right or left low transverse incisions.[8,9] Currently, personal operator preference dictates the approach used to extract colonic specimens.

However, this is an important consideration in any abdominal procedure requiring the removal of a biological specimen. These retrieval sites can become infected–either superficially or deep-seated, with other complications, including wound dehiscence, incisional hernia formation and risk of tumor seeding also being prevalent.

Factors such as post-operative pain, cosmesis and patients’ quality of life can all depend on the selection of the extraction site.

The objective of this study was to evaluate outcomes following specimen extraction through a midline incision versus ‘off midline’ sites with a focus on left-sided colorectal resections for bowel malignancies.


Design and study selection

The eligibility criteria, methodology and investigated outcome parameters of this study respected the standards of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.[10]

Inclusion criteria

  • All studies comparing outcomes of transumbilical midline versus off-midline extraction sites for laparoscopic left-sided colorectal resections
  • Patients of any age or gender
  • Resections for left colonic or rectal malignancies only.

Exclusion criteria

  • Studies reporting comparative outcomes of right-sided/transverse or open colorectal resections
  • Studies comparing two off-midline approaches, for instance, specimen extraction through a stoma site and natural orifice extraction
  • Studies using mesh closure of stoma sites
  • Benign colorectal resections
  • Robotic resections
  • Articles not in English.


Surgical site infection (SSI) and incisional hernia occurrence were the investigated primary outcomes. Total operative time, intraoperative blood loss, anastomotic leak (AL) rate and length of hospital stay (LOS) were the secondary outcomes of interest.

Literature search strategy

We constructed a comprehensive search strategy based on thesaurus headings, search operators and limits in MEDLINE, EMBASE, CINAHL and Cochrane Central Register of Controlled Trials. Two reviewers independently evaluated the reference lists of the included studies and reviews to identify relevant trials and studies. The primary literature search ended on 15th December 2021. We conducted an updated literature search on 27th November 2022, which did not reveal any further articles meeting our inclusion criteria.

Appendix 1 presents the search strategy that was used for the literature search.

Selection of studies

Two authors independently assessed the title and abstract of articles found in the literature search. Where appropriate, full texts of relevant articles were retrieved and carefully assessed against the eligibility criteria. Studies that met the inclusion criteria were considered for inclusion. Disagreement in this process was resolved by discussion between the authors. In the event of an ongoing disagreement, a third author was consulted.

Data extraction and management

An electronic data extraction spreadsheet according to the Cochrane recommendations for intervention reviews was created and pilot-tested in randomly selected articles and adjusted accordingly. Information was extracted from each of the included studies by two independent reviewers and included:

  • Study-related data (first author, publication year, country of origin of the corresponding author, journal in which the study was published, study design, sample size in each group, procedure performed and indication of operation)
  • Baseline demographic and clinical information of the study populations (age, gender, American Society of Anaesthesiologists grade, body mass index (BMI) and previous abdominal operations)
  • Primary and secondary outcome data.

Two authors extracted all data independently. Discrepancies at this stage were resolved following consultation with a third author.

Assessment of risk of bias

Four of the included studies were observational, so the assessment of their methodological quality and risk of bias were conducted by two authors using the Newcastle–Ottawa scale, which is a star-based scoring system with a maximum score of nine.[11] The included studies were assessed with respect to the selection of the study groups, the comparability of the groups and the ascertainment of the outcome of interest. Studies with a score of nine stars were deemed to be at negligible risk of bias, studies with a score of seven or eight stars were deemed to be at medium risk of bias and those that scored six or less were judged to be at high risk.

One of the included studies was a randomised controlled trial (RCT), and therefore, the risk of bias was evaluated by the Cochrane risk of bias tool by two independent authors.[12] Two investigators independently graded the risk as ‘high’, ‘low’ or ‘unclear’ in the following categories: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting and other sources of bias.

Disagreements at this stage were resolved by discussion between the assessing authors. A third reviewer was consulted if the discrepancies remained unresolved.


For dichotomous outcomes (intraoperative and post-operative complications), the odds ratio (OR) with 95% confidence intervals (CIs) was determined as the summary measure. The OR is the odds of an adverse event in the off-midline group compared to the midline group. An OR of <1 would favour the off-midline group. For continuous parameters (quantity of blood loss, total procedure time and length of hospital stay), we calculated the mean difference (MD) with 95% CIs between the two groups. When mean values were not available for continuous outcomes, data on the median and low and high ends of the range were extracted and subsequently converted to mean and standard deviation using the established equation described by Hozo et al.[13]

The unit of analysis regarding all evaluated outcomes was an individual participant. Where possible, data regarding dropouts, withdrawals and other missing information were recorded.

One reviewer independently entered the extracted data into Review Manager 5.4 software for data synthesis.[14] The entered data were subsequently checked by a second independent review author. Random-effects modelling was used for analysis. We reported the results of our analysis for each outcome parameter in a forest plot with 95% CIs.

Heterogeneity amongst the studies was assessed using the Cochran Q-test (χ2). We quantified inconsistency by calculating I2 and interpreted it using the following guide: 0%–50% represented low heterogeneity; 50%–75% represented moderate heterogeneity and 75%–100% represented substantial heterogeneity.


The initial literature search resulted in 3216 articles. Of these, 30 studies were shortlisted for potential inclusion following assessment of their titles, abstracts or full texts. A further 25 studies were excluded as they did not meet the inclusion criteria of reporting outcomes of midline and off-midline extraction sites for left-sided colorectal resections. Five comparative studies were deemed appropriate for inclusion in our analysis [Figure 1].[4,5,15–17] The total number of included patients was 1187 patients, of whom 486 had off-midline extraction site and the remaining 701 patients had midline extraction sites.

Figure 1:
PRISMA flow chart. PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-analyses

Table 1 presents the date of publication and country of origin, journal and study design of the included studies. Table 2 demonstrates the baseline characteristics of the included studies. The included study populations were of comparable age, gender and BMI in each group.

Table 1:
Characteristics of selected studies
Table 2:
Baseline characteristics from reported studies; NR: Not reported

Risk of bias assessment

The risk of bias assessment of the included observational studies is shown in Table 3. The risk of bias was judged as low (1 study) and moderate (3 studies). An overview of the risk of bias for the included RCT is shown in Figure 2. The RCT was judged to have a minimal risk of selection bias as random sequence generation and allocation concealment was achieved by using concealed envelop. There was an elevated risk of performance and detection bias due to a lack of blinding.

Table 3:
Methodological quality of the observational studies assessed with the Newcastle-Ottawa scale
Figure 2:
Summary of methodological quality assessment for the included RCT. RCT: Randomised controlled trial

Outcome synthesis

Outcomes are summarised in Figure 3.

Figure 3:
Forest plots of outcomes: (a) Volume of blood loss. (b) Procedure time. (c) Surgical site infections. (d) Anastomotic leaks. (e) Incisional hernias. (f) Length of hospital stay

Intraoperative blood loss

Three studies (n = 447) reported the volume of blood loss. The pooled analysis demonstrated that off midline extraction site had a mean blood loss of 168.56 ± 113.64 ml in comparison to 168.83 ± 121.66 ml with midline extraction. This difference in blood loss was not statistically significant (MD: 2.31, 95% CI [−38.75–43.37], P = 0.91). The heterogeneity amongst the studies was low (I2 = 48%, P = 0.15).

Total operative time

Five studies with a total number of 1187 patients reported on total operative time. Mean procedure time in the off-midline and midline groups were 186.63 ± 64.9 min and 185.1 ± 50.2 min, respectively. There was no statistically significant difference in procedure time between the two groups (MD: 0.13; 95% CI [−27.95–28.22], P = 0.99). The between-study heterogeneity was high (I2:94%, P < 0.00001).

Surgical site infection

SSI was reported in five studies with a total of 1187 patients. The SSI rate in the off-midline group was 4.12% compared to 7.85% in the midline group. Although the rate was higher in the midline group, this did not reach statistical significance (OR: 0.71, 95% CI [0.14–3.61], P = 0.68). High heterogeneity was detected amongst the included studies (I2:77%, P = 0.0002).

Anastomotic leak

Three studies with 447 patients were included in the analysis of AL. The rate of AL in the off-midline and midline groups was 3.43% and 5.35%, respectively. There was no statistically significant difference between the two groups (OR: 0.76; 95% CI [0.22–2.63], P = 0.66). Low heterogeneity was detected between the included studies (I2:27%, P = 0.002).

Incisional hernia

The formation of incisional hernias was reported in five studies with a total of 1187 patients. The rate of incisional hernia occurrence in the off-midline and midline groups was 2.26% and 7.13%, respectively. Vertical midline incisions demonstrated a higher rate of hernia formation, but this did not reach statistical significance (OR: 0.65; 95% CI [0.10–4.10], P = 0.64). There was high heterogeneity detected between the included studies (I2:70%, P = 0.009).

Length of hospital stay

Five studies (n = 1187) were included in the analysis for the length of hospital stay (LOS). The mean LOS in the off-midline and midline groups was 10.87 ± 3.96 days and 12.21 ± 5.76 days, respectively. There was no statistically significant difference in LOS between the two groups (MD: 0.78, 95% CI [−1.91–0.36], P = 0.18). Heterogeneity between the studies was low (I2: 48%, P = 0.11).


In this study, we compared outcomes between specimen extraction through a midline incision versus an off-midline approach following laparoscopic left-sided colonic resections performed for bowel cancers. We included four observational studies and 1 RCT with a total of 1187 patients, of which 486 were in the off-midline group and the remaining 701 were in the midline group.

We found no statistically significant difference in total operative time and volume of blood loss encountered between the two groups. Although the SSI rate and the incidence of incisional hernia occurrence tended to be higher in the midline group, this did not reach statistical significance. Moreover, the AL rate and LOS were also similar between the two groups.

In a retrospective cohort study, Orcutt et al. found that the Pfannenstiel incision was associated with a decreased risk of short-term wound complications when compared to the midline incision.[18] A previous meta-analysis by Sajid et al.[8] demonstrated similar rates of SSIs in the midline and off-midline approaches for laparoscopic colorectal resections.

Morita et al. found significantly higher wound infection rates in their left lower transverse incision group.[15] However, Campagnacci et al. reported significantly higher wound infection rates in their midline group.[17] Although our analysis found a lower SSI rate in the off-midline group compared to patients having specimen extracted through a midline incision (4.1% vs. 7.9%), this difference was not statistically significant.

The off-midline approach used to extract specimens in laparoscopic colorectal resections is associated with a lower rate of developing post-operative incisional hernia.[4,5] This is an important surgical consideration due to complications associated with hernias (including incarceration and strangulation) and the resulting morbidity and mortality. Our analysis failed to demonstrate a statistical significance between the two approaches (midline vs. off-midline), although there was a lower rate in the off-midline cohort (2.3% vs. 7.1%).

Mass closure (including small bites suture technique) is often employed for midline wounds. Off-midline incisions often involve two separate fascial layers and a muscle layer to buttress the wound closure. This ‘reinforced’ technique may be responsible for this observation, but further studies would be required to substantiate this. In addition, further analysis is warranted on suture material and surgical technique used for the two groups.

DeSouza et al.[19] supported the use of a Pfannenstiel incision as it was associated with the lowest rate of incisional hernia formation and therefore considered the incision of choice for extracting specimens during minimally invasive surgery involving colorectal resections. However, this is applicable for anorectal lesions and may not be generalisable for all left-sided colon resections.

Lee et al. in their meta-analysis of laparoscopic colorectal resections found a significant increase in incisional hernias with the midline approach, which contrasts with the findings of our study.[9]

Benlice et al. reported in their study (n = 2148) that Pfannenstiel and off-midline incisions should be adopted for the extraction site to prevent incisional hernia formation in laparoscopic colorectal resections.[20] However, a recent study by Choi et al. (2022) found no statistically significant difference between midline and transverse extractions in terms of consequent incisional hernia formation.[21]

Mörner et al. reported that perioperative blood loss of 250 ml or greater in colorectal procedures adversely affects short- and long-term outcomes.[22] However, total operative time may not necessarily be a good marker or indicator of perioperative outcomes.[23] In our analysis, total procedure time and blood loss were greater in the off-midline group, but this difference was not statistically significant.

LOS is dependent on several factors, including clinical, surgical and social. It can be regarded as a secondary indicator of an approach with lesser complications. Laparoscopy surgery has significantly decreased LOS[24] in comparison to open procedures. We demonstrated that LOS was less in the off-midline group (although not reaching statistical significance). This could be related to less post-operative pain and reduced risk of SSI amongst other factors.

AL is a feared complication in colorectal surgery, and it can be catastrophic. However, AL rates have remained stable over the last few years.[25] Extracting specimens from a site far from the midline could potentially cause a traction injury on the supplying mesenteric blood vessels if resection is completed externally, which is customary practice. This could lead to excess blood loss, decreased vascularity at the join and thereby AL. In our study, we noted that the AL rate was lower in the off-midline group, but this did not reach statistical significance. Thus, no correlation has been shown linking ALs to different extraction sites in this study.

We did not analyse differences in post-operative pain and cosmesis in this study. Two studies did report pain on the 1st post-operative day between the two groups, but no statistically significant difference was noted.[4,5] Morita et al. reported no difference in mean Visual Analogue Score (VAS) from post-operative days 1–7 between the two groups.[15]

Tan et al. demonstrated no statistical difference in EQ-5D scores, VAS for cosmesis and Hollander cosmesis score between left iliac fossa and midline extraction sites.[5]

The heterogeneity between studies in this analysis for SSIs and incisional hernia formation was found to be high and moderate, respectively. The between-study heterogeneity for parameters such as blood loss (ml), ALs and LOS were not significant making our findings more robust for these outcomes.

This study of the best available evidence, including four observational studies (level 3) and 1 RCT (level 2), failed to show any significant differences between extracting specimens through an off-midline incision compared to a vertical midline incision in laparoscopic left-sided colonic resections. Although the data did demonstrate some favourability towards the off-midline incision, we are unable to make any robust recommendations. Therefore, at present, extraction site following such procedures remains a personal preference on the part of the operating surgeon.

There were a few limitations to our meta-analysis. Only one RCT was included in the data synthesis, and the remaining studies were observational. The risk of bias assessment was judged to be low to moderate in the comparative studies. Minimal risk of selection bias, but an elevated risk of performance and detection bias was found in the RCT. This may bias our results in favour of either off midline or midline approach. There was significant heterogeneity detected in our outcomes of SSIs and incisional hernia formation. Pfannenstiel incision was a desirable intervention of interest to compare with midline extraction; however, we did not find studies comparing the two which met our inclusion criteria. Post-operative pain and cosmesis were desirable outcomes to assess, but this was not possible as we did not find sufficient data required for analysis of these outcomes from our selected studies. Finally, we limited our inclusion criteria to only left-sided resections as there is more variability in favoured resection sites in comparison to right-sided or total colonic resections where conventionally, a midline approach is commonly employed. Further comprehensive review and analysis may be conducted to include all laparoscopic colorectal resections to discern if outcomes differ based on the side of resection.


Our meta-analysis of the current best available evidence demonstrated that off-midline and midline extraction sites for laparoscopic left-sided colorectal resections have comparable perioperative outcomes with similar rates of SSI, operative blood loss, total procedure time, AL rate, LOS and occurrence of incisional hernias. Future high-quality studies are needed to make more evidence-based, robust conclusions and recommendations on the optimal approach.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.



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Colorectal resections; extraction site; laparoscopic surgery; midline extraction; off-midline extraction; surgical incisions

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