Pelvic Anatomy as a Factor in Laparoscopic Rectal Surgery: A Prospective Study

Accuracy of Post-Neoadjuvant Therapy MRI for the Assessment of Anal Sphincter Involvement in Patients with Rectal Cancer

Purpose To assess the accuracy of post-neoadjuvant therapy (NAT) MRI, as compared with that of pathologic evaluation, to determine anal sphincter involvement in patients with rectal cancer. Materials and Methods This retrospective study included patients diagnosed with rectal cancer between January 2015 and December 2017 whose baseline MRI showed anal sphincter involvement and who then underwent NAT, post-NAT MRI, and abdominoperineal resection. Four radiologists (with 20 years, 5 years, 2 years, and 1 year of experience) independently reviewed MRI findings. Resected specimens were reviewed by a gastrointestinal pathologist. Interreader agreement between the radiologists and pathologist was assessed using the Cohen κ statistic. Conditional sensitivity, specificity, and positive predictive value (PPV) of the radiologists were calculated among patients for whom the radiologists and the pathologist agreed that the anal canal was involved. Results Thirty-two patients were included (mean age ± SD, 60 years ± 15; 19 male, 13 female). For the post-NAT assessment of anal sphincter involvement, agreement between readers 1, 2, and 4 and the pathologist was moderate (κ = 0.55 [95% CI: 0.18, 0.91], 0.45 [95% CI: -0.06, 0.82], and 0.53 [95% CI: 0, 0.89], respectively). There was fair agreement between reader 3 and the pathologist (κ = 0.30 [95% CI: -0.09, 0.67]). Radiologists had high sensitivity for the detection of anal sphincter involvement (88%-100%), high PPV (88%-96%), and moderate to high specificity (50%-80%); the senior radiologist had the highest sensitivity, PPV, and specificity. Conclusion Radiologists had fair to moderate interreader agreement with the pathologist for post-NAT assessment of anal sphincter involvement in patients with rectal cancer and showed high conditional sensitivity regardless of their level of experience. Keywords: Abdomen/GI, Rectum, Oncology, Post-Neoadjuvant Therapy MRI Supplemental material is available for this article. © RSNA, 2025.

Multi-Modal Machine Learning for Evaluating the Predictive Value of Pelvimetric Measurements (Pelvimetry) for Anastomotic Leakage After Restorative Low Anterior Resection

Background/Objectives: Anastomotic leakage (AL) remains a major complication after restorative rectal cancer surgery, with accurate preoperative risk stratification posing a significant challenge. Pelvic measurements derived from magnetic resonance imaging (MRI) have been proposed as potential predictors of AL, but their clinical utility remains uncertain. Methods: This retrospective, multicenter cohort study analyzed rectal cancer patients undergoing restorative surgery between 2013 and 2021. Pelvic dimensions were assessed using MRI-based pelvimetry. Univariate and multivariate regression analyses identified independent risk factors for AL. Subsequently, machine Learning (ML) models-logistic regression, random forest classifier, and XGBoost-were developed to predict AL using preoperative clinical data alone and in combination with pelvimetry. Model performance was evaluated using F1 scores, with the area under the receiver operating characteristic (ROC-AUC) and precision-recall curves (AUC-PR) as primary metrics. Results: Among 487 patients, the overall AL rate was 14%. Multivariate regression analysis identified distance to the anorectal junction, pelvic inlet width, and interspinous distance as independent risk factors for AL (p < 0.05). The logistic regression model incorporating pelvimetry achieved the highest predictive performance, with a mean ROC-AUC of 0.70 ± 0.09 and AUC-PR of 0.32 ± 0.10. Although predictive models that included pelvic measurements demonstrated higher ROC-AUCs compared to those without pelvimetry, the improvement was not statistically significant. Conclusions: Pelvic dimensions, specifically pelvic inlet and interspinous distance, were independently associated with an increased risk of AL. While ML models incorporating pelvimetry showed only moderate predictive performance, these measurements should be considered in developing clinical prediction tools for AL to enhance preoperative risk stratification.

Deep learning-based pelvimetry in pelvic MRI volumes for pre-operative difficulty assessment of total mesorectal excision

BACKGROUND

Specific pelvic bone dimensions have been identified as predictors of total mesorectal excision (TME) difficulty and outcomes. However, manual measurement of these dimensions (pelvimetry) is labor intensive and thus, anatomic criteria are not included in the pre-operative difficulty assessment. In this work, we propose an automated workflow for pelvimetry based on pre-operative magnetic resonance imaging (MRI) volumes.

METHODS

We implement a deep learning-based framework to measure the predictive pelvic dimensions automatically. A 3D U-Net takes a sagittal T2-weighted MRI volume as input and determines five anatomic landmark locations: promontorium, S3-vertebrae, coccyx, dorsal, and cranial part of the os pubis. The landmarks are used to quantify the lengths of the pelvic inlet, outlet, depth, and the angle of the sacrum. For the development of the network, we used MRI volumes from 1707 patients acquired in eight TME centers. The automated landmark localization and pelvic dimensions measurements are assessed by comparison with manual annotation.

RESULTS

A center-stratified fivefold cross-validation showed a mean landmark localization error of 5.6 mm. The inter-observer variation for manual annotation was 3.7 ± 8.4 mm. The automated dimension measurements had a Spearman correlation coefficient ranging between 0.7 and 0.87.

CONCLUSION

To our knowledge, this is the first study to automate pelvimetry in MRI volumes using deep learning. Our framework can measure the pelvic dimensions with high accuracy, enabling the extraction of metrics that facilitate a pre-operative difficulty assessment of the TME.

Predictive model of the surgical difficulty of robot-assisted total mesorectal excision for rectal cancer: a multicenter, retrospective study

Rectal cancer robotic surgery is becoming more and more common, but evidence for predicting surgical difficulty is scarce. Our goal was to look at the elements that influence the complexity of robot-assisted total mesorectal excision (R-TME) in the medical care of middle and low rectal cancer as well as to establish and validate a predictive model on the basis of these factors. Within this multicenter retrospective investigation, 166 consecutive patients receiving R-TME between January 2021 and December 2022 with middle and low rectal cancer were included and categorized according to the median operation time. A nomogram was created to forecast the procedure's complexity after variables that could affect its difficulty were found using logistic regression analysis. Using R software, a total of 166 patients were randomly split into two groups: a test group (48 patients) and a training group (118 patients) at a ratio of 7 to 3. The median operation time of all patients was 207.5 min; patients whose operation time was ≥ 207.5 min were allocated to the difficult surgery group (83 patients), and patients whose operation time was < 207.5 min were allocated to the nondifficult surgery group. Multivariate analysis revealed that body mass index (BMI), the gap between the tumor and the anal verge and the posterior rectal mesenteric thickness were independent predictors of surgical duration. A clinical predictive model was created and assessed employing the above independent predictors. The results of the receiver operating characteristic (ROC) analysis revealed the adequate discriminative ability of the predictive model. Our study revealed that it is feasible to predict surgical difficulty by obtaining clinical and magnetic resonance parameters for imaging (the gap between the anal verge and the tumour, and posterior mesorectal thickness), and these predictions could be useful in making clinical decisions.

Essential knowledge and technical tips for total mesorectal excision and related procedures for rectal cancer

Total mesorectal excision (TME) has greatly improved rectal cancer surgery outcomes by reducing local recurrence and enhancing patient survival. This review outlines essential knowledge and techniques for performing TME. TME emphasizes the complete resection of the mesorectum along embryologic planes to minimize recurrence. Key anatomical insights include understanding the rectal proper fascia, Denonvilliers fascia, rectosacral fascia, and the pelvic autonomic nerves. Technical tips cover a step-by-step approach to pelvic dissection, the Gate approach, and tailored excision of Denonvilliers fascia, focusing on preserving pelvic autonomic nerves and ensuring negative circumferential resection margins. In Korea, TME has led to significant improvements in local recurrence rates and survival with well-adopted multidisciplinary approaches. Surgical techniques of TME have been optimized and standardized over several decades in Korea, and minimally invasive surgery for TME has been rapidly and successfully adopted. The review emphasizes the need for continuous research on tumor biology and precise surgical techniques to further improve rectal cancer management. The ultimate goal of TME is to achieve curative resection and function preservation, thereby enhancing the patient's quality of life. Accurate TME, multidisciplinary-based neoadjuvant therapy, refined sphincter-preserving techniques, and ongoing tumor research are essential for optimal treatment outcomes.

Integrating a tumour appropriate transanal or robotic assisted approach to total mesorectal excision in high-volume rectal cancer practice is safe and cost-effective

Total mesorectal excision (TME) is accepted as the gold standard for oncological resection in rectal cancer. The best approach to TME is debated and often surgeons will select a preferred approach. In this study, we aimed to describe how both robotic (R-TME) and transanal (TaTME) TME can be integrated into high-volume rectal cancer surgeon practice with a comparison of clinical and oncological outcomes and cost analysis. A prospective comparative cohort study was performed in a high-volume rectal cancer centre comparing the previous 50 R-TME and 50 TaTME performed by the same surgeon. A comparison of tumour characteristics was performed to highlight a specific role for each technique. Clinical outcomes (operative duration, length of stay (LOS) and perioperative morbidity), cancer quality indicators (resection margin and completeness of TME) and cost analysis were compared. Statistical analysis was performed using IBM SPSS, version 20. R-TME was preferred in mid-rectal cancer, compared to TaTME preferred in low rectal cancer (9 cm vs. 5 cm, p < 0.001). Operative duration was longer in R-TME compared to TaTME (265 vs. 179 min, p < 0.001). Major complications (CD III-IV complications) were experienced in 10% of R-TME and 14% of TaTME (p = 0.476). A 98% (n = 49) clear R0 resection margin was achieved with both R-TME and TaTME and mesorectum quality defined as 'complete' in 86% (n = 43) in R-TME and 82% (n = 41) in TaTME. Length of hospital stay was shorter in R-TME (5 vs. 7 days, p = 0.624). An overall difference of €131 was observed favouring TaTME. In high-volume rectal cancer surgery practice, both R-TME and TaTME can be practised and tailored according to patients and tumour characteristics, with comparable clinical and cancer outcomes and is cost-effective.

Robotic male and laparoscopic female sphincter-preserving total mesorectal excision of mid-low rectal cancer share similar specimen quality, complication rates and long-term oncological outcomes

The aim of this study was to compare perioperative and long-term oncological outcomes between laparoscopic sphincter-preserving total mesorectal excision in female patients (F-Lap-TME) and robotic sphincter-preserving total mesorectal excision in male patients (M-Rob-TME) with mid-low rectal cancer (RC). A retrospective analysis of a prospectively maintained database was performed. 170 cases (F-Lap-TME: 60 patients; M-Rob-TME: 110 patients) were performed by a single surgeon (January 2011-January 2020). Clinical characteristics did not differ significantly between the two groups. Operating time was longer in M-Rob-TME than in F-Lap-TME group (185.3 ± 28.4 vs 124.5 ± 35.8 min, p < 0.001). There was no conversion to open surgery in both groups. Quality of mesorectum was complete/near-complete in 58 (96.7%) and 107 (97.3%) patients of F-Lap-TME and M-Rob-TME (p = 0.508), respectively. Circumferential radial margin involvement was observed in 2 (3.3%) and 3 (2.9%) in F-Lap-TME and M-Rob-TME patients (p = 0.210), respectively. Median length of follow-up was 62 (24-108) months in the F-Lap-TME and 64 (24-108) months in the M-Rob-TME group. Five-year overall survival rates were 90.5% in the F-Lap-TME and 89.6% in the M-Rob-TME groups (p = 0.120). Disease-free survival rates in F-Lap-TME and M-Rob-TME groups were 87.5% and 86.5% (p = 0.145), respectively. Local recurrence rates were 5% (n = 3) and 5.5% (n = 6) (p = 0.210), in the F-Lap-TME and M-Rob-TME groups, respectively. The robotic technique can potentially overcome some technical challenges related to the pelvic anatomical difference between sex compared to laparoscopy. Laparoscopic and robotic approach, respectively in female and male patients provide similar surgical specimen quality, perioperative outcomes, and long-term oncological results.

Predictors of operative difficulty in robotic low anterior resection for rectal cancer

AIM

This study evaluates the relationship of tumour and anatomical features with operative difficulty in robotic low anterior resection performed by four experienced surgeons in a high-volume colorectal cancer practice.

METHODS

Data from 382 patients who underwent robotic low anterior resection by four expert surgeons between January 2016 and June 2019 were included in the analysis. Operating time was used as a measure of operative difficulty. Univariate and multivariate mixed models were used to identify associations between baseline characteristics and operating time, with surgeon as a random effect, thereby controlling for variability in surgeon speed and proficiency. In an exploratory analysis, operative difficulty was defined as conversion to laparotomy, a positive margin or an incomplete mesorectum.

RESULTS

Median operating time was 4.28 h (range 1.95-11.33 h) but varied by surgeon from 3.45 h (1.95-6.10 h) to 5.93 h (3.33-11.33 h) (P < 0.001). Predictors of longer operating time in multivariate analysis were male sex, higher body mass index, neoadjuvant radiotherapy, low tumour height, greater sacral height and larger mesorectal area at the S5 vertebral level. Conversion occurred in two cases (0.5%), and incomplete mesorectum and positive margins were found in nine (2.4%) and 19 (5.0%) patients, respectively. Neoadjuvant radiotherapy and larger pelvic outlet were the only characteristics associated with the exploratory measure of difficulty.

CONCLUSION

Predicting operative difficulty based on easy to identify, preoperative radiological and clinical variables is feasible in robotic anterior resection.

Available prediction scores of conversion for laparoscopic rectal cancer surgery seem to be unsuitable for nowadays rectal cancer management

Introduction

This study aimed to externally evaluate the accuracy of four predictive scores for conversion to open surgery after rectal laparoscopic resection. None of the four scores achieved external validation previously.

Methods

This was a retrospective analysis of two prospectively maintained databases from two academic centers in France and Morocco. All consecutive patients who underwent laparoscopic resection for rectal adenocarcinoma between 2005 and 2020 were included. Logistic regression was used to assess the association between the factors present in the four scores and conversion. The accuracy of each score was assessed using the area under the curve (AUC). Observed and predicted conversion rates were compared for each score using the Chi-square goodness-of-fit test.

Results

Four hundred patients were included. There were 264 men (66%) with a mean age of 65.95 years (standard deviation 12.2). The median tumor height was 7 cm (quartiles 4–11) and 29% of patients had low rectal tumors. Conversion rate was 21.75%. The accuracy to predict conversion was low with an AUC lower than 0,62 for the four models. The observed conversion rates were significantly different from the predicted rates, except for one score.

Conclusions

The four models had low accuracy in predicting the conversion to open surgery for laparoscopic rectal resection. There is a need for new well-designed studies, analyzing more specific variables, in a multicentric design to ensure generalizability of the results for daily surgical practice.

Transanal versus Laparoscopic Total Mesorectal Excision in Male Patients with Low Tumor Location after Neoadjuvant Therapy: A Propensity Score-Matched Cohort Study

Background. Since Sylla and Lacy successfully reported the transanal total mesorectal excision in 2010, taTME was considered to have the potential to overcome some problematic laparoscopic cases in male, low advanced rectal cancer. However, the evidence is still lacking. This study compared the short and long outcomes of taTME with laTME in these “challenging” patients to explore the advantages of taTME among the patients. Method. After propensity score matching analysis, 106 patients were included in each group from 325 patients who met the including standard. Statistical analysis was used to compare the differences of perioperative outcomes, histopathological results, and survival results between taTME and laTME groups. Results. The mean time of pelvic operation in the taTME group was significantly shorter than in the laTME group ( $62.2\pm 14.2$ mins vs $81.1\pm 18.9$ mins, $P=0.003$ ). The complication incidence rate and the rate of protective loop ileostomy in the taTME group were significantly lower than those in the laTME group (19.8% vs 38.7%, $P=0.003$ and 70.8% vs 92.5%, $P<0.001$ ). In long-term result, there was no significant difference between the two groups for 3-year OS (87.3% vs 85.4%, $P=0.86$ ) or 3-year DFS (74.9% vs 70.1%, $P=0.92$ ). The 2-year cumulative local recurrence rate was similar between the two groups (1.1% vs 5.8%, $P=0.22$ ). Conclusion. This study demonstrated that taTME might reduce the incidence of postoperative complications, especially of anastomotic leakage in these “challenging” patients. taTME may be considered to have clear advantages for “challenging” patients.

Human factors in pelvic surgery

In the pelvis, anatomic complexity and difficulty in visualization and access make surgery a formidable task. Surgeons are prone to work-related musculoskeletal injuries from the frequently poor design and flow of their work environment. This is exacerbated by the strain of surgery in the pelvis. These injuries can result in alterations to a surgeons practice, inadvertent patient injury, and even early retirement. Human factors examines the relationships between the surgeon, their instruments and their environment. By bridging physiology, psychology, and ergonomics, human factors allows a better understanding of some of the challenges posed by pelvic surgery. The operative approach involved (open, laparoscopic, robotic, or perineal) plays an important role in the relevant human factors. Improved understanding of ergonomics can mitigate these risks to surgeons. Other human factors approaches such as standardization, use of checklists, and employing resiliency efforts can all improve patient safety in the operating theatre.

Can MRI pelvimetry predict the technical difficulty of laparoscopic rectal cancer surgery?

PURPOSE

Selection of an open or minimally invasive approach to total mesorectal excision (TME) is generally based on surgeon preference and an intuitive assessment of patient characteristics but there consensus on criteria to predict surgical difficulty. Pelvimetry has been used to predict the difficult surgical pelvis, typically using only bony landmarks. This study aimed to assess the relationship between pelvic soft tissue measurements on preoperative MRI and surgical difficulty.

METHODS

Preoperative MRIs for patients undergoing laparoscopic rectal resection in the Australasian Laparoscopic Cancer of the Rectum Trial (ALaCaRT) were retrospectively reviewed by two blinded surgeons and pelvimetric variables measured. Pelvimetric variables were analyzed for predictors of successful resection of the rectal cancer, defined by clear circumferential and distal resection margins and completeness of TME.

RESULTS

There was no association between successful surgery and any measurement of distance, area, or ratio. However, the was a strong association between the primary outcome and the estimated total pelvic volume on adjusted logistic regression analysis (OR = 0.99, P = 0.01). For each cubic centimeter increase in the pelvic volume, there was a 1% decrease in the odds of successful laparoscopic rectal cancer surgery. Intuitive prediction of unsuccessful surgery was correct in 43% of cases, and correlation between surgeons was poor (ICC = 0.18).

CONCLUSIONS

A surgeon's intuitive assessment of the difficult pelvis, based on visible MRI assessment, is not a reliable predictor of successful laparoscopic surgery. Further assessment of pelvic volume may provide an objective method of defining the difficult surgical pelvis.

Urogenital function following robotic and laparoscopic rectal cancer surgery: meta-analysis

BACKGROUND

Mixed results are reported on clinical and cancer outcomes in laparoscopic rectal cancer surgery (LRCS) compared with robotic rectal cancer surgery (RRCS). However, more favourable functional outcomes are reported following RRCS. This study compared urinary and sexual function following RRCS and LRCS in male and female patients.

METHODS

A systematic review and meta-analysis of urinary and sexual function after RRCS and LRCS was performed following PRISMA and MOOSE guidelines, and registered prospectively with PROSPERO (ID:CRD42020164285). The functional outcome reporting tools most commonly included: the International Prostate Symptom Score (IPSS), International Index of Erectile Function (IIEF) and Female Sexual Function Index (FSFI). Mean scores and changes in mean scores from baseline were analysed using RevMan version 5.3.

RESULTS

Ten studies were included reporting on 1286 patients. Some 672 patients underwent LRCS, of whom 380 (56.5 per cent) were men and 116 (17.3 per cent) were women (gender not specified in 176 patients, 26.2 per cent). A total of 614 patients underwent RRCS, of whom 356 (58.0 per cent) were men and 83 (13.5 per cent) were women (gender not specified in 175 patients, 28.5 per cent). Regarding urinary function in men at 6 months after surgery, IPSS scores were significantly better in the RRCS group than in the LRCS group (mean difference (MD) -1.36, 95 per cent c.i. -2.31 to -0.40; P = 0.005), a trend that persisted at 12 months (MD -1.08, -1.85 to -0.30; P = 0.007). ΔIIEF scores significantly favoured RRCS at 6 months [MD -3.11 (95%CI -5.77, -0.44) P <0.021] and 12 months [MD -2.76 (95%CI -3.63, -1.88) P <0.001] post-operatively. Mixed urinary and sexual function outcomes were reported for women.

CONCLUSION

This meta-analysis identified more favourable urinary and erectile function in men who undergo robotic compared with conventional laparoscopic surgery for rectal cancer. Outcomes in women did not identify a consistently more favourable outcome in either group. As robotic rectal cancer surgery may offer more favourable functional outcomes it should be considered and discussed with patients.

Mesorectal fat area and mesorectal area affect the surgical difficulty of robotic-assisted mesorectal excision and intersphincteric resection respectively in different ways

AIM

Many studies have demonstrated predictors of the difficulty of laparoscopic anterior resection for rectal cancer. Few studies focus on the influence of pelvic dimensions on robotic-assisted mesorectal excision (ME) and intersphincteric resection (ISR). This study aimed to evaluate the influences of the mesorectal fat area (MFA) and mesorectal area on the difficulty of robotic sphincter-saving surgery.

METHODS

We included 156 patients with middle and low rectal cancer who underwent robotic sphincter-saving surgery. Clinical and anatomical factors, including the pelvic dimensions, were collected. Linear regression was performed for variables associated with surgical duration. We also performed subgroup analyses for robotic-assisted ME and ISR. Logistic regression was used to find variables associated with transanal dissection.

RESULTS

For patients with middle or low rectal cancer, the sacral length and tumour distance from the anal verge were independently associated with surgical duration. The pT stage, sacral length and the MFA were independent predictors for the surgical duration of robotic-assisted ME. By contrast, a small mesorectal area was independently related to a longer duration of robotic-assisted ISR. The pelvic outlet length was independently associated with the use of transanal dissection for ISR.

CONCLUSION

It is suggested that a large MFA could affect the difficulty of ME in robotic-assisted ME, while a small mesorectal area could increase the surgical difficulty of robotic-assisted ISR for low rectal cancer. Besides, the pelvic outlet length was associated with the use of transanal dissection. Further studies are needed to validate the results and draw more scientific conclusions.

Impact of pelvic dimensions on anastomotic leak after anterior resection for patients with rectal cancer

AIM

The impact of pelvis on the development of anastomotic leak (AL) in rectal cancer (RC) patients who underwent anterior resection (AR) remains unclear. The aim of this study was to evaluate the impact of pelvic dimensions on the risk of AL.

METHODS

A total of 1058 RC patients undergoing AR from January 2013 to January 2016 were enrolled. Pelvimetric parameters were obtained using abdominopelvic computed tomography scans.

RESULTS

Univariate analyses showed that pelvic inlet, pelvic outlet, interspinous distance, and intertuberous distance were significantly associated with the risk for AL (P < 0.05). Multivariate analysis confirmed that pelvic inlet and intertuberous distance were independent risk factors for AL (P < 0.05). Significant factors from multivariate analysis were assembled into the nomogram A (without pelvic dimensions) and nomogram B (with pelvic dimensions). The area under curve (AUC) of nomogram B was 0.72 (95% CI 0.67-0.77), which was better than the AUC of nomogram A (0.69, [95% CI 0.65-0.74]), but didn't reach a statistical significance (P = 0.199). Decision curve supported that nomogram B was better than nomogram A.

CONCLUSION

Pelvic dimensions, specifically pelvic inlet and intertuberous distance, seemed to be independent predictors for postoperative AL in RC patients. Pelvic inlet and intertuberous distance incorporated with preoperative radiotherapy, preoperative albumin, conversion, and tumor diameter in the nomogram might provide a clinical tool for predicting AL.

Prediction of surgical difficulty in minimally invasive surgery for rectal cancer by use of MRI pelvimetry

Background

Technical difficulties in rectal surgery are often related to dissection in a limited surgical field. This study investigated the clinical value of MRI pelvimetry in the prediction of surgical difficulty associated with minimally invasive rectal surgery.

Methods

Patients with rectal cancer who underwent laparoscopic or robotic total mesorectal excision between 2005 and 2017 were reviewed retrospectively and categorized according to surgical difficulty on the basis of duration of surgery, conversion to an open procedure, use of the transanal approach, postoperative hospital stay, blood loss and postoperative complications. Preoperative clinical and MRI‐related parameters were examined to develop a prediction model to estimate the extent of surgical difficulty, and to compare anastomotic leakage rates in the low‐ and high‐grade surgical difficulty groups. Prognosis was investigated by calculating overall and relapse‐free survival, and cumulative local and distant recurrence rates.

Results

Of 121 patients analysed, 104 (86·0 per cent) were categorized into the low‐grade group and 17 (14·0 per cent) into the high‐grade group. Multivariable analysis indicated that high‐grade surgical difficulty was associated with a BMI above 25 kg/m² (odds ratio (OR) 4·45, P = 0·033), tumour size 45 mm or more (OR 5·42, P = 0·042), anorectal angle 123° or more (OR 5·98, P = 0·028) and pelvic outlet less than 82·7 mm (OR 6·62, P = 0·048). All of these features were used to devise a four‐variable scoring model to predict surgical difficulty. In patients categorized as high grade for surgical difficulty, the anastomotic leakage rate was 53 per cent (9 of 17 patients), compared with 9·6 per cent (10 of 104) in the low‐grade group (P < 0·001). The high‐grade group had a significantly higher local recurrence rate than the low‐grade group (P = 0·002).

Conclusion

This study highlights the impact of clinical variables and MRI pelvimetry in the prediction of surgical difficulty in minimally invasive rectal surgery.

Prediction of transabdominal total mesorectal excision difficulty according to the angle of pelvic floor muscle

BACKGROUND

Total mesorectal excision (TME) is challenging to perform in a deep, narrow pelvis. While previous studies used pelvimetry to assess bony pelvic structures, there is no consensus on exact definition of deep, narrow pelvis. We hypothesized that the shape of pelvic floor muscle may impact the performance of transabdominal pelvic dissection. We aimed to evaluate which parameters of the shape of pelvic floor muscle impact the difficulty of TME and present a predictive reference value for TME difficulty.

METHODS

From January 2015 to December 2015, 85 consecutive patients who had undergone curative resection for middle to lower rectal cancer were retrospectively studied. Pelvimetry was performed using preoperative T2-weighted magnetic resonance imaging. Predictive factor analysis for surgical duration was studied using linear regression. Mann-Whitney U test, comparing surgical duration between two groups classified by predictive factor, was used for the analysis of reference value.

RESULTS

Multivariate analysis revealed that body mass index, protective stoma, number of surgeon, and incline angle of pelvic floor muscle (β) were independent predictors of surgical duration. Test statistics of Mann-Whitney U for the difference in surgical duration between groups above and below a β of 54° were maximized.

CONCLUSIONS

The incline angle of pelvic floor muscle is an independent predictor of surgical duration. In patients with steeper incline of PFM, transabdominal TME is expected to be difficult. This index is novel, but needs to be further validated.

Is patient-specific pre-operative preparation feasible in a clinical environment? A systematic review and meta-analysis

Technical difficulty of an operation is associated with patient and disease characteristics, indicating the necessity for surgeons to exercise patient-specific preparation. Such methods have been shown to be effective in the simulation suite, however, application in a real clinical environment has been sporadic. This systematic review attempts to answer if patient-specific preparation in challenging surgical procedures is feasible. A systematic review of OvidMedline, Embase and all Evidence Based Medicine review databases, was conducted in search of studies who described surgical rehearsals in all specialties. Following the application of defined inclusion and exclusion criteria relevant data were extracted and summarised. Descriptive synthesis was performed for all included studies and meta-analysis of data was applied when possible. Of fourty-nine studies included, thirty-seven were case-series, ten were non-randomised comparative trials and two randomised controlled trials. Accuracy of applied methods ranged from 66.7 to 100% and a good outcome was seen in 60-100% of operations. Meta-analysis of studies comparing rehearsals to real procedures (same patients) showed that simulated procedures were significantly faster than real ones (SMD = -1.56 [-2.19, -0.93] p < 0.00001) but were similar in other outcomes (fluoroscopy time: SMD = -0.1 [-0.63, 0.42] p = 0.7, fluoroscopy volume: SMD = -0.43[-0.97, 0.11], p = 0.12). Meta-analysis of studies comparing pre-operative rehearsals to standard treatment (two distinct groups of patients), demonstrated that real procedures were performed quicker if pre-operative rehearsal took place (SMD = -0.47 [-0.79, -0.16], P  = 0.003) but the immediate clinical outcome was similar for practiced and not practiced operations (SMD =0.03[-0.23, 0.29], p = 0.82). Current evidence suggests that patient-specific pre-operative preparation is feasible and safe and decreases operational time.

Learning Curve of Robotic Rectal Surgery With Lateral Lymph Node Dissection: Cumulative Sum and Multiple Regression Analyses

OBJECTIVE

This study aimed to assess the learning curve of robotic rectal surgery, a procedure that has gained increasing focus in recent years because it is expected that the advanced devices used in this approach provide advantages resulting in a shorter learning curve than that of laparoscopic surgery. However, no studies have assessed the learning curve of robotic rectal surgery, especially when lateral lymph node dissection is required.

DESIGN

This was a nonrandomized, retrospective study from a single institution.

SETTING

All consecutive patients who underwent robotic rectal or sigmoid colon surgery by a single surgeon between February 2012 and July 2016 in the University of Tokyo Hospital were enrolled. The learning curve for console time was assessed using a cumulative sum analysis and multiple linear regression analysis.

PARTICIPANTS

A total of 131 consecutive patients underwent robotic rectal or sigmoid colon surgery performed by a single experienced surgeon. Of these, 41 patients received lateral lymph node dissection.

RESULTS

A cumulative sum plot for console time demonstrated that the learning period could be divided into 3 phases: Phase I, Cases 1 to 19; Phase II, Cases 20 to 78; and Phase III, Cases 79 to 131. Multiple linear regression analysis indicated that console time decreased significantly from one phase to another (Phase I-II, Δconsole time 83.0 minutes; Phase II-III, Δconsole time 40.1 minutes). Other factors affecting console time included body mass index, operative procedure, and lateral lymph node dissection, but not neoadjuvant therapy (such as chemoradiotherapy) or depth of invasion. Lateral lymph node dissection required an additional 138.4 minutes.

CONCLUSIONS

Our findings suggest that the first phase of the learning curve consists of the first 19 cases, which seems sufficient to master the manipulation of robotic arms and to understand spatial relationships unique to the robotic procedure.

MRI-based score to predict surgical difficulty in patients with rectal cancer

BACKGROUND

Rectal cancer surgery is technically challenging and depends on many factors. This study evaluated the ability of clinical and anatomical factors to predict surgical difficulty in total mesorectal excision.

METHODS

Consecutive patients who underwent total mesorectal excision for locally advanced rectal cancer in a laparoscopic, robotic or open procedure after neoadjuvant treatment, between 2005 and 2014, were included in this retrospective study. Preoperative clinical and MRI data were studied to develop a surgical difficulty grade.

RESULTS

In total, 164 patients with a median age of 61 (range 26-86) years were considered to be at low risk (143, 87·2 per cent) or high risk (21, 12·8 per cent) of surgical difficulty. In multivariable analysis, BMI at least 30 kg/m² (P = 0·021), coloanal anastomosis (versus colorectal) (P = 0·034), intertuberous distance less than 10·1 cm (P = 0·041) and mesorectal fat area exceeding 20·7 cm² (P = 0·051) were associated with greater surgical difficulty. A four-item score (ranging from 0 to 4), with each item (BMI, type of surgery, intertuberous distance and mesorectal fat area) scored 0 (absence) or 1 (presence), is proposed. Patients can be considered at high risk of a difficult or challenging operation if they have a score of 3 or more.

CONCLUSION

This simple morphometric score may assist surgical decision-making and comparative study by defining operative difficulty before surgery.

Prediction of Anastomotic Leakage After Laparoscopic Low Anterior Resection in Male Rectal Cancer by Pelvic Measurement in Magnetic Resonance Imaging

OBJECTIVE

Anastomotic leakage after laparoscopic low anterior resection in male rectal cancer patients with a narrow pelvis cannot be easily resolved. The objective of this study is to assess numerical information of narrow pelvis and to determine whether prediction of morbidity can be possible.

METHODS

Retrospective medical record review was performed. From July 2007 to January 2013, 43 consecutive male patients with low rectal cancer who underwent laparoscopic low anterior resection were divided into the anastomotic leakage-negative group and anastomotic leakage-positive group. Eleven anatomic parameters were measured from preoperative magnetic resonance imaging of pelvis and a new index called "pelvic index" was calculated.

RESULTS

The pelvic index (difference between the interspinous distance and the diameter of the mesorectum divided by the depth of the cavity of the lesser pelvis) in the leakage-positive group was significantly smaller than that in the negative group (P=0.038). Comparison between those 2 groups at the border of the cut-off value of the pelvic index (13.0) showed a significant difference.

CONCLUSIONS

Preoperative assessment by the pelvic index can predict the narrow pelvis and risk of anastomotic leakage.

Robotic surgery for rectal cancer can overcome difficulties associated with pelvic anatomy

INTRODUCTION

Total mesorectal excision (TME) for rectal cancer can be challenging to perform in the presence of difficult pelvic anatomy. In our previous studies based on open and laparoscopic TME, we found that pelvic MRI-based pelvimetry could well reflect anatomical difficulty of the pelvis and operative time increased in direct proportion to the difficulty. We explored different outcomes of robotic surgery for TME based on classifications of difficult pelvic anatomies to determine whether this method can overcome these challenges.

METHODS

We reviewed data from 182 patients who underwent robotic surgery for rectal cancer between January 2008 and August 2010. Patient demographics, pathologic outcomes, pelvimetric results, and operative and postoperative outcomes were assessed. The data were compared between easy, moderate, and difficult groups classified by MRI-based pelvimetry.

RESULTS

Comparing the three groups, there was no difference between the groups in terms of operative and pathologic outcomes, including operation time. High BMI, history of preoperative chemoradiotherapy, and lower tumor levels were significantly associated with longer operation time (p < 0.001, p < 0.001, p = 0.009), but the pelvimetric parameter was not.

CONCLUSION

There was no difference between the easy, moderate, and difficult groups in terms of surgical outcomes, such as operation time, for robotic rectal surgery. The robot system can provide more comfort during surgery for the surgeon, and may overcome challenges associated with difficult pelvic anatomy.

Predicting the pathological features of the mesorectum before the laparoscopic approach to rectal cancer

Pelvic anatomy and tumour features play a role in the difficulty of the laparoscopic approach to total mesorectal excision in rectal cancer. The aim of the study was to analyse whether these characteristics also influence the quality of the surgical specimen. We performed a prospective study in consecutive patients with rectal cancer located less than 12 cm from the anal verge who underwent laparoscopic surgery between January 2010 and July 2013. Exclusion criteria were T1 and T4 tumours, abdominoperineal resections, obstructive and perforated tumours, or any major contraindication for laparoscopic surgery. Dependent variables were the circumferential resection margin (CMR) and the quality of the mesorectum. Sixty-four patients underwent laparoscopic sphincter-preserving total mesorectal excision. Resection was complete in 79.1% of specimens and CMR was positive in 9.7%. Univariate analysis showed tumour depth (T status) (P = 0.04) and promontorium-subsacrum angle (P = 0.02) independently predicted CRM (circumferential resection margin) positivity. Tumour depth (P < 0.05) and promontorium-subsacrum axis (P < 0.05) independently predicted mesorectum quality. Multivariate analysis identified the promontorium-subsacrum angle (P = 0.012) as the only independent predictor of CRM. Bony pelvis dimensions influenced the quality of the specimen obtained by laparoscopy. These measurements may be useful to predict which patients will benefit most from laparoscopic surgery and also to select patients in accordance with the learning curve of trainee surgeons.

Factors affecting operating time in laparoscopic anterior resection of rectal cancer

Background

The objective of this study is to clarify the relationship between demographic and surgical factors and operating time, and thus operative difficulty, in patients undergoing laparoscopic anterior resection for mid-low rectal cancer, since different studies have derived different results.

Methods

The records of patients with mid-low rectal cancer who underwent laparoscopic anterior resection were retrospectively studied. Demographic data, tumor characteristics, and pelvimetry measurements were collected and analyzed with respect to operating time, using correlation coefficient analysis, principle component analysis, and linear regression.

Results

A total of 14 patients (10 males, 4 females; 65.50 ± 7.12 years of age) were included. Demographic and tumor characteristics not correlated with operating time. Body mass index (BMI) (P = 0.001); interacetabular distance (IA) (P = 0.001); anatomical transverse distance (IP) (P = 0.008); interischial distance (IS) (P = 0.002); intertuberous distance (IT) (P = 0.005); distance between the coccyx and symphysis (CoSy) (P = 0.013); and the angle of the lower border of the symphysis pubis, upper border of symphysis pubis, and sacral promontory (angle 5) (P = 0.004) were significantly associated with operating time. The equation was:

operatingtime=0.653×BMI+0.818×angle5-0.404×IA-0.380×IP-0.512×IS-0.405×IT-0.570×CoSy+330.8.

Conclusions

Transverse diameters of the pelvis, BMI, angle 5, and CoSy played the most important role in affecting operating time. The equation can be a very useful tool for preoperative assessment.