Robotic approach to colonic resection: For some or for all patients?

The robotic approach is rapidly gaining momentum in colorectal surgery. Its benefits in pelvic surgery have been extensively discussed and are well established amongst those who perform minimally invasive surgery. However, the same cannot be said for the robotic approach for colonic resection, where its role is still debated. Here we aim to provide an extensive debate between selective and absolute use of the robotic approach for colonic resection by combining the thoughts of experts in the field of robotic and minimally invasive colorectal surgery, dissecting all key aspects for a critical view on this exciting new paradigm in colorectal surgery.

Robotic transanal minimally invasive surgery (r-TAMIS): perioperative and short-term outcomes for local excision of rectal cancers.

BACKGROUND: Transanal minimally invasive surgery (TAMIS) is an advanced technique for excision of early rectal cancers. Robotic TAMIS (r-TAMIS) has been introduced as technical improvement and potential alternative to total mesorectal excision (TME) in early rectal cancers and in frail patients. This study reports the perioperative and short-term oncological outcomes of r-TAMIS for local excision of early-stage rectal cancers. METHODS: Retrospective analysis of a prospectively collected r-TAMIS database (July 2021-July 2023). Demographics, clinicopathological features, short-term outcomes, recurrences, and survival were investigated. RESULTS: Twenty patients were included. Median age and body mass index were 69.5 (62.0-77.7) years and 31.0 (21.0-36.5) kg/m2. Male sex was prevalent (n = 12, 60.0%). ASA III accounted for 66.7%. Median distance from anal verge was 7.5 (5.0-11.7) cm. Median operation time was 90.0 (60.0-112.5) minutes. Blood loss was minimal. There were no conversions. Median postoperative stay was 2.0 (1.0-3.0) days. Minor and major complication rates were 25.0% and 0%, respectively. Seventeen (85.0%) patients had an adenocarcinoma whilst three patients had an adenoma. R0 rate was 90.0%. Most tumours were pT1 (55.0%), followed by pT2 (25.0%). One patient (5.0%) had a pT3 tumour. Specimen and tumour maximal median diameter were 51.0 (41.0-62.0) mm and 21.5 (17.2-42.0) mm, respectively. Median specimen area was 193.1 (134.3-323.3) cm2. Median follow-up was 15.5 (10.0-24.0) months. One patient developed local recurrence (5.0%). CONCLUSIONS: r-TAMIS, with strict postoperative surveillance, is a safe and feasible approach for local excision of early rectal cancer and may have a role in surgically unfit and elderly patients who refuse or cannot undergo TME surgery. Future prospective multicentre large-scale studies are needed to report the long-term oncological outcomes.

International standardization and optimization group for intersphincteric resection (ISOG-ISR): modified Delphi consensus on anatomy, definition, indication, surgical technique, specimen description and functional outcome.

AIM: Intersphincteric resection (ISR) is an oncologically complex operation for very low-lying rectal cancers. Yet, definition, anatomical description, operative indications and operative approaches to ISR are not standardized. The aim of this study was to standardize the definition of ISR by reaching international consensus from the experts in the field. This standardization will allow meaningful comparison in the literature in the future. METHOD: A modified Delphi approach with three rounds of questionnaire was adopted. A total of 29 international experts from 11 countries were recruited for this study. Six domains with a total of 37 statements were examined, including anatomical definition; definition of intersphincteric dissection, intersphincteric resection (ISR) and ultra-low anterior resection (uLAR); indication for ISR; surgical technique of ISR; specimen description of ISR; and functional outcome assessment protocol. RESULTS: Three rounds of questionnaire were performed (response rate 100%, 89.6%, 89.6%). Agreement (≥80%) reached standardization on 36 statements. CONCLUSION: This study provides an international expert consensus-based definition and standardization of ISR. This is the first study standardizing terminology and definition of deep pelvis/anal canal anatomy from a surgical point of view. Intersphincteric dissection, ISR and uLAR were specifically defined for precise surgical description. Indication for ISR was determined by the rectal tumour's maximal radial infiltration (T stage) below the levator ani. A new surgical definition of T3isp was reached by consensus to define T3 low rectal tumours infiltrating the intersphincteric plane. A practical flowchart for surgical indication for uLAR/ISR/abdominoperineal resection was developed. A standardized ISR surgical technique and functional outcome assessment protocol was defined.

A meta-analysis comparing hand-assisted laparoscopic right hemicolectomy and open right hemicolectomy for right-sided colon cancer.

BACKGROUND: Mini-invasive colorectal cancer surgery was adopted widely in recent years. This meta-analysis aimed to compare hand-assisted laparoscopic surgery (HALS) with open right hemicolectomy (OS) for malignant disease. METHODS: PRISMA guidelines with random effects model were adopted using Review Manager Version 5.3 for pooled estimates. RESULTS: Seven studies that involved 506 patients were included. Compared to OS, HALS improved results in terms of blood loss (MD = 53.67, 95% CI 10.67 to 96.67, p = 0.01), time to first flatus (MD = 21.11, 95% CI 14.99 to 27.23, p < 0.00001), postoperative pain score, and overall hospital stay (MD = 3.47, 95% CI 2.12 to 4.82, p < 0.00001). There was no difference as concerns post-operative mortality, morbidity (OR = 1.55, 95% CI 0.89 to 2.7, p = 0.12), wound infection (OR = 1.69, 95% CI 0.60 to 4.76, p = 0.32), operative time (MD = - 16.10, 95% CI [- 36.57 to 4.36], p = 0.12), harvested lymph nodes (MD = 0.59, 95% CI - 0.18 to 1.36, p = 0.13), and recurrence (OR = 0.97, 95% CI 0.30 to 3.15, p = 0.96). CONCLUSIONS: HALS is an efficient alternative to OS in right colectomy which combines the advantages of OS with the mini-invasive surgery.

Minimally invasive right colectomy anastomosis study (MIRCAST): protocol for an observational cohort study of surgical complications using four surgical techniques for anastomosis in patients with a right colon tumor.

BACKGROUND: Right colectomy is the standard surgical treatment for tumors in the right colon and surgical complications are reduced with minimally-invasive laparoscopy compared with open surgery, with potential further benefits achieved with robotic assistance. The anastomotic technique used can also have an impact on patient outcomes. However, there are no large, prospective studies that have compared all techniques. METHODS/DESIGN: MIRCAST is the Minimally-Invasive Right Colectomy Anastomosis Study that will compare laparoscopy with robot-assisted surgery, using either intracorporeal or extracorporeal anastomosis, in a large prospective, observational, multicenter, parallel, four-cohort study in patients with a benign or malignant, non-metastatic tumor of the right colon. Over 2 years of follow-up, the study will prospectively evaluate peri- and postoperative complications, postoperative recovery, hospital stay, and mid-term results including survival, local recurrence, metastases rate, and conversion rate. The primary composite endpoint will be the efficacy of the surgical method regarding surgical wound infections and postoperative complications (Clavien-Dindo grade III-IV complications at 30 days post-surgery). Secondary endpoints include long-term oncologic results, conversion rate, operative time, length of stay, and quality of life. DISCUSSION: This will be the first large, international study to prospectively evaluate the use of minimally-invasive laparoscopy or robot-assisted surgery during right hemicolectomy and to control for the impact of the anastomotic technique. The research will contribute to current knowledge regarding the medical care of patients with malignant or benign tumors of the right colon, and enable physicians to determine which technique may be the most appropriate for their patients. TRIAL REGISTRATION: This study was registered on Clinicaltrials.gov (clinicaltrials.gov identifier: NCT03650517 ) on August 28th 2018 (study protocol version CI18/02 revision A, 21 February 2018).

The Use of Enhanced Technologies in Robotic Surgery and Its Impact on Outcomes in Rectal Cancer: A Systematic Review.

The main advantage of the robotic approach is the surgical precision that the technology offers. It is particularly useful in rectal cancer as this is a technically challenging procedure. The technological advantage of the robot leads to better postoperative outcomes. Apart from the 3D vision and endowrist instrumentation in comparison to laparoscopy, the options of using fluorescence imaging, endowrist stapler, and table motion have revolutionised the way of performing an anterior resection. Thus, the true benefit of these advances will be the quality of the surgery, which leads to better postoperative outcomes. This article focuses on the current status of applications of new modalities and technology development in robotic rectal surgery. A systematic literature search was performed using PubMed, MEDLINE, and cochrane database. The studies included were considered based on the following (1) articles written in English, (2) full text is available, (3) whether the topic is related to the use of novel technologies during robotic rectal surgery, and (4) sample: adult patients and malignant rectal disease. The primary end point was to analyse the current use of technological advances in robotic rectal surgery. Only a few studies are currently available on the use of these different technologies in robotic colorectal surgery. Many of these reports describe promising results, although with short-term outcomes. The use of technologies in robotic colorectal surgery is safe and feasible and can be used together to improve short-term outcomes. Intraoperative fluorescence angiography has demonstrated to reduce the rate of anastomotic leak, whereas the robotic stapler and the table motion simplify anatomic resection.

Robotic Approach to Paediatric Gastrointestinal Diseases: A Systematic Review.

INTRODUCTION: The use of minimally invasive surgery (MIS) for paediatric surgery has been on the rise since the early 2000s and is complicated by factors unique to paediatric surgery. The rise of robotic surgery has presented an opportunity in MIS for children, and recent developments in the reductions in port sizes and single-port surgery offer promising prospects. This study aimed to present a systematic overview and analysis of the existing literature around the use of robotic platforms in the treatment of paediatric gastrointestinal diseases. MATERIALS AND METHODS: In accordance with the PRISMA Statement, a systematic review on paediatric robotic gastrointestinal surgery was conducted on Pubmed, Cochrane, and Scopus. A critical appraisal of the study was performed using the Newcastle Ottawa Scale. RESULTS: Fifteen studies were included, of which seven were on Hirschsprung's disease and eight on other indications. Included studies were heterogeneous in their populations, age, and sex, but all reported low incidences of intraoperative complications and conversions in their robotic cohorts. Only one study reported on a comparator cohort, with a longer operative time in the robotic cohort (180 vs. 152 and 156 min, p < 0.001), but no significant differences in blood loss, length of stay, intraoperative complications, postoperative complications, or conversion. CONCLUSIONS: Robotic surgery may play a role in the treatment of paediatric gastrointestinal diseases. There is limited data available on modern robotic platforms and almost no comparative data between any robotic platforms and conventional minimally invasive approaches. Further technological developments and research are needed to enhance our understanding of the potential that robotics may hold for the field of paediatric surgery.

Laparoscopic versus Open Emergency Surgery for Right Colon Cancers.

BACKGROUND: A laparoscopic approach to right colectomies for emergency right colon cancers is under investigation. This study compares perioperative and oncological long-term outcomes of right colon cancers undergoing laparoscopic or open emergency resections and identifies risk factors for survival. METHODS: Patients were identified from a prospectively maintained institutional database between 2009 and 2019. Demographics, clinicopathological features, recurrence, and survival were investigated. Cox regression analysis was performed for risk factor analysis. RESULTS: A total of 202 right colectomies (114 open and 88 laparoscopic) were included. ASA III-IV was higher in the open group. The conversion rate was 14.8%. Laparoscopic surgery was significantly longer (156 vs. 203 min, p < 0.001); pTNM staging did not differ. Laparoscopy was associated with higher lymph node yield, and showed better resection clearance (R0, 78.9 vs. 87.5%, p = 0.049) and shorter postoperative stay (12.5 vs. 8.0 days, p < 0.001). Complication rates and grade were similar. The median length of follow-up was significantly higher in the laparoscopic group (20.5 vs. 33.5 months, p < 0.001). Recurrences were similar (34.2 vs. 36.4%). Open surgery had lower five-year overall survival (OS, 27.1 vs. 51.7%, p = 0.001). Five-year disease-free survival was similar (DFS, 55.8 vs. 56.5%). Surgical approach, pN, pM, retrieved LNs, R stage, and complication severity were risk factors for OS upon multivariate analysis. Pathological N stage and R stage were risk factors for DFS upon multivariate analysis. CONCLUSIONS: A laparoscopic approach to right colon cancers in an emergency setting is safe in terms of perioperative and long-term oncological outcomes. Randomized control trials are required to further investigate these results.

Robotic beyond total mesorectal excision (TME) for locally advanced or recurrent rectal cancer: a systematic review protocol.

INTRODUCTION: The surgical treatment for locally advanced or recurrent rectal cancer requires oncological clearance with a pelvic exenteration or a beyond total mesorectal excision (TME). The aim of this systematic review is to explore the safety and feasibility of robotic surgery in locally advanced and recurrent rectal cancer by evaluating perioperative outcomes, oncological clearance rates, and survival and recurrence rates postrobotic beyond TME surgery. METHODS: The systematic review will include studies published until the end of December 2023. The MEDLINE, EMBASE and Scopus databases will be searched. The screening process, study selection, data extraction, quality assessment and analysis will be performed by two independent reviewers. Discrepancies will be resolved by consensus with a third independent reviewer. The risk of bias will be assessed with validated scores. The primary outcomes will be oncological clearance, overall and disease-free survival, and local and systemic recurrence rates post robotic or robot-assisted beyond TME surgery for locally advanced or recurrent rectal cancer. Secondary outcomes will include perioperative outcomes. ETHICS AND DISSEMINATION: No ethical approval is required for this systematic review as no individual patient cases are studied requiring access to individual medical records. The results of the systematic review will be disseminated with conference presentations and peer-reviewed paper publications. PROSPERO REGISTRATION OF THE STUDY: CRD42023408098.

Long-Term Outcomes of Robotic Versus Laparoscopic Total Mesorectal Excisions: A Propensity-Score Matched Cohort study of 5-year survival outcomes.

Objective: To compare long-term outcomes between laparoscopic and robotic total mesorectal excisions (TMEs) for rectal cancer in a tertiary center. Background: Laparoscopic rectal cancer surgery has comparable long-term outcomes to the open approach, with several advantages in short-term outcomes. However, it has significant technical limitations, which the robotic approach aims to overcome. Methods: We included patients undergoing laparoscopic and robotic TME surgery between 2013 and 2021. The groups were compared after propensity-score matching. The primary outcome was 5-year overall survival (OS). Secondary outcomes were local recurrence (LR), distant recurrence (DR), disease-free survival (DFS), and short-term surgical and patient-related outcomes. Results: A total of 594 patients were included, and after propensity-score matching 215 patients remained in each group. There was a significant difference in 5-year OS (72.4% for laparoscopy vs 81.7% for robotic, P = 0.029), but no difference in 5-year LR (4.7% vs 5.2%, P = 0.850), DR (16.9% vs 13.5%, P = 0.390), or DFS (63.9% vs 74.4%, P = 0.086). The robotic group had significantly less conversion (3.7% vs 0.5%, P = 0.046), shorter length of stay [7.0 (6.0-13.0) vs 6.0 (4.0-8.0), P < 0.001), and less postoperative complications (63.5% vs 50.7%, P = 0.010). Conclusions: This study shows a correlation between higher 5-year OS and comparable long-term oncological outcomes for robotic TME surgery compared to the laparoscopic approach. Furthermore, lower conversion rates, a shorter length of stay, and a less minor postoperative complications were observed. Robotic rectal cancer surgery is a safe and favorable alternative to the traditional approaches.

Robotic beyond total mesorectal excision for locally advanced rectal cancers: Perioperative and oncological outcomes from a multicentre case series.

BACKGROUND: Around 20% of rectal tumors are locally advanced with invasion into adjacent structures at presentation. These may require surgical resections beyond boundaries of total mesorectal excision (bTME) for radicality. Robotic bTME is under investigation. This study reports perioperative and oncological outcomes of robotic bTME for locally advanced rectal cancers. MATERIALS AND METHODS: A multicentre, retrospective analysis of prospectively collected robotic bTME resections (July 2015-November 2020). Demographics, clinicopathological features, short-term outcomes, recurrences, and survival were investigated. RESULTS: One-hundred-sixty-eight patients (eight centres) were included. Median age and BMI were 60.0 (50.0-68.7) years and 24.0 (24.4-27.7) kg/m2. Female sex was prevalent (n = 95, 56.8%). Fifty patients (29.6%) were ASA III-IV. Neoadjuvant chemoradiotherapy was given to 125 (74.4%) patients. Median operative time was 314.0 (260.0-450.0) minutes. Median estimated blood loss was 150.0 (27.5-500.0) ml. Conversion to laparotomy was seen in 4.8%. Postoperative complications occurred in 77 (45.8%) patients; 27.3% and 3.9% were Clavien-Dindo III and IV, respectively. Thirty-day mortality was 1.2% (n = 2). R0 rate was 92.9%. Adjuvant chemotherapy was offered to 72 (42.9%) patients. Median follow-up was 34.0 (10.0-65.7) months. Distant and local recurrences were seen in 35 (20.8%) and 15 patients (8.9%), respectively. Overall survival (OS) at 1, 3, and 5-years was 91.7, 82.1, and 76.8%. Disease-free survival (DFS) at 1, 3, and 5-years was 84.0, 74.5, and 69.2%. CONCLUSION: Robotic bTME is technically safe with relatively low conversion rate, good OS, and acceptable DFS in the hands of experienced surgeons in high volume centres. In selected cases robotic approach allows for high R0 rates during bTME.

Robotic CME in obese patients: advantage of robotic ultrasound scan for vascular dissection.

Complete mesocolic excision (CME) in right-sided colon cancers appears to confer oncological benefits compared to conventional colectomy. Identification of the superior mesenteric vein (SMV) remains challenging. We describe the novel use of intra-operative robotic ultrasound scan (rUSS) in obese patients (BMI ≥ 29). All consecutive patients having robotic CME for colon cancer between 2014 and 2017 were included in this retrospective cohort study. Data were recorded on an ethics approved prospective database and included patient demographics, clinical and oncological outcomes. Patients were divided into group 1 (BMI ≤ 28) and group 2 (BMI ≥ 29). SMV first approach was employed in all cases and SMV detection was aided using rUSS in group 2. Primary outcome was postoperative morbidity. Secondary outcomes included conversion rate, operative time and length of stay (LOS). 41 (group 1, median 66 years) were compared to 32 patients (group 2, median 63 years). There were no conversions to laparoscopy or laparotomy. Median operative times for group 2 were 30 min longer (186 vs. 216 min, p = 0.05). Overall morbidity was similar (20% vs. 19% in group 1 and 2, p = 0.26). There was no significant difference between the two groups with regard to LOS (median 7 vs. 6 days, p = 0.48), readmissions (2 vs. 5, p = 0.13), R0 resection rate (98% vs. 94%, p = 0.43) and lymph node harvest (median 31 vs. 30, p = 0.28).CME can be technically more challenging than conventional colectomy in obese patients and is associated with longer operative times. The use of rUSS in obese patients can help to identify SMV and allow safer dissection.

Robotic Lateral Pelvic Lymph Node Dissection in Rectal Cancer: A Feasibility Study from a European Centre.

INTRODUCTION: The role of robotic lateral pelvic lymph node dissection (LPLND) for lateral pelvic nodal disease (LPND) in rectal cancer has yet to be investigated in the Western hemisphere. This study aims to investigate the safety and feasibility of robotic LPLND by utilising a well-established totally robotic TME protocol. METHODS: We conducted a retrospective study on 17 consecutive patients who underwent robotic LPLND for LPND ± TME for rectal cancer between 2015 and 2021. A single docking totally robotic approach from the left hip with full splenic mobilisation was performed using the X/Xi da Vinci platform. All patients underwent a tri-compartmental robotic en bloc excision of LPND with preservation of the obturator nerve and pelvic nerve plexus, leaving a well-skeletonised internal iliac vessel and its branches. RESULTS: The median operative time was 280 min, which was 40 min longer than our standard robotic TME. The median BMI was 26, and there were no conversions. The median inpatient stay was 7 days with no Clavien-Dindo > 3 complications. One patient (6%) developed local recurrence and metastatic disease within 5 months. The proportion of histologically confirmed LPND was 41%, of which 94% were well to moderately differentiated adenocarcinoma. Median pre-operative lateral pelvic node size was significantly higher in positive nodes (14 mm vs. 8 mm (p = 0.01)). All patients had clear resection margins on histology. DISCUSSION: Robotic LPLND is safe and feasible with good peri-operative and short-term outcomes, with the ergonomic advantages of a robotic TME docking protocol readily transferrable in LPLND.

Local Excision Versus Total Mesorectal Excision After Favourable Response to Neoadjuvant Therapy in Low Rectal Cancer: a Multi-centre Experience.

The gold standard surgical management of curable rectal cancer is proctectomy with total mesorectal excision. Adding preoperative radiotherapy improved local control. The promising results of neoadjuvant chemoradiotherapy raised the hopes for conservative, yet oncologically safe management, probably using local excision technique. This study is a prospective comparative phase III study, where 46 rectal cancer patients were recruited from patients attending Oncology Centre of Mansoura University and Queen Alexandra Hospital Portsmouth University Hospital NHS with a median follow-up 36 months. The two recruited groups were as follows: group (A), 18 patients who underwent conventional radical surgery by TME; and group (B), 28 patients who underwent trans-anal endoscopic local excision. Patients of resectable low rectal cancer (below 10 cms from anal verge) with sphincter saving procedures were included: cT1-T3N0. The median operative time for LE was 120 min versus 300 in TME (p < 0.001), and median blood loss was 20 ml versus 100 ml in LE and TME, respectively (p < 0.001). Median hospital stay was 3.5 days versus 6.5 days (p = 0.009). No statistically significant difference in median DFS (64.2 months for LE versus 63.2 months for TME, p = 0.85) and median OS (72.9 months for LE versus 76.3 months for TME, p = 0.43). No statistically significant difference in LARS scores and QoL was observed between LE and TME (p = 0.798, p = 0.799). LE seems a good alternative to radical rectal resection in carefully selected responders to neoadjuvant therapy after thorough pre-operative evaluation, planning and patient counselling.

Impact of the English National Training Programme for laparoscopic colorectal surgery on training opportunities for senior colorectal trainees.

BACKGROUND: There is growing concern that the recently introduced National Training Programme for consultants in laparoscopic colorectal surgery will have a negative impact on the training of senior colorectal trainees by minimizing the opportunities available. This study aimed to determine the impact that local implementation of the National Training Programme has had on the operating experience of senior colorectal trainees. METHODS: A prospective study was conducted at a designated national training center for laparoscopic colorectal surgery based in a large district general hospital in England, United Kingdom. All patients undergoing laparoscopic colorectal surgery in our unit between October 2006-September 2008 and October 2008-September 2010 were included in the study. The study variables included number and type of procedure, patient demographics, American Society of Anesthesiology grade, body mass index, conversion rates, previous abdominal surgery, and median operating time. The main outcome measure was the number of procedures performed by senior colorectal trainees before and after commencement of National Training Programme training in October 2008. RESULTS: A total of 746 laparoscopic colorectal resections were performed. Senior colorectal trainees performed 175 cases before commencement of the National Training Programme and 184 cases afterward. The difference was not significant. National Training Programme consultants performed 126 cases. Data were analyzed using Fisher's exact test and the Mann-Whitney U test. The study groups were found to be well matched. The median operating time was significantly longer after commencement of the National Training Programme. The study was limited in terms of ability to extrapolate results to smaller units wishing to participate in training programs. CONCLUSION: Implementation of the National Training Programme in our hospital has not had a negative impact on the training opportunities for senior colorectal trainees. However, any unit wishing to participate in the National Training Programme must ensure that an adequate operative caseload and extra resources for operative lists are available for training.

Emergency robotic colorectal surgery during COVID-19 pandemic: A retrospective case series study.

Objective: While interest in elective robotic surgery is growing, use in emergency setting remains limited due to challenges posed by sicker patients, advanced pathology and logistical issues. During the COVID-19 pandemic, robotic surgery could provide the benefit of having the surgeon away from the bedside and reducing the number of directly exposed medical staff. The objective of this study was to report patient outcomes and initial learning experience of emergency robotic colorectal surgery during the COVID-19 pandemic. Methods: A case series study was conducted, including patients undergoing emergency robotic colorectal surgery between February 2020 and February 2021 at Queen Alexandra Hospital in Portsmouth, UK. Patient data were collected from an ethics approved prospective database. Patient demographics, operative time, conversions and postoperative complications were recorded. In addition, readmissions, length of stay and short-term oncological outcomes were analyzed. Results: Ten patients with median age 64 y (range, 36-83 y) were included. Four patients had robotic complete mesocolic resection for obstructing cancers. Six had colorectal resections for benign disease in emergency setting. All were R0 with a mean lymph node harvest of 54 ± 13. Mean operative time was 249 ± 117 min, the median length of stay was 9.4 d (range, 5-22 d). Only one patient was given a temporary diverting ileostomy. There were no grade III/V complications and no 30-day mortality. Conclusions: Provided an experienced team and peri-operative planning, emergency robotic colorectal surgery can achieve favorable outcomes with benefits of radical lymph node dissection in oncological cases and avoidance of diverting stoma.