Total mesorectal excision with intraoperative assessment of internal anal sphincter innervation provides new insights into neurogenic incontinence

Low anterior resection syndrome: can it be prevented?

Surgery remains the cardinal treatment in colorectal cancers but changes in bowel habits after rectal cancer surgery are common and disabling conditions that affect patients' quality of life. Low anterior resection syndrome is a disorder of bowel function after rectal resection resulting in a lowering of the QoL and recently has been defined by an international working group not only by specified symptoms but also by their consequences. This review aims to explore an extensive bibliographic research on preventive strategies for LARS. All "modifiable variables," quantified by the LARS Score, such as type of anastomosis, neoadjuvant therapy, surgical strategy, and diverting stoma, were evaluated, while "non-modifiable variables" such as age, sex, BMI, ASA, preoperative TMN, tumor height, and type of mesorectal excision were excluded from the comparative analysis. The role of defunctioning stoma, local excision, neoadjuvant radiotherapy, and non operative management seems to significantly affect risk of LARS, while type of anastomosis and surgical TME approach do not impact on LARS incidence or gravity in the long term period. Although it is established that some variables are associated with a greater onset of LARS, in clinical practice, technical difficulties and oncological limits often make difficult the application of some prevention plans. Transtomal irrigations, intraoperative neuromonitoring, pelvic floor rehabilitation before stoma closure, and early transanal irrigation represent new arguments of study in preventive strategies which could, if not eliminate the symptoms, at least mitigate them.

Intraoperative neuromonitoring in rectal cancer surgery: a systematic review and meta-analysis

PURPOSE

The aim of this study is to evaluate the role of pelvic intraoperative neuromonitoring (pIONM) in rectal cancer surgery.

METHODS

A systematic review of the literature and a meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and the Cochrane Handbook for Systematic Reviews of Interventions.

RESULTS

Overall, nine studies were identified. Quantitative analysis was performed only in three trials. Bilateral pIONM improved postoperative anorectal and urogenital functional outcomes. However, unilateral pIONM displayed a significant effect only on erectile function (p = 0.001).

CONCLUSIONS

Our findings suggest a positive effect of pIONM on postoperative functional outcomes and quality of life after rectal cancer surgery. Due to several limitations, further trials are required in order to elucidate the exact role of pIONM.

Optimising functional outcomes in rectal cancer surgery

Background

By improved surgical technique such as total mesorectal excision (TME), multimodal treatment and advances in imaging survival and an increased rate of sphincter preservation have been achieved in rectal cancer surgery. Minimal-invasive approaches such as laparoscopic, robotic and transanal-TME (ta-TME) enhance recovery after surgery. Nevertheless, disorders of bowel, anorectal and urogenital function are still common and need attention.

Purpose

This review aims at exploring the causes of dysfunction after anterior resection (AR) and the accordingly preventive strategies. Furthermore, the indication for low AR in the light of functional outcome is discussed. The last therapeutic strategies to deal with bowel, anorectal, and urogenital disorders are depicted.

Conclusion

Functional disorders after rectal cancer surgery are frequent and underestimated. More evidence is needed to define an indication for non-operative management or local excision as alternatives to AR. The decision for restorative resection should be made in consideration of the relevant risk factors for dysfunction. In the case of restoration, a side-to-end anastomosis should be the preferred anastomotic technique. Further high-evidence clinical studies are required to clarify the benefit of intraoperative neuromonitoring. While the function of ta-TME seems not to be superior to laparoscopy, case-control studies suggest the benefits of robotic TME mainly in terms of preservation of the urogenital function. Low AR syndrome is treated by stool regulation, pelvic floor therapy, and transanal irrigation. There is good evidence for sacral nerve modulation for incontinence after low AR.

The 'multilayer' theory of Denonvilliers' fascia: anatomical dissection of cadavers with the aim to improve neurovascular bundle preservation during rectal mobilization

AIM

Denonvilliers' fascia is thought to be a multilayered fascial structure, based on its embryological development with the neurovascular bundle embedded within it. Recently, this theory had been proven histologically and by confocal microscopy in many published articles. However, the literature does not report on how surgeons can identify these structures. We aimed to determine the optimal surgical approach for preserving these critical structures.

METHOD

Eighteen cadavers (13 male/five female) were included and treated according to the ethical considerations stated in the donation consent of our institution. Dissection was performed with the assistance of binocular loupes for better anatomical detail. The compositions of the prerectal fascia and the neurovascular bundle were observed and recorded at different levels of dissection using a high-definition camera.

RESULTS

The theoretical multilayered fascia was found in male specimens as three fascial layers originating from the perineal body, seminal vesicles and posterior bladder neck. The first layer merged posterolaterally and fused with the rectosacral fascia (Waldeyer's fascia). The neurovascular bundle in male specimens was observed piercing the second and third layers, while the first layer acted as a protective cover. Dissection of female specimens demonstrated only one layer in the prerectal space.

CONCLUSION

Intiating anterior rectal mobilization by incising the peritoneum posterior to its reflection seems to be anatomically correct to preserve DVF. However, its applicability may be difficult in a narrow chanllenging pelvis. The lateral rectal ligaments and Waldeyer's fascia should be dissected from their attachments to the proper fascia of the rectum.

Extracorporeal Stimulation of Sacral Nerve Roots for Observation of Pelvic Autonomic Nerve Integrity: Description of a Novel Methodological Setup

INTRODUCTION

Neurophysiologic monitoring can improve autonomic nerve sparing during critical phases of rectal cancer surgery.

OBJECTIVES

To develop a system for extracorporeal stimulation of sacral nerve roots.

METHODS

Dedicated software controlled a ten-electrode stimulation array by switching between different electrode configurations and current levels. A built-in impedance and current level measurement assessed the effectiveness of current injection. Intra-anal surface electromyography (sEMG) informed on targeting the sacral nerve roots. All tests were performed on five pig specimens.

RESULTS

During switching between electrode configurations, the system delivered 100% of the set current (25 mA, 30 Hz, 200 μs cathodic pulses) in 93% of 250 stimulation trains across all specimens. The impedance measured between single stimulation array contacts and corresponding anodes across all electrode configurations and specimens equaled 3.7 ± 2.5 kΩ. The intra-anal sEMG recorded a signal amplitude increase as previously observed in the literature. When the stimulation amplitude was tested in the range from 1 to 21 mA using the interconnected contacts of the stimulation array and the intra-anal anode, the impedance remained below 250 Ω and the system delivered 100% of the set current in all cases. Intra-anal sEMG showed an amplitude increase for current levels exceeding 6 mA.

CONCLUSION

The system delivered stable electric current, which was proved by built-in impedance and current level measurements. Intra-anal sEMG confirmed the ability to target the branches of the autonomous nervous system originating from the sacral nerve roots.

SIGNIFICANCE

Stimulation outside of the operative field during rectal cancer surgery is feasible and may improve the practicality of pelvic intraoperative neuromonitoring.

Effectiveness between early and late temporary ileostomy closure in patients with rectal cancer: A prospective study

A temporary stoma is often used in rectal cancer surgery to protect a distal anastomosis, which remains a major concern after rectal cancer surgery, particularly after low anterior resection. The temporary stoma is scheduled for closure. However, the optimal time of closure of the protecting stoma remains unclear because of sparse studies and data. We aimed to detect the efficacy between early and late temporary ileostomy closure in patients with rectal cancer during or after neoadjuvant chemoradiotherapy. We conducted a prospective, 2-group design between early and late ileostomy closure group in patients after rectal cancer surgery with temporary stoma. Participants were recruited in a teaching hospital in Guangzhou, China. A total of 161 patients confirmed diagnosis of rectal cancer underwent curative surgery and temporary ileostomy. Participants with temporary ileostomy received closure surgery after 1 (early) or 6 (late) months were assessed by clinical parameters and quality of life. Patients in late closure group received more adjuvant chemotherapy cycles but with comparable incidence of stoma closure-related complications and length of hospital stay compared to early closure group. Participants in late closure group with standardized postoperative chemotherapy might have a better prognosis compared with those in early closure group. An increased emphasis should be given to choose the optimal closure time of patients with rectal cancer having temporary ileostomy. Colorectal nurses could provide support to physician for observation of prognosis of different closure time.

Effect of preservation of Denonvilliers' fascia during laparoscopic resection for mid-low rectal cancer on protection of male urinary and sexual functions

The aim of this study was to investigate the effect of preservation of Denonvilliers' fascia (DF) during laparoscopic resection for mid-low rectal cancer on protection of male urogenital function. Whether preservation of DF during TME is effective for protection of urogenital function is largely elusive.Seventy-four cases of male mid-low rectal cancer were included. Radical laparoscopic proctectomy was performed, containing 38 cases of preservation of DF (P-group) and 36 cases of resection of DF (R-group) intraoperatively. Intraoperative electrical nerve stimulation (INS) on pelvic autonomic nerve was performed and intravesical pressure was measured manometrically. Urinary function was evaluated by residual urine volume (RUV), International Prostatic Symptom Score (IPSS), and quality of life (QoL). Sexual function was evaluated using the International Index of Erectile Function (IIEF) scale and ejaculation function classification.Compared with performing INS on the surfaces of prostate and seminal vesicles in the R-group, INS on DF in the P-group exhibited higher increasing intravesical pressure (7.3 ± 1.5 vs 5.9 ± 2.4 cmH2O, P = 0.008). In addtion, the P-group exhibited lower RUV (34.3 ± 27.2 vs 57.1 ± 50.7 mL, P = 0.020), lower IPSS and QoL scores (7 days: 6.1 ± 2.4 vs 9.5 ± 5.9, P = 0.002 and 2.2 ± 1.1 vs 2.9 ± 1.1, P = 0.005; 1 month: 5.1 ± 2.4 vs 6.6 ± 2.2, P = 0.006 and 1.6 ± 0.7 vs 2.1 ± 0.6, P = 0.003, respectively), higher IIEF score (3 months: 10.7 ± 2.1 vs 8.9 ± 2.0, P = 0.000; 6 months: 14.8 ± 2.2 vs 12.9 ± 2.2, P = 0.001) and lower incidence of ejaculation dysfunction (3 months: 28.9% vs 52.8%, P = 0.037; 6 months: 18.4% vs 44.4%, P = 0.016) postoperatively.Preservation of DF during laparoscopic resection for selective male mid-low rectal cancer is effective for protection of urogenital function.

Effect of intra-operative autonomic nerve stimulation on pelvic nerve preservation during radical laparoscopic proctectomy

AIM

This study assessed the effect of intra-operative electrical nerve stimulation (INS) on pelvic autonomic nerve preservation (PANP) during laparoscopic resection for rectal cancer.

METHOD

A total of 189 consecutive cases of radical laparoscopic proctectomy were included. PANP was assessed visually or with INS. Urinary function was evaluated by residual urine volume (RUV), International Prostatic Symptom Score (IPSS) and recatheterization rate. Erectile function was evaluated using the International Index of Erectile Function (IIEF-5) scale.

RESULTS

INS successfully confirmed PANP in 65 (91.5%) patients, while direct vision confirmed PANP in only 72 (61.0%) patients. Compared with the successfully confirmed patients, failed patients in the INS group exhibited higher postoperative RUV (100.0 ± 34.6 vs 25.2 ± 13.6 ml, P = 0.003), higher IPSS (7 days, 20.0 ± 8.6 vs 6.5 ± 2.4, P = 0.012; 1 month, 13.5 ± 6.0 vs 5.3 ± 1.9, P = 0.020; 6 months, 11.7 ± 5.1 vs 4.5 ± 1.7, P = 0.018), a greater number of incidences of a micturition disorder (66.7% vs 1.5%, P = 0.000), higher recatheterization rates (33.3% vs 1.5%, P = 0.017) and a lower IIEF score at 3 months (8.25 ± 0.96 vs 10.93 ± 1.99, P = 0.012) and 6 months (12.50 ± 1.29 vs 15.63 ± 1.65, P = 0.001) postoperatively. Compared with the vision group, the INS group had less deterioration in postoperative RUV (31.5 ± 26.4 vs 54.0 ± 46.7 ml, P = 0.000), lower IPSS (7 days, 7.7 ± 5.0 vs 11.0 ± 6.6, P = 0.000; 1 month, 6.0 ± 3.3 vs 7.6 ± 5.4, P = 0.012) and higher IIEF score (3 months, 10.69 ± 2.07 vs 9.42 ± 2.05, P = 0.001; 6 months, 15.36 ± 1.85 vs 13.64 ± 2.00, P = 0.000) as well as a lower incidence of urination disorders (7.0% vs 17.8%, P = 0.038).

CONCLUSION

INS is effective for the accurate evaluation of PANP during radical laparoscopic proctectomy. Combined with INS, laparoscopic proctectomy is more effective in urogenital function protection.

Impact of inhalation vs. intravenous anaesthesia on autonomic nerves and internal anal sphincter tone

BACKGROUND

Pelvic intraoperative neuromonitoring (pIONM) aims to identify and spare the autonomic nerves and maintain patients' quality of life. The effect of anaesthetic agents on the pIONM signal is unknown; therefore, the aim of the present study was to compare the influences of inhalation anaesthesia (IA) and total intravenous anaesthesia (TIVA).

METHODS

Twenty rectal cancer patients undergoing open nerve-sparing total mesorectal excision (TME) were assigned to pIONM under either IA or TIVA (n = 10 per group). IA was maintained with sevoflurane and TIVA with propofol. During surgery, pelvic autonomic nerves were electrically stimulated under electromyography (EMG) of the internal anal sphincter (IAS). These triggered EMG signals were analysed.

RESULTS

The absolute EMG amplitude during pIONM increased to 1.20 μV (interquartile range (IQR): 0.94-1.6) for IA and 1.49 μV (IQR: 0.84-2.75) for TIVA (P = 0.002). The relative EMG amplitude increase also was significantly lower for IA (0.59; IQR: 0.30-0.81; TIVA: 0.99; IQR: 0.62-2.5), (P = 0.001).

CONCLUSIONS

This is the first study to compare the influences of IA and TIVA on the autonomic nervous system. While both anaesthetic regimens proved useful for pIONM, TIVA with propofol may provide better signal quality than IA with sevoflurane.

Topography of the extrinsic internal anal sphincter nerve supply during laparoscopic-assisted TAMIS TME: five key zones of risk from the surgeons' view

PURPOSE

Sparing the extrinsic autonomic innervation of the internal anal sphincter during total mesorectal excision is important for the preservation of anal sphincter function. This study electrophysiologically confirmed the topography of the internal anal sphincter nerve supply during laparoscopic-assisted transanal minimally invasive surgery for total mesorectal excision.

METHODS

This prospective study was conducted at two large multispecialty referral centers. Six patients (five males and one female) aged between 45 and 65 years with low rectal cancer (≤5 cm from the anal verge) were enrolled. Surgery was performed under electric stimulation of the pelvic autonomic nerves with observation of the electromyographic signals of the internal anal sphincter.

RESULTS

The minimally invasive transanal surgical approach enabled advantageous visualization of the pelvic autonomic nerves in all patients. In particular, extrinsic innervation to the internal anal sphincter near the levator muscle was consciously spared under electrophysiological confirmation. The evoked absolute electromyographic amplitudes of the internal anal sphincter during transanal minimally invasive surgery were significantly lower than the initial results of the laparoscopic approach [3.7 μV (interquartile range 2.4; 5.7) vs. 4.3 μV (interquartile range 3.1; 8.6); p = 0.002]. Five key zones of risk for pelvic autonomic nerve damage were identified. No complications occurred.

CONCLUSIONS

The electromyographic results of this preliminary study indicate advantages for sparing the internal anal sphincter innervation during transanal minimally invasive mesorectal dissection considering the specific in situ neuroanatomical topography.

Percutaneous nerve evaluation based on electrode placement under control of autonomic innervation

BACKGROUND

Foramen needle electrode placement for percutaneous nerve evaluation (PNE) is currently carried out while observing the somatic motor response. This study investigated electrode placement while observing the autonomic as well as the somatic response.

METHODS

A consecutive series of ten patients (seven women) with a median age of 51.9 (range 30-75) years undergoing PNE for faecal incontinence (n = 6) and obstipation (n = 4) were investigated prospectively. Electrode placement was carried out under simultaneous electromyography (EMG) of the external anal sphincter (EAS) and internal anal sphincter (IAS) and cystomanometry.

RESULTS

PNE under control of somatic and autonomic nerve responses was carried out in all patients. In three out of ten patients, initial needle electrode placement showed single evoked EMG signals from the EAS. Final electrode placement resulted in adequate somatic motor and autonomic responses in all patients. Comparison of the increases in IAS EMG amplitude on the right and left stimulation sites for sacral nerves S3 and S4 demonstrated significant differences [S3 right: median 15.3 (interquartile range (IQR) 10.4; 20.1) µV vs. S3 left: median 11.6 (IQR 8.6; 16.0) µV, p = 0.034 and S4 right: median 24.1 (IQR 20.1; 37.2) µV vs. S4 left: median 12.0 (IQR 10.7; 13.7) µV, p = 0.012]. Stimulation-induced bladder activation was achieved in all seven patients with concomitant urinary dysfunction.

CONCLUSIONS

Control of not just the somatic motor response but also the autonomic nerve response during foramen needle electrode placement may objectify PNE.

Nerve-oriented mesorectal excision (NOME): autonomic nerves as landmarks for laparoscopic rectal resection

PURPOSE

We have developed nerve-oriented mesorectal excision (NOME) as a novel concept in rectal cancer surgery by which autonomic pelvic nerves serve as landmarks for a standardized navigation along fascial planes. This article describes the technique step by step and presents our results from 2008 to 2012.

MATERIAL AND METHODS

The key steps are: preparation of the splanchnic nerves at the mid-posterior sidewall, the hypogastric nerves at the upper sidewall, and the urogenital nerve branches (Walsh) at the caudal-anterior sidewall. The dissection of the lateral ligament is strictly performed as the last step. NOME was applied in 274 consecutive mesorectal excisions (partial 20.4%, total 79.6%); a subgroup of 42 male patients underwent a questionnaire-based interview on sexual activity.

RESULTS

The conversion rate was 0.7%. High (complete) specimen quality and circumferential margin negativity were achieved in 90.1% and 95.3%, respectively. Anastomotic leaks occurred in 13 (4.7%) patients. Mortality was 1.8%. The frequency of prolonged urinary catheter was 1.8%. Of 22 sexually active males interviewed, 18 (81.8%) maintained activity postoperatively.

CONCLUSIONS

NOME achieves high-quality mesorectal specimens and a high rate of preservation of autonomic nerve function. The concept of using nerves as laparoscopic landmarks may help to standardize and master laparoscopic rectal cancer surgery.

Laparoscopic neuromapping in pelvic surgery: scopes of application

BACKGROUND

New developments in intraoperative electrophysiological neuromonitoring for conventional surgery are providing further insights into functional neuroanatomy and nerve-sparing in the minor pelvis. The aim of this study was to open up potential scopes of application in laparoscopy.

METHODS

Ten patients with different indications for surgery (presacral tumor excision, n = 2; resection rectopexy. n = 2; low anterior rectal resection, n = 2; proctocolectomy. n = 2; abdomino-perineal excision of the rectum, n = 2) were investigated prospectively. The pelvic autonomic nerves were bilaterally mapped by laparoscopic electric stimulation under simultaneous electromyography of the internal anal sphincter and manometry of the bladder. Stimulation results were compared to patients' anorectal and urogenital functional outcome.

RESULTS

In all the operations laparoscopic neuromapping (LNM) was technically feasible. Laparoscopy enabled excellent visibility of pelvic neural structures for simple and differentiated electric stimulation. In all cases LNM resulted in significantly evoked electromyographic potentials and intravesical pressure rises. The technique facilitated electrophysiological determination of functional neuroanatomical topography in the minor pelvis. The stimulation results were suitable to confirm laparoscopic nerve-sparing and compatible with patients' anorectal and urogenital functional outcome.

CONCLUSIONS

LNM is technically feasible and opens up a new dimension for verification of functional nerve integrity. Further developments and investigations are mandatory to evaluate its role for laparoscopic nerve-sparing procedures.

Is intraoperative neuromonitoring associated with better functional outcome in patients undergoing open TME? Results of a case-control study

AIMS

Intraoperative neuromonitoring (IONM) aims to control nerve-sparing total mesorectal excision (TME) for rectal cancer in order to improve patients' functional outcome. This study was designed to compare the urogenital and anorectal functional outcome of TME with and without IONM of innervation to the bladder and the internal anal sphincter.

METHODS

A consecutive series of 150 patients with primary rectal cancer were analysed. Fifteen match pairs with open TME and combined urogenital and anorectal functional assessment at follow up were established identical regarding gender, tumour site, tumour stage, neoadjuvant radiotherapy and type of surgery. Urogenital and anorectal function was evaluated prospectively on the basis of self-administered standardized questionnaires, measurement of residual urine volume and longterm-catheterization rate.

RESULTS

Newly developed urinary dysfunction after surgery was reported by 1 of 15 patients in the IONM group and by 6 of 15 in the control group (p = 0.031). Postoperative residual urine volume was significantly higher in the control group. At follow up impaired anorectal function was present in 1 of 15 patients undergoing TME with IONM and in 6 of 15 without IONM (p = 0.031). The IONM group showed a trend towards a lower rate of sexual dysfunction after surgery.

CONCLUSIONS

In this study TME with IONM was associated with significant lower rates of urinary and anorectal dysfunction. Prospective randomized trials are mandatory to evaluate the definite role of IONM in rectal cancer surgery.

Evaluation of two-dimensional intraoperative neuromonitoring for predicting urinary and anorectal function after rectal cancer surgery

PURPOSE

The aim of this study was to compare the results of two-dimensional intraoperative neuromonitoring (IONM) with the postoperative urinary and anorectal function of rectal cancer patients.

METHODS

A consecutive series of 35 patients undergoing low anterior resection were investigated prospectively. IONM was performed with electric stimulations of the pelvic splanchnic nerves under simultaneous manometry of the bladder and electromyography (EMG) of the internal anal sphincter (IAS). Urinary and anorectal function were evaluated preoperatively and at follow-up by standardized questionnaires, digital rectal examination scoring system, and long-term catheterization rate.

RESULTS

The rate of postoperative newly developed bladder dysfunction was 17 %. IONM with bladder manometry had a sensitivity of 100 %, specificity of 96 %, positive predictive value of 83 %, negative predictive value of 100 %, and overall accuracy of 97 %, respectively. The proportion of patients with severely impaired anorectal function at follow-up was 8 %. The sensitivity, specificity, and positive and negative predictive values for IONM with EMG of the IAS were, respectively, 100, 96, 67, and 100 % with an accuracy of 96 %. The degree of agreement for IONM with EMG of the IAS was good for anorectal function (к = 0.780) and poor for urinary function (к = 0.119). IONM with bladder manometry yielded a very good degree of agreement for urinary function (к = 0.891) and a fair agreement for anorectal function (к = 0.336).

CONCLUSIONS

The two-dimensional IONM method is suitable for verification of bladder and IAS innervation. Accurate prediction of urinary and anorectal function necessitates both bladder manometry and EMG of the IAS.

Resection rectopexy--laparoscopic neuromapping reveals neurogenic pathways to the lower segment of the rectum: preliminary results

PURPOSE

Nerve sparing in functional pelvic floor surgery is strongly recommended as intraoperative damage to the autonomic nerves may predispose to persistent or worsened anorectal and urogenital function. The aim of this study was to investigate the intraoperative neural topography above the pelvic floor in patients undergoing laparoscopic resection rectopexy in combination with electrophysiologic neuromapping.

METHODS

Ten consecutive female patients underwent laparoscopic resection rectopexy for rectal prolapse. Intraoperative identification of pelvic autonomic nerves was carried out with a novel intraoperative neuromonitoring system based on electric stimulation under simultaneous electromyography of the internal anal sphincter and manometry of the bladder. Neuromonitoring results were compared to patients' preoperative anorectal and urogenital function and their functional results at the 3-month follow-up.

RESULTS

Laparoscopy in combination with electrophysiologic neuromapping revealed neurogenic pathways to the lower segment of the rectum during surgical mobilization. In all procedures, intraoperative neuromonitoring finally confirmed functional nerve integrity to the internal anal sphincter and the bladder. Patients with preoperatively diagnosed fecal incontinence were continent at the 3-month follow-up. The Wexner score improved in median from preoperative 4 (range 1-18) to 1 (range 0-3) at follow-up (p = 0.012). Cleveland Clinical Constipation Score improved in median from 10 (range 5-17) to 3 (range 1-7; p = 0.005). In none of the investigated patients a new onset of urinary dysfunction did occur. No change in sexual function was observed.

CONCLUSIONS

Laparoscopy in combination with electrophysiologic neuromapping during nerve-sparing resection rectopexy identified and preserved neurogenic pathways heading to the lower segment of the rectum above the level of the pelvic floor.

Total mesorectal excision--does the choice of dissection technique have an impact on pelvic autonomic nerve preservation?

BACKGROUND

The aim of this experimental study was to assess the quality of pelvic autonomic nerve preservation of different dissection techniques.

MATERIAL AND METHODS

Twelve pigs underwent low anterior rectal resection (LARR) with scissors, ultracision, monopolar diathermy, and waterjet, each in three animals. Assessment of pelvic autonomic nerve preservation was carried out by stimulation of the pelvic splanchnic nerves under electromyography of the internal anal sphincter (IAS). Neurostimulation was performed bilaterally after posterior dissection, after complete mesorectal dissection, and after rectal resection.

RESULTS

Stimulation resulted in significantly increased amplitudes of the time-based electromyographic signal of the IAS, confirming nerve preservation. The stimulation results after complete mesorectal dissection showed comparable median amplitude increases for dissection with scissors (10.34 μV (interquartile range [IQR], 5.58; 14.74)) and ultracision (9.79 μV (IQR, 7.63; 11.6)). Lower amplitude increases were observed for monopolar diathermy (4.47 μV (IQR, 2.52; 10.46)) and waterjet (0.61 μV (IQR, 0.07; 2.11)) (p = 0.038). All animals undergoing dissection with scissors, ultracision, and monopolar diathermy had bilateral positive results. Of three animals undergoing LARR with waterjet, one had bilateral positive results. Two had unilateral negative results, indicating incomplete nerve preservation.

CONCLUSION

Scissors, ultracision, and monopolar diathermy might have comparable nerve-sparing potentials and differed from waterjet.

Continuous intraoperative monitoring of autonomic nerves during low anterior rectal resection: an innovative approach for observation of functional nerve integrity in pelvic surgery

PURPOSE

The aim of this study was to develop a methodological setup for continuous intraoperative neuromonitoring with intent to improve nerve-sparing pelvic surgery.

METHODS

Fourteen pigs underwent low anterior rectal resection. Continuous stimulation of pelvic autonomic nerves was carried out with a newly developed tripolar surface electrode during lateral, anterolateral, and anterior mesorectal dissection. Neuromonitoring was performed under electromyography of the autonomic innervated internal anal sphincter.

RESULTS

Continuous neuromonitoring resulted in significantly increased electromyographic amplitudes of the internal anal sphincter, confirming intact innervation throughout the whole dissection in each animal (median 0.9 μV, interquartile range 0.5; 1.5 vs. median 3.4 μV, interquartile range 2.1; 4.7) (p < 0.001). The median dissection time in each animal was 10 min within a median number of ten (range 8-13) tripolar electric stimulations.

CONCLUSION

The present study is the first to demonstrate that continuous intraoperative monitoring of pelvic autonomic nerves during low anterior rectal resection is feasible.