Earlier diagnosis, improved accuracy of preoperative imaging, preoperative (chemo)radiology and the introduction of total mesorectal excision (TME) technique has strongly improved the prognosis of rectal cancer the last decade. However, the poor functional outcome after rectal cancer treatment is a major problem and has an enormous impact on quality of life. 
There is a unique central, somatic, autonomic and enteric nervous system cooperation in maintaining faecal and urinary continence. Surgical procedures and radiotherapy have impact on this continence mechanism. This can lead to bowel dysfunction (Low Anterior Resection Syndrome: LARS 41%) urinary incontinence (38%), difficulty in bladder emptying (30%) (1) and sexual dysfunction (33%)(2). 
Studies showed sphincter weakness with anorectal manometry, however the specific role of the function of all layers of the pelvic floor musculature appeared to be underexposed. 
The aim of this study was to clarify the correlation between EMG values of the individual muscles of the pelvic floor during contractions and relaxation and functional outcomes (LARS) after rectal cancer treatment.

This is a cross-sectional study. All patients older than 18 years treated for rectal cancer, Low Anterior Resection (LAR), LAR preceded by Short Course Radiotherapy (SCRT), LAR preceded by Chemoradiotherapy (CRT), or CRT alone,  in our hospital between January 2014 and December 2018 were eligible for selection. Exclusion criteria were abdomino- perineal resection (APR), Hartman resection, patients with a diverting colostoma neurological comorbidity (spinal lesion or cerebrovascular accident (CVA)) or muscle disease (Multiple Sclerosis (MS)),  local relapse and metastasis in a distant organ. 
Seventy-six of two hundred twenty eight patients were eligible to participate in this study and invited to participate. 
All participants completed five questionnaires containing 24 questions for women and 24 questions for men, the LARS score, the Vaizey score, the International Prostate Symptom Score (IPSS), the International Consultation on Incontinence Questionnaire Urinary Incontinence Short Form (ICIQ-UI SF) , the International Index of Erectile Function (IIEF-5) questionnaire (only for men) and Item 34 in the EORTC-QLQ-CR 29 questionnaires about sexual functioning in women (only for women). 
For EMG- assessment of the pelvic floor muscles we use the Multi Array Probe Leiden, the MAPLe®  (Novuqare Pelvic Health B.V. CE 0344). The MAPLe®  is a probe for EMG registration of the pelvic floor musculature (PFM)  with a matrix of 24 electrodes enabling the measurement of EMG activity from the different sides and layers of the PFM(3).    
Participants were asked to perform three consecutive tasks according to a standardized protocol: one-minute rest, ten maximum voluntary contractions (MVC’s), and three endurance contractions. Mean raw EMG values per electrode (24 in total) were calculated for tone at rest, for mean MVC and mean endurance contraction. 
Correlations between the LARS score and the EMG values consecutively calculated per specific layers of the pelvic floor muscles, the m.puborectalis and m.sphincter ani externus, and per specific nerves, n.pudendus, n.levator ani.  In these analyses we take into account to calculate separately the EMG values of rest, MVC’s and endurance contractions.  
From these correlations p-values were obtained.
A sample size of 46 achieves 80% power to detect a difference of -0.40000 between the null hypothesis correlation of 0.00000 and the alternative hypothesis correlation of 0.40000 using a two-sided hypothesis test with a significance level of 0.05000.  
In order to correct for multiple testing, correlation between EMG values of the pelvic floor and the IPSS score, Vaizey score, ICIQ, IIEFF we used a significance level of 0.00500.

In this study 27 participants, 7 women and 20 men, were included. Time from treatment up to EMG assessment was 46,74 (SD 15,91) month’s. All questionnaires of all participants were completed. Mean LARS score (0-42) was 24,11 (sd 10,78), mean Vaizey score (0-24) 4,11 (sd 3,33), mean IPSS (0-35)  7,96 (sd 5,7), mean ICIQ_UI_SF (0-24) 2 (sd 2,5), mean IIEF5 (0-30) 12,95 (sd 7,8). 
Of all participants we calculated EMG rest values of all electrodes. Update of the software  causes miscounted raw EMG values of several electrodes in the assessment of MVC’s an endurance contractions in 14 participants. We were able to repeated measures in 10 willing participants. 
Finally we calculated EMG values of 23 MVC’s and 24 endurance contractions

There was no (significant) correlation between the LARS score and the EMG values of the pelvic floor musculature. This was the case for the EMG values of the individual muscles, the m.puborectalis and the  m.sphincter ani externus as well for the EMG values for the individual nerves, the n.pudendus and the n.levator ani. This applied to the EMG values of rest, MVC’s and endurance contractions. 
Correlation between the IPSS score and increasing EMG values of the superficial layers of the pelvic floor musculature, the n.pudendus, in MVC’s contractions was significant (p-value 0.0045). For the EMG values of the m.sphincter ani externus in Endurance contractions nearly significant. (p-value 0.0105)

This is the first research evaluating EMG activity in rest and during contractions of the different muscle layers of the pelvic floor muscles and how these were associated with functional outcomes in patients who underwent treatment for rectal cancer.   
We found no (significant) correlation between the LARS score and the EMG values of the different layers of the pelvic floor musculature. 
It is worth noting that the correlation between the IPSS score and the superficial layers of the pelvic floor muscles were significant, Furthermore, it is remarkable that it represents an increasing muscle activity.

We conclude that in our study functional outcomes, like bowel and bladder dysfunction, appear not to be related to loss of pelvic floor muscle activity.

Lange MM, Maas CP, Marijnen CA, Wiggers T, Rutten HJ, Kranenbarg EK, et al. Urinary dysfunction after rectal cancer treatment is mainly caused by surgery. The British journal of surgery. 2008;95(8):1020-8.
Croese AD, Lonie JM, Trollope AF, Vangaveti VN, Ho YH. A meta-analysis of the prevalence of Low Anterior Resection Syndrome and systematic review of risk factors. Int J Surg. 2018;56:234-41.
Voorham-van der Zalm PJ, Voorham JC, van den Bos TW, Ouwerkerk TJ, Putter H, Wasser MN, et al. Reliability and differentiation of pelvic floor muscle electromyography measurements in healthy volunteers using a new device: the Multiple Array Probe Leiden (MAPLe). Neurourology and urodynamics. 2013;32(4):341-8.