Electrical contraction of the anal sphincter for intraoperative visualization of anal function

Background: Repairing sphincter defects to restore the anal aperture is a cornerstone of surgical treatment in cases of anal preserving surgery. Such procedures are selected and performed according to the surgeons’ experience. In the present study, we aimed to investigate a method for clear and intuitive intraoperative assessment of anal function under general anesthesia. Methods: This study was conducted in three-month-old female (35 kg) domestic swine (n = 8) under standard general anesthesia. Electrical stimulation of the anal sphincter was performed using prototype electric devices, and then the anal pressure was measured by manometry. We generated an anal dysfunctional model by excising the left puborectalis muscle. Anal function was semi-quantified and visualized using anorectal manometry. Results: Electrical stimulation with 12.5 mA output current and 15% duty ratio produced maximum anal pressure using the smallest amount of electricity. Histological examination confirmed the safety of the electrical muscular stimulation. Three-dimensional reconstruction of the results from the pressure curves of each sensor-enabled visualization of the functional anal canal. Monitoring using manometry under general anesthesia revealed the recovery of anal function upon suturing the excised puborectalis. Conclusions: Electrical muscular stimulation feasibly enabled visualization of anal function under general anesthesia in a porcine model.