title: Defining the histopathological changes induced by nonablative radiofrequency treatment of faecal incontinence--a blinded assessment in an animal model.
abstract: OBJECTIVE
  Nonablative radiofrequency (RF) sphincter remodelling has been used to treat gastro-oesophageal reflux disease (GERD) and faecal incontinence (FI). Its mechanism of action is unclear. We aimed to investigate the histomorphological and pathophysiological changes to the internal and external anal sphincter (IAS and EAS) following RF remodelling.
  
  
  METHODS
  An experimental FI model was created in 12 female pigs: eight underwent RF 6 weeks following induction of FI (FI+RF) and four were untreated (UFI). Four animals served as controls (CG). Two blinded pathologists examined all haematoxylin and eosin and trichrome stained slides.
  
  
  RESULTS
  Compared with the UFI group, histological examination of the IAS in the FI+RF group demonstrated an increased smooth muscle (SM)/connective tissue ratio (77.2 vs 68.1%, P < 0.05) and increased collagen I compared with collagen III content (67.2 vs 54.9%, P < 0.001). The RF+FI group exhibited greater SM bundle thickness compared with the UFI group (SM width 486.93 vs 338.59 μm, P < 0.01; height 4384.4 vs 3321.0 μm, P < 0.05). The EAS of the FI+RF animals showed a significantly higher type I/II fibre ratio (33.5 vs 25.2%, P = 0.023) and fibre type I diameter (67.2 vs 59.7 μm, P < 0.001) compared with the UFI group. Post-RF manometry showed higher basal (18.8 vs 0 mmHg, P < 0.001) and squeeze (76.8 vs 12.4 mmHg, P < 0.05) anal pressures. After RF treatment, the number of interstitial cells of Cajal was significantly reduced compared with the UFI and CG groups [0.9 (FI+RF) vs 6.7 (UFI) vs 0.7 (CG) per mm(2) , P < 0.001].
  
  
  CONCLUSIONS
  In an animal model nonablative RF appeared to induce morphological changes in the IAS and EAS leading to an anatomical state reminiscent of normal sphincter structure.
authors.affiliation: Jagiellonian University Medical College, Krakow, Poland.
authors.forename: R M
authors.initials: RM
authors.lastname: Herman
authors.forename: M
authors.initials: M
authors.lastname: Berho
authors.forename: M
authors.initials: M
authors.lastname: Murawski
authors.forename: M
authors.initials: M
authors.lastname: Nowakowski
authors.forename: J
authors.initials: J
authors.lastname: Ryś
authors.forename: T
authors.initials: T
authors.lastname: Schwarz
authors.forename: D
authors.initials: D
authors.lastname: Wojtysiak
authors.forename: S D
authors.initials: SD
authors.lastname: Wexner
mesh_terms: D001003:Anal Canal / Q000378:metabolism / Q000473:pathology*; D000818:Animals; D024042:Collagen Type I / Q000378:metabolism; D024061:Collagen Type III / Q000378:metabolism; D003238:Connective Tissue / Q000378:metabolism / Q000473:pathology*; D004195:Disease Models, Animal; D005242:Fecal Incontinence / Q000473:pathology* / Q000628:therapy; D005260:Female; D008365:Manometry; D009130:Muscle, Smooth / Q000378:metabolism / Q000473:pathology*; D061208:Pulsed Radiofrequency Treatment / Q000379:methods*; D016037:Single-Blind Method; D013552:Swine
chemical_list: D024042:Collagen Type I; D024061:Collagen Type III
keywords: Faecal incontinence; radiofrequency anal remodelling; sphincter morphology