title: The learning curve of laparoendoscopic single-site adrenalectomy: an analysis of over 100 cases.
abstract: Recently, laparoendoscopic single-site adrenalectomy (LESS-A) has been developed as an alternative treatment for adrenal tumors. Although LESS-A is more technically complex than conventional laparoscopic adrenalectomy, its learning curve and the factors associated with poor surgical outcomes are poorly understood. We analyzed the learning curve of LESS-A and attempted to identify risk factors associated with worse surgical outcomes.
  
  
  
  We identified 103 patients who underwent LESS-A [performed by the same surgeon (A.M.)] from 2009 to 2015. The learning curve was analyzed using the moving average method (the 10-case moving average), and we assessed potential risk factors for a prolonged pneumoperitoneum time.
  
  
  
  The learning curve stabilized at 30 cases. The cases were divided into two groups, the learning stage (LS) (cases 1-29) and master stage (MS) (cases 30-103) groups. The percentage of females and the frequency of previous abdominal surgery were higher in the LS group (p = 0.022 and 0.001, respectively). In the LS group, the mean pneumoperitoneum time was 92 ± 35 min, which was significantly longer than the equivalent value for the MS group (55 ± 18 min, p < 0.001). In the LS group, univariate analysis revealed that tumor size (≥50 mm) and the visceral fat area (VFA)/total fat area (TFA) ratio (≥0.49) were significantly associated with a prolonged pneumoperitoneum time (p = 0.046 and 0.046, respectively). In the multivariate analysis, tumor size and the VFA/TFA ratio were confirmed to be associated with a prolonged pneumoperitoneum time (p = 0.029 and 0.029, odds ratio 20.83 and 20.83, respectively). On the other hand, none of the examined factors were found to be associated with a prolonged pneumoperitoneum time in the MS group.
  
  
  
  LESS-A was performed safely in most cases. However, surgeons who are learning the LESS-A procedure need to pay attention to tumor size and visceral obesity.
authors.affiliation: Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-0016, Japan.
authors.forename: Keishiro
authors.initials: K
authors.lastname: Fukumoto
authors.affiliation: Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-0016, Japan. akiram@a8.keio.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Miyajima
authors.affiliation: Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-0016, Japan.
authors.forename: Seiya
authors.initials: S
authors.lastname: Hattori
authors.affiliation: Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-0016, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Matsumoto
authors.affiliation: Center for Clinical Research, Keio University School of Medicine, Tokyo, Japan.|Biostatistics at Center for Clinical Research, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Abe
authors.affiliation: Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Kurihara
authors.affiliation: Department of Diagnostic Radiology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Jinzaki
authors.affiliation: Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-0016, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Kikuchi
authors.affiliation: Department of Urology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-0016, Japan.
authors.forename: Mototsugu
authors.initials: M
authors.lastname: Oya
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000473:pathology / Q000601:surgery; D000315:Adrenalectomy / Q000193:education* / Q000379:methods*; D002983:Clinical Competence; D005260:Female; D006801:Humans; D050152:Intra-Abdominal Fat / Q000473:pathology; D007564:Japan; D010535:Laparoscopy / Q000193:education*; D059032:Learning Curve; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D061646:Operative Time; D011028:Pneumoperitoneum, Artificial
keywords: Laparoendoscopic single-site adrenalectomy; Laparoendoscopic single-site surgery; Learning curve; Surgical outcome