title: Intraoperative inspection of the ureteropelvic junction during pyeloplasty is not sufficient to distinguish between extrinsic and intrinsic causes of obstruction: Correlation with histological analysis.
abstract: BACKGROUND
  Based on current knowledge, it is possible to have an initial diagnosis of intrinsic or extrinsic ureteropelvic junction obstruction (UPJO) based solely on clinical and imaging findings. However, it may not be possible to strictly discriminate an intrinsic case with an additional extrinsic component from a primarily intrinsic stenosis because of lower pole aberrant vessels. These two disorders may coexist or trigger each other. Herein, we aimed to compare the histological changes observed in intrinsic and extrinsic types of UPJO. Our hypothesis is that inspecting the UPJ during pyeloplasty may not be a sufficient way to delineate the underlying cause of obstruction in every individual.
  
  
  METHODS
  We retrospectively reviewed the data of 56 patients who had dismembered pyeloplasty. The intrinsic and extrinsic groups consisted of 38 and 18 patients, respectively. Masson's trichrome stain, CD117, and connexin 43 (Cx43) antibody were used in histopathology and immunochemistry. Statistical calculations were done with chi-square and Mann-Whitney U tests.
  
  
  CONCLUSIONS
  Connexin 43 staining pattern, CD117 positive cell count, and the extent of fibrosis did not differ significantly between extrinsic and intrinsic cases. However, the difference with regard to the degree of muscular hypertrophy was close to statistical significance. The exact pathophysiological mechanism underlying UPJO has yet to be elucidated. A study directly comparing both groups histologically is indeed rare. Our study showed that there are no significant differences between the intrinsic and extrinsic groups in terms of the pacemaker activity, gap junctional communication, and extent of fibrosis. Muscular hypertrophy, which was marginally higher in our extrinsic group, may persist despite successful relocation of the obstructing vessel. The main drawbacks of our study are; the absence of a control group and the retrospective study design with its inherent selection biases.
  
  
  CONCLUSIONS
  Immunohistochemical profiles of intrinsic and extrinsic UPJOs resemble each other. Intraoperative inspection of the UPJ may not be enough for accurate discrimination for a surgical procedure that can correct only the extrinsic cause.
authors.affiliation: Department of Urology, VKF Amerikan Hospital, Istanbul, Turkey. Electronic address: tunamut@hotmail.com.
authors.forename: Tuna
authors.initials: T
authors.lastname: Mut
authors.affiliation: Department of Urology, School of Medicine, Koç University, Istanbul, Turkey.
authors.forename: Ömer
authors.initials: Ö
authors.lastname: Acar
authors.affiliation: Department of Urology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Tayfun
authors.initials: T
authors.lastname: Oktar
authors.affiliation: Department of Pathology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Işın
authors.initials: I
authors.lastname: Kılıçaslan
authors.affiliation: Department of Urology, School of Medicine, Koç University, Istanbul, Turkey.
authors.forename: Tarık
authors.initials: T
authors.lastname: Esen
authors.affiliation: Department of Urology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Haluk
authors.initials: H
authors.lastname: Ander
authors.affiliation: Department of Urology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Orhan
authors.initials: O
authors.lastname: Ziylan
mesh_terms: D002648:Child; D002675:Child, Preschool; D003949:Diagnostic Techniques, Surgical; D005260:Female; D006801:Humans; D007223:Infant; D007430:Intraoperative Care / Q000379:methods*; D007682:Kidney Pelvis / Q000601:surgery*; D008297:Male; D019651:Plastic Surgery Procedures; D012189:Retrospective Studies; D014517:Ureteral Obstruction / Q000209:etiology* / Q000473:pathology / Q000601:surgery*
keywords: Cajal cells; Connexin; Histopathology; Pyeloplasty; Ureteropelvic junction obstruction; Vascular hitch