Purpose: We evaluated the collagen content and differentiation of the ureteropelvic junction (UPJ) of patients who underwent Anderson-Hynes dismembered pyeloplasty after failure of antegrade endopyelotomy. Materials and Methods: A total of 12 UPJ obstructions were examined more than 12 months after endopyelotomy with both histochemical staining to analyze total collagen content and immunohistochemical staining to analyze collagen types I and III. The specimens were compared with 12 primary UPJ obstructions and 6 normal UPJs. Statistical analysis was performed using Fisher's test and Wilcoxon matched-pairs signed-rank test. Results: Immunohistochemical staining revealed that collagen type I was located in the interfascicular space and collagen type III in the intrafascicular space in all UPJs. We found more collagen in obstructed than in normal UPJs. Collagen type III was more abundant in secondary than in primary UPJ obstructions (P <0.01). In obstruction after endopyelotomy, the staining intensity of collagen type III was greater than the intensity of collagen type I (P <0.01). Conclusion: Our results suggest that the success of antegrade endopyelotomy was impaired by an inflammatory process. This condition determined a shift of collagen differentiation toward type III, which is more fibrous than type I.
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