Objectives. To analyze and identify collagen subtypes in the primary obstructed and refluxing megaureter of childhood.

Methods. Anticollagen monoclonal antibodies to collagen types I, III, and IV were used in control ureters (n = 4), obstructed (n = 7), and refluxing (n = 13) megaureters. Additionally, all were stained with Masson’s trichrome to further define the extracellular matrix. After staining and serial sectioning, representative ureteral sections, focusing on the muscularis and lamina propria regions, were digitized and analyzed with a color image analysis system.

Results. Immunohistochemical studies demonstrated increases in collagen types I and III for both obstructed and refluxing megaureters compared with controls (P <0.05). Collagen type IV was not detected in statistically significant amounts in any ureter. In control ureters most was type I (83% ± 9%) collagen. Obstructed megaureters produced similar results with virtually all collagen being type I (84% ± 26%) with very little type III collagen present, 5.3% ± 3%. Refluxing megaureters contained only 55% ± 15% type I collagen. However, there was an increase in type III collagen (16% ± 4%) versus (4.5% ± 2%) in controls (P <0.05).

Conclusions. These data suggest that the greater contribution of type III collagen may play a role in the pathophysiology of refluxing megaureters. Because type III collagen is a less distensible fiber, it may cause an intrinsically stiffer ureter and play a role in the lower surgical success in the reimplantation of refluxing megaureters.