A Quantitative Histological Analysis of the Dilated Ureter of Childhood

A quantitative histological study of the dilated ureter of childhood was performed on 26 ureters. The specimens were from 15 male and 11 female patients 10 days to 12 years old (mean age 2.0 years). A color image analysis system was used to examine and compare collagen and smooth muscle components of the muscularis layers to normal control ureters of similar age. In comparing primary obstructed (12) to primary refluxing (14) megaureters and control ureters (6), there was a statistically different collagen-to-smooth muscle ratio (p <0.001) between the primary obstructed and primary refluxing megaureter groups. For patients with primary refluxing megaureter there was a 2-fold increase in the tissue matrix ratio of collagen-to-smooth muscle when compared to patients with primary obstructed megaureter. In the primary obstructed megaureters the amount of collagen and smooth muscle was not statistically different from controls (p >0.01). The increased tissue matrix ratio of 2.0 ± 0.35 (collagen-to-smooth muscle) in the refluxing megaureter group compared to 0.78 ± 0.22 in the obstructed megaureter group and 0.52 ± 0.12 in controls was found to be due not only to a marked increase in collagen but also a significant decrease in the smooth muscle component of the tissue. Primary obstructed and normal control ureters had similar quantitative amounts of smooth muscle with 60 ± 5% and 61 ± 6%, respectively, while refluxing megaureters had only 40 ± 5% smooth muscle. The percentage collagen was 36 ± 5 in the obstructed megaureter group and 30 ± 5 in controls, with refluxing megaureters having 58 ± 5% collagen on analysis. Our findings emphasize the significant differences in the structural components (collagen and smooth muscle) of the dilated ureter of childhood, and provide us with further insight into the pathological nature of these dilated ureters and their surgical repair.