Idiopathic ureteropelvic junction stricture is not an uncommon disorder with resin. tant hydronephrosis of affecting kidney, and most frequently encountered it) infant and children. Multiple causes of stricture have been identified. Abnormal organization of smooth muscle bundles at the ureteropelvic junction has been reported, and electron microscopy has demonstrated excessive collagen deposition within the intramural stroma. However, the exact cause of obstruction of UPJ stricture is uncertain,
In order to identify more obviously the cause and pathogenesis, we examinated 23 cases with idiopathic hydronephrosis underwent dismembered pyeloplasty during the period from July, 1931 to June, 1987.
The following results were obtained.
1. Muscle thickness of UPJ segment is 0.54 + 0.11mm in control group, 0.50 + 0.24mn1 in study group, there is no significant difference in muscle thickness of UPJ segment in both groups. These results suggest changes of muscle thickness of UPJ strictured segment is not a possible cause of congenital UPJ stricutre.
Muscle thickness of pelvis is 0.54 0.12mm in control group, 1.46 0.61mm in study group. Meaningly increasing almost 3 times of muscle thickness of pelvis in study group may result from compensatory hypertrophy secondary to tlretcral obstruction.
2. Muscle: lamina propria to muscle end ratio to measure indirectly amount of collagen and connective tissue is significantly decrease in study group (111e-~l5n 0.59 0.11) in contrast to control group (mean 0.41 0.05). These results st igg,, st increasing of collagen amount is not a cause of congenital UPJ stricture.
3. In study group, fibrosis and inflammation is obvious in pelvis, but not in strictured segment.
4. Muscle arrangement of UPJ segment consisted of interwoven pattern in control
group. Put in study group, substiCuted to abundant outer circular layer irnsteald of
ii normal interwoven pattern like sphincter in 21 of 23 cases. These results sug*j{~est
abnormal muscle arrangement of strictured segment is a possible cause of (011-genital UPJ stricture. This abnormal muscle arrangement of strictured segment may result from maturation arrest during fetal ureteral growth and development, and this abnormal muscle arrangement may result in functional obstruction of urinary passage.
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