IN-UTERO PROGRESSION OF ISOLATED RENAL PELVIS DILATION

The objective of this study to determine the risk of in uteroprogressi on of renal pelvis dilation when detected on antenatal ultrasound exam ination. We reviewed 230 fetuses with evidence of renal pelvis dilatio n. At least one exam was subsequently performed prior to delivery in a ll cases. Renal pelvis dilation was defined as an anterior-posterior r enal pelvis measurement >4 mm at < 32 weeks' and >7 mm at greater than or equal to 32 weeks' gestation. Hydronephrosis was considered to be present when the renal pelvis measured + 10 mm independent of gestatio nal age. Multiple gestations and fetuses with additional congenital an omalies were excluded. The mean gestational age at diagnosis was 24 we eks. Renal pelvis dilation progressed to hydronephrosis in a total of 10.9% (25 of 230) of fetuses. There was a 3.3% chance of unilateral re nal pelvis dilation progressing to hydronephrosis versus 26.0% in bila teral dilation (OR 10.4 [95% Cl 3.5-33.3]). Or those fetuses with prog ression, 80% had bilateral dilation (p < 0.0001). There was no differe nce in progression between right and left kidneys. Additionally, gende r, gestational age at diagnosis and delivery, and birth weight did not differ between those fetuses with and without progression. The hydron ephrosis in 7 of 25 (28%) regressed to pyelectasis on a subsequent ult rasound exam. Thus, the overall rate of progression of renal pelvis di lation to persistent hydronephrosis was 7.8% (18 of 230). In conclusio n, the risk of isolated renal pelvis dilation progressing to hydroneph rosis is low. Although bilateral pelvis dilation carries a higher risk for progression, no fetus in our study required in utero intervention . A follow up scan prior to delivery may be considered to identify tho se fetuses who will require postpartum intervention.