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J Pediatr Urol. 2019 May;15(3):241.e1-241.e7. doi: 10.1016/j.jpurol.2019.02.010. Epub 2019 Feb 27.

Prenatal extravasation of urine seems to preserve renal function in boys with posterior urethral valves.

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Oslo University Hospital, Department of Pediatric Surgery, Norway. Electronic address:
Oslo University Hospital, Department of Pediatric Surgery, Norway.
Oslo University Hospital, Department of Medical Biochemistry, Norway.



A posterior urethral valve (PUV) may lead to extravasation of urine, resulting in prenatal ascites and/or perirenal urinoma. Extravasation has been presumed to act as a pop-off mechanism, preserving renal function, but previous reports addressing this presumption have been inconclusive.


The present study compares renal function in patients with PUV with and without extravasation.


Sixty boys with a confirmed diagnosis of PUV as neonates (gestational age [GA]<44 weeks) throughout 2001-2016 were included. Clinical data were collected from medical records. Renal function was assessed by nadir plasma creatinine, creatinine at the last follow-up, and glomerular filtration rate (GFR) at the last follow-up. The GFR was estimated using the Schwartz formula. Renal function was classified according to the kidney disease: improving global outcomes (KDIGO) guidelines' grades of chronic kidney disease (CKD). Glomerular filtration rate > 90 ml/min/1.73m2 at the last follow-up was classified as normal renal function.


Twelve patients (20%) had ascites and/or urinoma, and 48 (80%) did not. GA and birth weight were not different in patients with and without extravasation. PUV was suspected from prenatal ultrasound findings in 66.7% of the patients in both groups. Median nadir creatinine was 21 (range, 11-33) μmol/L in boys with ascites/urinoma, and all values were within the age-adjusted reference values. Nadir creatinine was 23 (14-199) μmol/L in boys without extravasation, and it was above the normal range in 14 boys. The incidence of elevated nadir creatinine was significantly different in the two groups (p < 0.025). One of the 12 patients with extravasation developed chronic renal failure (CKD 3). In the group of 48 patients without extravasation, 20 (42%) had chronic renal failure grade 2-5, and among these, 5 patients have had a renal transplant (CKD grade 5). The prevalence of CKD grade 2-5 was statistically different in the two groups (p = 0.03). These findings are presented in the summary figure.


Extravasation of urine was found in 12 of 60 (20%) boys with PUV. These patients had significantly lower prevalence of CKD at the last follow-up than patients without extravasation. This finding is important in prenatal counseling. It also indicates that prenatal decompression of the bladder and upper tract is beneficial in patients with PUV, which is relevant to the discussion of prenatal intervention in these fetuses.


Ascites; Posterior urethral valves; Prenatal diagnosis; Renal function; Urinoma

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