FETAL URINE ANALYSIS TO PREDICT POOR POSTNATAL FUNCTION IN TWO CASES OF CONGENITAL URINARY OBSTRUCTION

Background: Untreated fetal lower urinary tract obstructions have a mortality rate of up to 45%. We evaluated the clinical usefulness of fetal urine analysis for the prediction of poor postnatal renal function in two cases. Methods: Patient 1: 26th week, diagnosis of left fetal abdominal mass (suspected multicystic-dysplastic kidney). Patient 2: 14th week, diagnosis of fetal megabladder. In both cases, 7 echoguided cystocentesis were performed. Urine fetal samples were assayed for electrolytes, creatinine, albumin, osmolality, β2-Microglobulin and CystatinC on Cobas311-Roche, BNII nephelometer Siemens,Osmometer AI. Results: In patient 1, the parameters of renal function were elevated, supporting an impaired renal function (Na:130.1±3.1 mEq/L; K: 4.14±0.38 mEq/L; Cl:109.3±2.1 mEq/L; Osmolality: 258.1±7.4 mOsm/Kg; Creatinine: 8.8±1.4 mg/dl; β2- Microglobulin: 0.47±0.11 mg/dL; CystatinC: 0.07±0.01 mg/dl). At day 4 after birth, the child underwent left nephroureterectomy, with a definitive diagnosis of segmental form of renal dysplasia. The cystourethrography, performed at 3 months of age, showed a right healthy renal parenchyma, with a normal renal function. In patient 2, the fetal urine biochemical tests were normal (Na:61±16.6 mEq/L; K:2.57±0.5 mEq/L; Cl:50±18.4 mEq/L; Osmolality: 134.3±30.14 mOsm/Kg; Creatinine: 13.14±4.4 mg/dL; β2 Microglobulin: 0.40±0.23 mg/dL; CystatinC: 0.03±0.02 mg/dL) suggesting a normal renal function,even in the presence of megabladder, suggesting Prune-Belly syndrome. At birth, general conditions were fair with normal biochemical parameters and urinary tract ultrasound. The statistical analysis of biochemical tests of the two patients showed significant differences for Na, K, Cl, Osmolality and CystatinC (P <0.05), but not for creatinine and for β2-Microglobulin (Student’s test). Discussion: The use of echo guided invasive techniques has allowed to consider the fetus as a little patient and invasive approaches can be made with a very low risk-benefit ratio.The biochemical evaluations on fetal urines, have made possible the monitoring of the disease,leading to pregnancies up to 37th and 38th weeks,respectively, with appropriate approach and without aggressive treatment. In conclusion, the biochemical tests have been of great support to the formulation of the diagnosis and to reduce the intra-bladder pressure.