Is cystatin C a promising parameter to determine postnatal outcome of prenatally diagnosed infravesical obstruction?

PURPOSE: We investigated the prognostic power of cystatin C to determine renal functional outcome in patients with prenatally diagnosed infravesical obstruction.

MATERIALS AND METHODS: A total of 14 fetuses with ultrasound findings of bladder outlet obstruction were enrolled in the study. Amniotic fluid and fetal urine samples were obtained. Controls consisted of 25 fetuses undergoing amniocentesis for obstetrical reasons. Three consecutive bladder punctures were performed to obtain fetal urine samples. In addition to standard prognostic parameters, cystatin C was measured in urine and amniotic fluid samples.

RESULTS: Among the study group 6 pregnancies with poor prognostic parameters were terminated and 5 fetuses died postnatally. Two of 3 fetuses with favorable urinary indices by standard prognostic parameters and relatively low cystatin C levels survived postnatally. Mean serum creatinine was 0.2 mg/dl at 1-year followup after valve ablation. Mean +/- SD fetal urine levels of cystatin C were 1.44 +/- 1.53 mg/l (range 0.05 to 5.62), 1.35 +/- 1.43 mg/l (0.05 to 5.74) and 1.63 +/- 1.46 mg/l (0.05 to 5.89) in consecutive punctures. Mean +/- SD amniotic fluid cystatin C levels were 1.91 +/- 0.46 mg/l (range 1.1 to 2.8) in the study group and 1.12 +/- 0.20 mg/l (0.71 to 1.69) in controls (p = 0.0001). Amniotic fluid cystatin C levels were significantly higher in fetuses with suspected infravesical obstruction (study group and poor prognostic subgroup) compared to controls. There was a significant correlation between fetal urine (second and third punctures) and amniotic fluid in terms of cystatin C level (p = 0.038 and p = 0.04, respectively).

CONCLUSIONS: In fetuses with prenatal ultrasound signs consistent with infravesical obstruction urinary levels of cystatin C progressively increase in consecutive samples. Amniotic fluid may represent fetal urine sample in suspected prenatal infravesical obstruction in terms of cystatin C level. Amniotic fluid cystatin C level was significantly increased in obstructed fetuses compared to normal controls. Cystatin C level in amniotic fluid sample may be sufficient to provide prognostic information in prenatally diagnosed infravesical obstruction.