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Table 1 Summary of the pros and cons of different fetal parameters used to predict postnatal renal function and select candidates for antenatal intervention

From: Antenatal and postnatal management of posterior urethral valves: where do we stand?

Fetal parameters Pros Cons
Fetal bladder urinary electrolytes (urinary sodium > 100 mEq/L, chloride > 95 mEq/L, osmolarity > 210 mOsm/L)
 Sensitivity 40–100%
 Specificity 80%
Have been widely studied Invasive
Repeated sampling is usually required
Variable reference ranges
Levels vary with gestational age
Conflicting data on diagnostic performance
Fetal urinary ẞ2-mircroglobulin
 Sensitivity 57–81%
 Specificity 80–89%
Reflect glomerular damage Invasive
Variable reference ranges
Levels vary with gestational age
Fetal serum ẞ2-mircroglobulin Can be used to reflect the recoverability of fetal renal function following antenatal intervention Invasive
Technically difficult
More risky than fetal bladder urine sampling early in pregnancy
Variable reference ranges
Levels vary with gestational age
Fetal ultrasound (severity of hydronephrosis, gestational age at diagnosis, cortical echogenicity, cortical cysts, amniotic fluid volume)
 Sensitivity 57–66%
 Specificity 84–100%
Noninvasive
Widely available
Sedation is not required
Renal cortical appearance is highly predictive of renal dysplasia on autopsy or biopsy and is a good predictor of postnatal renal function
Limited specificity in distinguishing PUV from other causes of fetal lower urinary tract obstruction
Results are limited by maternal obesity, fetal movements, oligohydramnios and operator expertise
Gestational age at diagnosis, hydronephrosis and megacystis are poor predictors of postnatal renal function
Amniotic fluid volume does not reflect renal function in the first trimester
Renal parenchymal architecture is difficult to assess early in pregnancy (before 22–23 weeks)
Fetal MRI Better anatomic details
More reliably distinguish PUV from other causes of fetal obstructive uropathy
ADC of the fetal renal parenchyma has been used to predict postnatal renal function
Maternal sedation is sometimes required
Performing MRI late in pregnancy limits its value as a predictive tool for antenatal intervention
Fetal urinary omics
 Sensitivity 50–88%
 Specificity 68–95%
Better sensitivity and specificity for prediction of postnatal renal insufficiency Invasive
Expensive
Still investigational
Cutoff values do not exist
  1. ADC: apparent diffusion coefficient, MRI: magnetic resonance imaging, PUV: posterior urethral valve