Fetal serum beta2-microglobulin before and after bladder shunting: a 2-step approach to evaluate fetuses with lower urinary tract obstruction.

Purpose: The evaluation of renal function in fetuses with lower urinary tract obstruction by analysis of electrolytes and beta2-microglobulin in fetal urine has limitations. We measured fetal serum beta2-microglobulin before and after bladder shunting to evaluate renal function.

Materials And Methods: A total of 12 fetuses with lower urinary tract obstruction underwent vesicoamniotic shunting. In addition to the standard evaluation of urinary electrolytes and beta2-microglobulin, fetal renal status was assessed by pre-shunt and post-shunt fetal serum beta2-microglobulin.

Results: At 2 to 4 weeks after shunting 2 of the 12 fetuses had persistent oligohydramnios, demonstrated increased values of serum beta2-microglobulin and were confirmed to have renal dysplasia. In the remaining 10 fetuses there was reaccumulation of amniotic fluid for a minimum of 4 weeks after shunting. Serum beta2-microglobulin values increased after shunting in 4 fetuses, all of which developed renal failure, whereas serum beta2-microglobulin did not change or was decreased after shunting in 6, of which 4 had normal renal function at latest followup.

Conclusions: Urinary electrolytes, urinary beta2-microglobulin and pre-shunt serum beta2-microglobulin, whether increased or normal, failed to be predictive of potential response to prenatal intervention. Serial samples of fetal blood may provide distinction between patients who do and do not respond to prenatal treatment of lower urinary tract obstruction.