Outcomes in Fetal Lower Urinary Tract Obstruction: Analysis of Fetal Urinary Biochemistry and Ultrasound Features in Fetuses with and without Additional Upper Renal Tract Involvement

Author(s): Bijoya Mukherjee, Urvashi Chhikara, Dr Sujit Chowdhury, Akshatha Sharma, Anita Kaul*

Objective: We wished to assess if fetal urinary biochemistry assessment can improve the prediction of postnatal renal outcomes over traditional ultrasound features of renal cortical appearance, shape of bladder and amniotic fluid volume in fetuses with no upper renal tract involvement in antenatally diagnosed LUTO.

Methods: Retrospective analysis of data was done for 58 cases of LUTO over a period of 10 years. All cases of live births were subdivided into two groups: fetuses with upper renal tract involvement (hydronephrosis) and those with none. The outcome measures included stillbirths, neonatal deaths, live births with poor renal outcome (serum creatinine >60umol/L at minimum 2 years age) and live births with good long term renal outcome (serum creatinine <60umol/L at minimum 2 years age). Statistical analysis was done to determine the diagnostic accuracy of B2 microglobulin and ultrasound features in predicting postnatal outcome in both the groups.

Results: High B2 microglobulin was a good predictor of poor postnatal outcome irrespective of presence or absence of upper renal tract involvement. Among the ultrasound markers renal dysplasia or presence of renal cortical cysts faired as a good predictor (AUC 0.706) while morphology of bladder (floppy bladder) and amniotic fluid volume had low predictive accuracy (AUC 0.553 and AUC 0.595 respectively). Thus addition of B2 microglobulin in cases of LUTO improves the predictive accuracy of poor renal function, even in cases where there is no upper renal tract involvement and we generally expect a good postnatal outcome.

Conclusion: Inclusion of B2 microglobulin in antenatally detected cases of LUTO can improve the accuracy of expected postnatal outcome, and hence combination of ultrasound and B2 microglobulin should be used in all antenatally detected cases of LUTO.