Use of urinary beta-2-microglobulin to predict severe renal damage in fetal obstructive uropathy

Purpose: Establish a clinically relevant threshold for urinary beta(2)-microglobulin (beta(2)m) to predict the presence of several renal damage in fetuses with obstructive uropathies. Methods: Retrospective review was conducted of urinary beta(2)m levels, clinical outcomes, and pathological findings in 36 fetuses evaluated for presumed obstructive uropathy. Patients were divided into those free of renal injury (group 1, n = 13) and those with clinical or pathological evidence of severe irreversible renal injury (group 2, n = 23). Results: Including all patients, a threshold beta(2)m value of >6 was able to predict the presence of severe renal damage with a 83% sensitivity and 71% specificity. beta(2)m levels tended to decrease with increasing gestational age among those patients without renal injury (group 1), while beta(2)m levels increased among those with severe renal damage (group 2). There was no difference in mean beta(2)m levels in those <20 weeks (p = 0.065) while there was a high degree of difference in those >20 weeks of gestation (p < 0.001). In those >20 weeks, a threshold of >10 predicted the presence of severe renal damage with 100% sensitivity and specificity. Conclusions: Urinary beta(2)m, especially in the fetus >20 weeks, may be a clinically useful marker to detect the presence of severe renal damage due to obstructive uropathy and thus be an important adjuvant in the proper selection of fetuses for antenatal intervention.