Urinary beta 2-microglobulin as a marker for vesicoureteral reflux.

To determine whether urinary beta 2-microglobulin (beta 2 M) excretion would be elevated in patients with severity of vesicoureteral reflux, urinary beta 2 M/creatinine (Cr) ratios were measured on random urine samples in 56 children with various grades of reflux. Results were compared with ratios of 39 nonrefluxing patients matched for age and gender. Patients with evidence of renal insufficiency or urinary tract infection were excluded. Bladder urine was obtained at the time of the vesicoureterogram. Reflux was graded using the International Reflux Classification System. The mean urinary beta 2 M/Cr ratio was higher in the refluxing group (1.82 +/- 0.6 micrograms/mg Cr) than in the nonrefluxing control group (0.54 +/- 0.09 microgram/mg Cr. P < 0.01). When the mean urinary beta 2 M/Cr ratios were compared for each grade of reflux with the nonrefluxing control group, patients with grade IV and V reflux had significantly higher urinary beta 2 M/Cr values than the nonrefluxing patients (2.83 +/- 0.71 micrograms/mg Cr and 4.61 +/- 0.65 micrograms/mg Cr, P < 0.001, respectively). No patient with grade I, II, or III reflux had a urinary beta 2 M/Cr ratio above 0.92 microgram/mg Cr. Statistical analysis revealed no significant differences among the mean beta 2 M/Cr ratio for grade I (0.53 +/- 0.08), II (0.51 +/- 0.09), or III (0.59 +/- 0.17) refluxers or the nonrefluxing controls. Therefore, urinary beta 2 M/Cr ratios are increased in children with a high grade of reflux. Such values may be useful in the early detection of tubular damage in patients with vesicoureteral reflux.