My son aged 26 has received his renal graft from his mother in sep 14. Has cmv infection in Aug 16. Now has uti and pyelonephritis a month back and treated but reoccurrd in 14 days after the end of hospital. Again the gram negative urine culture and cr 3.1 . His baseline cr 1.9 before this. Again started same antbtcs. Dr planning biopsy..is it right to go for biopsy at this point or should we wait for the treatment