Biopsies in renal transplant patients with proteinuria: histological findings

Abstract

Introduction: Proteinuria is related to a poor prognosis for graft survival.

Materials and methods: We undertook a retrospective study of renal transplant biopsies between 2006 and 2009 performed because of proteinuria. Data were collected on demographic, analytical, and histological characteristics.

Results: The study included 49 biopsies from 65% men with an overall mean age of 52 ± 13 years. The mean time from transplant to biopsy was 6.5 ± 5.3 years. All cases displayed proteinuria: 2.2 g/24 h (1.2-3.2). In 56% of cases, it was also associated with worsening glomerular filtration rate (GFR) (MDRDa 33 ± 16 mL/min). In 14% of cases, the sample was insufficient to determine glomerular pathology, whereas 51% displayed glomerular disease, among which were transplant glomerulopathy (40%), glomerulonephritis (48%), and diabetes (12%). Interstitial fibrosis and tubular atrophy (IFTA) was present in 85%: 33% mild, 27% moderate, and 25% severe. Arteriolar hyalinosis was present in 60%. Thirty-four percent of subject lost their grafts at a mean of 11 ± 9 months after the biopsy. The GFR at the time of biopsy was worse among those subjects who returned to dialysis than those who retained function (MDRDa 22 ± 7.5 vs 34 ± 15 mL/min; P = .006). Proteinuria was also greater among those who lost their grafts (4.1 ± 3.4 vs 2.1 ± 1.6 g/24 h; P = .007). The absolute increase in the risk of graft loss was 52% among subjects who displayed moderate to severe versus those who had mild IFTA (relative risk [RR] 7; confidence interval [CI] 1.8-28; P < .001). The presence of glomerulosclerosis >50% was also associated with a 48% absolute increased risk of graft loss compared with those patients with no glomerulosclerosis or <50% (RR 3; CI 1.5-12; P = .02). After the biopsy, the dose of angiotensin converting enzyme inhibitors and/or angiotensin receptor antagonist was increased in 90%, with 34% of subjects, experiencing a change in immunosuppression.

Conclusions: Transplant patients undergoing a biopsy due to proteinuria, the occurrence of graft loss was associated with reduced GFR and the amount of proteinuria at the time of the biopsy, as well as with the degree of IFTA and of glomerular involvement.