R GERMANN, K RABINDRANATH
Waikato Hospital, Hamilton, New Zealand
Aim: To review all kidney biopsies done at a single centre in patients with non-nephrotic range proteinuria (NNRP) to ascertain whether the renal histology resulted in a signiﬁcant change in clinical management or unexpected
diagnosis of a systemic disease.
Background: Persistent nephrotic range proteinuria is a widely accepted indication for kidney biopsy. However when the protein excretion rate is less than 3.5g/day and laboratory testing for systemic diseases (e.g. lupus) or a monoclonal gammopathy is negative, the indication to do a kidney biopsy is less clear.
Methods: All patients who had a kidney biopsy at Waikato Hospital between January 2011 and June 2015 with NNRP (PCR 3-350 mg/mmol or ACR 3260 mg/mmol) and an eGFR of greater than 30ml/min/1.73m2 were included. Exclusion criteria were: AKI, rapidly progressive CKD, hypoalbuminaemia, diabetes, a monoclonal gammopathy or serological testing suggesting an underlying systemic disease or viral infection. Descriptive statistics were used to analyse clinical parameters, the renal histology and resulting changes in clinical management.
Results: Of 339 native biopsies screened, 109 biopsies were included. 62 were excluded based on the exclusion criteria. No patients were diagnosed with an unexpected systemic disease and 2 of 47 were commenced on steroids based on the renal histology. One of these patients had interstitial nephritis and the other IgA nephropathy.
Conclusion: In our study, performing a kidney biopsy in patients with NNRP and relatively stable renal function was unlikely to result in a signiﬁcant change in management or identify a systemic disease that could not be detected through laboratory tests. This study will help inform physicians of the pre-test probability for a change in management resulting from a kidney biopsy in patients with NNRP.