Aim: There is conflict in published reports on the extent of availability of the functional renal reserve (RR) in healthy adults and in various stages of chronic kidney disease (CKD). The aim of the present study was to determine the RR in various stages of CKD.
Methods: Baseline glomerular filtration rate (GFR) and 'stimulated GFR' following amino acid infusion were measured in 25 volunteers and 100 patients at various stages of CKD by measuring plasma clearance of Tc99m diethyl triamine pentaacetic acid. Any obtained difference between stimulated and basal GFR was considered as RR and expressed as percentage.
Results: The mean renal reserve was 23.4% in the healthy control group, 19.08% in CKD stage 1, 15.4% in CKD stage 2, 8.9% in CKD stage 3 and 6.7% in CKD stage 4, respectively.
Conclusion: Renal reserve falls relentlessly with progression of CKD from 23.4% in normal to 6.7% in stage 4 CKD. However, RR may also get completely exhausted even with a normal or with a minimal decline basal GFR. Kidneys may retain some RR even up to the GFR level of 15 mL/min.