Renal Reserve in the Oldest Old

Introduction: Decline in glomerular filtration rate (GFR) is one of several changes in renal physiology in the elderly. Renal reserve (RR) is the kidney's capacity to increase its basal GFR by at least 20% after a protein overload. Even though it has already been reported that RR is preserved in healthy old people, there is no information whether RR is also preserved in the healthy very old one (older than 74 of age), which we decided to study and report our findings in this paper.

Material And Method: We studied RR in 16 healthy persons divided into three age groups: young: 20-40 years old (n: 5): 64-74 years old (n: 6) and oldest old: >74 years old (n: 5). Renal reserve test was performed by assessing creatinine clearance with cimetidine before and after an oral protein load. Statistical analysis was performed using ANOVA test.

Results: Even though renal reserve response was present in all age groups, its magnitude (delta GFR) was significantly higher in the healthy young group (103.6 ± 53 ml/min) compared to the old one (34.1 ± 40 ml/min) (P = 0.002), while it was significantly lower in the healthy oldest old (20.7 ± 0.7 ml/min) group compared to the other two groups (P = 0.002).

Conclusion: Renal reserve is preserved in healthy very old people, but its magnitude decreases significantly with age.