Renal creatinine handling in very old patients with chronic renal disease

Renal creatinine handling is basically the result of its glomerular filtration and proximal tubular secretion. However, creatinine reabsorption has been documented in certain conditions, such as premature babies, newborns, and healthy elderly people. Additionally, it is known that there is an increase in the proportion of secreted creatinine in chronic renal disease. In this paper, we report our studies on the characteristic reabsorption pattern of creatinine in the elderly with chronic renal disease. We studied twenty-seven volunteers with chronic kidney disease, eleven of whom were young and the rest were very old (age >75 years old). We measured creatinine clearance without (Ccr) and with cimetidine (CcrWC) and Ccr/CcrWC ratio from each volunteer, in timed urine samples. Then, Ccr, CcrWC, and Ccr/CcrWC ratio were compared between young and very old people in two chronic kidney disease subgroups: stages II–III and stages IV–V. Statistical analysis was performed applying a non-parametric test (Wilcoxon). We observed a tendency towards a lower Ccr/CcrWC ratio in the very old stage II–III group compared with the young one: 1 (0.96–1.26) (very old) vs 1.3 (1.1–1.5) (young), P = 0.09, on the contrary, there was no significant difference in Ccr/CcrWC ratio between very old and young person with stage IV–V CKD: 1.66 (1.41–2.21) (young) vs 1.77 (1.1–2.7) (young), P = NS. Creatinine secretion pattern in very old patients with advanced chronic renal disease is similar to that observed in young ones with similar level of CKD.