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CORRESPONDENCE SECTION |
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| Year : 2000 | Volume
: 17
| Issue : 1 | Page : 69-70 |
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The creatinine clearance in the elderly
P Sudhakar1, V Sivakumar2, Durai Sabhapathi3
1 Junior Consultant, Uro-Nephrology, India
2 Senior Addl. Consultant, Uro-Nephrology, India
3 Associate Professor in Statistics, University of Sciences, Philadelphia, USA
Correspondence Address:
Durai Sabhapathi
Sri Sathya Sai Institute of Higher Medical Sciences, Prashantigram, Anantapur District, Andhra Pradesh - 515 134, India
 Source of Support: None, Conflict of Interest: None  | Check |
How to cite this article:
Sudhakar P, Sivakumar V, Sabhapathi D. The creatinine clearance in the elderly. Indian J Urol 2000;17:69-70 |
Sir,
With increasing age in humans, the function of glomeruli decrease resulting in reduction in glomerular filtration rate (GFR). It is estimated that after the age of 30 years, there is a 7.5 to 8 ml/minute decline in GFR per decade. [1],[2] Creatinine clearance (Ccr) is commonly used in clinical medicine to assess GFR. With increasing age when muscle mass comes down, the production of creatinine from muscle creatine comes down, hence serum creatinine can be deceptively low inspite of significant reduction in Ccr. Hence Ccr is considered a better indicator of renal function but not serum creatinine value. [1],[2] In the elderly Ccr estimation helps not only in assessment of renal functional status evaluation but also in prescribing and modifying the drug dosage of nephrotoxic or renal eliminated drugs. Ccr estimation is done by 24-hours' endogenous creatinine clearance estimation conventionally. But this procedure is time consuming and cumbersome and needs accurate collection of urine, needing bladder catheterization and susceptibility to urinary tract infection.
Ccr estimation by Cockcroft and Gault formula is easy and reliable and is the preferred method of estimating creatinine clearance over 24-hours' endogenous creatinine clearance estimation. [1],[3] Cockcroft and Gault formula does not take muscle mass of the individual into consideration while calculating Ccr. Hence application of a correction factor is needed in case of individuals with muscle atrophy. Serum-albumin-related formula for Ccr estimation takes the muscle mass of the individual into consideration in calculating Ccr. [4] We studied all the 3 formulae for Ccr estimation in our patients.
Ten in-patients of Benign Prostatic Hypertrophy of the age range of 56 to 72 years with mean age of 70.5 years were included in this study. None of them had renal insufficiency or urinary tract infection. Ccr was calculated by 3 methods, i.e., 24-hours' endogenous creatinine clearance, calculated creatinine clearance by Cockcroft and Gault formula and Serum-albumin-related formula.
Cockcroft and Gault formula for Ccr estimation in men: [3]
Serum albumin related formula for Ccr calculation in men: [4]
The summary of the results being, number of patients= 10, mean age range 70.5 years, mean serum creatinine 1.148mg%.
One way analysis of variance (ANOVA) statistical technique was used to study the difference between the various procedures of Ccr estimation and it was found that there was no significant differences between the procedures at 5% level concluding that any method is equally suitable for Ccr calculation and the decision to choose a procedure depends on clinician's preference.
In the present study, we emphasize the fact that even when serum creatinine was within normal limits, creatinine clearance can be significantly low in elderly unlike in young. Hence clinician should only depend upon Ccr value but not serum creatinine in decision making. Regarding the choice of method for Ccr calculation, Serumalbumin-related formula may be preferable as it is not only as reliable as other methods but also it takes the patient's muscle mass also into consideration. So the clinician need not make extra effort to assess the patient's muscle mass.
Thus bedside renal function assessment by Ccr estimation helps in planning the type and duration of surgery, type and volume of irrigating fluid to be used in prostatic surgery and also helps in deciding the dose of a drug to be given.
 References | |  |
| 1. | Porush JG, Faubert PF. Effect of age on glomerular filtration rate. In: Porush JG, Faubert PF (eds.). Renal disease in the elderly. Boston: Little Brown 1991: 4-6.  |
| 2. | Baylis C. Schmidt R. The aging glomerulus. Seminars in Nephrology 1996; 16: 265-276. |
| 3. | Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976; 16: 31-41. [PUBMED] |
| 4. | Sanaka M, Takano K, Shimakura K, Kokie Y, Mineshita S. Serum albumin for estimating creatinine clearance in the elderly with muscle atrophy. Nephron 1996; 16: 137-144. |
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