Occult renal disease (ORD) is defined as the presence of a glomerular filtration rate <60ml/min, along with normal serum creatinine levels. Only few studies have been aimed to understand what is the long term outcome of patients diagnosed with ORD. Here we report our 5-year follow-up results, concluding that the serum creatinine levels remained normal with reduced glomerular filtration rate (<60ml/min/1.73m2), with no significant variations as compared with baseline.1 In this letter we analyse the results of long-term follow-up.
In the study “Elderly People with Chronic Kidney Disease at Hospital General de Segovia”, which included 80 elderly patients recruited between January and April 2006. In 38 patients the serum creatinine levels was normal (≤1.1mg/dl).2 Those patients diagnosed with ORD were followed during a 10 year period.
Eighteen out of the 80 patients (22.5%), had ORD, they all were women and the mean age was 81.33±6 years. Diabetics were 33.3% and 83.3%had hypertension. Twelve of these 18 patients with ORD died during follow-up. The remaining 6 patients had a mean age of 87.33±6 years at 10 years. They also had no episodes of heart failure or ischaemic heart disease during the course of the study. None of the 18 patients progressed from kidney disease to end-stage kidney disease, so did not require renal replacement therapy.
Baseline and 10-year laboratory test data are shown in Table 1.
Data at baseline and after 10 years of follow-up of 6 patients diagnosed with occult renal disease who are still alive.
| Baseline | Ten years | p value | |
|---|---|---|---|
| Creatinine (mg/dl) | 1.01±0.04 | 1.01±0.23 | NS |
| Glucose (mg/dl) | 129.00±34 | 129.40±52 | NS |
| Potassium (mmol/l) | 4.18±0.38 | 4.86±0.60 | 0.018 |
| Calcium (mg/dl) | 9.56±0.42 | 9.30±0.77 | NS |
| Haematocrit (%) | 40.30±4 | 39.13±6 | NS |
| MDRD (ml/min/1.73m2) | 56.01±2 | 58.12±17 | NS |
NS: not significant.
We consider that 10-year follow-up period is sufficient for kidney disease to manifest clinical signs; our elderly female patients who are still alive continue to present with the same characteristics as those at baseline, i.e., a glomerular filtration rate <60ml/min/1.73m2, stable, as the only renal manifestation, with serum creatinine levels that remain normal. They do not present other manifestations of kidney disease, such as anaemia or hypocalcaemia. On the other hand, those who are still alive at 10 years have a mean age above the current life expectancy for women,3 have been asymptomatic in terms of heart disease, and have not progressed from kidney disease to end-stage kidney disease. As a result, we consider them to be an example of healthy people, and yet they are diagnosed as sick based on the ORD concept.
In conclusion, our elderly patients do not have a hidden kidney disease. The ORD concept should not be used to describe a reduction of GFR in elderly women with normal serum creatinine levels.
Please cite this article as: Heras M, Guerrero MT, Fernández-Reyes MJ, Muñoz A. Enfermedad renal «oculta» en ancianos: ¿deja de ocultarse a los 10 años de seguimiento? Nefrologia. 2017;37:547–548.
