Introduction: Patients with chronic kidney disease (CKD) often continue to progress spontaneously towards end stage renal disease (ESRD). In this report we studied the natural history of progression of CKD in a cohort of patients with stage 4 and 5 CKD.
Methods: We retrospectively studied a cohort of patients in stage 4 and 5 CKD who started their follow up at Sheffield Kidney Institute in the period between January 1999 and July 2004. The glomerular filtration rate (GFR) was estimated using the Modification of Diet in Renal Disease (MDRD) formula. The rate of estimated GFR decline was correlated to different demographic, clinical and laboratory data.
Results: The study group consisted of 152 patients aged 24-89 years. The mean fall of estimated GFR in stage 4 and stage 5 CKD was 2.3 and 1.7 ml/min/year, respectively. Overall, 66.4% of patients progressed towards ESRD with a rate of GFR decline exceeding 1ml/min/year. Male gender and use of sodium bicarbonate were significantly commoner among progressors compared to non-progressors (60.4% versus 47.1% and 45.5% versus 33.3% respectively, P<0.05). Progressors had significantly lower mean age (61±14 versus 67±14 years, P=0.04), higher urinary protein excretion (2.4±2.4 versus 1.4±1.6 g/day, P =0.002), higher calcium-phosphorus product (42.7±9.2 versus 37.5±8.3 mg2/dl2, P= 0.00), lower serum bicarbonate level (23.7±2.9 versus 25.3±3.4 mmol/l, P=0.004) and lower serum cholesterol level (201±35 versus 212±46 mg/dl, P=0.03) compared to non-progressors. Logistic regression analysis confirmed low baseline serum bicarbonate level and high urinary protein excretion as independent predictors of progression to ESRD.
Conclusion: Low serum bicarbonate level and high urinary protein excretion at baseline are independent predictors of progression in stage 4 and 5 CKD.
Keywords: Chronic kidney disease; End stage renal disease; Glomerular filtration rate; Progression