How relevant and frequent is the presence of mild renal insufficiency in essential hypertension?

Recent analyses of the influence of renal function on the cardiovascular outcome in essential hypertensive patients have confirmed the relevance of the kidney in cardiovascular prognosis even in the initial stages of renal failure. The evaluation of renal function in clinical practice is based mainly on the finding of changes in serum creatinine, but the estimation of creatinine clearance or its determination after 24-hour urine collection is not usually performed. The objective of this study was to analyze the prevalence of mild chronic renal insufficiency (MCRI) through the determination of creatinine clearance in patients with essential hypertension to reinforce the need to consider using this parameter in daily clinical practice. We analyzed clinical and biochemical data from 2686 essential hypertension patients referred to our unit from 1979-1999. MCRI was defined as a serum creatinine > or =1.5 mg/dL in men and > or =1.4 mg/dL in women, or a creatinine clearance estimated by the Cockroft-Gault formula or by a 24-hour urine collection of <60 mL/min. A prevalence of MCRI was found in 7.6% according to serum creatinine levels. This prevalence increased to 22.3% and 21.5% respectively when the diagnostic criteria for MCRI was the estimation of 24-hour creatinine clearance in urine, or its estimation using the Cockroft-Gault formula. When classified by creatinine clearance values, patients with MCRI were characterized by older age, elevated systolic blood pressure, higher serum total cholesterol, low-density lipoprotein cholesterol, and triglycerides, lower levels of high-density lipoprotein cholesterol, higher serum uric acid, fasting serum glucose, serum potassium, and higher levels of urinary albumin excretion. In summary, MCRI is more prevalent in essential hypertension than previously thought, particularly if the estimated creatinine clearance is used to define MCRI. The finding of an altered renal function is associated with a significant increase in cardiovascular risk. This fact reinforces the need to pay attention to any of the manifestations of renal damage observed in the usual clinical assessment of any hypertensive patient.