Renal function in patients over 40 with homozygous sickle-cell disease.

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Abstract
Renal function was examined in 25 patients aged 40-64 with homozygous sickle-cell (SS) disease. Investigations included intravenous urography and measurement of blood urea and creatinine concentrations and creatinine and protein excretion in 24-hour collections of urine. Serum creatinine concentrations did not differ significantly from those of 25 other patients with SS disease aged 18-39 years, but serum urea concentrations were significantly higher (p less than 0.001). Intravenous urography showed loss of caliceal cupping (nine patients), irregular renal outline (five), and cystic extension from the calix (one). Six patients had creatinine clearances below the fifth percentile for age and sex. Proteinuria was more common in these patients, and haemoglobin concentrations were much lower than in the 19 patients without renal insufficiency (mean 5.6 v 8.2 g/dl; p less than 0.001). Haemoglobin concentration was strongly correlated with creatinine clearance (r=0.70), particularly with clearances below 100 ml/min/1.73 m2 (r=0.96; p less than 0.001). A possible mechanism of renal insufficiency in SS disease is cortical scarring, which is asymptomatic, not associated with hypertension, and accompanied by only minor proteinuria. A falling haemoglobin concentration is a sensitive and early indicator of renal impairment in SS disease.