Abstract
Patients with sickle cell anemia (Hb SS) or sickle cell trait (Hb AS) may present several types of renal dysfunction; however, comparison of the prevalence of these abnormalities between these two groups and correlation with the duration of disease in a large number of patients have not been thoroughly investigated. In a cross-sectional study using immunoenzymometric assays to measure tubular proteinuria, microalbuminuria, measurement of creatinine clearance, urinary osmolality and analysis of urine sediment, we evaluated glomerular and tubular renal function in 106 adults and children with Hb SS (N = 66) or Hb AS (N = 40) with no renal failure (glomerular filtration rate (GFR) > 85 ml/min). The percentage of individuals with microalbuminuria was higher among Hb SS than among Hb AS patients (30 vs 8%, P < 0.0001). The prevalence of microhematuria was similar in both groups (26 vs 30%, respectively). Increased urinary levels of retinol-binding protein or beta 2-microglobulin were detected in only 3 Hb SS and 2 Hb AS patients. Urinary osmolality was reduced in patients with Hb SS or with Hb AS; however, it was particularly evident in Hb SS patients older than 15 years (median = 393 mOsm/kg, range = 366-469) compared with Hb AS patients (median = 541 mOsm/kg, range = 406-722). Thus, in addition to the frequently reported early reduction of urinary osmolality and increased GFR, nondysmorphic hematuria was found in 26 and 30% of patients with Hb SS or Hb AS, respectively. Microalbuminuria is an important marker of glomerular injury in patients with Hb SS and may also be demonstrated in some Hb AS individuals. Significant proximal tubular dysfunction is not a common feature in Hb SS and Hb AS population at this stage of the disease (i.e., GFR > 85 ml/min).
Highlights
The kidney of the homozygous sickle cell anemia (Hb SS) patient is affected by the hemodynamic changes of chronic anemia and by the consequences of vaso-occlusion, especially in the renal medulla [1,2]
In a cross-sectional study using immunoenzymometric assays to measure tubular proteinuria, microalbuminuria, measurement of creatinine clearance, urinary osmolality and analysis of urine sediment, we evaluated glomerular and tubular renal function in 106 adults and children with Hb SS (N = 66) or Hb AS (N = 40) with no renal failure (glomerular filtration rate (GFR) >85 ml/min)
In children and young adults the glomerular filtration rate (GFR) exceeds the normal value; there is a gradual decrease in GRF which may result in chronic renal failure associated or not with glomerular changes
Summary
The kidney of the homozygous sickle cell anemia (Hb SS) patient is affected by the hemodynamic changes of chronic anemia and by the consequences of vaso-occlusion, especially in the renal medulla [1,2]. In children and young adults the glomerular filtration rate (GFR) exceeds the normal value; there is a gradual decrease in GRF which may result in chronic renal failure associated or not with glomerular changes. The contribution of the deteriorating glomerular function to morbidity and mortality in older patients has not been widely recognized [5,6]. While asymptomatic and relatively common, proteinuria seems to be associated with reduced creatinine clearance in Hb SS patients older than 40 years
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