Sickle cell nephropathy

Renal Tubular Acidoses, Types I and II These syndromes are predominantly characterized by loss of bicarbonate because of decreased tubular secretion of (distal or type I RTA) or decreased reabsorption of HCO3 (proximal or type II RTA). Because the major urine-acidifying power of the kidneys rests in the distal tubules, the proximal and distal RTAs may be differentiated by measurement of urine pH. In proximal RTA, urine pH becomes <5.5, whereas in distal RTA the distal tubules are compromised and urine pH is >5.5. When distal RTA is associated with obstructive nephropathy, sickle cell disease, or systemic lupus erythematosus, hyperkalemia may... 

De long PE, Statius van Eps LW. Sickle cell nephropathy new insights into its pathophysiology. Kidney Int 1985 27 711-719. Allen M, Lawson L, Eckman IR, Delaney V, Bourke E. Effects of nonsteroidal anti-inflammatory drugs on renal function in sickle cell anemia. Kidney Int 1988 34 500-506. 

Hyperkalemic distal (type IV) RTA resulting from generalized distal tubule defects is less common than hyporeninemic hypoaldosteronism, but is more common than classic distal (type I) RTA. Patients with this defect have impaired tubular potassium secretion in addition to impaired urinary acidification (urine pH >5.5 despite acidemia or acid loading). Urinary obstruction is the most frequent cause of this disorder, which may also be associated with sickle-cell nephropathy, systemic lupus erythematosus, HIV nephropathy, analgesic abuse nephropathy, amyloidosis, renal transplant rejection, and chronic cyclosporine nephrotoxicity. 

De long PE, Statius van Eps LW. Sickle cell nephropathy new insights into its pathophysiology. Kidney Int 1985 27 711-719. 

Hyperuricemia, uric acid overproduction, and hyperuricosuria are frequent clinical features of sickle cell anemia. Uric acid overproduction may result in hyperuricemia in some patients with sickle cell anemia. However, in other patients, enhanced urate excretion permits maintenance of a normal serum uric acid despite uric acid overproduction. Hyperuricosuria in normouricemic patients with sickle cell anemia may result from enhanced tTobular secretion of urate but is more likely to represent diminished urate reabsorption at a post-secretory site. Hyperuricosuria may protect the young patient with sickle cell anemia from gouty arthritis and tophi but may also increase the risk of tubular deposition of urate and nephropathy. 

A 43-year-old woman with sickle cell nephropathy and hypertension, who had undergone peritoneal dialysis for 1 year, had been given repeated blood transfusions and erythropoietin, leading to severe iron overload. She was given deferasirox 20 mg/kg/day, and her other medications included allopurinol, amlodipine, atenolol, darbepoetin alfa, folic acid, lanthanum carbonate, lisinopril, and losartan. The... 

Fig. 19.7a,b. Renal sonography in sickle cell disease, a Increased echogenicity of the medulla with consecutively inverted corticomedullary differentiation. In the absence of hypercalciuria, this pattern is typical for sickle cell nephropathy. b Amplitude-coded color Doppler sonography of the right kidney (cross section) shows a segmental parenchymal area without colour signals (arrow), consistent with a renal infarction in sickle cell disease... 

Treatment of sickle cell nephropathy is directed to prevent vaso-occlusive crises and to manage renal complications adequately. As a prophylactic measure, altitudes above 2,500 m without oxygen supply should be avoided as well as heavy exercise and fluid deprivation. Bed rest is recommended in gross haematuria, sometimes combined with intravenous fluids and diuretics. ACE inhibitors eventually can diminish proteinuria and ameliorate the progressive course of nephropathy. Renal transplantation seems to be a viable option for adolescents with end-stage renal disease (Warady and Sullivan 1998). 

Saborio P, Scheinman JI (1999) Sickle cell nephropathy. J Am Soc Nephrol 10 187-92... 

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