Children with sickle cell anemia or sickle cell trait may show an inability to concentrate the urine (hyposthenuria).
The key feature of hyposthenuria is an inability to concentrate urine to > 450 mOsm per kg water when water deprived.
Proposed pathogenesis: reduction in the vasa recta in inner medulla of the kidneys with loss of the exchange system of the inner medulla (Pham et al).
Complications:
(1) nocturia and enuresis
(2) dehydration, especially when ill
Interventions that can reduce the hyposthenuria in children:
(1) blood transfusion
(2) hydroxyurea
While potentially reversible in children it eventually becomes irreversible. The rate of decline in maximum urinary osmolality with age is -0.71 per year (Francis and Worthen).
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