Cortical morphologic changes in kidneys of patients with sickle cell anemia include vascular dilatation and engorgement of vessels with red blood cells, glomerular enlargement, hypertrophy and hypercellularity of glomerular mesangial cells, and iron deposits in various glomerular and tubular structures. Occasionally, glomerular sclerosis develops, with resultant end-stage renal failure. In the renal medulla, vascular congestion, edema, focal scarring, and occasional papillary necrosis are seen. Vascular dilatation and engorgement also occur in renal pelvis submucosa, where vessel rupture may cause hematuria. Young patients with sickle cell anemia have increased total renal blood flow while medullary blood flow is probably decreased. Glomerular filtration rate is also increased in young patients. A renal concentrating defect is reversible in younger age groups, becoming irreversible in older patients.