It is unclear why hematuria is more common in patients with sickle cell trait than in those with sickle cell disease, but it is probably related to the much greater prevalence of the former disorder. Hematuria can occur spontaneously or can follow mild trauma, is frequently recurrent, may be microscopic or macroscopic, and is usually unilateral. In most cases, the episode is mild and self-limited, lasting several days to several weeks and requiring no specific therapy. Most patients with this complication are asymptomatic, and renal function is usually unaffected. However, scar formation may predispose to urinary tract infections.
Renal infarcts can occur in patients with sickle cell disease or sickle cell trait.
This defect in concentrating ability is reversible after multiple blood transfusions in patients who are homozygous for the sickle gene and younger than 10 to 15 years, but it is irreversible in older patients. These changes are much less severe and occur at older ages in patients with sickle cell trait or sickle cell-hemoglobin C disease. The principal symptom caused by the impaired ability to concentrate the urine is polyuria. This effect may be particularly bothersome at night. Tubular damage in the cortical collecting tubule, which is the site of potassium secretion and of maximum urinary acidification, can lead to hyperkalemia and metabolic acidosis.