Impaired renal tubular potassium excretion has also been described in sickle cell disease and, in some cases, can result in a tendency toward modest hyperkalemia, which is hyporesponsive to kaliuretic agents such as furosemide. Hyperkalemia can increase as patients age. This condition is due to the increase in urate production associated with accelerated erythropoiesis coupled with a decreased renal clearance of urate. Hyperuricemia in SS disease responds poorly to uricosuric agents, but the uric acid level can be lowered with the use of allopurinol. Uric acid nephropathy is rare, but if recurrent uric acid stone formation occurs, urinary alkalinization with oral sodium bicarbonate is recommended.
Clinical gout is uncommon in sickle cell disease.
The bleeding is usually painless, although clot formation in the renal pelvis or ureter can produce renal colic. It is frequently unilateral, with the left kidney being involved in 80 percent of the cases. It can show a pattern of intermittency, lowgrade chronicity, or persistence. The pathogenic mechanism is thought to be sickling in the vasa recta, which leads to stasis and ischemia, with extravasation of blood into the renal parenchyma and collecting system, or in some cases to micropapillary or macropapillary necrosis. As with all patients who have hematuria, the differential diagnosis in patients with sickle cell disease includes papillary necrosis, glomerulonephritis, tuberculosis, tumor, stones, and urinary tract infection.