Acute uric acid nephropathy

Acute uric acid nephropathy (AUAN), also known as acute urate nephropathy, is a rapidly progressive reduction in kidney function (renal insufficiency) that is caused by high levels of uric acid in the urine.

Causes
Acute uric acid nephropathy is usually seen as part of the tumor lysis syndrome in patients undergoing chemotherapy or radiation therapy for the treatment of malignancies with rapid cell turnover, such as leukemia and lymphoma. It may also occur in these patients before treatment is begun, due to spontaneous tumor cell lysis.

Acute uric acid nephropathy can also be caused by an acute attack of gout.

Pathophysiology
Acute uric acid nephropathy is caused by deposition of uric acid crystals within the kidney interstitium and tubules, leading to partial or complete obstruction of collecting ducts, renal pelvis, or ureter. This obstruction is usually bilateral, and patients follow the clinical course of acute renal failure.

Diagnosis
The picture of acute renal failure is observed: decreased urine production and rapidly rising serum creatinine levels. Acute uric acid nephropathy is differentiated from other forms of acute renal failure by the finding of a urine uric acid/creatinine ratio > 1 in a random urine sample.

Prevention
Patients at risk for acute uric acid nephropathy should be treated with allopurinol prior to treatment with cytotoxic drugs.

Treatment
Treatment is focused on preventing deposition of uric acid within the urinary system by increasing urine volume with potent diuretics such as furosemide. The urine must also be alkalinized to pH > 7 using sodium bicarbonate and/or acetazolamide to increase uric acid solubility.

Dialysis (preferably hemodialysis) is started if the above measures fail.