Acute uric acid nephropathy (AUAN, also acute urate nephropathy) is a rapidly worsening (decreasing) kidney

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

 function (renal insufficiency) that is caused by high levels of uric acid

Uric acid

Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates such as ammonium acid urate. Uric acid is created when the body breaks down purine nucleotides. High blood concentrations of uric acid...

 in the urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 (hyperuricosuria

Hyperuricosuria

Hyperuricosuria is a medical term referring to the presence of excessive amounts of uric acid in the urine. Notable direct causes of hyperuricosuria are dissolution of uric acid crystals in the kidneys or urinary bladder, and hyperuricemia...

).

Causes

Acute uric acid nephropathy is usually seen as part of the tumor lysis syndrome

Tumor lysis syndrome

In medicine , tumor lysis syndrome is a group of metabolic complications that can occur after treatment of cancer, usually lymphomas and leukemias, and sometimes even without treatment...

 in patients undergoing chemotherapy or radiation therapy for the treatment of malignancies with rapid cell turnover, such as leukemia

Leukemia

Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

 and lymphoma

Lymphoma

Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...

. It may also occur in these patients before treatment is begun, due to spontaneous tumor cell lysis (high incidence in Burkitt's lymphoma).

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

Gout

Gout is a medical condition usually characterized by recurrent attacks of acute inflammatory arthritis—a red, tender, hot, swollen joint. The metatarsal-phalangeal joint at the base of the big toe is the most commonly affected . However, it may also present as tophi, kidney stones, or urate...

.

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

Acute renal failure

Acute kidney injury , previously called acute renal failure , is a rapid loss of kidney function. Its causes are numerous and include low blood volume from any cause, exposure to substances harmful to the kidney, and obstruction of the urinary tract...

.

Diagnosis

The picture of acute renal failure is observed: decreased urine production and rapidly rising serum creatinine

Creatinine

Creatinine is a break-down product of creatine phosphate in muscle, and is usually produced at a fairly constant rate by the body...

 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 can be given allopurinol

Allopurinol

Allopurinol is a drug used primarily to treat hyperuricemia and its complications, including chronic gout.- Mechanism of action :...

 or rasburicase

Rasburicase

Rasburicase is a recombinant version of a urate oxidase enzyme that occurs in many mammals but not in humans.-Uses:Rasburicase is approved for use by the U.S...

 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

Furosemide

Furosemide or frusemide is a loop diuretic used in the treatment of congestive heart failure and edema. It is most commonly marketed by Sanofi-Aventis under the brand name Lasix...

. Raising the urinary pH to a level higher than 7 (alkalinization) is often difficult to attain, although sodium bicarbonate

Sodium bicarbonate

Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...

 and/or acetazolamide

Acetazolamide

Acetazolamide, sold under the trade name Diamox, is a carbonic anhydrase inhibitor that is used to treat glaucoma, epileptic seizures, Idiopathic intracranial hypertension , altitude sickness, cystinuria, and dural ectasia...

are sometimes used in an attempt to increase uric acid solubility.

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