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Diagnosis: Gouty Nephropathy

Gouty nephropathy, also known as uric acid nephropathy, is a series of kidney disorders caused by an increase in uric acid in the serum, which accumulates in the renal tubules and interstitium over a long period of time. Renal damage is a common comorbidity of gout and as kidney function declines, uric acid excretion through the urine is reduced, leading to hyperuricemia (Mei Y, et al. Excess Uric Acid Induces Gouty Nephropathy Through Crystal Formation: A Review of Recent Insights. Front Endocrinol (Lausanne). 2022;13:911968. [PubMed link - full text]).

Acute gouty nephropathy is caused by precipitation of uric acid crystals in tubules, usually collecting ducts. Patients with acute gouty nephropathy present with severe hyperuricemia and acute oliguric or anuric kidney failure. This often occurs secondary to tumor lysis syndrome or crush injury. Uric acid calculi may occur in acute gouty nephropathy in 15%-20% of patients. Chronic gouty nephropathy is related to deposition of monosodium urate crystals primarily in the medulla and is usually seen in patients with gout, chronic hyperuricemia, and hypertension. Light microscopy: Acute gouty nephropathy shows intraluminal clusters of urate crystals in collecting ducts with associated acute tubular injury. Tubulointerstitial inflammation is mild when present. Needle-like birefringent crystals of monosodium urate can be seen in alcohol-fixed or frozen sections. These crystals are dissolved during processing of paraffin-embedded tissue and then appear as needle-like clefts. Chronic gouty nephropathy shows medullary intratubular and/or interstitial microtophi composed of central needle-shaped clefts with surrounding cellular reaction that includes syncytial giant cells, epithelioid macrophages, lymphocytes, and eosinophils. Tubulointerstitial fibrosis is variable (Lusco MA, et al. AJKD Atlas of Renal Pathology: Gouty Nephropathy. Am J Kidney Dis. 2017;69(1):e5-e6. [PubMed link]).

See the chapter: Renal involvement in hyperuricemia and others... of our Tutorial.

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