Crystal nephropathies and nephrocalcinosis
- Lesion
Uric acid, calcium and oxalate can precipitate in tubules and interstitium, blocking them or causing chronic scarring.
What it is
Crystals injure the kidney in three ways: by blocking tubules suddenly, by depositing in the interstitium and inciting chronic inflammation, and by forming stones. Acute urate nephropathy follows massive cell death in tumour lysis; chronic urate nephropathy is seen in long-standing gout. Hypercalcemia from hyperparathyroidism, myeloma, sarcoidosis, vitamin D excess or bone metastases causes calcium deposits (nephrocalcinosis) and concentrating defects. Oxalate deposits come from primary hyperoxaluria, gut fat malabsorption and ethylene glycol.
Structure
- Urate crystals dissolve in aqueous fixatives and leave clefts; alcohol fixation preserves them for polarized light.
- Tophi: crystal clusters surrounded by macrophages, foreign-body giant cells, lymphocytes and fibrosis.
- Calcium deposits stain dark purple on H&E and black with von Kossa.
- Calcium oxalate crystals are fan- or sheaf-shaped and strongly birefringent.
Crystal nephropathies
| Disorder | Setting | Kidney lesion |
|---|---|---|
| Acute urate nephropathy | Tumour lysis after chemotherapy | Crystals obstruct collecting ducts; acute kidney injury |
| Chronic urate nephropathy | Long-standing gout | Medullary tophi, chronic interstitial nephritis |
| Nephrocalcinosis | Hypercalcemia (hyperparathyroidism, myeloma, sarcoidosis, vitamin D excess) | Calcium in tubules and interstitium, polyuria, stones |
| Oxalate nephropathy | Primary hyperoxaluria, enteric hyperoxaluria, ethylene glycol | Oxalate crystals in tubules, acute or chronic injury |
Clinical notes
- Prevention of tumour lysis (hydration and lowering uric acid) protects the kidney during chemotherapy of bulky tumours.
- Hypercalcemia causes polyuria and thirst because calcium blunts the response to ADH.
Test yourself
Think of the answer, then tap the question to see it.
What causes acute urate nephropathy?
Massive release of uric acid after rapid cell death, typically during chemotherapy of leukemia or lymphoma, which precipitates in collecting ducts.
Why does nephrocalcinosis cause polyuria?
Calcium injures tubules and blunts the collecting duct response to ADH, so the urine cannot be concentrated.
What crystals are found in ethylene glycol poisoning?
Calcium oxalate crystals in tubules and in the urine.
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Renal Calculi, Nephrolithiasis (StatPearls (NCBI Bookshelf), 2024).
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Representative model, for educational purposes only.