Deposition of calcium in the renal parenchyma, tubules and interstitium
Classification:
- Microscopic (biopsy) vs macroscopic (imaging)
- Cortical (2 %) or medullary (98 %)
- Calcium oxalate (oxalosis) or calcium phosphate
Pathogenesis
Usually associated with hypercalciuria, with or without hypercalcaemia, hyperphosphaturia and hyperoxaluria.
Often seen in conjunction with stones/nephrolithiasis, but stones can occur without nephrocalcinosis, and vice versa.
Pathogenesis may be from Randall plaque formation (calcium phosphate crystals forming at Loop of Henle) which enlarge into surrounding interstitial tissue (or erode into collecting system forming stones).
Cortical nephrocalcinosis is rare (2 %) and caused by systemic conditions like primary oxalosis, chronic glomerulonephritis and renal cortical necrosis.
Medullary nephrocalcinosis is the common form and associated with:
- Hypercalciuria
- Hypercalcaemia
- Hyperphosphaturia
- Hyperparathyroidism
- Sarcoidosis
- Distal RTA
- Medullary sponge kidney
- Vitamin D excess
- Milk alkali syndrome
- Prolonged frusemide or loop diuretics
Clinical features
Often asymptomatic and found incidentally on imaging.
May present with renal colic or renal stones.
Occasionally can present with renal failure due to underlying cause (tumour lysis syndrome, phosphate nephropathy, hyperoxaluria).
Imaging
- Calcifications within the renal pyramids on ultrasound or CT
Evaluation
Determine the underlying cause in conjunction with a renal physician:
- Sarcoidosis
- Primary hyperparathyroidism
- Distal RTA
- Medullary sponge kidney
Tests may include routine bloods including CMP, urine analysis and culture, urine pH, 24 hour urine analysis, PTH levels, CXR looking for sarcoidosis, RTA testing etc.
Prognosis
Depends on underlying cause – some are reversible, some cause no long lasting renal impairment and some are associated with progression to renal failure (primary hyperoxaluria, Dent’s disease etc).