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Nephrocalcinosis is the generalized deposition of calcium salts within the renal parenchyma, usually in the medulla but sometimes in the cortex. It is distinct from nephrolithiasis (renal calculi), which refers to discrete stones in the collecting system.
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Mechanism: Calcium deposition occurs due to hypercalcemia, hypercalciuria, or both, often with impaired renal handling.
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Causes
| Medullary nephrocalcinosis (commonest) | Cortical nephrocalcinosis (less common, usually severe disease) | | --- | --- | | • Hyperparathyroidism (primary, tertiary) • Distal renal tubular acidosis (type 1 RTA) • Medullary sponge kidney • Hypervitaminosis D • Sarcoidosis • Milk-alkali syndrome • Chronic hypercalciuria (idiopathic, loop diuretics) | • Chronic glomerulonephritis. • Cortical necrosis (ischemic, obstetric, hemolytic-uremic syndrome). • Oxalosis (primary hyperoxaluria). • Renal tuberculosis. • Alport syndrome. |
Medullary Nephrocalcinosis || Ultrasound || Case 128
| Modality | Imaging features |
|---|---|
| XR | • Multiple tiny punctate or confluent calcifications, usually bilateral. |
| • Medullary nephrocalcinosis: calcification in renal pyramids. | |
| • Cortical nephrocalcinosis: thin rim or patchy peripheral calcification. | |
| US | • Medullary: echogenic pyramids with posterior acoustic shadowing (resembles “bright pyramids”). |
| • Cortical: echogenic cortical bands or rims. | |
| CT | • High-attenuation deposits in medulla (pyramidal distribution) or cortex. |
| • Detects early calcification not visible on X-ray/US. | |
| MR | Limited role; calcifications appear as signal voids. |
![Nephrocalcinosis refers to generalized deposition of calcium (i.e., calcium oxalate or calcium phosphate) within the renal parenchyma which may be caused by a variety of etiologies. It is an insidious process that is preceded by microscopic accumulation of calcium before it becomes evident on imaging. When parenchymal calcifications are identified, radiologists should first determine whether they are predominantly medullary, predominantly cortical, or combined (i.e., both medullary and cortical). Additionally, one should be mindful of common mimics of nephrocalcinosis, as will be discussed. Medullary nephrocalcinosis (97% of cases) is much more common than cortical nephrocalcinosis (< 3%); the combined form of medullary and cortical nephrocalcinosis is extremely rare (< 1%), although these data are based on a study from 1976 [4]. Given the rarity of combined medullary/cortical nephrocalcinosis and the significantly higher prevalence of medullary nephrocalcinosis, the possibility of medullary nephrocalcinosis with associated cortical atrophy producing the spurious appearance of combined medullary/cortical nephrocalcinosis should be considered when encountering an apparent case of combined medullary/cortical nephrocalcinosis.
****Thomas, J., Ludwig, D.R., Ballard, D.H. et al. Spilling the beans: an inside scoop on the imaging of renal parenchymal disease. Abdom Radiol 47, 2420–2441 (2022). https://doi.org/10.1007/s00261-022-03540-2](attachment:ce3c2cd0-bff0-40f2-9461-f1c77c7c165b:image.png)
Nephrocalcinosis refers to generalized deposition of calcium (i.e., calcium oxalate or calcium phosphate) within the renal parenchyma which may be caused by a variety of etiologies. It is an insidious process that is preceded by microscopic accumulation of calcium before it becomes evident on imaging. When parenchymal calcifications are identified, radiologists should first determine whether they are predominantly medullary, predominantly cortical, or combined (i.e., both medullary and cortical). Additionally, one should be mindful of common mimics of nephrocalcinosis, as will be discussed. Medullary nephrocalcinosis (97% of cases) is much more common than cortical nephrocalcinosis (< 3%); the combined form of medullary and cortical nephrocalcinosis is extremely rare (< 1%), although these data are based on a study from 1976 [4]. Given the rarity of combined medullary/cortical nephrocalcinosis and the significantly higher prevalence of medullary nephrocalcinosis, the possibility of medullary nephrocalcinosis with associated cortical atrophy producing the spurious appearance of combined medullary/cortical nephrocalcinosis should be considered when encountering an apparent case of combined medullary/cortical nephrocalcinosis.
****Thomas, J., Ludwig, D.R., Ballard, D.H. et al. Spilling the beans: an inside scoop on the imaging of renal parenchymal disease. Abdom Radiol 47, 2420–2441 (2022). https://doi.org/10.1007/s00261-022-03540-2
Radiologic grading:
| Grades | USG | CT |
|---|---|---|
| Grade 0 | No echogenicity | No calcific deposits |
| Grade 1 | Mild echogenicity around medullary pyramid borders | Pyramidal punctate calcifications |
| Grade 2 | Moderate echogenicity around and inside pyramids | Pyramidal punctate calcifications + increased pyramidal density |
| Grade 3 | Severe echogenicity of entire pyramids | Pyramidal punctate calcifications + calcification of pyramids |
Representative images for nephrocalcinosis grading system. Panels A–D are US images corresponding to grades 0, 1, 2, and 3, respectively. Panels E–H are CT images corresponding to grades 0, 1, 2, and 3 respectively. The arrow in panel F points to a single punctate calcification in the medullary periods typical of grade 1 nephrocalcinosis.
Alison M. Boyce and others, Ultrasound is Superior to Computed Tomography for Assessment of Medullary Nephrocalcinosis in Hypoparathyroidism, The Journal of Clinical Endocrinology & Metabolism, Volume 98, Issue 3, 1 March 2013, Pages 989–994, https://doi.org/10.1210/jc.2012-2747
Histopathology
