Nephrocalcinosis in a case of end-stage renal failure and recurrent ureteric calculi

Clinical History

A 41-year-old man was admitted with a two week history of diarrhoea and vomiting. Laboratory assessments revealed: calcium = 2.16 mmol/L, creatinine = 695 mm/l, eGFR = 8.2 ml/min and urine protein/creatinine ratio = 135.1. He was haemofiltered in intensive care via a right internal jugular vascath.

Imaging Findings

Ultrasound of the right kidney demonstrated a highly echogenic right kidney with a thin cortex and containing calculi within it. The renal vessels could not be clearly visualised (Fig. 1).

The axial (Fig. 2) and coronal (Fig. 3) CT images showed evidence of large confluent calcifications filling the renal medullary pyramid with thinning of the renal cortex. In addition, on the retrograde pyelogram images, extensive nephrocalcinosis was again demonstrated involving both the left (Fig. 4) and the right kidney (Fig. 5).

Chest radiographs, pre-renal transplant assessment and carotid artery Dopplers were normal.

Discussion

Background:

Nephrocalcinosis, the deposition of calcium salts within the renal parenchyma, can be classified by its location; either cortical or medullary.

Clinical Perspective:

1. Cortical nephrocalcinosis
Cortical nephrocalcinosis usually occurs as a consequence of chronic glomerulitis, renal cortical necrosis secondary to vascular insult, Alport syndrome, hyperoxaluria, ethylene glycol poisoning, sickle cell disease and rarely, transplant rejection. [1, 2]

2. Medullary nephrocalcinosis
The common causes of medullary nephrocalcinosis include: medullary sponge kidney, renal tubular acidosis, and hyperparathyroidism. Calculi may form in the cavities due to stasis and hypercalciuria, which can also lead to medullary nephrocalcinosis. [2]

Imaging Perspective:

The pattern of parenchymal calcification is described as resembling “railroad tracks” [3]. The calcification at the margins of the renal cortex may be visualised on plain radiographs or on CT. Increased renal cortical echogenicity with preservation of corticomedullary definition can also be seen on ultrasound. However, other medical conditions can mimic this presentation on sonograms, including the interstitial nephritis of AIDS, leukaemia, amyloidosis, subacute renal vein thrombosis, and acute tubular necrosis [4].

Medullary nephrocalcinosis may be demonstrated on plain radiograph or CT as calcific density in the pyramids. This appearance is indicative of a metabolic abnormality, generally hypercalcaemia or hypercalciuria, but it may also be seen with papillary necrosis and medullary sponge kidney. High pyramidal echogenicity however, may be visualised in the absence of nephrocalcinosis in diseases associated with renal tubular ectasia such as medullary sponge kidney, infantile polycystic kidney disease, and congenital hepatic fibrosis with tubular ectasia. Oxalosis is the only condition that characteristically demonstrates both cortical and medullary calcifications with a diffuse and regular pattern. Although renal oxalosis will produce increased cortical echogenicity early in its course, it will eventually result in echogenic kidneys without adequate differentiation between cortex and medulla [4].

Teaching Points:

To conclude, radiology makes it possible to differentiate between the different presentations of nephrocalcinosis. The two patterns of nephrocalcinosis can be visualised on the plain abdominal radiograph, providing a high degree of calcification is present. Computed tomography is a valuable adjunct as minute differences in density can be clearly demonstrated [5].

Differential Diagnosis List

Final Diagnosis

End stage renal failure secondary to nephrocalcinosis and ureteric calculi

URL:	https://eurorad.org/case/10941
DOI:	10.1594/EURORAD/CASE.10941
ISSN:	1563-4086