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Unenhanced CT findings can predict the development of urinary calculi in stone-free patients

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To determine if calcium deposits in the papillae can be identified by unenhanced computed tomography (uCT) even before renal stones develop.


A retrospective review of 413 patients with calculi identified 31 patients (stone-forming group) with a history of urinary tract calculi with a calculus demonstrated by uCT and a stone-free uCT before calculi had developed. The control group (n = 31) was composed of live kidney donors with no history of calculi and a stone-free uCT. CT attenuation was measured in all CTs using two regions of interest of 0.05 cm2 and 0.1 cm2 over the tip and the neighbouring area of the papillae. Student's and Wilcoxon t-tests were used for comparing results in the two groups.


The attenuation of the tip of the papilla was higher in the stone-forming group when compared to the controls after (45.2 HU versus 32.1 HU, P = 0.001) and even before frank calculi had developed (44.2 HU versus 32.1 HU, P = 0.003). There was no significant difference in papillary attenuation in the stone group before and after calculi had developed (45.2 HU versus 44.2 HU, P = 0.82).


Stone-forming patients exhibit higher papillary density even before calculi develop. This could define a population at risk of developing calculi.

Key Points

Unenhanced CT shows high density papillae in patients who subsequently develop calculi.

These probably correlate with Randall’s plaques.

Subjects at high risk of developing stone disease could be identified.

Targeted prophylaxis might be helpful.

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Control group


Region of interest


Stone group


Stone group previous to stone formation


Hounsfield units


Computed tomography


Stone disease


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Correspondence to Alexandru Ciudin.

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Ciudin, A., Luque Galvez, M.P., Salvador Izquierdo, R. et al. Unenhanced CT findings can predict the development of urinary calculi in stone-free patients. Eur Radiol 22, 2050–2056 (2012).

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