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Longitudinal follow-up of incidental renal calculi on computed tomography

  • Kidneys, Ureters, Bladder, Retroperitoneum
  • Published:
Abdominal Radiology Aims and scope Submit manuscript


Rationale and objectives

Measuring small kidney stones on CT is a time-consuming task often neglected. Volumetric assessment provides a better measure of size than linear dimensions. Our objective is to analyze the growth rate and prognosis of incidental kidney stones in asymptomatic patients on CT.

Materials and methods

This retrospective study included 4266 scans from 2030 asymptomatic patients who underwent two or more nonenhanced CT scans for colorectal screening between 2004 and 2016. The DL software identified and measured the volume, location, and attenuation of 883 stones. The corresponding scans were manually evaluated, and patients without follow-up were excluded. At each follow-up, the stones were categorized as new, growing, persistent, or resolved. Stone size (volume and diameter), attenuation, and location were correlated with the outcome and growth rates of the stones.


The stone cohort comprised 407 scans from 189 (M: 124, F: 65, median age: 55.4 years) patients. The median number of stones per scan was 1 (IQR: [1, 2]). The median stone volume was 17.1 mm3 (IQR: [7.4, 43.6]) and the median peak attenuation was 308 HU (IQR: [204, 532]. The 189 initial scans contained 291stones; 91 (31.3%) resolved, 142 (48.8%) grew, and 58 (19.9) remained persistent at the first follow-up. At the second follow-up (for 27 patients with 2 follow-ups), 14/44 (31.8%) stones had resolved, 19/44 (43.2%) grew and 11/44 (25%) were persistent. The median growth rate of growing stones was 3.3 mm3/year, IQR: [1.4,7.4]. Size and attenuation had a moderate correlation (Spearman rho 0.53, P < .001 for volume, and 0.50 P < .001 for peak attenuation) with the growth rate. Growing and persistent stones had significantly greater maximum axial diameter (2.7 vs 2.3 mm, P =.047) and peak attenuation (300 vs 258 HU, P =.031)


We report a 12.7% prevalence of incidental kidney stones in asymptomatic adults, of which about half grew during follow-up with a median growth rate of about 3.3 mm3/year.

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This research was supported by the Intramural Research Program of the National Institutes of Health, Clinical Center, and we utilized the computational resources of the National Institutes of Health high-performance computing Biowulf cluster.


This research was supported by the Intramural Research Program of the National Institutes of Health, Clinical Center (Z01 CL040003 and Z01 CL040004).

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Correspondence to Ronald M. Summers.

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Competing interests

Author RMS receives royalties from iCAD, Philips, ScanMed, PingAn, MGB and Translation Holdings and has received research support from Ping An (CRADA). PJP is an adviser or consultant for Zebra Medical Vision and Bracco Diagnostics, and shareholder in Cellectar, Elucent, and SHINE.

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This study was approved by the Institutional Review Board. The need for additional signed informed consent was waived.

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Mukherjee, P., Lee, S., Elton, D.C. et al. Longitudinal follow-up of incidental renal calculi on computed tomography. Abdom Radiol 49, 173–181 (2024).

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