Objective <p>To predict renal parenchymal involvement in patients with immunoglobulin G4-related disease (IgG4-RD) using texture- and volume-based analysis of unenhanced computed tomography (CT) images.</p> Materials and methods <p>Fifty-nine patients with IgG4-RD, diagnosed according to American College of Rheumatology/ European Alliance of Associations for Rheumatology classification criteria, who underwent both unenhanced CT and contrast-enhanced (CE)-CT) covering the kidneys before treatment (May 2007–July 2023), were enrolled. After excluding 15 cases, 44 patients remained for analysis. Clinical variables (sex, age, body weight, estimated glomerular filtration rate) and kidney volume-related and texture metrics extracted from unenhanced CT were analyzed for inter-reader repeatability and correlation with renal parenchymal involvement.</p> Results <p>Kidney involvement of IgG4-RD was determined on CE-CT by a rheumatologist and a radiologist in consensus, resulting in 23 cases with and 21 cases without renal parenchymal involvement. One radiologist and a radiology resident independently extracted metrics from unenhanced CT. Two metrics, kidney volume per body weight and gray-level co-occurrence matrix (GLCM) cluster shade, showed high repeatability (intraclass correlation coefficients 0.997 and 0.762, respectively) and significant association with renal parenchymal involvement (area under the receiver operating characteristic curve [AUROC] &gt; 0.75). Binary logistic regression combining these two metrics predicted renal parenchymal involvement with AUROCs of 0.872 and 0.896 for the two readers, respectively.</p> Conclusion <p>A combination of kidney volume per body weight and GLCM cluster shade derived from unenhanced CT can predict renal parenchymal involvement in IgG4-RD.</p> Relevance statement <p>The combination of two unenhanced CT-related metrics−kidney volume per body weight and GLCM cluster shade−can predict renal parenchymal involvement of immunoglobulin G4-related disease, with the AUROCs for the two readers being 0.872 and 0.896, respectively.</p> Key Points <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Unenhanced CT has been considered not to detect renal parenchymal involvement of IgG4-RD.</p> </ItemContent> <ItemContent> <p>By using image segmentation and texture analysis techniques, renal parenchymal involvement could be predicted in IgG4-RD.</p> </ItemContent> <ItemContent> <p>A combination of kidney volume per body weight and GLCM cluster shade could predict renal parenchymal involvement with high AUROC.</p> </ItemContent> </UnorderedList></p> Graphical Abstract <p></p>