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Objective: To assess the performance of computed tomography (CT)/magnetic resonance imaging (MRI) Liver Imaging Reporting and Data System (LI-RADS) among patients with non-cirrhotic steatotic liver disease (SLD)., Materials and Methods: This IRB-approved, retrospective study included 119 observations from 77 adult patients (36 women, 41 men; median 64 years) who underwent liver CT or MRI from 2010 to 2023. All patients had histopathologic evidence of SLD without cirrhosis. Three board-certified abdominal radiologists blinded to tissue diagnosis and imaging follow-up assessed observations with LI-RADS. The positive predictive value (PPV), sensitivity, specificity, accuracy, and inter-reader agreement were calculated., Results: Seventy-five observations (63%) were benign and 44 (37%) were malignant. PPV for hepatocellular carcinoma (HCC) was 0-0% for LR-1, 0-0% for LR-2, 0-7% for LR-3, 11-20% for LR-4, 75-88% for LR-5, 0-8% for LR-M, and 50-75% for LR-TIV. For LR-5 in identifying HCC, sensitivity was 79-83%, specificity was 91-97%, and accuracy was 89-92%. For composite categories of LR-5, LR-M, or LR-TIV in identifying malignancy, sensitivity was 86-89%, specificity was 85-96%, and accuracy was 86-93%. The most common false positives for LR-5 were hepatocellular adenomas. Only 59-65% of HCCs showed non-peripheral washout at CT versus 67-83% at MRI, though nearly all had an enhancing capsule. PPV and accuracy of LR-5 for HCC did not differ by modality. Inter-reader agreement for major features ranged from 0.667 to 0.830 and was 0.766 for the final category., Conclusion: Despite challenges such as the lower prevalence of non-peripheral washout at CT and overlapping imaging features between HCC and hepatocellular adenomas, LI-RADS may serve as an effective tool in assessing focal liver lesions in SLD., Clinical Relevance Statement: LI-RADS in non-cirrhotic steatotic liver disease can effectively diagnose hepatocellular carcinoma and malignancy at computed tomography and magnetic resonance imaging, thereby guiding clinical management decisions and expediting patient care pathways., Key Points: Performance of LI-RADS is unknown in non-cirrhotic patients with steatotic liver disease. LI-RADS 5 category showed a high pooled specificity of 91-97% for hepatocellular carcinoma. LI-RADS can non-invasively risk stratify focal liver observations in non-cirrhotic patients with steatotic liver disease., Competing Interests: Compliance with ethical standards Guarantor The scientific guarantor of this publication is Justin R. Tse. Conflict of interest Justin R. Tse receives grant support from GE Healthcare and Bayer Healthcare and is a consultant for Intuitive Surgical, Inc. and AbSolutions Med, Inc. Luke Yoon is a consultant for Intuitive Surgical, Inc. Statistics and biometry No complex statistical methods were necessary for this paper. Informed consent Written informed consent was waived by the Institutional Review Board. Ethical approval Institutional Review Board approval (Stanford University) was obtained. No animals were included in this study. Study subjects or cohorts overlap None study subjects or cohorts have been previously reported. Methodology RetrospectiveObservational studyPerformed at one institution, (© 2024. The Author(s), under exclusive licence to European Society of Radiology.)

Objectives: Some patients undergo both computed tomography (CT) and ultrasound (US) sequentially as part of the same evaluation for acute cholecystitis (AC). Our goal was to perform a systematic review and meta-analysis comparing the diagnostic performance of US and CT in the diagnosis of AC., Materials and Methods: Databases were searched for relevant published studies through November 2023. The primary objective was to compare the head-to-head performance of US and CT using surgical intervention or clinical follow-up as the reference standard. For the secondary analysis, all individual US and CT studies were analyzed. The pooled sensitivities, specificities, and areas under the curve (AUCs) were determined along with 95% confidence intervals (CIs). The prevalence of imaging findings was also evaluated., Results: Sixty-four studies met the inclusion criteria. In the primary analysis of head-to-head studies (n = 5), CT had a pooled sensitivity of 83.9% (95% CI, 78.4-88.2%) versus 79.0% (95% CI, 68.8-86.6%) of US (p = 0.44). The pooled specificity of CT was 94% (95% CI, 82.0-98.0%) versus 93.6% (95% CI, 79.4-98.2%) of US (p = 0.85). The concordance of positive or negative test between both modalities was 82.3% (95% CI, 72.1-89.4%). US and CT led to a positive change in management in only 4 to 8% of cases, respectively, when ordered sequentially after the other test., Conclusion: The diagnostic performance of CT is comparable to US for the diagnosis of acute cholecystitis, with a high rate of concordance between the two modalities., Clinical Relevance Statement: A subsequent US after a positive or negative CT for suspected acute cholecystitis may be unnecessary in most cases., Key Points: When there is clinical suspicion of acute cholecystitis, patients will often undergo both CT and US. CT has similar sensitivity and specificity compared to US for the diagnosis of acute cholecystitis. The concordance rate between CT and US for the diagnosis of acute cholecystitis is 82.3%., (© 2024. The Author(s), under exclusive licence to European Society of Radiology.)

Objectives: Magnetic resonance imaging (MRI) is the modality of choice for rectal cancer initial staging and restaging after neoadjuvant chemoradiation. Our objective was to perform a meta-analysis of the diagnostic performance of the split scar sign (SSS) on rectal MRI in predicting complete response after neoadjuvant therapy., Methods: MEDLINE, EMBASE, and Cochrane databases were searched for relevant published studies through June 2023. Primary studies met eligibility criteria if they evaluated the diagnostic performance of the SSS to predict complete response on pathology or clinical follow-up in patients undergoing neoadjuvant chemoradiation. A meta-analysis with a random-effects model was used to estimate pooled sensitivity and specificity, area under the curve (AUC), and diagnostic odds ratio (DOR) of the SSS., Results: A total of 4 studies comprising 377 patients met the inclusion criteria. The prevalence of complete response in the studies was 21.7-52.5%. The pooled sensitivity and specificity of the SSS to predict complete response were 62.0% (95% CI, 43.5-78.5%) and 91.9% (95% CI, 78.9-97.2%), respectively. The estimated AUC for SSS was 0.83 (95% CI, 0.56-0.94) with a DOR of 18.8 (95% CI, 3.65-96.5)., Conclusion: The presence of SSS on rectal MRI demonstrated high specificity for complete response in patients with rectal cancer after neoadjuvant chemoradiation. This imaging pattern can be a valuable tool to identify potential candidates for organ-sparing treatment and surveillance., Clinical Relevance Statement: SSS presents high specificity for complete response post-neoadjuvant. This MRI finding enhances rectal cancer treatment assessment and aids clinicians and patients in choosing watch-and-wait over immediate surgery, which can potentially reduce costs and associated morbidity., Key Points: •Fifteen to 50% of rectal cancer patients achieve complete response after neoadjuvant chemoradiation and may be eligible for a watch-and-wait strategy. •The split scar sign has high specificity for a complete response. •This imaging finding is valuable to select candidates for organ-sparing management., (© 2024. The Author(s).)

Objectives: Determine the proportion of malignancy within Bosniak v2019 classes., Methods: MEDLINE and EMBASE were searched. Eligible studies contained patients with cystic renal masses undergoing CT or MRI renal protocol examinations with pathology confirmation, applying Bosniak v2019. Proportion of malignancy was estimated within Bosniak v2019 class. Risk of bias was assessed using QUADAS-2., Results: We included 471 patients with 480 cystic renal masses. No class I malignant masses were observed. Pooled proportion of malignancy were class II, 12% (6/51, 95% CI 5-24%); class IIF, 46% (37/85, 95% CI 28-66%); class III, 79% (138/173, 95% CI 68-88%); and class IV, 84% (114/135, 95% CI 77-90%). Proportion of malignancy differed between Bosniak v2019 II-IV classes (p = 0.004). Four studies reported the proportion of malignancy by wall/septa feature. The pooled proportion of malignancy with 95% CI were class III thick smooth wall/septa, 77% (41/56, 95% CI 53-91%); class III obtuse protrusion ≤ 3 mm (irregularity), 83% (97/117, 95% CI 75-89%); and class IV nodule with acute angulation, 86% (50/58, 95% CI 75-93%) or obtuse angulation ≥ 4 mm, 83%, (64/77, 95% CI 73-90%). Subgroup analysis by wall/septa feature was limited by sample size; however, no differences were found comparing class III masses with irregularity to class IV masses (p = 0.74) or between class IV masses by acute versus obtuse angles (p = 0.62)., Conclusion: Preliminary data suggest Bosniak v2019 class IIF masses have higher proportion of malignancy compared to the original classification, controlling for pathologic reference standard. There are no differences in proportion of malignancy comparing class III masses with irregularities to class IV masses with acute or obtuse nodules., Key Points: • The proportion of malignancy in Bosniak v2019 class IIF cystic masses is 46% (37 malignant/85 total IIF masses, 95% confidence intervals (CI) 28-66%). • The proportion of malignancy in Bosniak v2019 class III cystic masses is 79% (138/173, 95% CI 68-88%) and in Bosniak v2019 class IV cystic masses is 84% (114/135, 95% CI 77-90%). • Class III cystic masses with irregularities had similar proportion of malignancy (83%, 97/117, 95% CI 75-89%) compared to Bosniak class IV masses (84%, 114/135, 95% CI 77-90%) overall (p = 0.74) with no difference within class IV masses by acute versus obtuse angulation (p = 0.62)., (© 2022. The Author(s), under exclusive licence to European Society of Radiology.)

Objective: To determine if CT axial images reconstructed at current standard of care (SOC; 2.5-3 mm) or thin (≤ 1 mm) sections affect categorization and inter-rater agreement of cystic renal masses assessed with Bosniak classification, version 2019., Methods: In this retrospective single-center study, 3 abdominal radiologists reviewed 131 consecutive cystic renal masses from 100 patients performed with CT renal mass protocol from 2015 to 2021. Images were reviewed in two sessions: first with SOC and then the addition of thin sections. Individual and overall categorizations are reported, latter of which is based on majority opinion with 3-way discrepancies resolved by a fourth reader. Major categorization changes were defined as differences between classes I-II, IIF, or III-IV., Results: Thin sections led to a statistically significant major category change with class II for all readers individually (p = 0.004-0.041; McNemar test), upgrading 10-17% of class II masses, most commonly to class IIF followed by III. Modal reason for upgrades was due to identification of additional septa followed by larger measurement of enhancing features. Masses categorized as class I, III, or IV on SOC sections were unaffected, as were identification of protrusions. Inter-rater agreements using weighted Cohen's kappa were 0.679 for SOC and 0.691 for thin sections (both substantial)., Conclusion: Thin axial sections upgraded up to one in six class II masses to IIF or III through identification of additional septa or larger feature. Other classes, including III-IV, were unaffected. Inter-rater agreements were substantial regardless of section thickness., Key Points: • Thin axial sections (≤ 1 mm) compared to standard of care sections (2.5-3 mm) led to identification of additional septa but did not affect identification of protrusions. • Thin axial sections (≤ 1 mm) compared to standard of care sections (2.5-3 mm) can upgrade a small proportion of cystic renal masses from class II to IIF or III when applying Bosniak classification, version 2019. • Inter-rater agreements were substantial regardless of section thickness., (© 2022. The Author(s), under exclusive licence to European Society of Radiology.)