Incidence, Presentation, and Natural History of Adrenal Hemorrhage: An Institutional Analysis.

INTRODUCTION: Adrenal hemorrhage (AH) can occur due to multiple etiologies with variable radiographic appearance, often indistinguishable from underlying adrenal neoplasms. There is a lack of AH literature and evidence-based guidelines. Our study aimed to understand the prevalence and etiology of AH, follow-up, and incidence of underlying neoplasm. METHODS: An institutional database was queried from January 2006 to October 2021 for patients with AH on imaging, excluding patients with known malignancies, adrenal masses, or prior adrenal surgery. Demographics, medical history, hematoma size, laterality, biochemical evaluation, intervention, and additional imaging were reviewed. RESULTS: Of 490,301 imaging reports queried, 530 (0.11%) with AH met inclusion criteria. Most imaging (n = 485, 91.5%) was performed during trauma evaluation. Two patients underwent dedicated intervention at presentation. Interval imaging was performed in 114 (21.5%) patients at a median of 2.6 (interquartile range 0.99-13.4) mo, with resolution (n = 84, 73.7%) or decreased size of AH (n = 21, 18.4%) in most patients. Only 10 patients (1.9%) saw an outpatient provider in our system to address AH or evaluate for underlying mass, and 9 (1.7%) underwent biochemical screening. Thirteen patients (11% of 118 patients with any follow-up) had evidence of an adrenal mass, confirmed on serial imaging (n = 10) or adrenalectomy (n = 3). Scans performed for nontrauma indications were significantly more likely to have an underlying mass (n = 6/26 [23.1%]) than those performed for trauma evaluation (n = 7/92 [7.6%], P = 0.04). CONCLUSIONS: AH is a rare finding associated with an increased rate of underlying adrenal mass, particularly when unrelated to trauma. Most AH resolves spontaneously without intervention. Follow-up imaging at 6 mo can help distinguish mass-associated AH from simple hemorrhage.

Performance of CT With Adrenal-Washout Protocol in Heterogeneous Adrenal Nodules: A Multiinstitutional Study.

BACKGROUND. CT with adrenal-washout protocol (hereafter, adrenal-protocol CT) is commonly performed to distinguish adrenal adenomas from other adrenal tumors. However, the technique's utility among heterogeneous nodules is not well established, and the optimal method for placing ROIs in heterogeneous nodules is not clearly defined. OBJECTIVE. The purpose of our study was to determine the diagnostic performance of adrenal-protocol CT to distinguish adenomas from nonadenomas among heterogeneous adrenal nodules and to compare this performance among different methods for ROI placement. METHODS. This retrospective study included 164 patients (mean age, 59.1 years; 61 men, 103 women) with a total of 164 heterogeneous adrenal nodules evaluated using adrenal-protocol CT at seven institutions. All nodules had an available pathologic reference standard. A single investigator at each institution evaluated the CT images. ROIs were placed on portal venous phase images using four ROI methods: standard ROI, which refers to a single large ROI in the nodule's center; high ROI, a single ROI on the nodule's highest-attenuation area; low ROI, a single ROI the on nodule's lowest-attenuation area; and average ROI, the mean of the three ROIs on the nodule's superior, middle, and inferior thirds using the approach for the standard ROI. ROIs were then placed in identical locations on unenhanced and delayed phase images. Absolute washout was determined for all methods. RESULTS. The nodules comprised 82 adenomas and 82 nonadenomas (36 pheochromocytomas, 20 metastases, 12 adrenocortical carcinomas, and 14 nodules with other pathologies). The mean nodule size was 4.5 ± 2.8 (SD) cm (range, 1.6-23.0 cm). Unenhanced CT attenuation of 10 HU or less exhibited sensitivity and specificity for adenoma of 22.0% and 96.3% for standard-ROI, 11.0% and 98.8% for high-ROI, 58.5% and 84.1% for low-ROI, and 30.5% and 97.6% for average-ROI methods. Adrenal-protocol CT overall (unenhanced attenuation ≤ 10 HU or absolute washout of ≥ 60%) exhibited sensitivity and specificity for adenoma of 57.3% and 84.1% for the standard-ROI method, 63.4% and 51.2% for the high-ROI method, 68.3% and 62.2% for the low-ROI method, and 59.8% and 85.4% for the average-ROI method. CONCLUSION. Adrenal-protocol CT has poor diagnostic performance for distinguishing adenomas from nonadenomas among heterogeneous adrenal nodules regardless of the method used for ROI placement. CLINICAL IMPACT. Adrenal-protocol CT has limited utility in the evaluation of heterogeneous adrenal nodules.

A Multicenter Assessment of Interreader Reliability of LI-RADS Version 2018 for MRI and CT.

Background Various limitations have impacted research evaluating reader agreement for Liver Imaging Reporting and Data System (LI-RADS). Purpose To assess reader agreement of LI-RADS in an international multicenter multireader setting using scrollable images. Materials and Methods This retrospective study used deidentified clinical multiphase CT and MRI and reports with at least one untreated observation from six institutions and three countries; only qualifying examinations were submitted. Examination dates were October 2017 to August 2018 at the coordinating center. One untreated observation per examination was randomly selected using observation identifiers, and its clinically assigned features were extracted from the report. The corresponding LI-RADS version 2018 category was computed as a rescored clinical read. Each examination was randomly assigned to two of 43 research readers who independently scored the observation. Agreement for an ordinal modified four-category LI-RADS scale (LR-1, definitely benign; LR-2, probably benign; LR-3, intermediate probability of malignancy; LR-4, probably hepatocellular carcinoma [HCC]; LR-5, definitely HCC; LR-M, probably malignant but not HCC specific; and LR-TIV, tumor in vein) was computed using intraclass correlation coefficients (ICCs). Agreement was also computed for dichotomized malignancy (LR-4, LR-5, LR-M, and LR-TIV), LR-5, and LR-M. Agreement was compared between research-versus-research reads and research-versus-clinical reads. Results The study population consisted of 484 patients (mean age, 62 years ± 10 [SD]; 156 women; 93 CT examinations, 391 MRI examinations). ICCs for ordinal LI-RADS, dichotomized malignancy, LR-5, and LR-M were 0.68 (95% CI: 0.61, 0.73), 0.63 (95% CI: 0.55, 0.70), 0.58 (95% CI: 0.50, 0.66), and 0.46 (95% CI: 0.31, 0.61) respectively. Research-versus-research reader agreement was higher than research-versus-clinical agreement for modified four-category LI-RADS (ICC, 0.68 vs 0.62, respectively; P = .03) and for dichotomized malignancy (ICC, 0.63 vs 0.53, respectively; P = .005), but not for LR-5 (P = .14) or LR-M (P = .94). Conclusion There was moderate agreement for LI-RADS version 2018 overall. For some comparisons, research-versus-research reader agreement was higher than research-versus-clinical reader agreement, indicating differences between the clinical and research environments that warrant further study. © RSNA, 2023 Supplemental material is available for this article. See also the editorials by Johnson and Galgano and Smith in this issue.

Prevalence of Malignancy in Adrenal Nodules With Heterogeneous Microscopic Fat on Chemical-Shift MRI: A Multiinstitutional Study.

BACKGROUND. Homogeneous microscopic fat within adrenal nodules on chemical-shift MRI (CS-MRI) is diagnostic of benign adrenal adenoma, but the clinical relevance of heterogeneous microscopic fat is not well established. OBJECTIVE. This study sought to determine the prevalence of malignancy in adrenal nodules with heterogeneous microscopic fat on dual-echo T1-weighted CS-MRI. METHODS. We performed a retrospective study of adult patients with adrenal nodules detected on MRI performed between August 2007 and November 2020 at seven institutions. Eligible nodules had a short-axis diameter of 10 mm or larger with heterogeneous microscopic fat (defined by an area of signal loss of < 80% on opposed-phase CS-MRI). Two radiologists from each center, blinded to reference standard results, determined the signal loss pattern (diffuse, two distinct parts, speckling pattern, central loss, or peripheral loss) within the nodules. The reference standard used was available for 283 nodules (pathology for 21 nodules, ≥ 1 year of imaging follow-up for 245, and ≥ 5 years of clinical follow-up for 17) in 282 patients (171 women and 111 men; mean age, 60 ± 12 [SD] years); 30% (86/282) patients had prior malignancy. RESULTS. The mean long-axis diameter was 18.7 ± 7.9 mm (range, 10-80 mm). No malignant nodules were found in patients without prior cancer (0/197; 95% CI, 0-1.5%). Four of the 86 patients with prior malignancy (hepatocellular carcinoma [HCC], renal cell carcinoma [RCC], lung cancer, or both colon cancer and RCC) (4.7%; 95% CI, 1.3-11.5%) had metastatic nodules. Detected patterns were diffuse heterogeneous signal loss (40% [114/283]), speckling (28% [80/283]), two distinct parts (18% [51/283]), central loss (9% [26/283]), and peripheral loss (4% [12/283]). Two metastases from HCC and RCC showed diffuse heterogeneous signal loss. Lung cancer metastasis manifested as two distinct parts, and the metastasis in the patient with both colon cancer and RCC showed peripheral signal loss. CONCLUSION. Presence of heterogeneous microscopic fat in adrenal nodules on CS-MRI indicates a high likelihood of benignancy, particularly in patients without prior cancer. This finding is also commonly benign in patients with cancer; however, caution is warranted when primary malignancies may contain fat or if the morphologic pattern of signal loss may indicate a collision tumor. CLINICAL IMPACT. In the absence of prior cancer, adrenal nodules with heterogeneous microscopic fat do not require additional imaging evaluation.

Adrenal Neoplasms: Lessons from Adrenal Multidisciplinary Tumor Boards.

The radiologic diagnosis of adrenal disease can be challenging in settings of atypical presentations, mimics of benign and malignant adrenal masses, and rare adrenal anomalies. Misdiagnosis may lead to suboptimal management and adverse outcomes. Adrenal adenoma is the most common benign adrenal tumor that arises from the cortex, whereas adrenocortical carcinoma (ACC) is a rare malignant tumor of the cortex. Adrenal cyst and myelolipoma are other benign adrenal lesions and are characterized by their fluid and fat content, respectively. Pheochromocytoma is a rare neuroendocrine tumor of the adrenal medulla. Metastases to the adrenal glands are the most common malignant adrenal tumors. While many of these masses have classic imaging appearances, considerable overlap exists between benign and malignant lesions and can pose a diagnostic challenge. Atypical adrenal adenomas include those that are lipid poor; contain macroscopic fat, hemorrhage, and/or iron; are heterogeneous and/or large; and demonstrate growth. Heterogeneous adrenal adenomas may mimic ACC, metastasis, or pheochromocytoma, particularly when they are 4 cm or larger, whereas smaller versions of ACC, metastasis, and pheochromocytoma and those with washout greater than 60% may mimic adenoma. Because of its nonenhanced CT attenuation of less than or equal to 10 HU, a lipid-rich adrenal adenoma may be mimicked by a benign adrenal cyst, or it may be mimicked by a tumor with central cystic and/or necrotic change such as ACC, pheochromocytoma, or metastasis. Rare adrenal tumors such as hemangioma, ganglioneuroma, and oncocytoma also may mimic adrenal adenoma, ACC, metastasis, and pheochromocytoma. The authors describe cases of adrenal neoplasms that they have encountered in clinical practice and presented to adrenal multidisciplinary tumor boards. Key lessons to aid in diagnosis and further guide appropriate management are provided. © RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Utility of combined gadoxetic acid and ferumoxytol-enhanced liver MRI for preoperative detection of colorectal cancer liver metastases: a pilot study.

BACKGROUND: Colorectal cancer (CRC) is the second-leading cause of cancer-related death worldwide and resection of CRC metastases confined to the liver is the treatment of choice when feasible. Ferumoxytol is an off-label contrast agent that opacifies vasculature and may be helpful in distinguishing metastases from small hemangiomas and blood vessels on gadoxetic acid-enhanced magnetic resonance imaging (MRI). PURPOSE: To compare the diagnostic accuracy of MRI using a standard gadoxetic acid protocol and a combined gadoxetic acid/ferumoxytol protocol in patients with suspected colorectal hepatic metastases. MATERIAL AND METHODS: In this institutional review board-approved, single-institution, retrospective study, eight patients underwent gadoxetic acid-enhanced liver MRI, supplemented with additional T1-weighted ferumoxytol enhanced sequences. Two radiologists in consensus identified all metastases using all available sequences, which served as the reference standard. Two different radiologists reviewed each exam twice, once using the standard protocol and once with additional ferumoxytol sequences. The detection rate was estimated as the predicted probability of a metastasis along with the 95% confidence interval (CI) using hierarchical logistic regression models. RESULTS: A total of 49 metastases were identified. The mean diameter was 10 mm, measured in greatest axial dimension (median=7 mm; range=2-70 mm). Readers 1 and 2 had detection rates of 69.6% (95% CI = 48.2-85.0) and 53.1% (95% CI = 35.2-70.3) for gadoxetic acid alone and 98.0% (95% CI = 86.3-99.7) and 83.5% (95% CI = 59.3-94.7) for combined protocol. CONCLUSION: In this preliminary investigation, adding ferumoxytol-enhanced sequences to gadoxetic acid liver MRI protocol increased the detection rate of CRC hepatic metastases and may aid in preoperative decision making.

Sonographic Assessment of Acute Versus Chronic Cholecystitis: An Ultrasound Probability Stratification Model.

OBJECTIVES: What sonographic variables are most predictive for acute cholecystitis? What variables differentiate acute and chronic cholecystitis? METHODS: The surgical pathology database was reviewed to identify adult patients who underwent cholecystectomy for cholecystitis and had a preceding ultrasound of the right upper quadrant within 7 days. A total of 236 patients were included in the study. A comprehensive imaging review was performed to assess for gallstones, gallbladder wall thickening, gallbladder distension, pericholecystic fluid, gallstone mobility, the sonographic Murphy's sign, mural hyperemia, and the common hepatic artery peak systolic velocity. RESULTS: Of 236 patients with a cholecystectomy, 119 had acute cholecystitis and 117 had chronic cholecystitis on surgical pathology. Statistical models were created for prediction. The simple model consists of three sonographic variables and has a sensitivity of 60% and specificity of 83% in predicting acute versus chronic cholecystitis. The most predictive variables for acute cholecystitis were elevated common hepatic artery peak systolic velocity, gallbladder distension, and gallbladder mural abnormalities. If a patient had all three of these findings on their preoperative ultrasound, the patient had a 96% chance of having acute cholecystitis. Two of these variables gave a 73-93% chance of having acute cholecystitis. One of the three variables gave a 40-76% chance of having acute cholecystitis. If the patient had 0 of 3 of the predictor variables, there was a 29% chance of having acute cholecystitis. CONCLUSIONS: Gallbladder distension, gallbladder mural abnormalities, and elevated common hepatic artery peak systolic velocity are the most important sonographic variables in predicting acute versus chronic cholecystitis.

Management of Incidentally Detected Gallbladder Polyps: Society of Radiologists in Ultrasound Consensus Conference Recommendations.

Gallbladder polyps (also known as polypoid lesions of the gallbladder) are a common incidental finding. The vast majority of gallbladder polyps smaller than 10 mm are not true neoplastic polyps but are benign cholesterol polyps with no inherent risk of malignancy. In addition, recent studies have shown that the overall risk of gallbladder cancer is not increased in patients with small gallbladder polyps, calling into question the rationale for frequent and prolonged follow-up of these common lesions. In 2021, a Society of Radiologists in Ultrasound, or SRU, consensus conference was convened to provide recommendations for the management of incidentally detected gallbladder polyps at US. See also the editorial by Sidhu and Rafailidis in this issue.

Incidental Adrenal Nodules in Patients Without Known Malignancy: Prevalence of Malignancy and Utility of Washout CT for Characterization-A Multiinstitutional Study.

BACKGROUND. Washout CT is commonly used to evaluate indeterminate adrenal nodules, although its diagnostic performance is poorly established in true adrenal incidentalomas. OBJECTIVE. The purpose of this study was to compare, in patients without a known malignancy history, the prevalence of malignancy for incidental adrenal nodules with unenhanced attenuation more than 10 HU that do and do not show absolute washout of 60% or more, thereby determining the diagnostic performance of washout CT for differentiating benign from malignant incidental adrenal nodules. METHODS. This retrospective six-institution study included 299 patients (mean age, 57.3 years; 180 women, 119 men) without known malignancy or suspicion for functioning adrenal tumor who underwent washout CT, which showed a total of 336 adrenal nodules with a short-axis diameter of 1 cm or more, homogeneity, and unenhanced attenuation over 10 HU. The date of the first CT ranged across institutions from November 1, 2003, to January 1, 2017. Washout was determined for all nodules. Reference standard was pathology (n = 54), imaging follow-up (≥ 1 year) (n = 269), or clinical follow-up (≥ 5 years) (n = 13). RESULTS. Prevalence of malignancy among all nodules, nodules less than 4 cm, and nodules 4 cm or more was 1.5% (5/336; 95% CI, 0.5-3.4%), 0.3% (1/317; 95% CI, 0.0-1.7%), and 21.1% (4/19; 95% CI, 6.1-45.6%), respectively. Prevalence of malignancy was not significantly different for nodules smaller than 4 cm with (0% [0/241]; 95% CI, 0.0-1.2%) and without (1.3% [1/76]; 95% CI, 0.0-7.1%) washout of 60% or more (p = .08) or for nodules 4 cm or larger with (16.7% [1/6]; 95% CI, 0.4-64.1%) and without (23.1% [3/13]; 95% CI, 5.0-53.8%) washout of 60% or more (p = .75). Washout of 60% or more was observed in 75.5% (243/322; 95% CI, 70.4-80.1%) of benign nodules (excluding pheochromocytomas), 20.0% (1/5; 95% CI, 0.5-71.6%) of malignant nodules, and 33.3% (3/9; 95% CI, 7.5-70.1%) of pheochromocytomas. For differentiating benign nodules from malignant nodules and pheochromocytomas, washout of 60% or more had 77.5% sensitivity, 70.0% specificity, 98.8% PPV, and 9.2% NPV among nodules smaller than 4 cm. CONCLUSION. Prevalence of malignancy is low among incidental homogeneous adrenal nodules smaller than 4 cm with unenhanced attenuation more than 10 HU and does not significantly differ between those with and without washout of 60% or more; wash-out of 60% or more has suboptimal performance for characterizing nodules as benign. CLINICAL IMPACT. Washout CT has limited utility in evaluating incidental adrenal nodules in patients without known malignancy.

Ultrasound Screening for Transplant Renal Artery Stenosis Risk Stratification Using Standardized Criteria in Structured Reporting: A Validation Study.

OBJECTIVES: To evaluate the effectiveness of templated ultrasound reports using transplant renal artery stenosis (TRAS) risk stratification (RS), particularly with regard to utilization of downstream angiographic studies and angiographic presence of TRAS. METHODS: Ultrasounds with TRAS-RS templated reports from August 2017 to May 2020 were included. Studies were excluded if performed <28 days posttransplant and where TRAS was not clinically considered. A total of 530 ultrasounds met inclusion/exclusion criteria. TRAS-RS criteria were recorded (renal artery velocity ≥300 cm/s, spectral broadening in the renal artery, and intraparenchymal acceleration time ≥0.1 second). Depending on the number of criteria present, recipients were stratified into low (0/3), intermediate (1/3), high (2/3), and very high (3/3) risk for TRAS. Student's t-test was performed to identify whether the TRAS-RS category was associated with 1) performance of angiography to assess for TRAS and 2) angiographic presence of TRAS. RESULTS: Of the 530 ultrasounds, 74 (14%) underwent angiography. Of these, 41 (55%) were positive for TRAS (overall positive rate, 8%). Number of ultrasounds, angiograms, and angiograms positive for TRAS, respectively, in each of the TRAS-RS categories for the 530 cases were: low probability: n = 370 (70% of all studied reports), 7 angiograms (2%), and 0 (0%) positive for TRAS; intermediate: n = 87 (16%), 24 angiograms (28%), and 8 (33%) positive; high: n = 46 (9%), 23 angiograms (50%), and 14 (61%) positive; and very high: n = 27 (5%), 20 angiograms (74%), and 19 (95%) positive. TRAS-RS score was associated with subsequent performance of angiography and positive rate for TRAS (P < .01). CONCLUSION: Implementing a defined ultrasound screening tool with templated reporting for TRAS allowed for effective selection of those requiring an angiogram.

Dynamic Positron Emission Tomography/Computed Tomography Imaging Correlate of Nonalcoholic Steatohepatitis.

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease characterized by lobular inflammation and hepatocyte injury and is a key determinant of clinical outcome.1 Liver biopsy remains the gold standard for diagnosis but is limited by risks of the procedure and interobserver variability. Although magnetic resonance imaging (MRI)-based technology may provide novel means to identify NASH,2 there remains a significant need for other modalities to diagnose NASH noninvasively. Glucose transport, an integral tissue process altered in NASH,3 is measurable with 18F-fluorodeoxyglucose positron emission tomography (FDG PET). Because unenhanced computed tomography (CT) scan can detect hepatic steatosis quite reliably,4 and PET combines unenhanced CT for attenuation correction, we hypothesized that measurement of the combination of glucose transport by PET and steatosis by CT could yield a reliable radiologic correlate of NASH.

Utilization and Yield of CT Urography: Are the American Urological Association Guidelines for Imaging of Patients With Asymptomatic Microscopic Hematuria Being Followed?

OBJECTIVE: The purposes of this study were to determine whether patients with asymptomatic microscopic hematuria undergoing CT urography (CTU) meet the American Urological Association criteria for radiologic evaluation and to determine the yield of CTU for upper tract malignancy. MATERIALS AND METHODS: A retrospective review was conducted of consecutive CTU examinations performed for asymptomatic microscopic hematuria in adult patients. Patients with clinical evidence suggestive of a benign cause of hematuria (stone, urinary tract infection, trauma) or prior urologic malignancy were excluded. The study group included 419 patients (173 men, 246 women). CT reports were reviewed to identify causes of hematuria in all cases. Evaluate for appropriateness was conducted with 200 randomly allocated patients. Urinalysis results were reviewed, and appropriate use of CTU was defined as more than 3 RBCs per high-power field in the absence of urinary tract infection. Cystoscopy results after CTU were noted. RESULTS: In total, 58 of 200 patients (29.0%; 95% CI, 23.2-35.6%) did not meet American Urological Association criteria for radiologic evaluation. Fifteen (7.5%) received dipstick analysis only. Thirty-eight (19.0%) had urinalysis results showing 0-2 RBCs per high-power field. Five patients (2.5%) were found to have urinary tract infections. No upper tract urothelial neoplasms were identified (0/419; 95% CI, 0.0-0.9%). One solid renal mass was identified without pathologic confirmation. One possible bladder mass was seen at CTU but not visualized at subsequent cystoscopy. CONCLUSION: In 29.0% of examinations, CTU is performed for patients who do not meet the criteria for radiologic evaluation. The yield of CTU for upper urinary tract malignancy is low.

Clinical Importance of Incidental Homogeneous Renal Masses That Measure 10-40 mm and 21-39 HU at Portal Venous Phase CT: A 12-Institution Retrospective Cohort Study.

BACKGROUND. Incidental homogeneous renal masses are frequently encountered at portal venous phase CT. The American College of Radiology Incidental Findings Committee's white paper on renal masses recommends additional imaging for incidental homogeneous renal masses greater than 20 HU, but single-center data and the Bosniak classification version 2019 suggest the optimal attenuation threshold for detecting solid masses should be higher. OBJECTIVE. The purpose of this article is to determine the clinical importance of small (10-40 mm) incidentally detected homogeneous renal masses measuring 21-39 HU at portal venous phase CT. METHODS. We performed a 12-institution retrospective cohort study of adult patients who underwent portal venous phase CT for a nonrenal indication. The date of the first CT at each institution ranged from January 1, 2008, to January 1, 2014. Consecutive reports from 12,167 portal venous phase CT examinations were evaluated. Images were reviewed for 4529 CT examinations whose report described a focal renal mass. Eligible masses were 10-40 mm, well-defined, subjectively homogeneous, and 21-39 HU. Of these, masses that were shown to be solid without macroscopic fat; classified as Bosniak IIF, III, or IV; or confirmed to be malignant were considered clinically important. The reference standard was renal mass protocol CT or MRI, ultrasound of definitively benign cysts or solid masses, single-phase contrast-enhanced CT or unenhanced MRI showing no growth or morphologic change for 5 years or more, or clinical follow-up 5 years or greater. A reference standard was available for 346 masses in 300 patients. The 95% CIs were calculated using the binomial exact method. RESULTS. Eligible masses were identified in 4.2% of patients (514/12,167; 95% CI, 3.9-4.6%). Of 346 masses with a reference standard, none were clinically important (0%; 95% CI, 0-0.9%). Mean mass size was 17 mm; 72% (248/346) measured 21-30 HU, and 28% (98/346) measured 31-39 HU. CONCLUSION. Incidental small homogeneous renal masses measuring 21-39 HU at portal venous phase CT are common and highly likely benign. CLINICAL IMPACT. The change in attenuation threshold signifying the need for additional imaging from greater than 20 HU to greater than 30 HU proposed by the Bosniak classification version 2019 is supported.

Prevalence of Malignancy on Contrast-Enhanced Computed Tomography of the Abdomen and Pelvis in Patients With Unexplained, Unintentional Weight Loss.

OBJECTIVE: The aim of the study was to evaluate the prevalence of malignancy on contrast-enhanced computed tomography (CT) of the abdomen and pelvis in patients with unexplained, unintentional weight loss (UUWL). METHODS: This is a retrospective review of 999 adult outpatient contrast-enhanced CT of the abdomen and pelvis for UUWL. Patients were stratified into 2 groups: (1) weight loss only (WLO, n = 222) and (2) UUWL with additional symptoms (UUWL+, n = 777). χ2 test was performed to compare malignancy detection rate in the WLO and UUWL+ groups. RESULTS: Prevalence of malignancy was 5.3% (95% confidence interval [CI], 4.2%-7.1%; 55 of 999). Prevalence of malignancy in the WLO group was 2.3% (95% CI, 0.7%-5.2%; 5 of 222), lower than the prevalence of 6.2% (95% CI, 4.6%-8.1%; 48 of 777) in the UUWL+ group (P = 0.02). Prevalence of malignancy was lower in patients younger than 60 years in all patients and in the UUWL+ subgroup (P < 0.01 in both cases). CONCLUSIONS: There is low prevalence of malignancy on contrast-enhanced CT of the abdomen and pelvis in patients with UUWL, particularly in younger patients and those without additional symptoms.

Clinical Importance of Incidentally Detected Hyperenhancing Liver Observations on Portal Venous Phase Computed Tomography in Patients Without Known Malignancy or Liver Disease.

OBJECTIVE: The aim of the study was to determine the prevalence of clinically important masses among incidental hyperenhancing liver observations on portal venous phase computed tomography (CT) in patients without known malignancy or liver disease. METHODS: Retrospective search of portal venous phase CTs was performed to identify hyperenhancing liver observations in patients without cancer or liver disease. Observations were assigned a morphology of homogeneous, hemangioma, or heterogeneous. The reference standard was pathology (n = 2), liver protocol CT/magnetic resonance imaging (n = 40), follow-up portal venous phase CT for 2 years or more (n = 81), or clinical follow-up for 5 years or more (n = 107). RESULTS: There were no clinically important masses among 83 observations with homogeneous morphology or 110 with hemangioma morphology. There were 2 clinically important masses (1 hepatocellular carcinoma and 1 hepatic adenoma) among 37 (5.4%) heterogeneous morphology observations. CONCLUSIONS: Incidental hyperenhancing liver observations on portal venous phase CT with homogeneous or typical hemangioma morphology in patients without known cancer or liver disease are highly likely benign.

Adrenal Tumors Found During Staging and Surveillance for Colorectal Cancer: Benign Incidentalomas or Metastatic Disease?

OBJECTIVE: To evaluate the incidence of adrenal metastases in patient with colorectal cancer (CRC) and determine the clinical and radiographic features associated metastatic CRC to the adrenal glands. MATERIALS AND METHODS: The review of consecutive adults with newly diagnosed CRC found to have adrenal tumors > 1 cm in size on staging or surveillance CT scans with at least two scans to evaluate progression or stability of disease. RESULTS: Fifty-eight of 856 (6.8%) CRC patients had an adrenal tumor. Forty-three patients (74%) with 46 adrenal tumors had benign adrenal tumors, and 15 (26%) patients with 17 adrenal tumors had metastatic disease. On univariate analysis, patients with metastatic CRC had larger adrenal tumors (26.7 mm vs 12.4 mm, p < 0.01), a higher mean CEA (239 ng/mL vs 14.2 ng/mL, p = 0.03), and were more likely to have other sites of metastatic disease seen on imaging 8/43 (19%) vs 14/15 (93%), p < 0.01. On multivariable analysis, adrenal tumor size > 1.8 cm (OR 49.6 CI 8-306), CEA > 2.5 ng/mL (OR 15.8 CI 1.7-144) and other metastatic disease seen on imaging (OR 68.1 CI 7-661) were independently associated with adrenal metastases. CONCLUSION: CRC patients with small adrenal tumors, normal CEA levels and no evidence of other metastatic disease are unlikely to have spread to the adrenal glands. Adrenal tumors found during staging and surveillance of CRC patients should be evaluated with appropriate imaging and biochemical analysis.

Radiation Dose Reduction of Unenhanced CT Limited to the Kidneys for Follow-Up of Patients With Known Nephrolithiasis Without Symptoms.

OBJECTIVE. The purpose of this study is to identify the landmarks and associated radiation dose reduction for limited CT of the kidneys of patients requiring follow-up for known nephrolithiasis. MATERIALS AND METHODS. This retrospective study included all adult patients who underwent CT examination type "CT abdomen + pelvis renal stone" at our institution during 2017. Several exclusion criteria were identified, including scoliosis and congenital renal abnormalities. A total of 299 patients met the inclusion and exclusion criteria. The radiation dose and z-axis length associated with the original CT scan were recorded. The upper and lower limits of both kidneys in relation to the vertebral body endplates were recorded, to determine the z-axis length for a CT scan limited to the kidneys. A commercially available radiation dose analytics software package was used to provide estimates of whole-body-and individual organ-equivalent doses for the original CT scan and the limited range CT scan. RESULTS. The superior endplate of T11 and the inferior endplate of L5 are landmarks that will include both kidneys on almost all scans. A limited z-axis range leads to a mean scan length reduction of 50%. The whole-body mean effective dose is reduced by 41.5%, and the doses to the breast and the gonadal and bladder organs are reduced by 71.7%, 73.8%, and 81.8%, respectively. CONCLUSION. For patients without symptoms who are undergoing CT surveillance to evaluate renal calculi growth, new stone formation, or both, a limited-range scan extending from the superior endplate of T11 to the inferior endplate of L5 results in a significant reduction in radiation dose.

Differences in Growth Rate on CT of Adrenal Adenomas and Malignant Adrenal Nodules.

OBJECTIVE. The purpose of this study is to determine the differences in growth rate of adrenal adenomas and malignant adrenal nodules. MATERIALS AND METHODS. This was a retrospective review of adults with an adrenal nodule seen at two different abdominal or chest CT examinations or PET/CT examinations. Patients in the adenoma group were included if they had a CT, MRI, or pathologic diagnosis of an adrenal adenoma. Patients in the malignant group were included if they had a pathologically proven malignant adrenal nodule. Nodule growth was defined as a change in the largest axial diameter greater than or equal to 3 mm. Growth rate was calculated by dividing the change in the longest axial diameter by the time between the first and last imaging examination. RESULTS. There were 105 adenomas and 26 malignant nodules. Of the 105 adenomas, 34 (32.4%; 95% CI, 23.6-42.2%) grew, three (2.9%; 95% CI, 0.6-8.1%) became smaller, and 68 (64.8%; 95% CI, 54.8-73.8%), were unchanged in size. All 26 (100%; 95% CI, 89.1-100%) malignant nodules grew. The mean (± SD) growth rate of adenomas was 1.0 ± 0.67 mm/year (range, 0.3-2.8 mm/year), compared with 58.4 ± 78.5 mm/year (range, 5.8-395.4 mm/year) for malignant nodules (p < 0.001). A growth rate of 3 mm/year distinguished adenomas from malignant nodules with a sensitivity of 100% (95% CI, 86.8-100%) and a specificity of 100% (95% CI, 96.6-100%). CONCLUSION. Approximately one-third of radiologically proven adrenal adenomas grew, all of which grew at a rate less than 3 mm/year. All malignant adrenal nodules grew, and all at a rate greater than 5 mm/year.

Pilot Study to Diagnose Nonalcoholic Steatohepatitis With Dynamic 18F-FDG PET.

OBJECTIVE: Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are major causes of chronic liver disease characterized by steatosis, inflammation, and fibrosis. Diagnosis of inflammation is limited by the need for liver biopsy. Dynamic PET with the widely used radiotracer 18F-FDG provides a novel method for evaluating spatial and temporal changes in liver inflammation. MATERIALS AND METHODS: Patients with NAFLD or NASH underwent dynamic FDG PET and MRI within 6 months of undergoing liver biopsy. Liver time-activity curves were extracted to estimate kinetic parameters representing various rate constants of FDG transport using tracer kinetic modeling. Liver biopsy specimens were scored on the basis of NASH Clinical Research Network criteria. RESULTS: This pilot study included 22 patients, 14 of whom were women. Patient age ranged from 18 to 70 years, and the mean body mass index (weight in kilograms divided by the square of height in meters) was 33.2 (range, 24-43.1). The K1 value, which represents the rate of FDG transport from blood to hepatic tissue, was significantly correlated with inflammation (r = -0.7284; p = 0.0001) and the overall NAFLD activity score (NAS; r = -0.6750; p = 0.0006). K1 values were inversely related to the hepatic inflammation score and NAS. Although heterogeneity in K1 values across eight liver segments was noted, distinct segregation existed among segmental K1 values dependent on the histologic inflammation score (p = 0.022) or NAS (p = 0.0091). K1 had a strong association with both inflammation (ROC AUC value, 0.88) and the NAS (ROC AUC value, 0.89), with K1 = 1.02 (mL/min/mL) corresponding to a sensitivity and specificity of 93% and 88%, respectively, for the NAS. CONCLUSION: Dynamic FDG PET with tracer kinetic modeling has the potential to determine liver inflammation in patients with NAFLD and NASH and can fill an essential gap in diagnosis.