Incidental Adrenal Nodules

To report hounsfeld units or not: There is no question

INTRODUCTION

Most adrenal incidentalomas are not appropriately evaluated. Reporting the mass in the radiology report summary and providing recommendations in the report can positively impact evaluation. This study evaluated the effect of reporting Hounsfield units(HU) on adrenal incidentaloma follow-up.

METHODS

Patients with adrenal incidentalomas identified on noncontrast CT scan from 2015 to 2020 ​at a tertiary care institution were studied. Chart review was conducted. Patient and imaging characteristics were compared between patients who did and did not have HU reported. Outcomes of interest were 1)outpatient referral, 2)biochemical evaluation, and 3)dedicated imaging if appropriate. Multivariate analysis determined the impact of HU, reporting in the summary and provision of recommendations on the outcomes.

RESULTS

363 patients were studied, 36(9.9 ​%) had HU reported. When HU were used in addition to recommendations and reporting in the summary, the likelihood of outpatient referral increased from 10.1 to 32.6-fold (95%CI 7.7-138.1, p ​< ​0.001). Similarly, the likelihood of biochemical workup increased from 2.5 to 7.8-fold (95%CI 2.5-24.1, p ​< ​0.001).

CONCLUSION

Recording adrenal incidentaloma HU on non-contrast CT scans was associated with increased rates of outpatient referral and biochemical workup.

Dual Energy-Derived Metrics for Differentiating Adrenal Adenomas From Nonadenomas on Single-Phase Contrast-Enhanced CT

BACKGROUND. Adrenal masses are often indeterminate on single-phase postcontrast CT. Dual-energy CT (DECT) with three-material decomposition algorithms may aid characterization. OBJECTIVE. The purpose of this study was to compare the diagnostic performance of metrics derived from portal venous phase DECT, including virtual noncontrast (VNC) attenuation, fat fraction, iodine density, and relative enhancement ratio, for characterizing adrenal masses. METHODS. This retrospective study included 128 patients (82 women, 46 men; mean age, 64.6 ± 12.7 [SD] years) who between January 2016 and December 2019 underwent portal venous phase abdominopelvic DECT that showed a total of 139 adrenal lesions with an available reference standard based on all imaging, clinical, and pathologic records (87 adenomas, 52 nonadenomas [48 metastases, two adrenal cortical carcinomas, one ganglioneuroma, one hematoma]). Two radiologists placed ROIs to determine the following characteristics of the masses: VNC attenuation, fat fraction, iodine density normalized to portal vein, and for masses with VNC greater than 10 HU, relative enhancement ratio (ratio of portal venous phase attenuation to VNC attenuation). Readers' mean measurements were used for ROC analyses, and clinically optimal thresholds were derived as thresholds yielding the highest sensitivity at 100% specificity. RESULTS. Adenomas and nonadenomas were significantly different (all p < .001) in VNC attenuation (mean ± SD, 18.5 ± 12.9 vs 34.1 ± 8.9 HU), fat fraction (mean ± SD, 24.3% ± 8.2% vs 14.2% ± 5.6%), normalized iodine density (mean ± SD, 0.34 ± 0.15 vs 0.17 ± 0.17), and relative enhancement ratio (mean ± SD, 186% ± 96% vs 58% ± 59%). AUCs for all metrics ranged from 0.81 through 0.91. The metric with highest sensitivity for adenoma at the clinically optimal threshold (i.e., 100% specificity) was fat fraction (threshold, ≥ 23.8%; sensitivity, 59% [95% CI, 48-69%]) followed by VNC attenuation (≤ 15.2 HU; sensitivity, 39% [95% CI, 29-50%]), relative enhancement ratio (≥ 214%; sensitivity, 37% [95% CI, 25-50%]), and normalized iodine density (≥ 0.90; sensitivity, 1% (95% CI, 0-60%]). VNC attenuation at the traditional true noncontrast attenuation threshold of 10 HU or lower had sensitivity of 28% (95% CI, 19-38%) and 100% specificity. Presence of fat fraction 23.8% or greater or relative enhancement ratio 214% or greater yielded sensitivity of 68% (95% CI, 57-77%) with 100% specificity. CONCLUSION. For adrenal lesions evaluated with single-phase DECT, fat fraction had higher sensitivity than VNC attenuation at both the clinically optimal threshold and the traditional threshold of 10 HU or lower. CLINICAL IMPACT. By helping to definitively diagnose adenomas, DECT-derived metrics can help avoid downstream imaging for incidental adrenal lesions.

Diagnosing and managing adrenal incidentalomas

ABSTRACT

Adrenal incidentalomas are commonly encountered because of the widespread use of high-resolution cross-sectional imaging. Adrenal incidentalomas may be benign or malignant, and also may demonstrate hormonal hypersecretion, so all patients with adrenal masses should undergo further assessment. Clinicians should have a basic understanding of adrenal incidentalomas, their workup, and when follow-up and referral are warranted.

Can 3-Phase Computed Tomography Urography Be Used to Characterize Adrenal Nodules? Results in 145 Patients

OBJECTIVE

The aim of the study is to determine whether computed tomography (CT) urography (CTU) can characterize incidental adrenal nodules.

METHODS

This retrospective cohort study was performed at an academic medical center. Patients were identified by free text search of CTU reports that contained the terms "adrenal mass" "adrenal nodule" and "adrenal lesion." Computed tomography urography technique consisted of unenhanced images and postcontrast images obtained at 100 seconds and 15 minutes. The final cohort included 145 patients with 151 adrenal nodules. Nodules were considered lipid-rich adenomas or myelolipomas based on unenhanced imaging characteristics. Absolute and relative washout values were calculated for the remaining nodules, using a cutoff of 60% and 40%, respectively, to diagnose adenomas. Reference standard for lipid-poor adenomas and malignant nodules was histopathology or imaging/clinical follow-up. Mann-Whitney U test was used for comparison of continuous variables, and Fisher exact test was used for categorical variables.

RESULTS

One hundred nodules were lipid-rich adenomas and 3 were myelolipomas. Forty-eight nodules were indeterminate at unenhanced CT, corresponding to 39 lipid-poor adenomas and 9 malignant nodules based on reference standards. Both absolute and relative washout correctly characterized 71% of nodules (34/48), with a sensitivity of 67% and specificity of 89%. Overall, 91% of all adrenal nodules (137/151) were correctly characterized by CTU alone. Lipid-poor adenomas were smaller than malignant nodules (P < 0.01) and were lower in attenuation on unenhanced and delayed images (P < 0.01).

CONCLUSIONS

Adrenal nodules detected at 3-phase CTU can be accurately characterized, potentially eliminating the need for subsequent adrenal protocol CT or magnetic resonance imaging.

Machine Learning for Adrenal Gland Segmentation and Classification of Normal and Adrenal Masses at CT

Background Adrenal masses are common, but radiology reporting and recommendations for management can be variable. Purpose To create a machine learning algorithm to segment adrenal glands on contrast-enhanced CT images and classify glands as normal or mass-containing and to assess algorithm performance. Materials and Methods This retrospective study included two groups of contrast-enhanced abdominal CT examinations (development data set and secondary test set). Adrenal glands in the development data set were manually segmented by radiologists. Images in both the development data set and the secondary test set were manually classified as normal or mass-containing. Deep learning segmentation and classification models were trained on the development data set and evaluated on both data sets. Segmentation performance was evaluated with use of the Dice similarity coefficient (DSC), and classification performance with use of sensitivity and specificity. Results The development data set contained 274 CT examinations (251 patients; median age, 61 years; 133 women), and the secondary test set contained 991 CT examinations (991 patients; median age, 62 years; 578 women). The median model DSC on the development test set was 0.80 (IQR, 0.78-0.89) for normal glands and 0.84 (IQR, 0.79-0.90) for adrenal masses. On the development reader set, the median interreader DSC was 0.89 (IQR, 0.78-0.93) for normal glands and 0.89 (IQR, 0.85-0.97) for adrenal masses. Interreader DSC for radiologist manual segmentation did not differ from automated machine segmentation (P = .35). On the development test set, the model had a classification sensitivity of 83% (95% CI: 55, 95) and specificity of 89% (95% CI: 75, 96). On the secondary test set, the model had a classification sensitivity of 69% (95% CI: 58, 79) and specificity of 91% (95% CI: 90, 92). Conclusion A two-stage machine learning pipeline was able to segment the adrenal glands and differentiate normal adrenal glands from those containing masses. © RSNA, 2022 Online supplemental material is available for this article.

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.

Incidence of malignancy in adrenal nodules detected on staging CTs of patients with potentially resectable colorectal cancer

OBJECTIVE

To measure the prevalence of adrenal nodules detected on staging CT in patients with resectable colorectal cancer, and the proportion of patients with malignant nodules among them.

METHODS

This retrospective study included 6474 patients (median age, 65; interquartile range, 56-73; 3902 men) who underwent staging CT for colorectal cancer between May 2003 and December 2018. The patients had potentially resectable colorectal cancer, including resectable hepatic or pulmonary metastases. Through retrospective CT image review, patients with adrenal nodules were identified for the prevalence of adrenal nodule. Among patients with adrenal nodules, per-patient proportions of malignant nodules, adrenal metastasis from colorectal cancer, and additional adrenal examinations (biopsy or imaging tests) were measured. A secondary analysis was performed using data from the official CT reports.

RESULTS

The prevalence of adrenal nodules was 5.6% (363 of 6474; 95% CI: 5.1, 6.2). The proportions of malignant nodules and adrenal metastasis from colorectal cancer were 0.8% (3 of 363; 0.2, 2.4) and 0.3% (1 of 363; 0.0, 1.5), respectively. 6.1% (22 of 363; 3.8, 9.0) of the patients underwent additional adrenal examination. According to official CT reports, the prevalence of adrenal nodules and proportions of malignant nodules, adrenal metastasis from colorectal cancer, and additional adrenal examination were 1.9% (125 of 6474; 1.6, 2.3), 1.6% (2 of 125; 0.2, 5.7), 0% (0 of 125; 0.0, 2.9), and 10.4% (1 of 125; 5.7, 17.1), respectively.

CONCLUSION

Adrenal nodules detected in staging CTs in patients with otherwise resectable colorectal cancers are rarely malignant.

KEY POINTS

• Among 6474 patients who underwent staging CT and had potentially resectable colorectal cancer, 363 had adrenal nodules (≥ 10 mm) detected in retrospective CT image review. • Three out of the 363 patients with adrenal nodules detected on staging CT had malignant adrenal nodules, one of whom had metastasis from colorectal cancer.