Adrenal imaging: a comprehensive review

Can MDCT Enhancement Patterns Be Helpful in Differentiating Secretory from Non-Functional Adrenal Adenoma?

Background and Objectives: Primary adrenal tumors (AT) are a heterogeneous group of neoplasms due to their functional heterogeneity, which results in the diverse clinical presentation of these tumors. The purpose of this study was to examine cross-sectional imaging characteristics using multi-detector computed tomography (MDCT) to provide insight into the lesion characterization and functional status of these tumors. The radionuclide imaging using Technetium-99m radiolabeled hydrazinonicotinylacid-d-phenylalanyl1-tyrosine3-octreotide (99mTc-HYNIC-TOC), was also used in the diagnostic evaluation of these tumors. Materials and Methods: This cross-sectional study included 50 patients with confirmed diagnoses of AT (21 hormone-secreting and 29 non-functional) at the University Clinical Center, Kragujevac, Serbia, during the 2019-2022 year period. The morphological and dynamic characteristics using MDCT were performed, using qualitative, semi-quantitative, and quantitative analysis. Absolute washout (APW) and relative washout (RPW) values were also calculated. A semi-quantitative analysis of all visual findings with 99mTc-HYNIC-TOC was performed to compare the tumor to non-tumor tracer uptake. Results: A statistically significant difference was found in the MDCT values in the native phase (p < 0.05), the venous phase (p < 0.05), and the delayed phase (p < 0.001) to detect the existence of adrenal tumors. Most of these functional adrenocortical lesions (n = 44) can be differentiated using the delayed phase (p < 0.05), absolute percentage washout (APW) (p < 0.05), and relative percentage washout (RPW) (p < 0.001). Furthermore, 99mTc-HYNIC-TOC could have a high diagnostic yield to detect adrenal tumor existence (p < 0.001). There is a positive correlation between radionuclide imaging scan and APW to detect all AT (p < 0.01) and adrenocortical adenomas as well (p < 0.01). Conclusions: The results can be very helpful in a diagnostic algorithm to quickly and precisely diagnose the expansive processes of the adrenal glands, as well as to learn about the advantages and limitations of the mentioned imaging modalities.

Image-Guided Precision Medicine in the Diagnosis and Treatment of Pheochromocytomas and Paragangliomas

In this comprehensive review, we aimed to discuss the current state-of-the-art medical imaging for pheochromocytomas and paragangliomas (PPGLs) diagnosis and treatment. Despite major medical improvements, PPGLs, as with other neuroendocrine tumors (NETs), leave clinicians facing several challenges; their inherent particularities and their diagnosis and treatment pose several challenges for clinicians due to their inherent complexity, and they require management by multidisciplinary teams. The conventional concepts of medical imaging are currently undergoing a paradigm shift, thanks to developments in radiomic and metabolic imaging. However, despite active research, clinical relevance of these new parameters remains unclear, and further multicentric studies are needed in order to validate and increase widespread use and integration in clinical routine. Use of AI in PPGLs may detect changes in tumor phenotype that precede classical medical imaging biomarkers, such as shape, texture, and size. Since PPGLs are rare, slow-growing, and heterogeneous, multicentric collaboration will be necessary to have enough data in order to develop new PPGL biomarkers. In this nonsystematic review, our aim is to present an exhaustive pedagogical tool based on real-world cases, dedicated to physicians dealing with PPGLs, augmented by perspectives of artificial intelligence and big data.

A retrospective analysis of the clinical characteristics of 207 hospitalized children with adrenal masses

Objective

The detection rates of adrenal masses (AMs) have recently increased. The present study aimed to examine the clinical characteristics of these adrenal masses for guiding the clinical diagnosis and treatment among hospitalized children.

Methods

The clinical data of AM cases admitted to our hospital from January 2014 to March 2023 were collected and analyzed retrospectively. The data included composition, sex, age, initial presentation, size and site of mass, functional tumor, intervention or surgery, pathological or clinical diagnosis, and imaging data.

Results

A total of 207 hospitalized children were included. Among them, adrenal hematoma was the most common finding (53.6%), followed by adrenal neuroblastoma (36.2%). Most masses were larger-sized (51.2%) and non-functional (94.7%). We found that adrenal hematoma commonly occurred in a neonate or child with abdominal trauma. Most adrenal hematoma cases were found in male patients (63.1%), on the right side (71.2%), and with sizes <4 cm (73.9%). Adrenal neuroblastoma was commonly detected in male patients (56.0%), on the right side (66.7%), and with sizes ≥4 cm (85.3%). Moreover, the metastases were frequently explored at the time of diagnosis. In addition, there was no significant difference between ultrasound and computed tomography (CT) scans under suspicion of hematoma (P > 0.05). However, CT showed a priority over ultrasound in the diagnosis of neuroblastoma (P < 0.05).

Conclusion

Most masses were non-functional and benign. Of these, adrenal hematoma was the most common type of pediatric AM, followed by adrenal neuroblastoma. They were both commonly found in male patients and on the right side. Neuroblastoma revealed a larger tumor size. Compared to cases of adrenal hematoma, cases of adrenal neuroblastoma required CT scans for further assessment.

CT of hemorrhagic adrenal adenomas: radiologic-pathologic correlation

PURPOSE

To describe the appearance of chronically hemorrhagic adenomas on adrenal protocol CT and correlate imaging with pathologic findings.

METHODS

Retrospective case series of adult patients with resected adrenal adenomas showing internal hemorrhage at histology. Seven of nine patients underwent pre-operative adrenal protocol CT and 2/7 underwent unenhanced CT with portal venous phase CT. Two abdominal radiologists in consensus assessed the CT images for the presence of calcifications, macroscopic fat, cystic/necrotic appearance, and the presence, pattern, and percent nodule volume of areas < 10 HU on unenhanced CT. Absolute washout was calculated using a large ROI, and ROIs on the highest and lowest attenuating regions on the portal venous phase.

RESULTS

Mean adenoma length was 4.9 cm. All adenomas had areas measuring < 10 HU on unenhanced CT, ranging from < 20 to > 80% nodule volume. Calcifications were present in 4/9 adenomas and gross fat in 4/9 on CT. Of the seven cases with adrenal protocol CT, the absolute washout was < 60% in 5/7 using the large ROI, 5/7 using the low attenuation ROI, and 7/7 using the high attenuation ROI. At histology, all nine cases had microscopic evidence of hemorrhage, lipid rich adenoma cells, and fibrosclerosis. Myelolipomatous changes were identified in 4/9 cases, with the remaining five cases showing lipomatous metaplasia without a myeloid component.

CONCLUSION

Chronically hemorrhagic adrenal adenomas demonstrated variable areas < 10 HU on unenhanced CT corresponding to lipid rich adenoma cells. Absolute washout was most often < 60%, hypothesized to be due to fibrosclerosis within the adenomas.

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 Lesions: A Review of Imaging

Adrenal lesions are frequently incidentally diagnosed during investigations for other clinical conditions. Despite being usually benign, nonfunctioning, and silent, they can occasionally cause discomfort or be responsible for various clinical conditions due to hormonal dysregulation; therefore, their characterization is of paramount importance for establishing the best therapeutic strategy. Imaging techniques such as ultrasound, computed tomography, magnetic resonance, and PET-TC, providing anatomical and functional information, play a central role in the diagnostic workup, allowing clinicians and surgeons to choose the optimal lesion management. This review aims at providing an overview of the most encountered adrenal lesions, both benign and malignant, including describing their imaging characteristics.

Diagnostic value of the relative enhancement ratio of the portal venous phase to unenhanced CT in the identification of lipid-poor adrenal tumors

PURPOSE

Adrenal incidentalomas are common lesions found on abdominal imaging, most of which are lipid-rich adrenal adenomas. Imaging diagnoses differentiating lipid-poor adrenal adenomas (LPA) from non-adenomas (NA) are presently challenging to perform. The aim of the study was to investigate the diagnostic performance of the relative enhancement ratio parameter in identifying LPA from NA.

METHODS

We retrospectively evaluated consecutively presenting patients with lipid-poor adrenal lesions (January 2015 to August 2021). Lesions were divided into LPA and NA (including hyperenhancing and hypoenhancing NA). Kruskal-Wallis and Bonferroni tests were used to determine the differences in feature parameters between these three groups. Receiver operating characteristic curve analysis was performed to determine the sensitivity for diagnosing LPA and NA at 95% specificity; the parameters were compared using the McNemar test.

RESULTS

A total of 253 patients (mean age, 55 ± 12 years; 135 men), 121 with LPA and 132 with NA, were analyzed herein. The sensitivity (achieved at 95% specificity) of the relative enhancement ratio was higher than that of unenhanced attenuation in differentiating LPA from NA (60% vs. 52%, p = 0.064). The relative enhancement ratio yielded a higher sensitivity than unenhanced attenuation (79% vs. 59%, p < 0.001) in differentiating LPA from hypoenhancing NA, and a lower sensitivity (26% vs. 69%, p < 0.001) in differentiating LPA from hyperenhancing NA.

CONCLUSION

The relative enhancement ratio showed better diagnostic performance than unenhanced attenuation in differentiating LPA from hypoenhancing NA, while simultaneously showing poor diagnostic performance in identifying LPA from all NA.

Optimal and novel imaging of the adrenal glands

PURPOSE OF REVIEW

Adrenal imaging forms an important role in the workup of adrenal masses. The purpose of this review is to briefly review the traditional role of imaging in adrenal diseases and highlight the most recent research and new applications aimed to improve diagnostic accuracy.

RECENT FINDINGS

The current review will focus on new applications of computed tomography (CT), MRI and PET/CT imaging, addressing the implications of artificial intelligence and radiomics in progressing diagnostic accuracy.

SUMMARY

The new applications of adrenal imaging are improving diagnostic accuracy and expanding the role of imaging, particularly with novel PET radiotracers and the use of artificial intelligence.

Can Radiomics Provide Additional Diagnostic Value for Identifying Adrenal Lipid-Poor Adenomas From Non-Adenomas on Unenhanced CT?

Background

It is difficult for radiologists to differentiate adrenal lipid-poor adenomas from non-adenomas; nevertheless, this differentiation is important as the clinical interventions required are different for adrenal lipid-poor adenomas and non-adenomas.

Purpose

To develop an unenhanced computed tomography (CT)-based radiomics model for identifying adrenal lipid-poor adenomas to assist in clinical decision-making.

Materials and methods

Patients with adrenal lesions who underwent CT between January 2015 and August 2021 were retrospectively recruited from two independent institutions. Patients from institution 1 were randomly divided into training and test sets, while those from institution 2 were used as the external validation set. The unenhanced attenuation and tumor diameter were measured to build a conventional model. Radiomics features were extracted from unenhanced CT images, and selected features were used to build a radiomics model. A nomogram model combining the conventional and radiomic features was also constructed. All the models were developed in the training set and validated in the test and external validation sets. The diagnostic performance of the models for identifying adrenal lipid-poor adenomas was compared.

Results

A total of 292 patients with 141 adrenal lipid-poor adenomas and 151 non-adenomas were analyzed. Patients with adrenal lipid-poor adenomas tend to have lower unenhanced attenuation and smoother image textures. In the training set, the areas under the curve of the conventional, radiomic, and nomogram models were 0.94, 0.93, and 0.96, respectively. There was no difference in diagnostic performance between the conventional and nomogram models in all datasets (all p < 0.05).

Conclusions

Our unenhanced CT-based nomogram model could effectively distinguish adrenal lipid-poor adenomas. The diagnostic power of conventional unenhanced CT imaging features may be underestimated, and further exploration is worthy.

[Diagnostic value of ct in examination of patients with adrenal cancer]

BACKGROUND

In most cases adrenal tumours are detected by accident while performing medical imaging tests for other diseases. These findings are treated as adrenal incidentaloma. Prevalence of incidentalomas detected on CT scans is up to 4%. According to different authors, 4-12% of all adrenal tumours are adrenocortical carcinomas. As for today, the most significant medical imaging technique is CT scan with bolus IV injection of contrast agent and assessment of tumour's density. The analysis of the results of CT imaging in 67 patients with ACC was carried out according to a single protocol. The main signs characteristic of this disease are described. It is very important to evaluate typical signs of ACC on CT scans for risk assessment of ACC before surgical treatment. If malignant tumour is suspected during preoperative examination, it is extremely important to choose the right surgical treatment strategy.

AIM

To evaluate the significance of CT as the main method of preoperative diagnosis in patients with malignant tumors of the adrenal cortex. Studying CT semiotics of adrenocortical cancer in a large group of patients using a single standard imaging protocol. Find the main radiological symptoms characteristic of adrenocortical cancerMATERIALS AND METHODS: Here are the results of retrospective study of CT scans performed on 67 patients with adrenocortical carcinoma who received treatment in the Department of Endocrine Surgery of Saint-Petersburg State University N.I. Pirogov Clinic of High Medical Technologies during 2012-2020. The diagnostic significance of CT in patients with ACC was assessed.

RESULTS

The most common features of ACC: tumour heterogeneity (84.3%), tumour's size 3-9 cm (75%), signs of invasion into surrounding structures (10%), pre-contrast density above +30 HU (75%), absolute contrast washout less than 60% (68.8%), relative contrast washout less than 40% (64.6%)CONCLUSION: CT scan with IV contrast was not able to show any definitive pathognomonic signs of ACC. Nevertheless, CT scan should be performed in all patients with suspected (or confirmed using other medical imaging technique) adrenal tumour according to standard protocol. Bolus injection of contrast agent should be performed in all patients with tumour's pre-contrast density above +5 HU.

Adrenal incidentaloma. Part 2. Modern concepts of computed tomography semiotics of adrenal gland incidentalomas: algorithm of differential diagnosis

While accidentally detecting an adrenal gland lesion (incidentaloma) during a routine computed tomography (CT) scan, the radiologist should correctly interpret revealed changes. The most common lesion is adenoma with high lipid content, but a lipid poor adenoma, pheochromocytoma, adrenocortical cancer, metastasis and other less common adrenal diseases are also worth of attention and require detailed knowledge of their CT semiotics. The article presents criteria of differential diagnosis of the adrenal incidentalomas on the basis of which an algorithm of differential diagnosis was proposed for the most common adrenal lesions.

Can we differentiate neoplastic and non-neoplastic spontaneous adrenal bleeding? Imaging findings with radiopathologic correlation

Spontaneous adrenal bleeding is a rare clinical event with non-specific clinical features. Life-threatening bleeding in the adrenal glands may be promptly diagnosed with imaging. Computed tomography (CT) is generally the first imaging modality to be used in these patients. However, in the acute phase of bleeding, it may be difficult to detect the underlying mass from the large hematoma. In these patients, additional imaging studies such as magnetic resonance imaging or positron emission tomography/CT may be utilized to rule out a neoplastic mass as the source of bleeding. In patients where an underlying neoplastic mass could not be identified at the time of initial diagnosis, follow-up imaging may be helpful after the acute phase subsides.

Adrenal metastases: early biphasic contrast-enhanced CT findings with emphasis on differentiation from lipid-poor adrenal adenomas

AIM

To evaluate the accuracy of unenhanced attenuation and early biphasic contrast-enhanced computed tomography (CT) in differentiating adrenal metastases (AMs) from lipid-poor adrenal adenomas (AAs).

MATERIALS AND METHODS

This retrospective study included 37 patients with 50 AMs and 86 patients with 89 lipid-poor AAs. Quantitative data including the longest diameter (LD), the shortest diameter (SD), LD/SD ratio, CT attenuation values (CTu, CTa, CTv), degree of enhancement (DEAP, DEPP, DEpeak, APW, RPW), and peak enhanced/unenhanced (PE/U) CT attenuation ratio were obtained. Qualitative data including enhancement pattern, location, shape, the presence of calcification or haemorrhage, and intra-lesion necrosis were analysed. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were also calculated.

RESULTS

The PE/U ratio (≤1.25), CTu (≥32.2 HU), DEpeak (≤43.15 HU), DEPP (≤37.65 HU), presence of intralesional necrosis, location (bilateral adrenal glands), and irregular shape were significant variables for differentiating AMs from lipid-poor AAs (p<0.05). Among them, PE/U ratio (≤1.25) was of greater value in differentiating the two adrenal diseases, with sensitivity, specificity, area under the receiver operating curve (ROC) curve (AUC) of 92%, 84%, 0.933, respectively. When at least any three of above criteria were combined, the sensitivity, specificity, PPV, and NPV for diagnosing AMs were 88%, 93%, 88%, and 88%, respectively.

CONCLUSIONS

These seven CT criteria are conducive to differentiate AMs from lipid-poor AAs. Early biphasic contrast-enhanced CT is a high-efficient and practical imaging tool in differentiating them.

Pitfalls and differential diagnosis on adrenal lesions: current concepts in CT/MR imaging: a narrative review

The purpose of this pictorial essay is to review the imaging findings of adrenal lesions. Adrenal lesions could be divided into functioning or non-functioning masses, primary or metastatic, and benign or malignant. Imaging techniques have undergone significant advances in recent years. The most significant objective of adrenal imaging is represented by the detection and, when possible, characterization of adrenal lesions in order to direct patient management correctly. The detection and management of adrenal lesions is based on cross-sectional imaging obtained with non-contrast CT (tumour density), contrast-enhanced CT including delayed washout (either absolute percentage washout or relative percentage one) and finally with MR chemical shift analysis (loss of signal intensity between in-phase and out-of-phase images including both qualitative and quantitative estimates of signal loss). The small incidental adrenal nodules are benign, in most of cases; some tumors such as lipid-rich adenoma and myelolipoma have characteristic features that can be diagnosed accurately in CT. On contrary, if the presenting contrast-enhanced CT shows an adrenal mass with uncertain or malignant morphologic features, particularly in patients with a known history of malignancy, further evaluations should be considered. The most significative implications for radiologists are represented by how to assess risk of malignancy on imaging and what follow-up to indicate if an adrenal incidentaloma is not surgically removed.

[Adrenal incidentaloma. Part 1. Computed tomography of adrenal incidentaloma: the possibilities and difficulties of differential diagnosis]

The adrenal incidentaloma is a lesion of a different etiology and found incidentally in patients who underwent a diagnostic study not about the disease of this organ. Lesions can be both hormonally inactive and hormonally active, can arise from different zones of the adrenal gland or have non-specific organ affiliation, can be benign or malignant. Computed tomography characterization of these lesions, especially the differential diagnosis of benign and malignant, is extremely important for the correct diagnosis in order to provide adequate management of the patient. The article presents the key computed tomography criteria that allow radiologist to characterize the lesion most accurately and consider appropriate diagnosis.

Adrenal Incidentaloma

An adrenal incidentaloma is now established as a common endocrine diagnosis that requires a multidisciplinary approach for effective management. The majority of patients can be reassured and discharged, but a personalized approach based upon image analysis, endocrine workup, and clinical symptoms and signs are required in every case. Adrenocortical carcinoma remains a real concern but is restricted to <2% of all cases. Functional adrenal incidentaloma lesions are commoner (but still probably <10% of total) and the greatest challenge remains the diagnosis and optimum management of autonomous cortisol secretion. Modern-day surgery has improved outcomes and novel radiological and urinary biomarkers will improve early detection and patient stratification in future years to come.

Imaging of Adrenal-Related Endocrine Disorders

Endocrine disorders associated with adrenal pathologies can be caused by insufficient adrenal gland function or excess hormone secretion. Excess hormone secretion may result from adrenal hyperplasia or hormone-secreting (ie, functioning) adrenal masses. Based on the hormone type, functioning adrenal masses can be classified as cortisol-producing tumors, aldosterone producing tumors, and androgen-producing tumors, which originate in the adrenal cortex, as well as catecholamine-producing pheochromocytomas, which originate in the medulla. Nonfunctioning lesions can cause adrenal gland enlargement without causing hormonal imbalance. Evaluation of adrenal-related endocrine disorders requires clinical and biochemical workup associated with imaging evaluation to reach a diagnosis and guide management.

Differential diagnosis and laparoscopic resection of an adrenal pseudocyst: A case report

BACKGROUND

Adrenal pseudocysts are infrequent entities and definite preoperative diagnosis is difficult. We present a case of left adrenal pseudocyst, which was intraoperatively identified as having an adrenal origin and was resected using a laparoscopic approach.

PRESENTATION OF CASE

A 41-year-old female was referred to our hospital for examination and treatment of a cystic lesion in the pancreatic tail. Preoperative diagnostic imaging studies showed a cystic lesion with intramural nodular structure, measuring 39 mm in the largest diameter and located between the pancreatic tail and the left adrenal gland. However, the origin of the cystic lesion remained unclear, and a definite preoperative diagnosis was not established. The cystic lesion was intraoperatively identified as having an adrenal origin after the division of the loose connective tissue layer around the lesion under the laparoscopic magnified view. Laparoscopic left adrenalectomy was performed as radical treatment and the histopathological diagnosis confirmed the presence of an adrenal pseudocyst.

DISCUSSION

We could not ascertain the origin of the cystic lesion from the left adrenal gland and establish a definite diagnosis based on the findings of the preoperative diagnostic imaging modalities. Laparoscopic surgery could be more advantageous than the conventional open approach as not only a minimally invasive treatment option but also as an intraoperative diagnostic tool for cystic lesions in the pancreatic tail.

CONCLUSION

This case report suggests that laparoscopic surgery could be clinically useful as not only a minimally invasive treatment but also an intraoperative diagnostic tool for cystic lesions in the pancreatic tail region.

Practical guide on the initial evaluation, follow-up, and treatment of adrenal incidentalomas Adrenal Diseases Group of the Spanish Society of Endocrinology and Nutrition

Initial evaluation of adrenal incidentalomas should be aimed at ruling out malignancy and functionality. For this, a detailed clinical history should be taken, and an adequate radiographic assessment and a complete blood chemistry and hormone study should be performed. The most controversial condition, because of the lack of consensus in its definition, is autonomous cortisol secretion. Our recommendation is that, except when cortisol levels <1.8μg/dL in the dexamethasone suppression test rule out diagnosis and levels ≥5μg/dL establish the presence of autonomous cortisol secretion, diagnosis should be based on a combined definition of dexamethasone suppression test ≥3μg/dL and at least one of the following: elevated urinary free cortisol, ACTH level <10 pg/mL, or elevated nocturnal cortisol (in serum and/or saliva). During follow-up, dexamethasone suppression test should be repeated, usually every year, on an individual basis depending on the results of prior tests and the presence of comorbidities potentially related to hypercortisolism. The initial radiographic test of choice for characterization of adrenal incidentalomas is a computed tomography scan without contrast, but there is no unanimous agreement on subsequent monitoring. Our general recommendation is a repeat imaging test 6-12 months after diagnosis (based on the radiographic characteristics of the lesion). If the lesion remains stable and there are no indeterminate characteristics, no additional radiographic studies would be needed. We think that patients with autonomous cortisol secretion with comorbidities potentially related to hypercortisolism, particularly if they are young and there is a poor control, may benefit from unilateral adrenalectomy. The indication for unilateral adrenalectomy is clear in patients with overt hormonal syndromes or suspected malignancy. In conclusion, adrenal incidentalomas require a comprehensive evaluation that takes into account the possible clinical signs and comorbidities related to hormonal syndromes or malignancy; a complete hormone profile (taking into account the conditions that may lead to falsely positive and negative results); and an adequate radiographic study. Monitoring and/or treatment will be decided based on the results of the initial evaluation.

Adrenal cortical carcinoma: pathology, genomics, prognosis, imaging features, and mimics with impact on management

Adrenocortical carcinoma (ACC) is a rare tumor with a poor prognosis. Most tumors are either metastatic or locally invasive at the time of diagnosis. Differentiation between ACC and other adrenal masses depends on clinical, biochemical, and imaging factors. This review will discuss the genetics, pathological, and imaging feature of ACC.

Adrenal cortical adenoma: current update, imaging features, atypical findings, and mimics

Adrenal adenoma is the most common adrenal lesion. Due to its wide prevalence, adrenal adenomas may demonstrate various imaging features. Thus, it is important to identify typical and atypical imaging features of adrenal adenomas and to be able to differentiate atypical adrenal adenomas from potentially malignant lesions. In this article, we will discuss the diagnostic approach, typical and atypical imaging features of adrenal adenomas, as well as other lesions that mimic adrenal adenomas.

Imaging features of adrenal gland masses in the pediatric population

The spectrum of adrenal masses in the pediatric population markedly differs from that in the adult population. Imaging plays a crucial role in detecting adrenal masses, differentiating malignant from benign lesions, recognizing extra-adrenal lesions in the suprarenal fossa, and directing further management. Ultrasound is the primary imaging modality of choice for the evaluation of adrenal masses in the neonatal period, whereas MRI or CT is used as a problem-solving tool. In older children, computed tomography or magnetic resonance imaging is often required after initial sonographic evaluation for further characterization of a lesion. Herein, we discuss the salient imaging features along with pathophysiology and clinical features of pediatric adrenal masses.

Bilateral adrenal abnormalities: imaging review of different entities

Bilateral adrenal abnormalities are not infrequently encountered during routine daily radiology practice. The differential diagnoses of bilateral adrenal abnormalities include neoplastic and non-neoplastic entities. The bilateral adrenal tumors include metastasis, lymphoma, neuroblastoma, pheochromocytoma, adenoma, and myelolipoma. Non-neoplastic bilateral adrenal masses include infectious processes and haematomas. There are different diffuse bilateral adrenal changes such as adrenal atrophy, adrenal enlargement, adrenal calcifications, and altered adrenal enhancement. In this pictorial review article, we will discuss the imaging features of these entities with emphasis on their clinical implications.

Interobserver agreement in distinguishing large adrenal adenomas and adrenocortical carcinomas on computed tomography

PURPOSE

Large adrenal masses pose a diagnostic dilemma. The purpose of this study was twofold: first, to assess the degree of interobserver agreement in evaluating the morphology of pathologically proven adrenal adenomas and adrenocortical carcinomas larger than 4 cm in diameter; and second, to identify morphologic characteristics that correlated with the pathologic diagnosis.

MATERIALS AND METHODS

For this blinded, retrospective study, we collected cases of 25 adrenal adenomas and 33 adrenocortical carcinomas measuring larger than 4 cm. Two radiologists evaluated morphologic characteristics of the lesions on CT. Interobserver agreement was evaluated using kappa statistics, and the correlation of imaging characteristics with the diagnosis was evaluated using a logistic regression model.

RESULTS

We found the highest interobserver agreement in the assessment of precontrast attenuation (Κ = 0.81) as well as substantial agreement in determining the shape and the presence of calcifications (Κ = 0.69 and 0.74, respectively). Readers agreed less often regarding the presence of fat (Κ = 0.48), as well as regarding the presence of necrosis, heterogeneity, and the overall impression (Κ = 0.15, 0.24, and 0.26, respectively). CT characteristics correlated with benignity included round shape (p = 0.02), an overall radiologic impression of a benign lesion (p < 0.0001), the presence of fat (p = 0.01), and a precontrast attenuation of less than 10 Hounsfield units (p < 0.0001). The latter two of these characteristics were highly specific for benign pathology (93% and 100%, respectively).

CONCLUSION

Our study suggests that CT has the ability to consistently identify characteristics significantly correlated with benign vs. malignant adrenal tumors.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

Utility of Intermediate-Delay Washout CT Images for Differentiation of Malignant and Benign Adrenal Lesions: A Multivariate Analysis

OBJECTIVE

The objective of this study was to identify features that impact the diagnostic performance of intermediate-delay washout CT for distinguishing malignant from benign adrenal lesions.

MATERIALS AND METHODS

This retrospective study evaluated 127 pathologically proven adrenal lesions (82 malignant, 45 benign) in 126 patients who had undergone portal venous phase and intermediate-delay washout CT (1-3 minutes after portal venous phase) with or without unenhanced images. Unenhanced images were available for 103 lesions. Quantitatively, lesion CT attenuation on unenhanced (UA) and delayed (DL) images, absolute and relative percentage of enhancement washout (APEW and RPEW, respectively), descriptive CT features (lesion size, margin characteristics, heterogeneity or homogeneity, fat, calcification), patient demographics, and medical history were evaluated for association with lesion status using multiple logistic regression with stepwise model selection. Area under the ROC curve (A_z) was calculated from both univariate and multivariate analyses. The predictive diagnostic performance of multivariate evaluations was ascertained through cross-validation.

RESULTS

A_z for DL, APEW, RPEW, and UA was 0.751, 0.795, 0.829, and 0.839, respectively. Multivariate analyses yielded the following significant CT quantitative features and associated A_z when combined: RPEW and DL (A_z = 0.861) when unenhanced images were not available and APEW and UA (A_z = 0.889) when unenhanced images were available. Patient demographics and presence of a prior malignancy were additional significant factors, increasing A_z to 0.903 and 0.927, respectively. The combined predictive classifier, without and with UA available, yielded 85.7% and 87.3% accuracies with cross-validation, respectively.

CONCLUSION

When appropriately combined with other CT features, washout derived from intermediate-delay CT with or without additional clinical data has potential utility in differentiating malignant from benign adrenal lesions.

Chemical shift magnetic resonance imaging could predict subclinical cortisol production from an incidentally discovered adrenal mass

CONTEXT

To investigate whether any association between chemical shift magnetic resonance (MRI) findings, cortisol secretion and pathological findings exists that could predict subclinical hypercortisolism (SCH) in patients with adrenal incidentalomas (AI).

DESIGN

Retrospective, cross-sectional study in a tertiary centre.

PATIENTS

Sixty-eight subjects with AIs and 13 patients with Cushing's syndrome (CS). Patients with AIs were categorized according to cortisol levels post 1 mg dexamethasone (post-DST).

MEASUREMENTS

Visual inspection of the lipid content of the adrenal tumour and calculation of adrenal-to-spleen ratio (ASR), the signal intensity index (SII), volume and the assessment of the association between pathological, radiological and hormonal findings in surgically treated patients.

RESULTS

Percentage of clear cells was correlated with ASR (r = -.525, P = .01), SII (r = .465, P = .025), post-DST cortisol (r = -.711, P < .001) and ACTH (r = .475, P = .046). By ANOVA and post hoc analysis, patients with CS and five subjects with a post-DST cortisol greater than 137 nmol/L differed significantly in ASR and SII from those with a post-DST cortisol less than 50 nmol/L. An ASR level higher than 0.245 (OR 19.7, 95% CI 1.5-257.5; P = .023) and a SII level lower than 78.37 (OR 15.6, 95% CI 1.2-20; P = .034) remained as the independent predictors for SCH while age, presence of arterial hypertension or tumour volume did not make significant contribution to the models.

CONCLUSIONS

Cortisol hypersecretion by adrenal adenomas is associated with distinctive MRI characteristics. The quantitative assessment of intracellular lipid in an AI could help distinguish patients with a clear phenotype of SCH.

Fat-containing Retroperitoneal Lesions: Imaging Characteristics, Localization, and Differential Diagnosis

The complex anatomy of the retroperitoneum is reflected in the spectrum of neoplastic and nonneoplastic conditions that can occur in the retroperitoneum and appear as soft-tissue masses. The presence of fat within a retroperitoneal lesion is helpful in refining the differential diagnosis. Fat is easily recognized because of its characteristic imaging appearance. It typically is hyperechoic at ultrasonography and demonstrates low attenuation at computed tomography (-10 to -100 HU). Magnetic resonance imaging is a more ideal imaging modality because it has better soft-tissue image contrast and higher sensitivity for depicting (a) microscopic fat by using chemical shift imaging and (b) macroscopic fat by using fat-suppression techniques. Whether a lesion arises from a retroperitoneal organ or from the soft tissues of the retroperitoneal space (primary lesion) is determined by examining the relationship between the lesion and its surrounding structures. Multiple imaging signs help to determine the organ of origin, including the "beak sign," the "embedded organ sign," the "phantom (invisible) organ sign," and the "prominent feeding artery sign." Adrenal adenoma is the most common adrenal mass that contains microscopic fat, while myelolipoma is the most common adrenal mass that contains macroscopic fat. Other adrenal masses, such as pheochromocytoma and adrenocortical carcinoma, rarely contain fat. Renal angiomyolipoma is the most common fat-containing renal mass. Other fat-containing renal lesions, such as lipoma and liposarcoma, are rare. Fatty replacement of the pancreas and pancreatic lipomas are relatively common, whereas pancreatic teratomas are rare. Of the primary retroperitoneal fat-containing lesions, lipoma and liposarcoma are common, while other lesions are relatively rare. (©)RSNA, 2016.

Update on CT and MRI of Adrenal Nodules

OBJECTIVE

The objective of this article is to review the current role of CT and MRI for the characterization of adrenal nodules.

CONCLUSION

Unenhanced CT and chemical-shift MRI have high specificity for lipid-rich adenomas. Dual-energy CT provides comparable to slightly lower sensitivity for the diagnosis of lipid-rich adenomas but may improve characterization of lipid-poor adenomas. Nonadenomas containing intracellular lipid pose an imaging challenge; however, nonadenomas that contain lipid may be potentially diagnosed using other imaging features. Multiphase adrenal washout CT can be used to differentiate lipid-poor adenomas from metastases but is limited for the diagnosis of hypervascular malignancies and pheochromocytoma.

Transperitoneal laparoscopic adrenalectomy: a review and single-center experience

Background: Laparoscopic adrenalectomy (LA) is the preferred approach to adrenal gland tumors.

Objective: To evaluate the perioperative and functional outcomes of transperitoneal LA.

Methods: We retrospectively reviewed data of all consecutive patients who underwent transperitoneal LA at our institution between April 2000 and December 2011.

Results: Two hundred two patients with mean age of 46 years were included in the study. There were 109 left, 89 right, and 4 bilateral tumors. Preoperative diagnosis included 126 aldosterone-producing adenomas (APA), 33 patients with Cushing syndrome, 19 pheochromocytomas, 20 nonfunctional tumors, and 4 adrenal metastases. Mean tumor size was 3.3 cm (range 0.4-22 cm). Mean operative time was 109 min and estimated blood loss 90 mL for unilateral adrenalectomy; and 195 min and 300 mL for bilateral adrenalectomy. Four patients with pheochromocytoma required transfusion and 2 required conversion to an open approach. Seven intraoperative complications and 18 30-day postoperative complications occurred. These included 5 major complications (Clavien-Dindo grade 3-5). Ninety-seven percent of APA patients had normal serum potassium levels after surgery. Among the patients with functioning endocrine tumors, complete resolution rate from secondary hypertension was significantly higher in the pheochromocytoma group compared with those with APA or Cushing syndrome (82% vs. 48% vs. 68% respectively, p = 0.02). Mean follow up was 35.2 months.

Conclusion: LA is the treatment of choice for most adrenal gland tumors with excellent outcomes and low complication rates. There was a high chance for complete resolution of secondary hypertension after surgery for pheochromocytoma.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

Imaging findings of adrenal primitive neuroectodermal tumors: a series of seven cases

OBJECTIVE

To explore the imaging features of adrenal primitive neuroectodermal tumors (PNETs).

MATERIALS AND METHODS

This retrospective study included seven patients with surgically and pathologically confirmed adrenal PNETs. Among them, six underwent computed tomography (CT) scans, and one underwent magnetic resonance imaging. The imaging findings, including size, shape, margin, hemorrhage, calcification, cystic degeneration, regional lymph nodes involvement, tumor thrombus formation and enhancement pattern, were retrospectively analyzed.

RESULTS

Among the seven adrenal PNET patients, six were male, and one was female. The median age was 26 years (range 2-56 years). The disease generally presented with either insidious symptoms (n = 4) or non-specific symptoms, including right flank pain (n = 1) and left upper abdominal discomfort (n = 2). On the pre-enhanced CT images, the tumor usually appeared as a well-defined, rounded or oval, heterogeneous mass without calcification. Certain tissue characteristics, such as cystic degeneration (n = 5), capsule (n = 4) and hemorrhage (n = 2), were observed. Regional lymph node involvement was observed in three cases, and renal vein thrombus was observed in one case. All cases showed mild heterogeneous enhancement of the tumor on the enhanced CT images.

CONCLUSION

An adrenal PNET commonly presents as a relatively large, well-defined, heterogeneous mass with cystic degeneration, necrosis and a characteristic mild contrast-enhancement pattern on multiphase enhanced images. PNET should be considered when the diagnosis of common tumors is not favored by signs on images.

CLINICAL TRIAL REGISTRATION STATEMENT

This study was approved by the medical ethics committee of Xiangya Hospital, Central South University. The approval number is 201512538.

Targeted Molecular Imaging in Adrenal Disease-An Emerging Role for Metomidate PET-CT

Adrenal lesions present a significant diagnostic burden for both radiologists and endocrinologists, especially with the increasing number of adrenal ‘incidentalomas’ detected on modern computed tomography (CT) or magnetic resonance imaging (MRI). A key objective is the reliable distinction of benign disease from either primary adrenal malignancy (e.g., adrenocortical carcinoma or malignant forms of pheochromocytoma/paraganglioma (PPGL)) or metastases (e.g., bronchial, renal). Benign lesions may still be associated with adverse sequelae through autonomous hormone hypersecretion (e.g., primary aldosteronism, Cushing’s syndrome, phaeochromocytoma). Here, identifying a causative lesion, or lateralising the disease to a single adrenal gland, is key to effective management, as unilateral adrenalectomy may offer the potential for curing conditions that are typically associated with significant excess morbidity and mortality. This review considers the evolving role of positron emission tomography (PET) imaging in addressing the limitations of traditional cross-sectional imaging and adjunctive techniques, such as venous sampling, in the management of adrenal disorders. We review the development of targeted molecular imaging to the adrenocortical enzymes CYP11B1 and CYP11B2 with different radiolabeled metomidate compounds. Particular consideration is given to iodo-metomidate PET tracers for the diagnosis and management of adrenocortical carcinoma, and the increasingly recognized utility of ¹¹C-metomidate PET-CT in primary aldosteronism.

Determination of a cutoff attenuation value on single-phase contrast-enhanced CT for characterizing adrenal nodules via chemical shift MRI

PURPOSE

This study aims to determine the optimal cutoff attenuation value on single-phase contrast-enhanced CT (CECT) at which chemical shift MRI (CSMRI) yields sufficient accuracy to replace the standard CT adrenal protocol for the diagnosis of adrenal adenomas.

METHODS

Between January 2010 and December 2014, a total of 49 patients (age: 20-81 years; 23 men and 26 women) with 60 adrenal tumors (48 adenomas and 12 non-adenomas) who underwent both CECT in portal venous phase and CSMRI were included in the study. Attenuation on portal venous phase CECT, adrenal-to-spleen chemical shift ratio (ASR), and signal-intensity index (SII) were obtained for each adrenal mass.

RESULTS

Among different cutoff values on CECT (from <70 to <120 HU), the diagnostic accuracies for those lesions measuring <80 HU were the highest and most similar to dedicated adrenal CT. The sensitivities and specificities of SII were up to 96% (25/26) and 100% (7/7) for those measuring <80 HU, but reduced to 73% (16/22) and 80% (4/5) for those ≥80 HU. The overall sensitivities and specificities for diagnosing adrenal adenoma using SII vs. ASR were 85% (41/48) and 92% (11/12) vs. 71% (34/48) and 100% (12/12), respectively.

CONCLUSIONS

CSMRI may replace CT adrenals in the work-up of patients with adrenal nodules below 80 HU on single-phase CECT, hence reducing radiation exposure and iodinated contrast administration. Adrenal nodules greater than 80 HU cannot be accurately diagnosed by CSMRI. CT adrenal protocol remains the appropriate investigative modality in those cases.

Use of Contrast-Enhanced Ultrasound in the Differential Diagnosis of Adrenal Tumors in Dogs

We evaluated the diagnostic accuracy of the contrast-enhanced ultrasonography (CEUS), using a second-generation microbubble contrast agent, in differentiating the different types of adrenal mass lesions in 24 dogs. At B-mode ultrasound, 9 lesions involved the right adrenal gland, 14 the left, and 1 was bilateral. Each dog received a bolus of the contrast agent into the cephalic vein, immediately followed by a 5-mL saline flush. The first contrast enhancement of each adrenal lesion was evaluated qualitatively to assess the degree of enhancement and its distribution during the wash-in and wash-out phases, as well as the presence of non-vascularized areas and specific vascular patterns. Pathological diagnoses were determined in all dogs by histopathology or by cytology. Combining enhancement degree and vascularity resulted in the best predictive model, allowing CEUS to differentiate adrenocortical adenoma (n=10), adenocarcinoma (n=7), and pheochromocytoma (n=7) with an accuracy of 91.7% (P &lt; 0.001). Combining enhancement degree and vascularity, CEUS can discriminate malignant versus benign adrenal lesions with a sensitivity of 100.0%, a specificity of 80.0%, and an accuracy of 91.7% (P &lt; 0.001). In conclusion, results of this study confirm that CEUS is useful for differentiating between the different types of adrenal tumors in dogs.

Minimally Invasive Adrenalectomy

Minimally invasive adrenalectomy has become the gold standard for removal of benign adrenal tumors. The imaging characteristics, biochemical evaluation, and patient selection for laparoscopic transabdominal and posterior retroperitoneoscopic approaches are discussed with details of surgical technique for both procedures.

Divergent Patterns of Incidence in Peripheral Neuroblastic Tumors

BACKGROUND

Prior research on trends in neuroblastoma incidence has conflicted. We aimed to compare how ganglioneuroblastoma and neuroblastoma incidence have changed.

PROCEDURE

Using the Surveillance Epidemiology and End Results (SEER) 9 population-based registry, we identified 2081 malignant peripheral neuroblastic tumors in patients 0 to 14 years from 1973 to 2009. Age-adjusted annual incidence rates were calculated using SEER*Stat, and Joinpoint Regression Program was used to calculate annual percent change (APC) and analyze trends. Data were stratified by histology, age, and stage.

RESULTS

Overall peripheral neuroblastic tumor incidence increased by an APC of 0.47 (P=0.045). However, ganglioneuroblastoma incidence decreased (APC=-1.48; P=0.003), whereas neuroblastoma incidence increased (APC=0.79; P=0.008). When divided by age and stage, locoregional neuroblastoma incidence increased in infants until a significant inflection point in 1996 (APC=4.19; P<0.001) and then decreased sharply (APC=-6.80; P=0.160).

CONCLUSIONS

Ganglioneuroblastoma incidence has decreased, whereas neuroblastoma incidence has increased. These changes could be real, or reflect bias from classification changes or increased detection. Neuroblastoma incidence increased most markedly in infants with locoregional disease only until 1996, then declined, which may reflect changes in tumor ascertainment and folate supplementation.