A variety of lesions could simulate adrenal tumors on images; however, careful recognition of the anatomical structures of the adrenal gland and adjacent structures are usually useful to differentiate these adrenal pseudotumors from true adrenal tumors. Adrenal pseudotumors include gastric diverticulum, accessory spleen, retroperitoneal tumors of para-adrenal location, pancreas lesion with posterior extension, renal upper polar mass with superior exophytic growth, hepatic tumor, and peri-adrenal varices [1]. Familiarity with the wide spectrum of imaging appearances of these adrenal pseudotumors aids in establishing correct diagnosis. For adrenal pseudotumors have extremely anatomical closeness to the adrenal glands, it remains a challenge to attain a correct preoperative diagnosis.

Adrenal tuberculosis (TB) is usually presenting with bilateral adrenal enlargements or adrenal masses with or without calcifications on images. The enlarged adrenal gland could have either homogeneous or heterogeneous enhancement. If the adrenal TB mass has a large necrotic area, it usually has a heterogeneous enhancement pattern with a central hypodense area after contrast medium administration on computed tomography and magnetic resonance. In prior healed adrenal TB infection, atrophic adrenal glands with calcifications may be seen. Adrenal TB could be found in patients with prior or coexisting renal TB as well [2]. In patients having bilateral enlarged adrenal glands shown on images, the presence of renal TB imaging findings might suggest the diagnosis of adrenal TB [2]. Otherwise, adrenal metastasis and primary adrenal tumors are the differential diagnoses.

Extramedullary hematopoiesis (EMH) usually occurs in patients with β-thalassemia or other hemoglobinopathies [3]. Adrenal EMH is extremely rare [4]. Adrenal EMH has been reported as homogeneous hypoechoic mass on ultrasound [4], which is different from the current case shown. On computed tomography (CT), adrenal EMH appear as a homogeneous or heterogeneous enhancing mass with focal lower density areas on computed tomography (CT) [3, 4]. In patients with related hemoglobinopathies of EMH, adrenal EMH should be listed in differential diagnosis of an adrenal mass. Histological examination of the adrenal mass could help establish the diagnosis of adrenal EMH and avoid unnecessary adrenal mass resection.

Adrenal hemorrhage could be diagnosed by its typical imaging characteristics or follow-up images in the presence of related histories, especially of acute hematoma stage. Acute hematoma of adrenal gland shows typical high density ranging from 50 to 90 Hounsfield units on unenhanced computed tomography (CT) [5]. On ultrasound, acute hematoma of the adrenal gland usually shows higher echogenicity than the liver parenchyma [5]. On magnetic resonance imaging (MRI), acute hematoma usually shows high or intermediate signal intensity on T1-weighted images [5]. The size of adrenal hemorrhage usually decreased over time [5]. The density of adrenal hematoma decreases gradually and becomes water density on unenhanced CT when it has been liquefied. A liquefied hematoma appears anechoic on ultrasound [5] and low signal intensity on T1-weighted images and high signal intensity on T2-weighted images on MRI. Another important imaging feature of adrenal hemorrhage on CT and MRI is the absence of enhancement of the hematoma itself unless there is active bleeding or hemorrhage in a preexisting adrenal tumor. Adrenal hemorrhage usually occurs in trauma patients, patients undertaking anticoagulation therapy, patients with sepsis or hypotension, or newborns suffering from birth trauma, hypoxia, or coagulopathy [5]. Ultrasound is a useful follow-up imaging tool for validation of the diagnosis of adrenal hemorrhage in newborns by demonstrating size reduction and liquefaction [5]. By using these imaging characteristics, adrenal hemorrhage could usually be diagnosed with confidence, and follow-up imaging helps in solving some cases of adrenal hemorrhage diagnosed with uncertainty.

Adrenal cysts could be easily diagnosed on images if they present with typical imaging characteristics as unilocular or multilocular cysts with or without thin calcifications [6]. There are four histological subtypes of adrenal cysts: endothelial cysts, pseudocysts, epithelial cysts, and parasitic cysts [6]. Among the four subtypes, endothelial cysts and pseudocysts are more common [6]. Adrenal pseudocysts may present as a hemorrhagic cyst with layering appearance because they usually come from hemorrhage of the adrenal gland [6]. Adrenal pseudocysts may have atypical imaging features with soft tissue density on computed tomography. However, no contrast enhancement of the soft tissue part in the lesion may suggest its nature as a pseudocyst rather than a true neoplasm [6].

Adrenal hyperplasia typically involves bilateral adrenal glands [5]. Bilateral adrenal hyperplasia most commonly appears as bilateral adrenal enlargements with smooth contours and maintenance of adrenal shape similar to normal ones [5]. The densities on CT and signal intensities on MRI of bilateral adrenal gland hyperplasia are similar to that of normal adrenal glands. Occasionally, bilateral adrenal hyperplasia may show micronodular or macronodular appearances in addition to adrenal gland enlargement [5]. These micro- or macronodules may show a density similar to or slightly lower than the adjacent adrenal parenchyma on unenhanced CT, which become more conspicuous by lower density contrast to normal adrenal parenchyma on enhanced CT. Bilateral adrenal hyperplasia could be seen in patients with Cushing’s syndrome, primary hyperaldosteronism, or adrenogenital syndrome [5]. The majority (80–85 %) of Cushing’s syndrome are adrenocorticotropic hormone (ACTH)-dependent, which usually results from pituitary lesions [7]. For patients with primary aldosteronism, mean adrenal limb width more than 5 mm with or without nodules has been reported as 100 % specificity for diagnosing bilateral adrenal hyperplasia and more than 3 mm as 100 % sensitivity [8]. However, adrenal venous sampling has been recommended for mean adrenal limb width between 3 and 5 mm for differentiating bilateral adrenal hyperplasia from aldosterone-producing adenomas (APA) in patients with primary aldosteronism [8]. Bilateral adrenal hyperplasia typically shows symmetric (i.e., bilateral) increased uptake in adrenal scintigraphy [9].