The adrenal glands are endocrine organs com­posed of two entities: the steroid hormone­producing cortex (aldosterone, cortisol, and androgens) and the catecholamine-synthesizing medulla, which have a dual embryological ori­gin. Around the 5th week of gestation, the cortex develops from the mesoderm of the urogenital ridge that later develops into the pro-, meso-, and metanephros. The medulla arises from the neural crest. In the fetus, the cortex is further divided into a wide inner fetal cortex and an outer zone that later becomes the adult cortex. This occurs via hemorrhagic and then necrotic involution of the fetal cortex and proliferation of the adult cor­tex towards the center of the gland which causes a 30–50 % reduction in the gland weight (Fig. 14.1) [2, 3]. Prior to this, the adrenal glands are 10–20 times larger than adult glands in relation to the total body weight and approximately one third the size of the neonatal kidney [4]. After involu­tion of the fetal cortex, the infant adrenal glands measure between 1 and 3.6 cm (mean 1.5 cm) in length and between 2 and 5 mm (mean 3 mm) in thickness [5, 6]. The adult cortex continues to de­velop until 3 years of age into three zones: zona glomerulosa, fasciculata, and reticularis.

The arterial blood supply is provided by the inferior phrenic artery, the aorta, and the renal ar­tery. These arteries further subdivide into small channels that span over the capsule of the gland and form a rich plexus within the gland. There is a single draining vein, but smaller accessory veins are usually found following the anatomic course of the smaller arteries [6].

rophies and is replaced by fibrous tissue, the hy­perechoic central stripe becomes broader, while the hypoechoic fetal cortex thins [12].

Primary adrenal neoplasms can be categorized by their origin and function. They arise from either the medulla or cortex, and they are usually non­functioning or hyperfunctioning. Medullary neo­plasms originate from the neural crest cells and therefore can occur anywhere along the sympa­thetic neural chain. These neoplasms include neu­roblastoma, ganglioneuroblastoma, ganglioneu­roma, and pheochromocytoma. Neoplasms aris­ing from the adrenal cortex include adrenocortical carcinoma and adenoma and are very uncommon in children. The rarer adrenal neoplasms of child­hood include teratoid rhabdoid tumor and smooth muscle tumors in patients with AIDS. In addition to masses of adrenal origin, extra-adrenal masses in the suprarenal fossa may be difficult to differ­entiate from primary masses of the adrenal glands. The most common examples are retroperitoneal lymphatic malformations and intra-abdominal ex­tralobar pulmonary sequestrations [7].

Clinically, neuroblastoma most commonly presents as a palpable mass, but can be an inci­dental finding on US or sequential imaging. If symptomatic, children can present with signs of increased adrenal medullary hormone production or symptoms from direct tumor growth or meta­static disease.

Local invasion can occur into the liver, kid­neys, and through the neural foramina into the spinal canal, causing cord compression symp­toms. Neuroblastomas typically show encase­ment or displacement of the vascular structures and only rarely invade the vasculature or ureter, which can be helpful to distinguish them from Wilms’ tumor. Distant metastases are present in half the cases at the time of diagnosis and are most commonly found in lymph nodes, bone marrow, liver, and skin [7].

US is often the first diagnostic imaging tool applied and can also be helpful in the diagnosis of metastatic disease, especially in liver involve­ment. On US, the neuroblastoma usually ap­pears as a heterogeneous mass, with hyperechoic areas caused by calcifications, with or without posterior acoustic shadowing. Hypoechoic and anechoic areas in neuroblastoma correspond to cystic, hemorrhagic, or necrotic changes and are less common than in Wilms’ tumor. Larger cystic areas are more often present in newborns, in whom bilateral cystic neuroblastoma with intracystic hemorrhage may occur (Fig. 14.2) [17].

Diagnosis of neonatal neuroblastoma is often more challenging for several reasons. Sono­graphic findings may resemble neonatal adrenal

arteries are common in sequestrations. Neuro­blastoma does not occur prior to the third trimes­ter of gestation because the neural tissue in the adrenal gland is too underdeveloped to give rise to neuroblastoma, therefore alternative diagnoses should be considered in an adrenal region mass discovered in this age group [7].

Ganglioneuroblastomas arise from both, the ma­ture ganglion cells and immature cells resem­bling neuroblastoma cells, resulting in a poten­tially malignant behavior. One third of the tumors arise in the adrenal gland, one third in the retro­peritoneum, and the remaining one third in the posterior mediastinum, with only rare manifesta­tions in the neck or pelvis [12].

Ganglioneuromas are the most mature neural crest tumors and are histologically benign. One third of the cases are located in the retroperito­neum, and only rarely do they arise in the adrenal gland. Ganglioneuromas occur in older children, can be completely asymptomatic, and are often incidental findings on US or chest radiographs. When they invade the spine, neurologic symp­toms can occur related to cord compression. Ganglioneuroblastomas and Ganglioneuromas cannot be distinguished from neuroblastoma with imaging alone, and therefore there is no standard imaging protocol for follow-up [12].

masses of varying echogenicity depending on the fat content [25]. Myelolipomas contain fatty as well as hematopoietic elements and appear rather homogenous and hyperechoic with no substantial vascularity. They can look impressive on im­aging as they can reach sizes reported as large as 10 cm; however, they are benign in nature (Fig. 14.5) [26].

Neonatal adrenal hemorrhage is a rare event commonly presenting within the first week of life with unexplained hyperbilirubinemia. Clinical findings can be subtle and vary. Reports include newborns with hypovolemia, anemia, abdomi­nal mass, or even scrotal or inguinal ecchymo­sis [27]. Infants at risk are usually macrosomic newborns who underwent stressful delivery, with a higher incidence in vaginal deliveries. In addi­tion, single reports mention an association with anoxia, sepsis, bleeding disorders, and maternal diabetes [28]. Hemorrhage more commonly oc­curs in the right adrenal gland than left. In the acute phase, US will reveal a heterogeneously hypoechoic mass with a hyperechoic rim [5].

embolization of adrenal hemorrhage as well as surgical exploration has been reported [37].

Generally, US changes appear to be complete­ly reversible with introduction of steroid replace­ment therapy, and fetuses who receive intrauter­ine therapy can have sonographically normal­appearing adrenal glands at birth [12].