adrenal gland
The adrenal (suprarenal) glands (often shortened to just the adrenals) are paired organs of the endocrine system, often asymmetric in shape.
Gross anatomy
Each gland is enclosed in the perirenal fascia and each has a body and two limbs: a medial limb and a lateral limb. However, the right adrenal gland is usually more pyramidal in shape while the left adrenal gland is more crescentic .
The right adrenal gland has a maximum width of 6.1 mm and the left adrenal gland has a maximum width of 7.9 mm . Proportionately, the adrenal size is larger in neonates and infants, being almost one-third of the size of the kidney .
The adrenal gland consists of two portions: an outer cortex and an inner medulla. The gland is covered by a collagenous capsule.
The cortex is subdivided into three zones (from outer to inner) :
The medulla (chromaffin cells) produces catecholamines (epinephrine, norepinephrine) as well as dopamine.
Locations
The adrenal glands lie superior and anteromedial to the kidneys.
Relations
Right adrenal gland
- medial: right crus of the diaphragm, right inferior phrenic artery
- lateral: right lobe (bare area) of the liver
- anterior: inferior vena cava (IVC)
- posterior: right kidney
Left adrenal gland
- medial: left crus of the diaphragm, left inferior phrenic artery
- anterior: lesser sac, stomach, splenic artery, pancreas
- lateral: spleen
- posterior: left kidney
Arterial supply
- arterial supply is via three adrenal arteries
- superior adrenal artery (from inferior phrenic artery)
- usually a group of 6-8 arteries arise
- superior adrenal artery (from inferior phrenic artery)
- middle adrenal artery (from abdominal aorta)
- inferior adrenal artery (from renal artery)
Venous drainage
- venous drainage
- adrenal veins emerge from the hilum and drain to different veins depending on the side:
- left adrenal vein drains to the left renal vein
- may join with the left inferior phrenic vein before entering the left renal vein
- right adrenal gland drains to the IVC
- left adrenal vein drains to the left renal vein
- adrenal veins emerge from the hilum and drain to different veins depending on the side:
Lymphatic drainage
- lymphatics are contained within the capsule and drain to the para-aortic nodes
Innervation
- presynaptic sympathetic fibers, from thoracic splanchnic nerves synapse directly with chromaffin cells
- post synaptic fibers from celiac, aorticorenal, and renal ganglia innervate surrounding vessels
Variant anatomy
- lying down adrenal sign
- takes on a flattened appearance
- often in the presence of a pelvic kidney or renal agenesis
- adrenal gland hypoplasia or agenesis
- accessory adrenal rests
- often near adrenal glands but may be found anywhere in the abdomen, pelvis or scrotum
- horseshoe adrenal gland
Radiographic features
Ultrasound
- anterior transverse scanning is the best approach but the adrenal glands are often difficult to see :
- left adrenal gland seen ~40% at least once during scan
- right adrenal gland seen ~80% at least once during scan
- left adrenal gland is more difficult to visualize than the right because it is often posterior to the stomach and obscured by gas; this can be overcome by
- intercostal scanning in the posterior axillary line
- scanning through the spleen and left kidney with the left side of the patient elevated
CT and MRI
The adrenal glands enhance after contrast administration to approximately 50-60 HU. Hyperenhancement of the adrenal gland is concerning for hypovolemic shock.
Right adrenal gland
- located superior and anteromedial to the upper pole of the right kidney
- appears as a linear, V-shape or comma-shape
Left adrenal gland
- located superior and anteromedial to the upper pole of the left kidney
- appears as a triangular or Y-shape
Related pathology
- adrenal gland trauma
- adrenal hemorrhage
- adrenal calcification
- tumors of the adrenal gland
- adrenal hyperplasia
Siehe auch:
- Nebennierenraumforderungen
- perirenal fascia
- Nebennierenblutung
- Nebennierenhyperplasie
- Verkalkungen der Nebennnieren
- adrenal gland trauma
- Varianten Nebennieren
- Hufeisennebenniere
- angeborene Nebennierenhypoplasie
- pancake adrenal gland
- adrenal gland agenesis
- accessory adrenal nests