ADRENAL GLANDS PATHOLOGY SCANNING
Category: Diagnostic Radiology
Abstract : THE ADRENAL GLANDS Normal appearances The normal adrenal glands can be
seen on ultrasound in the vast majority of patients, if you know where and how
to look. Each adrenal gland is constructed with a central fold or ridge, which
points anteromedially, from which extend two thin ‘wings’ of tissue—a medial and
a lateral wing. The ultrasound appearances are therefore o
THE ADRENAL GLANDS
Normal appearances
The normal adrenal glands can be
seen on ultrasound in the vast majority of patients, if you know where and how
to look. Each adrenal gland is constructed with a central fold or ridge, which
points anteromedially, from which extend two thin ‘wings’ of tissue—a medial and
a lateral wing.
The ultrasound appearances are therefore of a < shape in LS,
or a thin, linear structure as the transducer is moved medially towards the
central ridge. The wings of the gland appear hypoechoic and are no more than 2
mm in thickness.
Ultrasound technique
For the right adrenal, use the
liver as an acoustic window. Scan the upper pole of the kidney intercostally
through the liver, and angle slightly medially to the kidney, where the gland
can be located between the liver and the diaphragmatic crus. Continue angling
slightly medially towards the IVC and the central ridge of the gland is seen
behind the IVC. For the left gland the spleen must be used as a window. To avoid
overlying bowel this is best achieved with the patient supine, using a coronal
section. When the upper pole of the left kidney is located through the spleen,
the left adrenal can be seen in the small triangular area between the spleen,
kidney and diaphragmatic crus.
Pathology of the adrenal
glands
Adenoma
Small (less than 3 cm) solid adrenal nodules are a common,
incidental finding in non-symptomatic patients. Benign, non-hyperfunctioning
adenomas account for the majority of adrenal nodules, and are of no clinical
significance. Their incidence increases with age and they are present in around
2% of adult autopsies. Small nodules in asymptomatic patients generally require
no further action, but endocrine function may be evaluated to rule out a
functioning mass. A hyperfunctioning adenoma (a determination made by evaluation
of the endocrine function), although an essentially benign mass, usually
requires surgical resection. As a solitary abdominal finding in a patient with
no relevant clinical history, it is generally safe to assume a small adrenal
nodule requires no further action. However, because it is not possible to
distinguish benign, incidental nodules from other forms of more serious
pathology, incidental nodules of greater than 4 cm should be investigated
further to confirm their benign nature. Non-functioning adenomas will remain
stable in size on ultrasound follow-up.
Metastasis
The adrenal glands
are a common site for metastases, particularly from lung, breast and bowel
cancer. Although frequently accompanied by liver metastases, they may be present
in the absence of any other obvious abdominal deposits, and therefore the
adrenal glands should routinely be examined when staging malignant disease. The
adrenal glands are also commonly involved in non-Hodgkin’s lymphoma. Like
adenomas, they are often small, welldefined and hypoechoic on ultrasound. It is
not possible to differentiate between benign adenoma and metastasis on the
ultrasound appearances alone, but a small adrenal mass in the absence of a known
primary carcinoma is likely to be benign, and will remain stable on follow-up. A
solitary adrenal mass in the presence of known carcinoma requires biopsy for
diagnosis.
Adrenal cysts
Simple cysts are uncommon in the adrenal
gland, but are easily differentiated from solid lesions with ultrasound. Some
cysts may be the sequelae of previous haemorrhage, but most are simple,
epithelial cysts.
Myelolipoma
The adrenal myelolipoma is found,
uncommonly, as an incidental mass. It is highly echogenic and well-defined, due
to its fatty content. These are relatively rare, require no further management,
and are endocrinologically nonfunctioning.
Phaeochromocytoma
The
phaeochromocytoma is uncommon, but may be found in up to 1% of patients with
hypertension. It is a tumour arising in the chromaffin cells of the adrenal
medulla (most commonly) or in autonomic nervous tissue. It may be bilateral and
appears solid on ultrasound, although larger masses may have areas of necrosis
within them. Most are benign, but 5–10% are malignant. It presents on a
background of episodic, severe hypertension and the urine contains
catecholamines. (Although this is also a feature of adrenal neuroblastoma, the
latter is predominantly a childhood tumour.) These lesions should be treated
with great care—vigorous palpation may precipitate a severe hypertensive episode
and biopsy should therefore be avoided. Although most phaeochromocytomas arise
in the adrenal glands, and are therefore demonstrable on ultrasound, those
arising in the sympathetic chain may be obscured by bowel gas and are not
possible to exclude on ultrasound. If there remains biochemical evidence of
phaeochromocytoma in the presence of normal adrenal glands, a
Meta-Iodobenzylguanidine isotope scan will demonstrate increased activity in a
phaeochromocytoma and CT scan can then be targeted to the appropriate area.
Phaeochromocytomas are also associated with von Hippel–Lindau
syndrome.
Adrenal carcinoma
Primary adrenal carcinomas are rare in the
adult. They are commonly endocrinologically inactive in adults, and therefore
tend to present late when they are quite large. They may invade the IVC and
metastasize to the liver. Surgical removal of tumours in the absence of liver
metastases has a good prognosis and, in patients with metastases, radiofrequency
ablation of the adrenal mass may have some benefit in prolonging survival.
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