Diagnostic ultrasound ( PDFDrive )

1650 PART V Pediatric Sonography
A
B
FIG. 48.38 Parathyroid Adenoma and Hyperplasia. (A) Patient with hyperparathyroidism demonstrates a hypoechoic nodule (arrow) posterior
to the thyroid gland. (B) Patient with renal failure shows hypoechoic lenticular lesion (arrow) posterior to thyroid, consistent with parathyroid gland
hyperplasia.
Parathyroid Glands
he parathyroid glands are two paired endocrine glands arising
from the third and fourth branchial pouches. 130 Normal parathyroid
tissue is infrequently identiied separate from the thyroid
because their echotexture is similar. Sonographic imaging of the
parathyroid may be helpful in the presence of primary or secondary
hyperparathyroidism. Parathyroid adenomas are rare in
children but are the most common cause of primary hyperparathyroidism.
131,132 Children with chronic renal failure may develop
parathyroid gland hyperplasia caused by secondary hyperparathyroidism.
133 Four-gland parathyroid hyperplasia is more
common in patients with MEN I. 134 Ultrasound is 80% to 90%
sensitive in detecting parathyroid tumors and gland enlargement.
131 Typical sonographic imaging indings of an adenoma
and hyperplasia are similar, appearing as an oblong, sharply
demarcated, hypoechoic solid mass aligned craniocaudal and
posterior to the thyroid (Fig. 48.38). Less frequently, the mass
may be cystic, calciied, multilobular, and giant. 43 Enlargement
of the adjacent inferior thyroid artery may be identiied as an
arc of vascularity, providing clues to diagnosis of an adenoma. 135
Because 20% of the parathyroid tissue can be ectopic, MRI may
be considered if ultrasound is unsuccessful in identifying the
lesion. 136
Other Cystic Lesions
Foregut cysts represent defective budding of the respiratory
or intestinal tract. Bronchogenic cysts are usually mediastinal
and rarely may occur as a mass in the lower neck. 94,137
Esophageal cysts are typically centered close to the esophageal
wall. Foregut lesions usually occur as a palpable lump but can
enlarge rapidly, causing airway obstruction and dysphagia.
With sonography, the lesions are typically unilocular but may
be complicated by hemorrhage and infection, especially in
the presence of persistent communication with the airway or
esophagus.
Laryngoceles are air- or luid-illed dilations of the laryngeal
saccule, a small pouch arising from the roof of the laryngeal
ventricle. 93 Internal laryngoceles remain within the larynx, whereas
external masses project through the thyrohyoid membrane. 138
When the laryngeal saccule is totally obstructed, the outpouching
will appear as a smooth-walled anechoic mass projecting into
the endolaryngeal or preepiglottic space. 138 In 8% to 10% of
cases, laryngoceles develop superimposed infection, and there
is a 15% association with neoplasm. 93 Children typically have
airway obstruction or feeding diiculties.
LACKING DEFINITION BY THE HYOID
he carotid space and deep cervical fascial layers extend above
and below the hyoid bone. 6,7 he carotid space, enveloped by
all three layers, extends from the skull base to the aortic arch.
Its contents include the internal carotid artery, jugular vein,
cranial nerves IX to XII (vagus nerve, X), and deep cervical
lymph node chain. he retropharyngeal and prevertebral spaces
extend from the skull base to the level of the third thoracic
vertebral body. he danger space is within the retropharyngeal
space where a pathway exists for infection to spread inferiorly
into the posterior mediastinum. he retropharyngeal space
contains primarily lymph nodes, whereas the prevertebral space
contains vertebral bodies, spinal cord, paraspinal and scalene
muscles, and vertebral artery and vein. hese spaces are not
discussed separately because many diseases, especially nodal,
involve multiple spaces simultaneously. It should be noted that
ultrasound is especially useful in assessment of supericial lesions.
Ultrasound is of limited value in deep space lesions involving
the retropharyngeal space and prevertebral space, which typically
require CT or MRI for better evaluation. 139