Diagnostic ultrasound ( PDFDrive )

1646 PART V Pediatric Sonography
Graves disease is the most common cause of hyperthyroidism
in children. It is an autoimmune disease caused by thyroidstimulated
immunoglobulin binding to the thyroid-stimulating
hormone (TSH) receptor, increasing the production of thyroid
hormone. here is frequently a family history. It is more common
in girls (5 : 1 female-to-male ratio) and has a peak incidence in
adolescence, ages 11 to 15 years. 87,88 Diagnosis is usually clinical;
children have an enlarged thyroid gland, exophthalmos, and
hyperthyroidism. Fetuses and neonates born to mothers with
Graves disease are also at risk for transient thyroid dysfunction
and goiter because of transfer of thyroid-stimulating immunoglobulins.
88,103 During ultrasound examination, patients with
Graves disease demonstrate difuse enlargement of the thyroid
gland, which appears heterogeneous and difusely hypoechoic.
Doppler imaging demonstrates intense hypervascularity, also
known as “thyroid inferno” 90 (Fig. 48.31). Doppler waveform
shows increased peak systolic velocity and decreased RI. 106
Thyroid Masses
hyroid nodules in pediatrics are uncommon, with an incidence
of 1.5%. 107 Children with an asymptomatic palpable nodule
typically have normal thyroid function. 108 In a child or adolescent,
a solitary nodule should be approached with suspicion because
FIG. 48.30 Hashimoto Thyroiditis. Thyroid imaging with color
Doppler shows coarse heterogeneous pattern with multiple hypoechoic
micronodular areas, and mildly increased vascularity.
there is a 33% risk of malignancy. 103 Ultrasound and radionuclide
scintigraphy are the primary methods of imaging thyroid nodules.
Fine-needle aspiration (FNA), especially with ultrasound guidance,
may be helpful and has 80% to 95% accuracy for deining pathology
in pediatric patients. 107-109 If FNA is not diagnostic, surgical
excision may be required. 83 On sagittal imaging, the cricoid can
appear as a round or oval mass, similar in echotexture to the
normal thyroid and posteromedial to the gland. 110 A pseudonodule
of the thyroid can be produced by uncalciied cricoid
cartilage.
During ultrasound inspection, color Doppler low imaging
may be helpful to evaluate for injury to adjacent vessels. 111
hyroid cysts are the most common incidentally detected
thyroid lesions in children. 112 hese cysts are rarely true epitheliallined
cysts, usually degenerative because of necrosis within benign
thyroid nodules. Most of these lesions are complex with mixed
echotexture, thick irregular walls, septations, and in some cases,
luid-luid levels from previous hemorrhage. Bright, echogenic
internal areas result from colloid material, sometimes creating
comet-tail artifacts 84,87 (Fig. 48.32). Calciications in degenerative
lesions may create echogenic foci of acoustic shadowing or
peripheral eggshell calciications. Doppler sonography typically
shows peripheral vascularity, and nuclear medicine studies
demonstrate variable uptake.
Although uncommon, hemorrhage within the thyroid, related
to direct or indirect trauma, can mimic a nodule. he hematoma
on sonography typically appears heterogeneous and hypoechoic
(Fig. 48.33). Many of these masses contain cystic areas resulting
from hemorrhage or necrosis. Nuclear medicine studies show
variable uptake, with some follicular adenomas demonstrating
intense activity. Because malignancy may appear as a cystic mass,
close follow-up imaging and surgical diagnosis are typically
indicated. 103,113
Follicular adenomas, the most common benign lesions of
the thyroid, arise from an overproliferation of follicular cells
(hyperplasia). 90,107 Lesions may be solitary or multinodular, are
round and well deined, and have decreased, increased, or
honeycomb echotexture. About 60% of adenomas demonstrate
a peripheral, 1- to 2-mm hypoechoic halo caused by a ibrous
capsule and peripheral blood vessels best delineated with color
Doppler sonography 90 (Fig. 48.34). Despite benign imaging
A
B
FIG. 48.31 Graves Disease. (A) Thyroid is diffusely enlarged and heterogeneously hypoechoic. (B) Color Doppler ultrasound demonstrates
“thyroid inferno.”