- Right and left lobes on either side of the trachea
- Isthmus—thin strip of 2 to 4 mm inbetween the lobes, anterior to trachea
- Echogenicity—mildly hyperechoic and homogeneous
- Both lobes laterally related to the common carotid artery and internal jugular vein and the sternocleidomastoid muscle
- Anteriorly—the strap muscles of neck
- Posteriorly—Left lobe–esophagus is just medial to left lobe—posteromedially. Both lobes related to the longus colli muscles posteriorly.
Size and Dimension
- Normal dimensions (Adult) Size: Each lobe-AP (anterior-post)-12 to 17 mm × 15 to 22 mm (side to side) × 30 to 50 mm (length)
- Taller persons—the lobes are longer
- Shorter persons—the lobes are shorter and more oval
- Isthmus—thin strip of 3 to 5 mm width.
Normal Color Doppler Imaging
- The thyroid is a very vascular organ
- More vessels seen at the poles
- Main arteries—superior and inferior thyroid arteries for each lobe
- Main veins—superior and inferior thyroid vein
- Note close relation to common carotid artery and interior jugular vein
- Power Doppler is useful in detecting vascular lesion.
Fig. 1.2: The right and left lobes of the thyroid in longitudinal section. Note the homogeneous texture
Fig. 1.3: The right and left lobes of thyroid in longitudinal sections. Note the mildly hyperechoic nature of gland parenchyma
Fig. 1.4: Another subject. The normal thyroid in transverse section. The thyroid is hyperechoic compared to the strap muscles of the neck
Fig. 1.5: The normal right lobe in long section. The long section of the thyroid may not be visualized in a single field
Fig. 1.7: This long section of the right lobe shows the superior and inferior thyroid arteries at the upper and lower poles of the lobe
Fig. 1.11: The inferior thyroid vein draining the lower part of left lobe of the thyroid. Note the typical venous spectral waveform
Fig. 1.12: Transverse section of the thyroid. Note the close relation of the lateral part of each lobe to the common carotid artery
Fig. 1.13: The close relation of the internal jugular vein and common carotid arteries of each side to the lobes of the thyroid
- Ectopic thyroid tissue
- Thyroglossal duct cyst
- Congenital hypothyroid goiter
- Congenital thyroid cysts
- The thyroid may be partially or completely absent at birth.
- Complete agenesis may be detected within few months after birth due to symptoms like poor growth
- Hemiagenesis is detected much later in life (the right or left half of the thyroid is absent). Usually diagnosed by ultrasound or CT imaging.
Fig. 1.14: Color Doppler image showing the empty thyroid fossa (absence of the thyroid) in an infant
Fig. 1.15: Color Doppler image showing the empty thyroid fossa (absence of the thyroid) in an infant. CCA = common carotid artery
Fig. 1.16: Color Doppler image showing the empty thyroid fossa (absence of the thyroid) in an infant. The strap muscles of neck must not be mistaken for the thyroid (absent in this case of agenesis of thyroid)
Fig. 1.17: Color Doppler image showing the empty left thyroid fossa (absence of the thyroid) in an infant
Fig. 1.18: Color Doppler image showing the empty right thyroid fossa in infant. The trachea is in direct relation to the strap muscles
Fig. 1.19: Color Doppler image showing the empty thyroid fossa (absence of the thyroid) in an infant. The muscles of neck are often mistaken for the thyroid
- The right or left half of the thyroid is congenitally absent.
- Part or whole of the isthmus of thyroid may also be missing from birth.
Fig. 1.22: Same patient as in Figure 1.21. Showing the mildly enlarged left lobe and adjacent part of isthmus of thyroid. The right lobe is not visualized
Fig. 1.23: Color flow image shows empty right thyroid fossa with mildly enlarged left lobe of thyroid
Fig. 1.24: Same image as in Figure 1.23, with labels showing various structures
CONGENITAL THYROID CYST
- It is usually an incidental finding
- Cysts are usually small in size
Fig. 1.27: The fetal thyroid in sagittal section. The cyst is seen in posterior part(Image courtesy: Mr Shlomo Gobi, Israel)
- Thyroid gland or tissue can occur anywhere from the base of the tongue to the thyroid cartilage.
- Usually occurs in females.
- Commonest location is lingual or sublingual. It results from failure of the thyroid tissue to descend to neck.
- Sublingual thyroid—close relation to sublingual salivary glands.
- Accessory thyroid tissue may be present along the thyroglossal duct tract.
Case of Ectopic Thyroid
- Case 1: Sublingual thyroid: Here the thyroid is seen close to the sublingual salivary gland the right thyroid lobe being in close relation to it. The thyroid also showed cystic nodules in right and left lobes.
- Case 2: Ectopic thyroid: It is presented as a complex, midline, inhomogeneous nodule above its normal position, anterior to the trachea.
Fig. 1.28: The sublingual salivary gland is seen in proximity (arrows) to the right lobe of the sublingual thyroid. A hemorrhagic cyst is present in thyroid
Fig. 1.31: Sublingual salivary gland seen in relation to right lobe sublingual thyroid. Note the hemorrhagic cyst in the thyroid
Fig. 1.33: Another view of the left lobe of sublingual thyroid with colloid cyst(Image courtesy: Mr Shlomo Gobi, Israel)
Fig. 1.34: The thyroid is limited to a 2.7 × 1.7 cm sized heterogeneous nodule, in the midline, anterior to the trachea
Fig. 1.35: The ectopic thyroid gland shows small cystic areas, suggestive of colloid cysts. Mild increase in vascularity of the gland is noted
Fig. 1.38: The ectopic thyroid nodule is very mobile, almost like a “mouse” in the neck. Here it is displaced to left side of trachea
Fig. 1.40: Note the midline location of the nodule of ectopic thyroid, just anterior to the trachea. Ectopic thyroid tissue may be anywhere along the path of the thyroglossal duct
Fig. 1.41: Note the absence of the normal thyroid lobes. The ectopic nodule of thyroid is the only functional thyroid tissue in this patient
- Fetal goiter may result from maternal ingestion of antithyroid drugs (for hyperthyroidism). It can also result from passage of maternal immunoglobulins to the fetal circulation. This results in fetal hypothyroidism.
- Obstetric sonography shows persistent hyperextended fetal neck and enlargement of the fetal thyroid (Fig. 1.43).
Fig. 1.43: The fetal neck showing obvious enlargement of thyroid, extended fetal neck.(Image courtesy: Dr V Ganesan, Tamil Nadu, Chennai, India)
- Any nodule of the thyroid may be solid, cystic, or complex (primarily solid with cystic changes or primarily cystic with solid tissue within it) (Fig. 1.44). Ultrasound and color Doppler imaging are excellent in high resolution imaging of thyroid nodules. Realtime high resolution sonography shows details of up to 1 mm in the thyroid.
- Highly sensitive color Doppler imaging provides detail of the vascular pattern of the nodules or solid tissue helping identify the lesion as benign or malignant.
THYROGLOSSAL DUCT CYST
- Presents as a midline cystic swelling of the neck. Can be located anywhere along the path of origin (base of tongue) to path of descent of the thyroid (thyroglossal duct). Usually, it is closely related to the hyoid bone. 80 percent of thyroglossal duct cysts (TDC) are seen at or just below the hyoid bone.
- TDC may be seen within 2 cm on either side of the midline.
- 20 percent are located above the hyoid bone.
- Usually patient is a child or young adult.
- Typical sign—the mass moves up on protrusion of the tongue.
- Size of TDC-0.5 to 6 cm.
- Thin walled anechoic lesion near the hyoid bone or just below it. This is the typical appearance seen in just less than 50 percent of cases.
- Another presentation—hypoechoic mass with acoustic enhancement posterioly (increased through transmission).
- Some TDCs present as homogenous or heterogeneous masses.
- Various sonographic types of TDCs may be seen:
- Thin walled anechoic cyst
- Thick-walled cyst
- Inhomogeneous with pseudosolid appearance due to thick viscid material within the TDC.
- Inhomogeneous with septae and internal debris
- Typically all these subtypes show increase through transmission due to cystic nature of TDC.
- Complex or heterogeneous variety of TDC shows shift of debris on probe pressure.
Fig. 1.49: Few septae are also present in the TDC (thyroglossal duct cyst). Note the debris within the fluid
HEMORRHAGIC CYSTS OF THYROID
- This is usually the result of acute hemorrhage into a colloid cyst or into a thyroid nodule.
- Usually has history of acute onset of pain and swelling of the neck (thyroid region).
- Sonography shows an anechoic lesion (cystic) with either fluid-fluid layering or debris s/o bloody material within the cyst.
- May resolve spontaneously with reduction in size.
- Color Doppler imaging—absence of flow within the septae or material within the cyst.
Fig. 1.50: Middle aged male patient with typical hemorrhagic cyst (1.8 × 1.5 cm) of right lobe. The cyst is large in size with acute onset
Fig. 1.51: Magnified image of the same case—there is echogenic debris within the cyst fluid, s/o blood
Fig. 1.52: Same patient—follow-up ultrasound image shows marked reduction in size of the cyst (0.8 × 0.5 cm) in right lobe
Fig. 1.53: Color Doppler image of the cyst (follow-up of same patient). Spontaneous reduction in size of the lesion after few weeks
Fig. 1.54: A large hemorrhagic cyst of the left lobe of thyroid. Fluid level is seen with hemorrhagic material in dependent part
COLLOID CYST OF THYROID
- Colloid cysts occur almost always in adenomatous nodules (colloid nodules/ hyperplastic nodules) as a result of degenerative changes in the nodule.
- Rarely seen in benign follicular adenoma.
- Purely anechoic cyst suggests clear fluid; may be serous or colloid fluid.
- Brightly echogenic foci may be seen, producing the comet tail artefact. This is seen in dense colloid material within the cyst.
- Intracystic septae are thin and avascular on color Doppler imaging. They are formed by degenerative changes of the thyroid tissue.
Fig. 1.58: There are cystic lesions in both lobes of thyroid. Thin septae are seen in the right lobe in this section
Fig. 1.59: Longitudinal section reveals both cysts are septate. Note the thin nature of the septae with absence of solid nodules within cyst (suggesting benign nature)
Fig. 1.62: Longitudinal section shows absence of flow in septae on color Doppler imaging. This is typical of colloid cysts
Fig. 1.63: Another case showing small, avascular septae within the colloid cyst. Power Doppler image
Fig. 1.64: Color Doppler image showing absence of flow within the partial septae in the colloid cyst
Colloid Cyst (Aseptate) (Fig. 1.65)
Fig. 1.65: Purely anechoic colloid cyst of the right lobe. Note solid nodules also present. Note absence of septae within the cyst
Fig. 1.66: Multiple echogenic foci are seen within this large colloid cyst of the thyroid(Image courtesy: Dr Jaydeep Gandhi, MD, Mumbai, India)
Fig. 1.67: Echogenic foci are seen within this large colloid cyst. Note the comet tail artifact produced suggesting dense colloid within the cyst(Image courtesy: Dr Jaydeep Gandhi, MD, Mumbai, India)
Fig. 1.68: This middle aged female patient had 2 cystic nodules in the left lobe, one of which showed multiple echogenic foci
Fig. 1.69: Multiple echogenic foci in colloid cyst. This signifies evidence of dense colloid material within the cyst. Transverse section through the left lobe
Fig. 1.70: Long section through the left lobe shows the echogenic foci in the cystic lesions; colloid cysts with dense colloid material
Fig. 1.71: Same case as in Figure 1.71; color Doppler images of the left lobe (long section). Colloid filled cysts surrounded by vascular rim
The two commonest benign nodules are:
- Adenomatous nodules (also called hyperplastic nodules or colloid nodules).
- Follicular adenoma.
- Form 80% of nodular disease of thyroid.
- Usually multiple.
- Usually begin as isoechoic nodules, later become larger and hyperechoic. Still later, may undergo cystic change (colloid cysts).
- A thin hypoechoic halo may be present.
- These are usually heterogeneous.
- Poorly capsulated.
- Smaller in size, compared to the follicular adenoma.
- Color Doppler—peripheral rim of vessels. Few intranodular vessels (except if the nodule is hyperfunctioning).
Benign follicular adenoma
- Usually single.
- Homogeneous echotexture (likened to that of the testes).
- Well encapsulated (usually has a complete, thick surrounding halo).
- They are usually larger in size.
- form 5 to 10% of thyroid nodules.
- Usually are hyperechoic.
- Less likely to undergo cystic change.
- Color Doppler: Usually has a surrounding rim of vessels with often vessels passing from the surrounding region to the central part (spoke and wheel pattern).Subtypes
- Simple/colloid or macrofollicular is the commonest
- Hurthle cell or oncocytic.
Fig. 1.72: Multiple adenomatous nodules (large one in right and smaller one in left lobe). The nodule on left shows a peripheral hypoechoic halo
Fig. 1.74: The large right lobe nodule shows cystic changes, typical appearance of an adenomatous nodule
Fig. 1.75: Color Doppler image of same case (right lobe) shows a rim of vessels that form the halo (previous image). Note absence of vessels in center
Fig. 1.76: Power Doppler image shows abundant vessels along the rim of the mass. No vessels are seen in the central part
Fig. 1.77: Same case—hypoechoic halo around the smaller lesion in the left lobe. Power Doppler image shows the cause of halo—numerous vessels along the rim
Fig. 1.80: Showing poorly defined halo around the mass (same case as pervious image). Power Doppler shows rim of vessels
Fig. 1.81: Long section of the right lobe (same case as previous image), shows numerous vessels along the tumor margins
Fig. 1.83: Another case—mutliple small hyperechoic and isoechoic nodules present in right lobe. Egg shell calcification is present around 2 of them (highly suggestive of benign nature of nodule)
Fig. 1.84: Same case—large left lobe mass with egg shell calcification around part of the nodule. Note inhomogeneous echotexture suggesting adenomatous nodule
Fig. 1.85: A large follicular adenoma of the right lobe. This lesion is mildly hypoechoic to isoechoic, homogeneous and single
Fig. 1.86: The halo is seen, but is not thick or prominent. Note the absence of cystic change, which can be expected in a lesion of this size, if it were an adenomatous nodule
Fig. 1.87: Some (egg-shell) calcification is seen along the rim, suggesting the benign nature of the lesion
Fig. 1.88: Another view of the nodule. Note the typical oval shape and testes-like texture of the follicular adenoma
Fig. 1.89: Power Doppler image of the follicular adenoma. Vessels are seen entering the core of the mass—the “spoke and wheel” appearance
Fig. 1.91: Solitary hyperechoic, noncystic, well-encapsulated mass of the right lobe of thyroid. Typical appearance of a follicular adenoma
Fig. 1.94: Color Doppler image of the adenoma in the right lobe (long section). No cystic areas are present
Fig. 1.95: Color Doppler image of the right lobe in transverse section shows vessels along the rim of the adenoma
BENIGN VS. MALIGNANT NODULES
- Calcification—coarse, large, egg shell.
- Halo is usually present.
- Rim refractive shadow absent.
- Less hypoechoic.
- Less tall than wide.
- Microlobulation absent.
- Usually < 1.5 cm size.
- Color Doppler: Little intranodular flow.
- Lymph nodes are normal.
- Calcification: Punctate or microcalcification.
- Halo is absent or incomplete.
- May be present.
- More hypoechoic than strap muscles.
- More tall than wide.
- Microlobulation present.
- May be more than 1.5 cm.
- Increased, disorganized flow inside the nodule.
- Presence of enlarged, hypoechoic lymph nodes due to metastasis.
Fig. 1.96: A large nodule with egg shell calcification along the rim. A sign of benign nature of the mass
Fig. 1.98: The left lobe shows a large nodule with cystic areas and a coarse calcification. This is typical of multinodular goiter
Fig. 1.99: Left lobe in same patient shows very large calcific lesion with acoustic shadowing posteriorly. Note the cystic areas also
Fig. 1.100: A hypoechoic nodule with microcalcification in the left lobe of thyroid. Suggestive of malignancy
Fig. 1.101: Same case as in Figure 1.100—arrow points to microcalcification within the nodule. Note the hypoechoic nature of nodule compared to the adjacent strap muscles
Fig. 1.102: Markedly hypoechoic nodule with microcalcifications, in the right lobe. These findings suggest carcinoma of thyroid
Fig. 1.103: The nodule is hypoechoic, shows microcalcification and microlobulation of the borders. Also observe that the lesion is almost as tall as it is wide. These indicate possible malignancy of this nodule
Refractive Shadow from Edge (Fig. 1.105)
Fig. 1.105: The right lobe shows a solid nodule with shadows (arrow) radiating posteriorly from the rim of the mass. This may suggest a malignant process. But no other signs were present to support this diagnosis
Refractive Shadow from Rim (Fig. 1.106)
Fig. 1.106: Same case as previous image. Note the shadows on both sides from the edge of the nodule (arrows). This is more prominent in the right lobe
Microlobulation (Fig. 1.107)
Fig. 1.107: The right lobe shows a markedly hypoechoic, large mass showing irregular margins (arrow head). This is called microlobulation and is typical of a malignant mass. This is a case of papillary carcinoma
Fig. 1.108: Typical case of papillary carcinoma of the right lobe of thyroid. Note hypoechoic mass with microcalcification (bright echoes) in the mass(Image courtesy: Mr Shlomo Gobi, Israel)
Fig. 1.109: Typical case of papillary carcinoma of the right lobe of thyroid. Note abundant, disorganized vessels within the mass on color Doppler imaging
Fig. 1.110: The typical appearance of metastasis to lymph node. This node is enlarged, hypoechoic and rounded
Fig. 1.111: Another lymph node with metastasis from papillary carcinoma. It is enlarged and hypoechoic
Fig. 1.112: Microcalcification is not seen. This, if present is highly suggestive of metastasis to lymph node
Fig. 1.114: Affected cervical lymph node. Color Doppler shows absence of flow within the markedly hypoechoic node. Some degree of cystic change may be present
Fig. 1.115: Color Doppler image of metastasis to cervical lymph node. Early cystic change is likely in this node(Image courtesy: Mr Shlomo Gobi, Israel)
CARCINOMA OF THYROID
Thyroid carcinoma can be either of the following:
- By far the commonest malignancy of thyroid
- Forms about 75 to 90 % of all thyroid carcinoma
- Usually well differentiated (histopathology)
- Affects young adults, more in females
- Histopathology—shows calcific psammoma bodies— highly diagnostic of this variety of carcinoma.
- Ultrasound features:
- Presents usually as a hypoechoic nodule with enlarged lymph nodes s/o metastasis.
- Microlobulation or irregular margins.
- There is usually increased vascularity of mass on color Doppler imaging, with disorganized vessels within the nodule.
- Microcalcification is a diagnostic feature.
- Occurs more in females.
- Ultrasound features:
- Microlobulation of the margins.
- Halo surrounding the mass may be thick and irregular.
- Color Doppler shows disorganized vessels within the nodule.
- Has to be differentiated from follicular adenoma (a benign lesion).
- Forms 5% of all thyroid carcinoma.
- Originates from the parafollicular cells of the thyroid.
- This has very high incidence of cervical lymph node metastasis.
- Ultrasound features:
- Irregular margins
- Hypoechoic nature of nodule
- Echogenic foci may be present within the nodule (similar in appearance to the microcalcification of psammoma bodies in papillary carcinoma)
- Color Doppler shows hypervascularity within the nodule.
Papillary Carcinoma (Figs 1.116 to 1.124)
Fig. 1.122: Panoramic view of the mass. Note the hypoechoic mass with microcalcification (on right side of image). Margins appear irregular
Fig. 1.125: Arrow points to an obvious markedly hypoechoic solid nodule in the left of isthmus of thyroid. Note the microcalcifications within it
Fig. 1.126: Observe the microlobulation of the margins. The lesion is also taller than it is wide—a clear suggestion of malignancy(Image courtesy: Dr Ravi Kadasne, UAE)
- Thyroidectomy may be partial or total
Fig. 1.127: This young adult female patient underwent total thyroidectomy. Note the empty thyroid fossa
Fig. 1.128: Color Doppler image (transverse section) of the empty thyroid fossa, following thyroidectomy
Fig. 1.129: Power Doppler image of the same patient. Note absence of the thyroid in its normal location between the common carotid arteries and trachea
Fig. 1.130: This patient underwent total thyroidectomy for papillary carcinoma of thyroid. Transverse section shows a small hypoechoic nodule in the thyroid fossa. The mass is more hypoechoic than surrounding strap muscles
Fig. 1.131: Arrow head points to the recurrence of thyroid carcinoma. Note markedly hypoechoic nature of mass
Fig. 1.132: Color Doppler image of the same case as previous figure. The nodule shows marked internal vascularity. Note the disorganized nature of intranodular vessels
Fig. 1.133: Same case as previous figure—color Doppler imaging shows hypervascular nodule in empty thyroid bed suggesting recurrence of carcinoma after removal of entire thyroid(Image courtesy: Mr Shlomo Gobi, Israel)
DIFFUSE INVOLVEMENT OF THYROID
Besides nodular enlargement of the thyroid and neoplasia, the thyroid is affected by diffuse involvement.
- Diffuse enlargement of the thyroid is called goiter.
- Sonographically diagnosed by measuring the lobes and isthmus. The isthmus is very useful in measuring enlargement. Normal isthmus is 3 to 4 mm in thickness.
- In goiter, isthmus measures more than 5 to 10 mm in thickness (Anteroposterior width).
Types of Goiter
- Iodine deficiency or endemic goiter
- Multinodular goiter
- Toxic or hyperthyroid goiter
- Toxic multinodular goiter
- Nontoxic goiter (normal thyroid function)
- Hypothyroid goiter
- Goiter due to thyroiditis.
- This is a goiter with normal thyroid hormone production (i.e. neither hyperthyroid nor hypothyroid).
- Diffuse goiter may evolve into multinodular goiter.
- Diffuse nontoxic goiters:
- Hashimoto's thyroiditis
- Early Grave's disease or toxic goiter
- Endemic goiter
- Sporadic goiter
- Congenital goiter
- Physiologic goiter of puberty.
- Goiter with increased thyroid hormone production.
- Graves disease (diffuse toxic goiter)
- Toxic multinodular goiter
- Toxic adenoma (Plummer disease).
Endemic goiter: This type of goiter is caused by deficiency in dietary iodine intake resulting in hypothyroidism with resultant increase in TSH (thyroid stimulating hormone) levels.
This results in diffuse enlargement of the thyroid. Initially, the thyroid shows homogenous enlargement on ultrasound imaging.
Later: The gland become nodularity resulting in multinodular appearance. Still later, some of the nodules may become autonomous (releasing thyroid hormones without TSH control) with development of hyperthyroidism.
This is called toxic multinodular goiter.
- Multinodular goiter is characterized by enlargement of the thyroid with nodules of varying sizes, cystic areas and calcification.
- It is composed of multiple adenomatous nodules, some of which may undergo cystic degeneration.
- Sonographically, the thyroid shows multiple nodules, cystic areas, coarse calcification, egg-shell calcification, with a disorganized appearance. There may be asymmetrical enlargement of either lobe or isthmus.
- Ultrasound also is useful in determining any malignant change in any of the nodules.
- Color Doppler shows increased vascularity around the nodules with little intranodular vessels in benign nodules.
Fig. 1.134: A large nodule seen in right lobe in long section. Cystic degenerative change is seen in this mass that occupies the most part of the lobe
Fig. 1.135: Color Doppler study shows peripheral vessels around the mass in right lobe (long section)
Fig. 1.136: Transverse section. Power Doppler shows vessels along the mass in the right lobe. There is no evidence of malignancy
Fig. 1.137: Left lobe shows a smaller nodule with thick halo and rim of vessels on power Doppler imaging. Both lobes appear to contain benign adenomatous/colloid nodules
Fig. 1.138: Left lobe shows a large adenomatous nodule with egg-shell calcification (suggesting benign nature). The mass is inhomogeneous and mildly hyperechoic
Fig. 1.139: The right lobe is also diffusely enlarged with multiple small, solid colloid nodules, one of which shows egg-shell calcification. Image on right shows a nodule with rim shadow (must be investigated for malignancy)
Fig. 1.140: Color Doppler image of the left lobe shows multiple vessels along the rim of nodule. Few are seen entering the mass
Fig. 1.141: Color Doppler imaging of right lobe (right) shows multiple peripheral vessels. Image on left (right lobe) shows 2 nodules with egg-shell calcification. This is a typical MN goiter
Fig. 1.142: Transverse section shows both lobes studded with solid nodules with gross loss of homogeneity of thyroid
Fig. 1.144: Transverse section through both lobes shows cystic nodules of varying sizes bilaterally. This is another example of multinodular goiter
Fig. 1.146: Color Doppler image shows gross disorganized appearance of both lobes, and mild augmentation of vascularity (long section)
Fig. 1.147: Multinodular goiter primarily involving the right lobe. Observe large mass with cystic degenerative central area in right lobe. Left lobe shows normal size
Fig. 1.148: Long section of the right lobe shows the mass involving most of the right lobe. Note the inhomogeneous texture of the mass with multiple central cystic areas
Fig. 1.149: Another case of MN goiter. Transverse section thyroid shows multiple cystic and solid lesions in a grossly inhomogeneous gland
Fig. 1.151: Another view of the same thyroid (transverse section) shows enlarged nodular thyroid. Right lobe is larger than its counterpart
Fig. 1.152: This patient shows diffuse multinodular enlargement of the thyroid with extension to the retrosternal region (retrosternal goiter)
Fig. 1.153: The narrow tip of the endocavity probe provides better imaging of the retrosternal part of the thyroid goiter. Here the left lobe is seen
Fig. 1.154: The right lobe in long section—the lower end of the lobe is not visualized due to retrosternal extension. Observe coarse calcification and cystic area s/o multinodular goiter
Fig. 1.155: Coarse calcification in right lobe seen on linear high frequency probe. The lower extent of the goiter is hidden by the sternum. This difficulty is overcome by using a endocavity probe with narrow tip
Fig. 1.156: The left lobe shows multinodularity and inhomogeneous appearance in long section. Again the lower end of the lobe is hidden by the sternum
Fig. 1.157: Lateral chest X-ray of the same case shows opacity (mass lesion) in the upper mediastinum, posterior to the sternum. Retrosternal goiter is a common cause of such appearance
Fig. 1.158: Anteroposterior chest X-ray shows retrosternal goiter occupying the superior mediastinum, extending till the aortic knuckle
Fig. 1.159: This patient had a relatively large multinodular goiter with extension below into the retrosternal space. Sonographic image of right lobe shows multiple solid nodules with cystic area and coarse calcification
Fig. 1.160: Observe long section of the right lobe. Multiple well-defined solid nodules are present. The lower border of the right lobe is hidden by the sternum
Fig. 1.161: Same case: On swallowing the thyroid is lifted up and the lower extent of the right lobe is visible in this longitudinal section
Fig. 1.162: Same case: Transverse section of the right lobe shows typical features of multinodular goiter
Fig. 1.163: Transverse section through both lobes show the extent of goitrous enlargement of the thyroid. The right lobe is relatively larger than the left
Fig. 1.164: The left lobe shows a inhomogeneous hypoechoic nodule, in transverse section of the thyroid. Observe the marked increase in anteroposterior width of the isthmus (7.5 mm)
Fig. 1.165: Color Doppler image of transverse section of the thyroid: The hypoechoic nodule in left lobe does not show significant internal vascularity, suggesting benign nature
Fig. 1.166: Power Doppler image of the thyroid in transverse section: Note marked vascularity along the rim of nodules. No significant vessels are present internally
Fig. 1.167: Images of the left lobe in longitudinal section. Note the lower border of the left lobe is pulled up on swallowing (left). Image on right shows the left lobe partially hidden from view (in resting state)
Fig. 1.168: On using a high frequency endocavity probe, the lower extent (retrosternal part) of the thyroid is visualized (transverse section). The large vessel (intrathoracic part of right common carotid artery) is seen compressed by the goiter
Fig. 1.169: Sagittal section of the intrathoracic part of the right half of the thyroid shows the common carotid artery displaced by the retrosternal part of the thyroid. Image taken with an endocavity probe
Fig. 1.170: Color Doppler image of longitudinal section of the right lobe shows the relation of the right common carotid to the thyroid
ECTOPIC THYROID TISSUE
- The thyroid descends from the region of the base of tongue to the thyroid fossa, during the embryonic stage. This may be disrupted at any stage leading to ectopic thyroid tissue anywhere along the region from base of tongue to pretracheal region, usually in the midline. Most commonly, it is found in the base of tongue.
- This ectopic thyroid tissue may be the only functioning thyroid or may co-exist with orthotopic thyroid (i.e. thyroid in normal location).
- Rarely ectopic thyroid tissue may be intrathoracic or intra-abdominal.
- Ectopic thyroid tissue may undergo the same pathological processes as the normally located (orthotopic thyroid).
- Thus, many cases present as nodular enlargement (benign or malignant) of the ectopic thyroid.
- Ectopic thyroid may develop follicular or papillary carcinoma.
- Benign enlargement can occur simultaneously in both ectopic and in orthotopic co-existing thyroid tissue.
Fig. 1.171: Both lobes of thyroid in transverse section. Note cystic, complex nodules in the normally located (orthotopic) thyroid
Fig. 1.172: Mass seen at the level of the hyoid bone. This resembles the thyroid in all respects, with multiple cystic nodules within it s/o ectopic thyroid
Fig. 1.173: The ectopic thyroid tissue shows increased vascularity, due to multinodular nature (power Doppler image)
Fig. 1.175: Long section of left lobe orthotopic thyroid. Both, the ectopic and orthotopic thyroid tissue show cystic nodules, signifying the same underlying pathology in this patient
Fig. 1.176: Long section of both thyroid lobes shows increased vascularity of the nodular thyroid in this patient
Fig. 1.177: This patient showed symptoms of hypothyroidism, confirmed by serological studies. Ultrasound image (transverse section) shows diffuse, homogeneous enlargement of both lobes
Fig. 1.178: Same case: Longitudinal section through the right lobe shows homogeneous echotexture of the lobe with diffuse enlargement
Fig. 1.180: Left lobe longitudinal section shows similar appearance. Note the absence of complex nodules or cysts in the diffusely enlarged lobe
- Hashimoto's thyroiditis is a common autoimmune inflammation of the thyroid and the commonest cause of spontaneous hypothyroidism.
- This thyroiditis causes destruction of thyroid cells, resulting in decreased thyroid function.
- In early stage of the disease, there is increased vascularity and mild enlargement of thyroid.
- Later (end stage), the gland becomes small and atrophic.
- Hashimoto's thyroiditis is more common in females.
- Presents clinically as hypothyroidism.
- Lab investigations: Serology shows increased levels of anti-TPO (thyroid peroxidase) antibody. Also the TSH (thyroid stimulating hormone) levels are raised with low T4 and free T4 levels.
- Sonography of Hashimoto's thyroiditis:
- Sonographically there are following features seen:
- Diffuse enlargement of the thyroid with decreased echogenicity (hypoechoic).
- Pseudolobulation of the thyroid with thin fibrous bands within the parenchyma.
- Multiple minute cystic nodules (hypoechoic micronodules). These vary from 1 to 4 mm in size.
- Increased vascularity of the thyroid on Color Doppler imaging.
- The last (end) stage of the thyroid is the phase where following chronic disease, the gland becomes small, fibrotic with heterogeneous echotexture. The margins of the gland are poorly defined.
- Hypoechoic: The enlarged thyroid becomes more hypoechoic than the strap muscles of the neck. (Normally, the thyroid is hyperechoic compared to the strap muscles).
- Hypervascularity: This is the result of increased activity within the thyroid following increased TSH stimulation. The appearances can mimic the increased vascularity of thyrotoxicosis (hyperthyroidism).
- As we will see in the images that follow, there are many variations and combinations of the various features that were described earlier. Some cases will show pure enlargement with hypoechoic tissue but normal vascularity. Others may display hypervascularity and also goiterous enlargement, etc.
Fig. 1.181: This thyroid shows moderate enlargement (goiter). The gland is diffusely hypoechoic and also shows multiple microcystic nodules. This image is transverse section through both lobes
Fig. 1.184: Color Doppler image of the long section of the left lobe. Note normal vascularity of the gland
Fig. 1.185: Transverse section through the thyroid shows normal sized, but markedly hypoechoic gland with inhomogeneous echotexture
Fig. 1.186: Normal echogenicity and echotexture of the thyroid gland. Note the hyperechoic nature of the gland
Fig. 1.187: Another image of normal thyroid. Note normal size and the echogenicity of the gland. The adjacent strap muscles are hypoechoic as compared to the gland
Fig. 1.188: Long sections through both lobes of the thyroid shows hypoechoic, inhomogeneous gland. This appearance is typical of Hashimoto's thyroiditis. Note also microcystic nodules
Fig. 1.189: Color Doppler image of both lobes shows normal vascularity of the gland. Not all features of Hashimoto's thyroiditis may be seen in the same case
Fig. 1.190: Long section of both lobes. Note multiple microcystic lesions within the gland parenchyma
Fig. 1.191: Markedly hypoechoic, inhomogeneous thyroid gland. Transverse section through both lobes also shows thin fibrous bands (hyperechoic bands) traversing the gland
Fig. 1.192: Long section of the right lobe shows the features distinctly. Note the patchy hypoechoic areas
Fig. 1.194: Color Doppler image of the thyroid (long section) shows marked increase in vascularity of the thyroid. This appearance may also be seen in hyperthyroidism
Fig. 1.195: Color Doppler image of transverse section of the thyroid shows markedly hypoechoic gland with hypervascularity
Fig. 1.196: Hypoechoic thyroid gland seen in transverse section of the thyroid. The adjacent strap muscles appear hyperechoic
Fig. 1.199: Color Doppler image of long section through both lobes shows a thyroid that is markedly hypervascular
Fig. 1.200: Transverse section through the left lobe (image on right), and power Doppler image (left) show marked hypervascularity of the thyroid
Fig. 1.201: Transverse section through the right lobe (image on right), and power Doppler image (left) show marked hypervascularity
Fig. 1.202: Transverse section through both lobes shows markedly hypoechoic thyroid with minute cystic lesions (microcysts) throughout the gland
Fig. 1.203: Long section through the right lobe shows diffusely enlarged gland with microcystic nodules. These micronodules are about 1 to 2 mm in size
Fig. 1.205: Same case—Long section through the right lobe and power Doppler image (left) shows marked hypervascularity of the thyroid
Fig. 1.208: Long section through the thyroid lobes shows fine fibrotic bands coursing through the parenchyma. These findings suggest a gland in end stage fibrotic changes
Fig. 1.209: Note the hypoechogenicity of the gland in this transverse section, with poorly defined margins. In end stage fibrosis, the gland becomes shrunken