Sonographic Evaluation of the Pediatric Thyroid, Parathyroid, and Adrenal Glands - HD

Introduction

Hi, my name is C Silva.

I'm a pediatric radiologist working out of Yale in New Haven, Connecticut in the United States.

Today we're gonna talk about ultrasound of thyroid parathyroid and adrenal glands in children.

I have no disclosures.

We'll discuss the appearances of normal and abnormal glands in infants and older children, starting with the thyroid gland.

Thyroid Gland

Quiz on Thyroid Echogenicity in Infants

The thyroid gland in infants is less echogenic than it is in adults. Is it as echogenic as it is in adults or is it more echogenic than it is in adults? What do you think? I'll give you one second to think.

And it is as echogenic as in adults.

Normal Appearances

The normal appearances of the thyroid glands are similar in all age groups and the gland is slightly hyperechoic to the adjacent musculature.

Imaging of the thyroid gland is done mainly for the evaluation of congenital hypothyroidism, thyroid enlargement and palpable nodules.

Congenital Hypothyroidism

Starting with congenital hypothyroidism, that is a deficiency of thyroid hormone at birth and it may be transient or permanent.

Transient causes include maternal thyroid blocking antibodies, maternal anti-thyroid medication, maternal iodine deficiency or iodine overload in the baby. Often if they are going through too much of iodine, basic iodine based antiseptics.

Permanent causes include thyroid dysgenesis. That's most of the time and we'll go through each of those topics.

These are agenesis and less commonly hypoplasia.

Imaging of congenital hypothyroidism. There's a little bit of controversy there, the need for imaging. Some people think that it's worth doing imaging because you will evaluate the cause. You may give some hints as to the prognosis and you may guide management, whereas other people think that imaging may not change your management at all.

If you do do imaging though, you are probably gonna use either radionuclide scintigraphy or ultrasound.

Scintigraphy traditionally is the gold standard for anatomical diagnosis. However, it involves radiation exposure and transient hypothyroidism may be misdiagnosed as agenesis.

Ultrasound is an alternative to radionuclides and involves no radiation exposure. However, ectopia may be misdiagnosed as agenesis.

Agenesis and Hemi-Agenesis

Let's look at some of the abnormalities starting with agenesis and that is easy. You will not be seeing thyroid tissue either on ultrasound or on scintigraphy. Hemi agenesis. That is a failure of development of one thyroid lobe, which is almost always the left. This condition is often asymptomatic and it is incidentally found. However, at times it may be seen in newborns leading to congenital hypothyroidism.

Thyroid Hypoplasia

Thyroid hypoplasia, that again is easy. The thyroid is smaller than what it should be, and you have here some reference standards for the size for the thyroid gland in infants and young children. So anything less than that, it's probably hypoplasia, thyroid ectopia.

Thyroid Ectopia

That's when you have thyroid tissue. That is not where it should be and it's anywhere from the base of the tongue to the level of the thyroid cartilage as on this example here in this child, this is the tongue and this little nodule that you have there, that was the only thyroid tissue this child had. So this is thyroid ectopia and with thyroid ectopia scintigraphy will be usually more sensitive than ultrasound, thyroid dysgenesis.

Thyroid Dysgenesis

This is an inborn error of metabolism. And with that the thyroid gland will appear ectopic but enlarged on ultrasound and typically on scintigraphy there will be increased uptake.

So those are the conditions that we see with congenital hypothyroidism.

Diffuse Thyroid Enlargement

Now let's look at diffuse thyroid enlargement in children.

Diffuse thyroid enlargement is often due to one of those four conditions you're seeing on the image most common of them, chronic lymphocytic thyroiditis, which is Hashimoto's disease. You may also have nodular hyperplasia, diffuse hyperplasia, which is Graves disease or diffuse papillary thyroid cancer.

Hashimoto's Disease

Hashimoto's disease is much more common than Grave's disease in childhood with an incidence of about one in 100 children. It peaks in late childhood and early teenage years and has a female predominance on ultrasound.

The patients will be sent to you for scanning because the clinicians are feeling an enlargement of the gland. But when you do your ultrasound, you'll see that the gland doesn't quite look that large and really what happens is that the gland is very stiff and with a stiff gland, the clinician will think that it's large, but again not that much. And that in the later stages of the disease, the patient will have atrophy of the gland.

The echogenicity of the gland in the initial phases is normal, but later on it'll be decreased. Echotexture will be heterogeneous secondary to pseudomicronodular pattern and we say pseudo because these are actually cystic spaces, but they appear nodular on ultrasound and interspaced by fibrotic septations you'll be seeing lobulated borders as well.

Endovascularity initially is normal, then it becomes increased and at this stage it is difficult to differentiate Hashimoto's from graves and later on you have a more typical appearance of a decreased vascularity.

Nodular Hyperplasia

Nodular hyperplasia that is usually due either to dietary iodine deficiency, which is actually the most common cause worldwide or to congenital defects in hormonal synthesis. It also peaks in early teenage years and has a female predominance. On ultrasound one will be seeing diffuse enlargement of the gland with a heterogeneous echotexture, both macro and micro nodules, some of them with liquefaction and at times colloid stagnation.

Vascularity is usually normal.

Graves Disease

Graves disease that is rare in childhood, such to be about one in 5,000 children. It also peaks in early teenage years and has a female predominance. On ultrasound, there's diffuse enlargement of the gland, heterogeneous echotexture and increased vascularity with advanced disease. One may see large colloid cysts, hyperechoic and coarse echotexture and enlarged extraocular muscles as seen on this MRI.

Papillary Thyroid Cancer

Papillary Thyroid cancer that can present as diffuse enlargement of the thyroid. When you are dealing with a diffuse sclerosing variant, which is actually rare on ultrasound, one will see irregular or nodular gland enlargement at times with sparing of parts of the gland, one may see micro calcifications and at times cervical lymphadenopathy.

Palpable Thyroid Nodules

Finally, Another scenario where you'll be asked to evaluate the thyroid gland is if one presents clinically with a palpable nodule.

Nodules are less common in children than they are in adults, however, they are more likely to be malignant and that said, they actually have a better prognosis than what they have in adults.

Benign nodules are often hyperplastic, colloid, focal adenomas or focal Hashimoto's disease.

Malignant nodules are usually carcinomas and carcinomas of thyroid. In the pediatric population, just like in adults, the most common is papillary cancer in children more than 90% of the time that is followed by follicular carcinoma about 10% of the time and other types of cancer in children like medullary carcinoma and anaplastic carcinoma are rare.

Thyroid cancer in the pediatric population will peak in the teenage years and will have a female predominance. The incidence seems to be increasing, but again, the prognosis is much better than what one has in adults.

Papillary Carcinoma

For papillary carcinoma, a major risk factor is radiation exposure. These tumors are often multifocal and may be bilateral. There's a very high rate of regional lymph node metastasis, but the lesion is indolent with long-term survival rates.

Follicular Carcinoma

Follicular carcinoma here, a major risk factor is iodine deficiency. These lesions are usually unifocal and are less aggressive than papillary carcinoma. If metastasis occur, they are usually to lungs and to bones and are uncommon to have metastasis, truly to lymph nodes.

Ultrasound Evaluation of Palpable Nodules

Ultrasound evaluation of a palpable thyroid nodule. When you're doing that, there are some suspicious findings in the solid component of the nodule that may warrant FNA. That is fine needle aspiration and those are hypoechogenicity of the nodule, meaning the nodule is less echogenic than the remainder of the thyroid gland.

Irregular or ill-defined margins as one sees here increased intranodular blood flow calcifications, especially when they are smaller than two millimeters there, they're the so-called micro calcifications suspicious cervical lymph nodes and we'll talk about that in a second.

At this point in 2016, we're not quite sure what is the role of elastography in determining if the nodule warrants or not FNA. There's just not enough numbers in the pediatric series and one caveat is that if suspicious findings are present, a size less than one centimeter of the nodule should not discourage fine needle aspiration. That is different from the guidelines for adults where when they're less than one centimeter, typically you don't do FNA, but in children you should not be discouraged, such as on this patient with a histology proven follicular carcinoma that was measuring less than one centimeter.

Ultrasound Evaluation of Cervical Lymph Nodes

Ultrasound evaluation of the cervical lymph nodes. What are the suspicious findings that may warrant FNA? Round lymph nodes rounded shape loss of a central hilum, you will remember that a normal lymph node will have a central hilum that is echogenic. If you lose that, that is a suspicious finding. Short axis that is greater than five millimeters or depending on where you read more than eight millimeters for lymph nodes in level two, cystic appearance to the lymph node. Micro calcifications, just like on the thyroid nodule itself, micro calcifications are suspicious, highly suspicious in lymph nodes, peripheral vascularity and again, as of 2016, similar to the thyroid nodules for lymph nodes, we still are not quite sure what is the role of elastography in that we don't have large pediatric series.

Management of Nodules

What about management of those nodules? Let's suppose you do a fine needle aspiration and that nodule turns out to be benign. Then according to the American Thyroid Association guidelines, you should do an ultrasound follow up or they recommend an ultrasound follow up in six to 12 months following the fine needle aspiration and then every one to two years you shouldn't repeat the FNA. If there is a new suspicious feature or if there is continued growth, that would be more than 50% of the volume or more than 20% increase in at least two dimensions. And they advise to do a lobectomy if there is substantial growth or if the nodule is measuring more than four centimeters.

What if you do an FNA and there are suspicious indeterminate or even malignant findings, then you will, they will recommend surgical resection and following resection, you will be doing ultrasound follow-ups every six months and then every six months to 12 months for at least five years. One caveat is that this ultrasound follow-ups are less important in follicular carcinomas whenever you want.

Now let's talk about parathyroid gland and just to get you situated when you are imaging this thyroid, usually we will have we start talking about right thyroid inferior gland and they're deep.

Parathyroid Gland

Normal Appearances

Now moving onto parathyroid gland, typically Normal parathyroid glands ectopic are seen at times they're paired. So you have superior glands and you have inferior glands and they're situated deep to the thyroid.

An ultrasound normal gland, however ectopic gland are seen at times and they may happen in the neck or in the mediastinum. Less than five millimeters in size in normal gland is actually very difficult to see. With ultrasound of the not always they are isoechoic to the thyroid gland and they're smaller than five millimeters. So again, typically it will not be seen.

Hyperparathyroidism

Typically, if the patient has a problem with their parathyroids, they will present clinically with hyperparathyroidism and that is usually on the basis of either hyperplasia, which could be primary or secondary or adenomas.

Imaging is used for preoperative localization of adenomas and primary hyperplasias and that is to guide minimally invasive parathyroidectomy ultrasound and scintigraphy seems to be complimentary in imaging of hyperparathyroidism.

Ultrasound will give you a better anatomical delineation, especially in the relationship of the abnormality of the thyroid gland. Scintigraphy in turn may detect ectopic mediastinal lesions, especially if when they are in the mediastinum.

An emerging modality is 4D CT, which seems to be a win-win in the sense that it has good anatomical delineation like we have on ultrasound and it may detect ectopic mediastinal lesions like on scintigraphy. Maybe however, a big caveat for pediatrics is that it involves a much higher radiation than scintigraphy maybe, so we tend not to use in children.

Primary Parathyroid Hyperplasia

Primary, primary parathyroid hyperplasia. That is usually due to sporadic or genetic disorders such as MEN1 MEN2 syndromes or neonatal severe hyperparathyroidism. It usually presents with bone damage from increased PTH secretion giving osteopenia brown tumors, pathological fractures and will also present with kidney damage from hypercalcemia leading into nephrocalcinosis and nephrolithiasis.

Secondary Parathyroid Hyperplasia

Secondary parathyroid hyperplasia has a different mechanism. It starts with chronic renal failure. The patients are on dialysis and that will lead into hypocalcemia, decreased levels of calcitriol and increased levels of phosphorus. That leads into a multiglandular hyperplasia and that in turn will lead into hyperparathyroidism. These patients will present with bone damage from increased PTH secretion, leading to osteopenia, brown tumors and pathological fractures. There will be no kidney damage in the sense that there's no hypercalcemia on ultrasound.

Primary and secondary parathyroid hyperplasias will present with glandular enlargement. The enlarged gland is hypoechoic to the thyroid gland. It'll be separated usually from the thyroid gland by an echogenic line, which is a capsular interface, but at times the lesion may seem to arise from the thyroid gland itself. Those lesions are usually indistinguishable from parathyroid adenomas.

Parathyroid Adenomas

Adenomas are usually sporadic and or may also be due to genetic disorders such as MEN1 MEN2 neoplasia adenomas will present with bone damage from increased PTH secretion and kidney damage from hypercalcemia like we've seen before. Osteopenia, brown tumors, pathological fractures, nephrocalcinosis, nephrolithiasis on ultrasound, these lesions will be oval. They are hypoechoic to the thyroid gland. If you see here, here you have your adenoma and that's the adjacent thyroid gland. You see that the lesion is hypoechoic to the thyroid gland. They're such a being compressible, so graded compression will may increase lesion conspicuity just like with appendicitis where you do your graded compression and you are often able to get structures out of the way and you see the appendix better. That's the same with parathyroid adenomas. Sometimes, especially for the upper lesions, they are deeper to the thyroid, they're much deeper and you are not seeing well. You may increase your chances of seeing it if you do graded compression. Another thing that is such to be typical is the extrathyroidal polar feeding vessel giving you a peripheral vascular rim. So peripheral vascular rim, that's a typical feature for adenomas. Occasionally there will be adjacent regional thyroid hypervascularity.

Adrenal Glands

Initial Evaluation

Now let's talk about adrenal glands.

Ultrasound is the modality of choice for the initial evaluation of the adrenal in neonates and that is because the adrenal is relatively large in neonates in other infants and children, the fetal cortex will involute and then you just don't see that gland well with ultrasound and imaging will be performed with MRI and or CT.

Quiz on Adrenal Findings

Now another quiz, a cerebriform surface and a steepled pattern of the central stripe are findings that are usually seen in which of the following adrenal conditions. Hemorrhage disease, adrenal congestion. That's usually in the setting of perinatal stress, congenital adrenal hyperplasia or Cushing's disease. What do you think? Give it some try and the answer is congenital adrenal hyperplasia. We'll look at that in a minute.

Normal Appearances in Neonates

The adrenal glands in neonates, they are again relatively large due to the presence of the fetal cortex. There are a varied description of shapes. You can have adrenal glands that look like a V or Y an S Z an H or omega, but all of those will have in common a central echogenic stripe and a peripheral hypoechoic rim and the glands will have a smooth surface. Very important to differentiate from congenital adrenal hyperplasia.

Other Adrenal Conditions

Ectopic Adrenal Rests

Ectopic adrenal rests may be seen and they are tissue break offs from the adrenal in the mid embryonic life they may appear in the chest, in the abdomen, in the pelvis, and often in the scrotum.

Adrenal Agenesis

Adrenal agenesis you could have that as unilateral adrenal agenesis that's often associated with ipsilateral renal agenesis and bilateral adrenal agenesis is actually rare anomalies of adrenal shape.

Anomalies of Adrenal Shape

The most common one is a horseshoe shaped adrenal that tells you that there was never a kidney adjacent to that adrenal. So usually is a sign of renal agenesis. Renal ectopia or renal dysplasia.

Horseshoe shaped adrenal that is rare is due to fusion of the medial limbs and is seen in association with asplenia renal anomalies and central nervous system anomalies.

Adrenal Congestion

Adrenal congestion that is often seen in the setting of perinatal stress and one will see enlargement of the gland, loss of the echogenic stripe thickening and increased echogenicity of the peripheral ring.

Adrenal Hemorrhage

Adrenal hemorrhage. This is actually the most common adrenal lesion that is seen in neonates and it's like adrenal congestion is usually seen in the setting of perinatal stress. On ultrasound, there's a variety of described appearances for adrenal hemorrhage, but what they all have in common is that the lesion will decrease in size over time. The differential diagnosis of adrenal hemorrhage is made with cystic neuroblastoma and it's often impossible to differentiate both by imaging as they have overlapping features and both will regress congenital adrenal hyperplasia.

Congenital Adrenal Hyperplasia

That is an inborn error of the metabolism because of an abnormal enzyme in the cortisol production pathway. Congenital adrenal hyperplasia manifests in the neonatal period by ambiguous genitalia or by salt wasting dehydration. On ultrasound one will see gland enlargement, the so-called cerebriform surface, meaning the surface will be very bumpy or nodular and at times you can have the central stripe with a steepled pattern wolman disease.

Wolman Disease

That is another inborn error of metabolism due to lipid accumulation in multiple organs including the adrenals. And in the adrenal glands you'll see enlargement and they will also be densely calcified. There is usually also hepatomegaly and hepatic steatosis pathologies that you can have with the adrenal glands.

Pathologies Beyond Neonatal Life

Beyond the neonatal life, you can have diffuse enlargement in cases of hyperplasia or focal masses in cases usually of neoplasms, Adrenal hyperplasia beyond the neonatal life may be primary or secondary. For example, from a pituitary adenoma, usually it'll manifest by hormonal over secretion. On imaging, there will be bilateral gland enlargement, which is usually smooth and imaging is typically performed with MRI as those glands beyond the neonatal life, even if they are hyperplastic, they're usually not easily depicted by ultrasound.

Now, focal masses, that's a different story. Those often you are able to see with ultrasound and they are usually neoplastic. You can have neuroblastoma or one of its cousins, which is the ganglioneuroblastoma, and the ganglioneuroma. You could be dealing with pheochromocytoma or with adrenal cortical neoplasms, neuroblastomas, ganglioneuroblastomas, ganglioneuromas.

These arise from the adrenal medulla or the sympathetic chains, which can be anywhere from the neck to the pelvis. Neuroblastoma is the malignant cousin, ganglioneuroma is the benign one and ganglioneuroblastoma is the one that has intermediate malignant potential. These three tumors have similar appearances on imaging. Neuroblastoma is actually the most common extracranial solid tumor in children on ultrasound. Those lesions are most of them are solid heterogeneous. Often with calcifications there will often be displacement of the adjacent kidney, Anterior displacement of the aorta and the IVC often with vessel encasement and doppler is usually used to check for vessel patency. There may be direct liver invasion or hematogenous liver metastasis when there are metastasis, this may be diffused or focal. Staging of neuroblastoma is done with MRI and MIBG bone scan and PET scans. PET scans often when you have a tumor that is not MIBG avid pheochromocytoma.

Pheochromocytoma

Now if neuroblastoma was somehow common in the pediatric population, pheochromocytoma on the other hand is uncommon when seen. It's mostly in adolescents. These tumors arise from the adrenal medulla or from the sympathetic chains and usually manifests by hormonal over secretion. The rule of tens that we learn in medical school, they do not apply in pheochromocytomas in children. So in adults it's said that about 10% of them are extra adrenal in children it's about 30% and mostly are located in the upper abdomen. In adults, again, they're said that about 10% of those tumors are bilateral. In children, it's more than that. About 25%, much more than 10% are familial. For example, in MEN2 syndrome neurofibromatosis, one hemihypertrophy and thankfully a very small percentage, so much less than 10% are malignant On ultrasound. Those lesions are echogenic. At times they are heterogeneous due to hemorrhage, necrosis or calcifications. Ultrasound cannot reliably exclude multifocal disease, so full staging is done with MR and MIBG or MIBG.

Adrenal Cortical Neoplasms

Adrenal cortical neoplasms. So again, neuroblastomas are common, pheochromocytomas are uncommon, and adrenal cortical neoplasms are rare in children. That said, if you were to have one of them, carcinomas are much more common than adenomas. In the pediatric population. There is an increased incidence in patients with Beckwith-Wiedemann and in patients with hemihypertrophy. These lesions usually manifest by hormonal over secretion On ultrasound, smaller lesions are typically homogeneous and larger lesions are heterogeneous at times due to hemorrhage, necrosis, calcifications. These lesions may invade the kidney and the IVC MRI Is performed for full staging of those lesions.

Summary

So that's it. In summary, we discussed the sonographic findings of normal and abnormal thyroid, parathyroid and adrenal glands in infants and older children. If you have any questions, just send me an email. Thank you very much.