135©Elsevier & CTSUM. All rights reserved. J Med Ultrasound 2007 • Vol 15 • No 3

Introduction

Thyroid and parathyroid ultrasonography is a non-invasive, quick, and convenient method for observing

morphologic abnormalities of the thyroid [1] andparathyroid glands [2]. Although thyroid ultrasonog-raphy has been considered a screening methodwithout evidence of efficacy [3], it is currently

R E V I E W

A R T I C L E

Clinical Application of Thyroid and ParathyroidUltrasonography in the Outpatient Clinic

Tien-Chun Chang*

Thyroid and parathyroid ultrasonography is a noninvasive, quick, and convenient methodfor observing morphologic abnormalities of the thyroid and parathyroid glands. The exami-nation is also inexpensive in some countries. Given these qualities, the method can be usedin outpatient clinics as a stethoscope for physical examination. When a pure cyst is ob-served, aspiration can be performed to treat the lesion, without the additional cost of cytol-ogy. Ultrasonography enables subacute thyroiditis to be easily differentiated from otherlesions. If a hypoechoic lesion is observed associated with microcalcification, papillary ormedullary thyroid cancers can be suspected early on the basis of ultrasonography. Com-bining information regarding the extent of the cancer lesions using ultrasonography anddifferentiation of cancer lesions by cytomorphology enables the most suitable method of sur-gery and management to be chosen for patients. This examination method is also importantin the follow-up of papillary thyroid cancer recurrence in the neck lymph nodes, with or with-out elevation of serum thyroglobulin levels. Color Doppler is helpful in following up activityin Graves disease to determine whether medication can be discontinued. Ultrasonographyis also useful in determining when to operate on patients with Graves disease or Hashimotothyroiditis associated with thyroid nodules, and in avoiding unnecessary surgery in euthyroidpatients with ectopic thyroid nodules. In patients with elevated serum calcium and parathy-roid hormone levels, parathyroid ultrasonography is useful in determining the location ofabnormal parathyroid glands and in reducing the need for a parathyroid sestamibi scan.In conclusion, it is of economic and medical importance to move the ultrasonographymachine out of the examination laboratory and into the outpatient clinic.

KEY WORDS — aspiration cytology, outpatient clinic, parathyroid adenoma,parathyroid ultrasonography, thyroid cancer, thyroid ultrasonography

■ J Med Ultrasound 2007;15(3):135–140 ■

Department of Internal Medicine, National Taiwan University Hospital and College of Medicine, National TaiwanUniversity, Taipei, Taiwan.

*Address correspondence to: Dr. Tien-Chun Chang, Department of Internal Medicine, National Taiwan University Hospital,7 Chung-Shan South Road, Taipei 100, Taiwan. E-mail: tienchunchang@ntu.edu.tw

recommended as an initial test in the routine eval-uation of thyroid nodules [4]. Thyroid or parathyroidultrasonography is also inexpensive in some coun-tries, e.g. Taiwan, where it costs less than US$20.With these benefits in mind, this examinationmethod can be used in the outpatient clinic as astethoscope for physical examination. The appoint-ment time for thyroid and parathyroid ultrasonogra-phy is commonly arranged on a different day to thepatient’s clinic visit, especially in medical centers;however, it is worthwhile performing this examina-tion on the same day as the visit to the outpatientclinic. This article outlines previous experiences withthis approach and its advantages.

Confirming that a Nodule is a Thyroid Cyst

When a pure thyroid cyst is observed, aspiration canbe immediately performed at the outpatient clinicto treat the lesion [5]. It is not necessary to proceedwith aspiration cytology if a thyroid nodule is notfound following aspiration [5]; thus, the cost ofcytology can be saved. If the lesion is partially cystic,however, aspiration cytology will be needed underultrasound guidance to obtain a biopsy samplefrom the solid part (Fig. 1).

Confirming the Diagnosis of Subacute Thyroiditis

Subacute thyroiditis is also easily differentiated fromother lesions by ultrasonography [6]. In addition toa history of upper respiratory tract infection beforeoccurrence of the disease and tenderness and firmconsistency during physical examination, the appear-ance of a focal, ill-defined hypoechoic lesion at thearea of tenderness supports the diagnosis of sub-acute thyroiditis (Fig. 2). Interestingly, thyroid ultra-sonography can also be used in follow-up of thecourse (Fig. 2). Regression of sonographic hypo-echogenicity parallels the disappearance of acuteinflammatory cells and gradual improvement in thedegenerated follicular cells [6].

Suspected Diagnosis of PapillaryThyroid Carcinoma or MedullaryThyroid Carcinoma

Early suspicion of papillary thyroid cancers andmedullary thyroid cancers can be made underultrasonography when a hypoechoic lesion is asso-ciated with discrete particles without acoustic sign[1,7] (Fig. 3). These findings correspond to micro-calcifications in the papillary thyroid cancer [1]and calcification in the amyloid in medullary thy-roid cancers.

Designing the Best Treatment Protocolfor Patients with Thyroid Cancer

The common use of thyroid ultrasonography inscreening for thyroid lesions in health examina-tions means that thyroid nodules can be detectedeven when there is no palpable lesion. A previoussurvey found that 72.2% of persons undergoinghealth examinations had no palpable goiter; how-ever, thyroid lesions could be found in 18.5% ofthese subjects with impalpable thyroid [8]. A prelim-inary study indicates that the progression rate ofnonpalpable papillary microcarcinoma to clinically

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Fig. 1. Sagittal section of the left lobe of the thyroid by ultra-sonography shows a partially cystic lesion; the arrow indicates thesolid component.

significant lesions may be very low [9]. The cytologicfeatures in fine-needle aspiration cytology samplesof papillary thyroid carcinoma were recently foundto have prognostic significance [10] (Fig. 4).Therefore, combining information regarding theextent of the cancer lesions using ultrasonographyand differentiation of cancer lesions by cytomor-phology enables the most suitable method of sur-gery and patient management to be identified.

Follow-up of Neck RecurrenceFollowing Surgery in Patients withPapillary or Medullary Thyroid Cancers

Lymph node recurrence is common in the neckfollowing surgery to papillary thyroid cancers, espe-cially in patients with metastatic lymph nodes foundduring surgery [11]. Although serum thyroglobulin

levels can detect the recurrence of differentiatedthyroid cancers, these levels can be normal if necklymph node metastasis alone is present in papillarythyroid cancer [12]. Thyroid ultrasonography is veryuseful in detecting local recurrence of papillarythyroid cancer [11]. In comparison, lymph nodemetastasis is also common in medullary thyroidcancer [13] (Fig. 5), meaning that thyroid ultra-sonography is useful for follow-up in recurrence of medullary thyroid cancer in the neck, especiallywhen the serum calcitonin level is elevated.

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Fig. 2. Presence of a focal, ill-defined hypoechoic lesion(arrow) supports the diagnosis of subacute thyroiditis. The regres-sion of hypoechogenicity over time parallels the disappearanceof acute inflammatory cells and gradual improvement in thedegenerated follicular cells. T = trachea.

Fig. 3. Transverse section of the right lobe of the thyroid byultrasonography reveals a hypoechoic lesion (arrow) associatedwith discrete particles without acoustic sign in a case of papil-lary thyroid cancer.

Fig. 4. Irregular shape of nuclei in fine-needle aspiration cytologysamples of papillary thyroid carcinoma is a poor prognostic sign(Riu’s stain, 200×).

Determining Discontinuation of Antithyroid Medications and theChoice of Surgery in Graves Disease by Thyroid Ultrasonography

Graves disease is the most common hyperthyroiddisorder. The hyperthyroidism in this disease is easilycontrolled by antithyroid drugs; however, the highrecurrence rate after discontinuation of the drugs[14] results in a choice between ablative therapywith radioactive iodine and surgery followingtreatment with antithyroid drugs for a period of

time. Determination of a resistive index by thyroidDoppler ultrasonography could assist in determin-ing the likelihood of relapse following discontinua-tion of the antithyroid drugs [15]. A previous studyfound that withdrawal of antithyroid drugs couldbe considered for a resistive index of less than 0.6and with a normal serum TSH level; however, giventhat not all patients with Graves disease have dif-fuse goiter, a combination of thyroid ultrasonogra-phy and aspiration cytology in assessing nodularlesions in Graves disease (Fig. 6) can assist in decid-ing whether thyroidectomy or radioiodine shouldbe chosen [16].

Determining Whether Medication orSurgery Should be Chosen to TreatHashimoto Thyroiditis

Thyroid ultrasonography in patients withHashimoto thyroiditis usually reveals a diffuselyhypoechoic appearance, especially in patients withhypothyroidism [1,17,18]. Such patients can betreated with thyroxin; however, nodular lesions aresometimes observed by thyroid ultrasonography(Fig. 7), and these can be malignant. Fine-needleaspiration cytology with or without ultrasound

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Fig. 7. Sagittal section of the thyroid by ultrasonography showsan isoechoic nodular lesion (arrow) in the heterogeneous hypo-echoic left lobe in a patient with Hashimoto thyroiditis.

Fig. 5. Case of medullary thyroid cancer treated surgically 7 years ago, with a lymph node metastasis detected recently. C = carotid artery.

Fig. 6. Sagittal section of the thyroid by ultrasonography showsan isoechoic nodular lesion (arrow) in the hypoechoic right lobein a patient with Graves disease.

guidance can assist in determining when to oper-ate on patients with Hashimoto thyroiditis withnodular lesions [19].

Diagnosis of Nodular Goiter as Ectopic Thyroid

Ectopic thyroid is a rare entity that can occur ineuthyroid or hypothyroid patients. In a euthyroidpatient with ectopic thyroid tissue appearing in theforeneck, surgery will cause permanent hypothy-roidism. Preoperative thyroid ultrasonography candiagnose a nodular goiter as ectopic thyroid if nor-mal thyroid tissue is absent in the usual position ofthe thyroid [20].

Localizing Parathyroid Lesions

Parathyroid ultrasonography is useful in determin-ing the location of abnormal parathyroid glands inpatients with primary hyperparathyroidism andelevated serum calcium, low phosphate, and highparathyroid hormone levels (Fig. 8); it also reducesthe need for a parathyroid sestamibi scan, savesoperation time, and reduces the size of the surgicalwound [2,21–23]. However, ectopic parathyroidglands can only be detected by scintigraphy [21].

Conclusion

In conclusion, given the economic and medicalbenefits stated above, it is of value to move theultrasonography machine out of the examinationlaboratory and into the outpatient clinic.

References

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Fig. 8. Parathyroid ultrasonography shows an abnormal enlarge-ment of the parathyroid gland (arrow) in a patient with primaryhyperparathyroidism. T = trachea.

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