Ultrasound

Thyroid Echography of Subacute Thyroiditis 1 Manfred Blum, M.D., Anthony M. Passalaqua, M.D., Jay P. Sackler, M.D., and Rochelle Pudlowskl, M.D. Ultrasound was usedto study 10 patients with subacute thyroiditis. With gray-scale technique, a "washed-out" appearance was seen during the active phase of the Illness. Clinical migration of the inflammation was accompanied by migration of the sonographic abnormality. Ultrasound can be especially helpful In the diagnosis of unilateral subacute thyroiditis and the differentiation of true cysts from hemorrhagic degeneration of goiter. INDEX TERMS:

Goiter. Thyroid, Inflammation . Thyroid, ultrasound studies, 2[73].1298

Radiology 125:795-798, December 1977

U

LTRASONOGRAPHY IS a safe, useful, and reliable tool

RESULTS

for differentiating cystic and solid masses of the thyroid gland. We report thyroid echographlc observations derived from 10 patients with subacute thyroiditis (SAT), which is also called nonsuppurative thyroiditis or deQuervaln's thyroiditis.

A very homogeneous low-amplitude echo pattern was observed in all patients during the active phase of SAT. Characteristically, the affected lobe or lobes of the thyroid are enlarged. As our initial studies with A':mode and bistable B scanning technique suggest, internal echoes are lacking at low sensitivity settings. With increasing sensitivity, low-amplitude uniform echoes appear from within the lobes; but even at very high sensitivity, apparent sonolucent areas may remain (Fig. 1). These areas lack terminal , high-amplitude sharp echoes that represent the deep wall of a true cyst (Fig. 2, A). Using gray-scale technique, one observes very low-amplitude uniform echoes from the thyroid. The deeper portions of the lobes

METHODS AND MATERIALS

Ten patients with subacute thyroiditis were studied with ultrasound during the active phase of their illness. Seven of them were studied again after recovery. Each had typical symptoms and laboratory findings. Four had unilateral tenderness of the thyroid gland and in 3 contralateral or bilateral Involvement followed; 6 had bilateral Involvement from the start. All had fever, an elevated erythrocyte sedimentation rate (ESR), normal or elevated serum concentration of thyroxine, and low uptake of 131 1by the thyroid. After recovering from the thyroiditis, all patients returned to an euthyroid state. Echography performed before January 1976 consisted of A-mode or contact bistable B scanning as described by Blum et al (1). After that date echography was performed with gray-scale equipment using an open water bath and a 3.5-MHz transducer focused 3-5 cm from Its face (2). Extreme care should be exercised; the thyroid gland is exquisitely tender during the active phase of SAT and therefore palpation and placement of the transducer must be very gentle. Abundant gel for acoustic coupling of the skin to the transducer and the least possible pressure on the neck are required for the A-mode and contact b1stable B scanning. Failure to follow these admonitions creates artifacts, which may lead to erroneous conclusIOns and will also detract from patient cooperation. The water bath 01fers the advantage of greater patient comfort by obviating the need for direct contact between the transducer and the skin. Mineral 011 is used to provide acoustic coupling of the water bath and the neck. The weight of the water insures proper contact.

Fig. 1. A-mode echograms over the right lobe of the thyroid In a patient with SAT. A. Echogram taken at low gain, showing an apparent echo-free zone and no high-Intensity terminal echo spike . B. Echogram taken at high gain in the same region, showing lowIntensity echoes.

1 From the Departments of Medicine (M.B.) and Radiology (A.M.P., J.P.S., and R.P.), New York University Medical Center, New York . Accepted wJw for publication In August 1977.

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Fig. 2. Echogram of a simple cyst of the thyroid . A. A-mode echogram of a simple cyst of the thyroid taken at high gain. Note the high-intensity terminal echo spike . B. Transverse gray-scale scan of the thyroid showing a simple cyst (C) and the carotid arteries (A) .

A R

/.........SAT

1 em

c

L..----V -----' T

have a "washed-out" appearance, demonstrating fewer and fewer echoes, and again there is no deep-wall accentuation. Enlargement of the thyroid is shown by the backward and lateral displacement of the extra-thyroid soft tissues that reflect denser echoes. Differentiation of cyst from SAT is facilitated by gray-scale echography (Figs. 2, Band 3). With unilateral SAT (4 of 10 patients) only the tender, involved lobe of the thyroid showed this "washed-out" appearance; the contralateral lobe remained well-defined and appeared ultrasonically normal (Fig. 4, A). In 3 of 4 patients with unilateral SAT , the pain and tenderness spread to the opposite lobe after a variable time . Extension of the illness was accompanied by migration of the " washed-out" ultrasonic appearance to the previously

Fig. 3. Transverse gray-scale scan from a patient with bilateral SAT . The patient's right side (R). trachea (n. carot id vessels (V) . and thyroid lobes (L) are indicated. A. Scan taken during the acutely symptomatic period. Note the " washed-out" appearance (arrows) of the deep part of both thyroid lobes. The lobes are enlarged with posterior displacement of the musculature. B. Scan taken three weeks later when the patient was improving. C. Scan taken after recovery, show ing a normal thyroid .

normal lobe. The fourth patient did not experience discomfort in the contralateral lobe. The echogram returned to normal in 6 of the 7 patients who were studied after recovery (Figs. 3, C and 4, C). The seventh patient had a persistent, non-tender, firm thyroid nodule after she recovered from SAT. The nodule was "cold" on 1311imaging and ultrasonically solid. There was a history of radiation therapy for acne during adolescence. Surgery disclosed that the nodule was a papillary carcinoma. Three patients did not have echography after recovery. DISCUSSION

Subacute thyroiditis is characteristically a self-limiting

THYROID ECHOGRAPHY OF SUBACUTE THYROIDITIS

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inflammation of the thyroid gland (3-5). The etiology is undetermined. The illness normally lasts from one to three months, occasionally longer, and is usually followed by complete spontaneous recovery. The thyroid is slightly to moderately enlarged , very firm, and very tender. The pain radiates to an ear or the back of the head. Asymmetric and migratory involvement is common. Fever, systemic symptoms, transient hyperthyroidism, an elevated ESR and paradoxical elevation of thyroxine, and reduced 131 1uptake by the thyroid are characteristic of the early phase of the disorder. There may be temporary hypothyroidism after a month or more. Histopathologically, one observes a marked inflammatory reaction, giant cells, and considerable edema. Complete resolution without functional thyroid damage is the rule . Blum et al. (1) and Miskin et al. (6) have reported, in their preliminary work with A-mode and bistable B scan thyroid echography, that subacute thyroiditis has a "pseudocystic" ultrasonic picture different from normal solid tissue. With these early techniques, it was possible to show that, in contrast to SAT, the normal thyroid reflects mediumamplitude uniform echoes. Cystic areas remain echo free even at high gain, and are associated with a distinct, sharp echo that is representative of the back wall . Solid lesions show multiple internal echo spikes. With increasing sensitivity, cystic structures fill in from the periphery while solid structures generally show central echoes first. Recently, gray-scale echography has yielded enhanced information; one can identify the normal lobe, a cyst, a solid nodule, and a complex pattern representing a degenerated nodule . In SAT, gray-scale echography demonstrates that the thyroid gland is acoustically almost homogeneous and of

Fig. 4. Transverse gray-scale scans from a patient with migratory SAT. The patient's right side (R), trachea (n. thyroid lobes (L), and carotid vessels (V) are indicated. A. Scan obtained when the patient initially presented with pain, swelling, and tenderness of the right lobe . B. Scan obtained five weeks later when the left lobe was involved clinically and the right lobe was asymptomatic. C. Scan taken six months later when the patient had recovered.

very low echogenicity. In contrast with a cyst, sharp terminal echoes, which are inscribed by the posterior wall, are not identified with SAT. Instead, during the active phase of SAT, uniform very low-amplitude echoes are seen. These give the gray-scale echogram a "washed-out" pattern corresponding to the anatomical localization of the illness. Clinical migration of unilateral disease to the opposite lobe is accompanied by spread of the echographic abnormality. The acoustic homogenicity of the echo pattern may be related to the intense inflammation and edema seen in this disorder. Recovery is associated with a return of normal functional and sonic characteristics of the thyroid. Sonography, especially gray-scale, differentiates unilateral subacute thyroiditis from acute hemorrhage in the thyroid. These conditions may be confused clinically because both cause local pain, which radiates to the ear, and decreased uptake of radio-iodine on imaging. Other criteria, which help in the differentiation of these conditions, include the migratory behavior, fever, and elevated ESR of SAT. Cystic or hemorrhagic degeneration of tumors or goiter is rarely confused with SAT either clinically or ultrasonically. With hemorrhagic degeneration the ultrasonic pattern consists of one or more cystic structures, each with a discrete back wall. The cystic region is smaller than the nodule or the cold area on scintiscan, and on gray-scale echography solid echogenic nodular tissue may be demonstrated around the hemorrhage. The echographic pattern of decreased echogenicity is not specific for SAT. It probably reflects inflammatory disease rather than specific pathology. A similar pattern has been described in pancreatitis (7).

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The importance of recognizing and properly treating residual unrelated thyroid disease after recovery from SAT is demonstrated by the patient with a history of exposure to ionizing radiation and a residual "cold," "solid" nodule that proved to be a carcinoma; this type of thyroid nodule has recently been reviewed (8).

December 1977

2. Blum M, Passalaqua AM, Sackler JP: Gray scale echotomography of the thyroid. Abst Endocrinol 98 (Suppl T5), 1976 3. Greene IN: Subacute thyroiditis: diagnostic difficulties and simple treatment. Am J Med 51:97-108, Jul 1971 4. HamburgerJI: Subacute thyroiditis. J Nucl Med 15:81-89, Feb

1974 5. Volpe R, Row VV, Ezrin C: Circulating viral and thyroid antibodies in subacute thyroiditis. J Clin Endocrinol 27: 1275-1284, Sep

1967 SUMMARY

Echographic examination of 10 patients with subacute thyroiditis revealed a decreased echo pattern with a "washed-out" appearance. Clinical migration of inflammation was accompanied by migration of the sonographic abnormality; remission, resulted in a normal echogram. SAT should not be confused with a true cyst or hemorrhagic degeneration of goiter. Echography may be especially helpful in the diagnosis of unilateral subacute thyroiditis.

REFERENCES 1. Blum M, Goldman AB, Herskovic A, et al: Clinical applications of thyroid echography. N Engl J Med 287:1164-1169,7 Dec 1972

6. Miskin M, Rosen IB, Walfish PG: Ultrasonographyof the thyroid gland. Radlol Clin North Am 13:479-492, Dec 1975 7. Leopold GR: Echographic study of the pancreas. JAMA 232: 287-289, 21 Apr 1975 8. Blum M: Enhanced clinical diagnosis of thyroid disease using echography. Am J Med 59:301-307, Sep 1975

Anthony M. Passalaqua, M.D. Department of Radiology New York University Medical Center 560 First Ave. New York, N. Y. 10016