Role of color flow Doppler sonography for discovering the etiologic diagnosis of hyperthyroidism

Topic: DOPPLER ULTRASONOGRAPHY & HYPERTHYROIDISM

Title: Color Flow Doppler Sonography for the Etiologic Diagnosis of Hyperthyroidism.

Authors: Erdogan MF, Anil C, Cesur M, Baskal N, and Erdogan G.

Reference: Thyroid 17: 223-228, 2007

Summary

Background

Color flow Doppler sonography is gaining importance for the functional evaluation of thyroid disorders.

Purpose

The objective of this study was to determine the value of Color flow Doppler sonography for the etiological diagnosis of hyperthyroidism.

Material and methods

Fifty-five patients with hyperthyroidism (29 Graves- disease & 26 toxic adenomas), 24 patients with Hashimoto-s thyroiditis, and 39 euthyroid controls were investigated. Etiological diagnoses were ascertained using standard methods. Conventional gray scale sonography was performed, followed by Color flow Doppler sonography. The Doppler patterns of the glands were scored and peak systolic velocity measurements were obtained from the intrathyroidal, perithyroidal, and perinodular vasculature.

Results

The vascular patterns were significantly more prominent, and the mean peak systolic velocity values were significantly higher in the Graves- disease patients compared to the Hashimoto-s thyroiditis patients (p<0.001) and controls (p<0.001). Perinodular and intranodular signals and the mean perinodular peak systolic velocity values were significantly higher in toxic adenomas compared to controls. Color flow Doppler sonography could differentiate the untreated Graves- disease from Hashimoto-s thyroiditis, which had similar gray scale findings. Hot nodules could also be differentiated from cold nodules with more prominent vascular patterns and significantly higher mean perinodular peak systolic velocity values.

Conclusions

Color flow Doppler sonography, an inexpensive, fast, and non-invasive imaging procedure, could be helpful in the initial clinical evaluation of patients that are referred for thyroid ultrasonography and may avoid scintigraphy in a substantial number of thyrotoxic patients.

Commentary

It would be advantageous if one thyroid imaging technique could simultaneously provide reliable anatomic information about function as well as structure. It would be all the better if the test were free of the constraints imposed by iodine excess or deficiency, and if ionizing radiation and multiple visits to a laboratory could be avoided. Is ultrasonography with Color flow Doppler interrogation up to this challenge? The authors present evidence that Color flow Doppler sonography could be helpful in the initial clinical evaluation of thyrotoxic patients and may avoid scintigraphy in a substantial number of them.

Color flow Doppler sonography can demonstrate enhanced vascularity and increased blood-flow in the thyroid gland and in some thyroid nodules. Generalized or focal hyper-dynamic circulation correlate imperfectly with hyperthyroidism that is caused a diffuse process like Graves- Disease, where very brisk hemodynamics have been likened to an inferno, or TSH producing tumor, focal lesions like autonomous nodule or toxic nodular goiter, and benign or malignant tumors. Some thyroid follicular tumors, toxic nodules among them, may have an abundant vascular pattern within the mass. But, can color flow Doppler sonography distinguish with high sensitivity and specificity the various types of hyperthyroidism? Will it be cost-effective by supplanting other examinations? Or, will the demonstration of abundant blood-flow merely be an interesting phenomenon that radiologists can display at conferences? Erdogan et al. conclude that based on their observations, color flow Doppler sonography could be helpful in the initial clinical evaluation of thyrotoxic patients and may avoid a substantial number of scintigraphy examinations.

In the simplest terms, a physician obtains a sonogram of the neck to investigate a non-thyroid problem, to elucidate a thyroid lesion, or to examine the region routinely. When an ultrasonogram is done for a non-thyroid investigation, the discovery of increased blood flow and vascularity can alert the neurologist, orthopedist or other practitioner to the possibility of hyperthyroidism, and that is important but not accurate diagnosis or an essential prelude to therapy. Let-s call that -incidental-functionopathy- to be symmetric with the well-known -incidentaloma-. When a generalist or an endocrinologist performs a sonogram to investigate thyroid disease, finer and more specific information is required. Indeed, many patients consult their primary physician or an endocrinologist for correct answers because of such incidentally-discovered sonographic abnormality.

When a clinician selects a diagnostic thyroid ultrasonogram because of thyroid disease, it may be the initial and sometimes the only thyroid test. Scintigraphy should be reserved for patients whose TSH is suppressed because of actual or relative hyperthyroxinemia or triiodothyroninemia to differentiate conditions that are characterized by generalized increased radioiodine uptake ( hyperthyroidism ) and deficient iodine accumulation ( thyrotoxicosis without hyperthyroidism ) on the one hand, and to map excessive, focal production of the hormones on the other. The former group has either excessive production of the hormones as in Graves- disease (high radioiodine uptake), or assorted abnormalities including ingestion of excessive thyroid hormone and passive release of preformed thyroid hormone because of subacute thyroiditis, silent thyroiditis, or irradiation induced thyroiditis (low radioiodine uptake). This distinction is achieved by the radioiodine uptake test and is critical for selection of proper therapy. In addition, identifying excessive, focal production of the hormones in toxic autonomous nodule, or toxic nodular goiter is also an important diagnostic contribution of scintiscanning.

The main defect in this paper is the absence of subjects who have thyrotoxicosis without hyperthyroidism (i.e. hyperthyroxinemia) and lack active, intra-glandular production of hormone. The treatment of these diverse, relatively common groups of patients is radically different from patients with hyperthyroidism. In contrast, the data in a small, retrospective sample suggests that Color flow Doppler sonography can identify many hyperthyroid glands and nodules and thus is useful. Further, prospective investigation of larger numbers will be needed before accurate sensitivity and specificity can be assessed and one can consider replacing the scintiscan as the test of choice in these patients. For instance, there were two cases with prominent Doppler signals that had normal TSH and thus were not hyperthyroid. It is unfortunate that Thyroid Stimulating Immunoglobulin was not assayed in these patients or in any of the other subjects. Another example of lack of specificity is demonstrated by the authors- observation of -a few overlaps- of Color flow Doppler sonography patterns between Graves- disease and Hashimoto-s thyroiditis, similar to what has been reported in the literature. In other words, a hyper-dynamic thyroid circulation is neither pathognomonic nor specific for Graves- hyperthyroidism. Separation of patients with euthyroid and toxic nodules was also imperfect. Although the observations were made by an experienced sonologist who was unaware of the diagnoses, it is unclear how many physicians interpreted the images and the inter-observer variation. My own conclusion is that ultrasonography with Color flow Doppler interrogation does not replace scintigraphy in the diagnosis of Graves- disease, silent or other thyroiditis, or toxic nodules. There are, however, significant and strong correlations between thyroid hyper-function (very low TSH) and Doppler parameters that can help the clinician considerably especially when this easy, inexpensive, fast, safe, and non-invasive imaging procedure is used before the patient gets to dedicated thyroid evaluation. My speculation would be that neither sensitivity nor specificity will be adequate for diagnosis unless, perhaps, contrast sonography offers a break-through, which could happen.

( Summary and commentary prepared by Manfred Blum )

Present summary and commentary are related to Chapter N- 6c of TDM