Neurologic Imaging

What Is the Best Initial Imaging for a Suspected Goiter? An ACR-Guided Workflow

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What Is the Best Initial Imaging for a Suspected Goiter? An ACR-Guided Workflow

A 58-year-old woman presents to your primary care clinic complaining of a “fullness” in her neck and occasional difficulty swallowing, which she has noticed over the past year. On physical examination, you palpate a diffusely enlarged, non-tender thyroid gland that moves with swallowing. There are no discrete, dominant nodules. You suspect a goiter, but the differential is broad, ranging from benign enlargement to something more concerning. You need to choose the right initial imaging study to characterize the gland, assess for nodules, and guide the next steps in her management. This article details the American College of Radiology (ACR) Appropriateness Criteria for this exact scenario, explaining why a specific modality is the recommended first step. For the initial imaging of a suspected goiter, a US thyroid is rated Usually appropriate.

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Who Fits This Clinical Scenario?

This guidance applies to adult patients presenting for initial evaluation of a suspected goiter. The clinical suspicion typically arises from a physical examination finding of a diffusely enlarged thyroid gland, with or without palpable irregularities. Patients may be asymptomatic or present with symptoms related to the size of the gland, such as neck fullness, a visible mass, dysphagia (difficulty swallowing), dyspnea (shortness of breath), or a sensation of pressure.

This workflow is specifically for the initial imaging workup. It is crucial to distinguish this presentation from related but distinct clinical questions that follow different diagnostic pathways:

  • Discrete Palpable Nodule: If the primary finding is a single, distinct thyroid nodule without diffuse glandular enlargement, the workup follows the ACR variant for a palpable thyroid nodule.
  • Thyrotoxicosis: If the patient presents with clear clinical and biochemical evidence of hyperthyroidism (e.g., low TSH), the imaging choice is guided by the need to determine the cause of the excess hormone production, which may involve a radionuclide scan. See the sibling scenario on thyrotoxicosis for more detail.
  • Known Thyroid Cancer: Patients with a history of thyroid cancer being evaluated for recurrence or preoperative planning have their own dedicated ACR guidelines and are not covered here.

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What Diagnoses Are You Working Up in This Scenario?

Ordering imaging for a suspected goiter aims to differentiate between several potential underlying causes. The findings will directly influence whether the patient needs surveillance, further testing like a biopsy, or surgical consultation.

The most common diagnosis is a multinodular goiter (MNG). This condition involves the development of multiple nodules within the thyroid gland, leading to its overall enlargement. MNG is highly prevalent, especially in older women, and is often benign. Imaging is essential to identify any specific nodules that have suspicious features warranting further investigation.

Another frequent cause is simple diffuse goiter, where the entire gland is enlarged without the presence of discrete nodules. This can be endemic (due to iodine deficiency) or sporadic. The primary role of imaging here is to confirm the diffuse nature of the enlargement and rule out an underlying nodular process.

Autoimmune thyroiditis, most commonly Hashimoto’s thyroiditis, is a key consideration. This condition can cause diffuse or nodular enlargement of the thyroid, often accompanied by hypothyroidism. Ultrasound has a characteristic appearance in Hashimoto’s, showing diffuse hypoechogenicity and micronodulation, which can support the clinical diagnosis.

Less commonly, a goiter can be the presentation of a thyroid malignancy. While most goiters are benign, a rapidly enlarging gland, a dominant or highly suspicious nodule within a goiter, or associated lymphadenopathy raises concern for cancer. Imaging is critical for risk stratification.

Finally, imaging helps assess for a substernal or retrosternal goiter, where a portion of the enlarged thyroid extends below the thoracic inlet. This is a crucial diagnosis to make, as it can cause significant compressive symptoms like stridor and is not fully assessable by physical exam alone.

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Why Is US Thyroid the Recommended Initial Study for a Suspected Goiter?

The ACR rates US thyroid as Usually appropriate for the initial evaluation of a suspected goiter, making it the clear first-line imaging choice. The rationale is based on its high diagnostic accuracy for thyroid pathology, lack of ionizing radiation, and wide availability. Ultrasound provides unparalleled detail of the thyroid parenchyma, allowing for precise measurement of gland volume, identification and characterization of nodules, and assessment for features of background thyroiditis. It is the ideal tool for guiding fine-needle aspiration (FNA) if a suspicious nodule is found.

Interestingly, CT neck without IV contrast is also rated Usually appropriate. However, it is not the preferred initial study for most patients. Its primary role is as a problem-solving tool, typically reserved for cases where there is a strong clinical suspicion of a large substernal goiter or significant tracheal compression that cannot be fully evaluated by ultrasound. While excellent for defining the anatomic extent of a goiter and its relationship to adjacent structures like the trachea and esophagus, CT exposes the patient to ionizing radiation (☢☢☢ 1-10 mSv) and provides less detail of the internal architecture of thyroid nodules compared to ultrasound. Therefore, the workflow begins with ultrasound (O 0 mSv), reserving CT for specific indications that arise from the initial workup.

Other modalities are rated lower for this initial presentation. For example, MRI neck without and with IV contrast is rated May be appropriate. It can provide excellent soft tissue contrast and assess for substernal extension without radiation, but it is more costly, less accessible, and often offers no significant advantage over the combination of US and, if needed, CT for the initial goiter evaluation. Nuclear medicine studies like an I-123 uptake scan are also rated May be appropriate but are used to assess thyroid function (i.e., “hot” vs. “cold” nodules), a question that typically arises after a goiter or nodule is identified, particularly if the patient is thyrotoxic.

Once you’ve decided on the top procedure, our protocol guide covers the technique, contrast, and reading principles: US Thyroid.

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What’s Next After US Thyroid? Downstream Workflow

The results of the thyroid ultrasound will dictate the subsequent management plan, creating a clear decision tree for the referring clinician.

  • If the US confirms a simple, diffuse goiter without suspicious nodules: The next step is clinical and biochemical correlation. Thyroid function tests (TFTs) should be checked. If the patient is euthyroid and asymptomatic, a strategy of periodic monitoring with physical exams and repeat TFTs is often sufficient.
  • If the US identifies a multinodular goiter: The focus shifts to risk-stratifying the identified nodules. Radiologists will typically use a standardized system like the ACR Thyroid Imaging Reporting and Data System (TI-RADS) to score each nodule based on suspicious features (e.g., solid composition, hypoechogenicity, irregular margins, microcalcifications). Nodules exceeding a certain TI-RADS score and size threshold will be recommended for ultrasound-guided FNA.
  • If the US is inconclusive or suggests a large substernal component: If a patient has significant compressive symptoms (e.g., stridor, positional dyspnea) and the ultrasound cannot visualize the inferior extent of the gland, this is the primary indication to proceed to cross-sectional imaging. A CT of the neck and chest without contrast is the next logical step to define the degree of substernal extension and tracheal compression.
  • If the US findings are characteristic of Hashimoto’s thyroiditis: This sonographic diagnosis should be correlated with serum anti-thyroid peroxidase (TPO) antibody levels and TFTs to confirm the diagnosis and assess for associated hypothyroidism, which requires treatment.

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Pitfalls to Avoid (and When to Get Help)

When working up a suspected goiter, several common pitfalls can delay diagnosis or lead to unnecessary testing.

1. Skipping Straight to CT: Ordering a CT as the first-line study for an uncomplicated goiter is a frequent misstep. This exposes the patient to unnecessary radiation and may require a follow-up ultrasound anyway for better nodule characterization.
2. Ignoring Compressive Symptoms: Do not dismiss symptoms like dysphagia or shortness of breath in a patient with a goiter. If the ultrasound does not explain the symptoms, consider a large retrosternal component and proceed to CT.
3. Failing to Correlate with Labs: Imaging findings must always be interpreted in the context of the patient’s thyroid function tests. A goiter in a hyperthyroid patient has a different differential and workup than one in a euthyroid patient.
4. Not Using a Nodule Scoring System: When nodules are found, ensure the report uses a standardized risk stratification system like TI-RADS. This provides clear, actionable recommendations for which nodules require biopsy versus surveillance.

If you identify a large, complex goiter with significant mass effect, or if a biopsy returns suspicious or malignant results, escalation to an endocrinologist and/or an otolaryngology (ENT) or endocrine surgeon is the appropriate next step.

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Related ACR Topics and Tools

This article focuses on one specific clinical scenario. For a comprehensive overview of imaging for all thyroid-related presentations, from thyrotoxicosis to cancer surveillance, please see our parent topic hub.

Frequently Asked Questions

Why is ultrasound preferred over CT for an initial goiter workup if both are ‘Usually Appropriate’?

Ultrasound is the preferred initial study because it provides superior characterization of the thyroid tissue and any nodules without using ionizing radiation. CT is reserved for specific questions that ultrasound cannot answer, such as evaluating the full extent of a goiter that extends into the chest (substernal goiter) or assessing the degree of airway compression.

If a patient has a goiter and difficulty swallowing, should I order a CT scan first?

No, the recommended first step is still a thyroid ultrasound. The ultrasound can assess the size of the goiter and its relationship to the esophagus. If the ultrasound is unable to fully visualize the gland or if the symptoms are severe and disproportionate to the ultrasound findings, then a CT of the neck and chest would be the appropriate next step to evaluate for a retrosternal component or other causes of compression.

Does every nodule found within a goiter need to be biopsied?

No, not at all. Most nodules found within a multinodular goiter are benign. The decision to biopsy is based on a combination of the nodule’s size and its suspicious features on ultrasound, as categorized by a system like ACR TI-RADS. Only a small subset of nodules meet the criteria for fine-needle aspiration (FNA).

What if the patient’s thyroid function tests (TFTs) show hyperthyroidism?

If the patient is hyperthyroid (thyrotoxic), the clinical scenario changes. While an ultrasound is still often performed to evaluate the gland’s structure, a radionuclide thyroid uptake and scan (using I-123 or Tc-99m pertechnetate) becomes a key part of the workup. This nuclear medicine study helps determine the cause of the hyperthyroidism (e.g., Graves’ disease vs. a toxic nodule). This falls under the ‘Thyrotoxicosis’ ACR variant.

Can an MRI be used to evaluate a goiter?

Yes, MRI is rated as ‘May be appropriate.’ It can be a useful problem-solving tool, especially for complex cases, evaluating substernal extension in patients who cannot receive iodinated CT contrast, or for pre-operative planning in some centers. However, due to its higher cost and longer scan time, it is not recommended for the routine initial evaluation of a suspected goiter.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 29, 2026