Parathyroid Scan

Parathyroid Scan

 

Definition

A parathyroid scan is sometimes called a parathyroid localization scan or parathyroid scintigraphy. This scan uses radioactive pharmaceuticals that are readily taken up by cells in the parathyroid glands to obtain an image of the glands and any abnormally active areas within them.

Purpose

The parathyroid glands, embedded in the thyroid gland in the neck, but separate from the thyroid in function, control calcium metabolism in the body. The parathyroid glands produce parathyroid hormone (PTH). PTH regulates the level of calcium in the blood.
Calcium is critical to cellular metabolism, as well as being the main component of bones. If too much PTH is secreted, the bones release calcium into the bloodstream. Over time, the bones become brittle and more likely to break. A person with levels of calcium in the blood that are too high feels tired, run down, irritable, and has difficulty sleeping. Additional signs of too much calcium in the blood are nausea and vomiting, frequent urination, kidney stones and bone pain. A parathyroid scan is administered when the parathyroid appears to be overactive and a tumor is suspected.

Precautions

Parathyroid scans are not recommended for pregnant women because of the potential harm to the developing fetus. People who have had another recent nuclear medicine procedure or an intravenous contrast test may need to wait until the earlier radioactive markers have been eliminated from their system in order to obtain accurate results from the parathyroid scan.

Description

A parathyroid scan is a non-invasive procedure that uses two radiopharmaceuticals (drugs with a radioactive marker) to obtain an image of highly active areas of the parathyroid glands. The test can be done in two ways.

Immediate scan

If the test is to be performed immediately, the patient lies down on an imaging table with his head and neck extended and immobilized. The patient is injected with the first radiopharmaceutical. After waiting 20 minutes, the patient is positioned under the camera for imaging. Each image takes five minutes. It is essential that the patient remain still during imaging.
After the first image, the patient is injected with a second radiopharmaceutical, and imaging continues for another 25 minutes. Total time for the test is about one hour: injection 10 minutes, waiting period 20 minutes, and imaging 30 minutes.
Another way to do this test is as follows. After the first images are acquired, the patient returns two hours later for additional images. Time for this procedure totals about three hours: injection 10 minutes, waiting period two hours and 20 minutes, and imaging 30 minutes.

Delayed scan

In a delayed parathyroid scan, the patient is asked to swallow capsules containing the first radiopharmaceutical. The patient returns after a four hour waiting period, and the initial image is made. Then the patient is injected with the second radiopharmaceutical. Imaging continues for another 25 minutes. The total time is about four hours and 40 minutes: waiting period four hours, injection 10 minutes, and imaging 30 minutes.

Preparation

No special preparations are necessary for this test. It is not necessary to fast or maintain a special diet. The patient should wear comfortable clothing and no metal jewelry around the neck.

Aftercare

The patient should not feel any adverse effects of the test and can resume normal activities immediately.

Key terms

Cyst — An abnormal sac containing fluid or semisolid material.
Goiter — Chronic enlargement of the thyroid gland.
Neoplasm — An uncontrolled growth of new tissue.

Risks

The only risk associated with this test is to the fetus of a pregnant woman.

Normal results

Normal results will show no unusual activity in the parathyroid glands.

Abnormal results

A concentration of radioactive materials in the parathyroid gland beyond background levels suggests excessive activity and the presence of a tumor. False positive results sometimes result from the presence of multinodular goiter, neoplasm, or cysts. False positive tests are tests that interpret the results as abnormal when this is not true.

Resources

Other

"Parathyroid Scan." HealthGate Page. June 13, 1998. http://www.healthgate.com.

parathyroid scan

a nuclear scan used to determine the number of parathyroid glands involved in hyperparathyroidism. Enlargement of all four glands indicates parathyroid hyperplasia. Enlargement of only one indicates adenoma or cancer.

Parathyroid Scan

Synonym/acronym: Parathyroid scintiscan.

Common use

To assess the parathyroid gland toward diagnosing cancer and to perform postoperative evaluation of the parathyroid gland.

Area of application

Parathyroid.

Contrast

IV technetium-99m (Tc-99m) pertechnetate, Tc-99m sestamibi, oral iodine-123, and thallium.

Description

Parathyroid scanning is performed to assist in the preoperative localization of parathyroid adenomas in clinically proven primary hyperparathyroidism; it is useful for distinguishing between intrinsic and extrinsic parathyroid adenomas. It is also performed after surgery to verify the presence of the parathyroid gland in children, and it is done after thyroidectomy as well.

The radionuclide is administered 10 to 20 min before the imaging is performed. The thyroid and surrounding tissues should be carefully palpated.

Fine-needle aspiration biopsy guided by ultrasound is occasionally necessary to differentiate thyroid pathology, as well as pathology of other tissues, from parathyroid neoplasia.

This procedure is contraindicated for

  • high alertPatients who are pregnant or suspected of being pregnant, unless the potential benefits of a procedure using radiation far outweigh the risk of radiation exposure to the fetus and mother.

Indications

  • Aid in the diagnosis of hyperparathyroidism
  • Differentiate between extrinsic and intrinsic parathyroid adenoma but not between benign and malignant conditions
  • Evaluate the parathyroid in patients with severe hypercalcemia or in patients before parathyroidectomy

Potential diagnosis

Normal findings

  • No areas of increased perfusion or uptake in the thyroid or parathyroid

Abnormal findings related to

  • Intrinsic and extrinsic parathyroid adenomas

Critical findings

    N/A

Interfering factors

  • Factors that may impair clear imaging

    • Inability of the patient to cooperate or remain still during the procedure because of age, significant pain, or mental status.
    • Ingestion of foods containing iodine (e.g., iodized salt) and medications containing iodine (e.g., cough syrup, potassium iodide, vitamins, Lugol’s solution, thyroid replacement medications), which can decrease uptake of the radionuclide.
    • Other nuclear scans or iodinated contrast medium radiographic studies done within the previous 24 to 48 hr.
    • Metallic objects (e.g., jewelry, body rings) within the examination field, which may inhibit organ visualization and cause unclear images.
  • Other considerations

    • Improper injection of the radio-nuclide that allows the tracer to seep deep into the muscle tissue produces erroneous hot spots.
    • Consultation with a health-care provider (HCP) should occur before the procedure for radiation safety concerns regarding younger patients or patients who are lactating. Pediatric & Geriatric Imaging Children and geriatric patients are at risk for receiving a higher radiation dose than necessary if settings are not adjusted for their small size. Pediatric Imaging Information on the Image Gently Campaign can be found at the Alliance for Radiation Safety in Pediatric Imaging (www.pedrad.org/associations/5364/ig/).
    • Risks associated with radiation overexposure can result from frequent x-ray or radionuclide procedures. Personnel working in the examination area should wear badges to record their level of radiation exposure.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this procedure can assist in diagnosing parathyroid disease.
  • Obtain a history of the patient’s complaints or clinical symptoms, including a list of known allergens, especially allergies or sensitivities to latex, anesthetics, sedatives, or radionuclides.
  • Note any recent procedures that can interfere with test results, including examinations using iodinated contrast medium or radioactive nuclides.
  • Obtain a history of the patient’s endocrine system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Record the date of the last menstrual period and determine the possibility of pregnancy in perimenopausal women.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Address concerns about pain related to the procedure and explain that some pain may be experienced during the test. Inform the patient that the procedure is performed in a nuclear medicine department, usually by an HCP specializing in this procedure, with support staff, and takes approximately 30 to 60 min.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Explain that an IV line may be inserted to allow infusion of IV fluids such as normal saline, anesthetics, sedatives, radionuclides, medications used in the procedure, or emergency medications.
  • Instruct the patient to remove jewelry and other metallic objects from the area to be examined.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.
  • Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.

Intratest

  • Potential complications:
  • Although it is rare, there is the possibility of allergic reaction to the radionuclide. Have emergency equipment and medications readily available. If the patient has a history of allergic reactions to any substance or drug, administer ordered prophylactic steroids or antihistamines before the procedure.

  • Establishing an IV site and injection of radionuclides is an invasive procedure. Complications are rare but do include bleeding from the puncture site related to a bleeding disorder, or the effects of natural products and medications known to act as blood thinners; hematoma related to blood leakage into the tissue following needle insertion; infection that might occur if bacteria from the skin surface is introduced at the puncture site; or nerve injury that might occur if the needle strikes a nerve.

  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.
  • Ensure that the patient has removed all external metallic objects from the area to be examined prior to the procedure.
  • Instruct the patient to void prior to the procedure and to change into the gown, robe, and foot coverings provided.
  • Record baseline vital signs and assess neurological status. Protocols may vary among facilities.
  • Establish an IV fluid line for the injection of saline, anesthetics, sedatives, radionuclides, or emergency medications.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Have emergency equipment readily available.
  • Instruct the patient to cooperate fully and to follow directions. Instruct the patient to remain still throughout the procedure because movement produces unreliable results.
  • Observe that technetium-99m (Tc-99m) pertechnetate is injected IV before scanning.
  • Place the patient in a supine position under a radionuclide gamma camera. Images are preformed 15 min after the injection.
  • With the patient in the same position, Tc-99m sestamibi is injected, and a second image is obtained after 10 min.
  • Iodine-123 may be administered orally in place of Tc-99m pertechnetate; the imaging sequence, as described previously, is performed 24 hr later.
  • Remove the needle or catheter and apply a pressure dressing over the puncture site.
  • Observe/assess the needle/catheter insertion site for bleeding, inflammation, or hematoma formation.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Observe/assess the needle/catheter insertion site for bleeding, inflammation, or hematoma formation.
  • Instruct the patient in the care and assessment of the injection site.
  • Advise the patient to drink increased amounts of fluids for 24 to 48 hr to eliminate the radionuclide from the body, unless contraindicated. Tell the patient that radionuclide is eliminated from the body within 6 to 24 hr.
  • If a woman who is breastfeeding must have a nuclear scan, she should not breastfeed the infant until the radionuclide has been eliminated. This could take as long as 3 days. She should be instructed to express the milk and discard it during the 3-day period to prevent cessation of milk production.
  • Instruct the patient to flush the toilet immediately and to meticulously wash hands with soap and water after each voiding for 24 hr after the procedure.
  • Instruct all caregivers to wear gloves when discarding urine for 24 hr after the procedure. Wash gloved hands with soap and water before removing gloves. Then wash hands after the gloves are removed.
  • Recognize anxiety related to test results, and be supportive of perceived loss of independent function. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be needed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include calcitonin, calcium, CT thoracic and MRI chest, PTH, phosphorus, US thyroid and parathyroid, and vitamin D.
  • Refer to the Endocrine System table at the end of the book for related tests by body system.
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