Adrenal Gland Computed Tomography

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Adrenal Gland Computed Tomography

Definition

Adrenal gland computed tomography is a diagnostic imaging examination in which a computer uses multiple x-ray images to reconstruct either cross-sections or three-dimensional images of a specific part of the body, in this case, the adrenal glands.

Purpose

The adrenal glands are small, triangular endocrine organs that lie just above each kidney. Each adrenal gland is made of two types of tissue. The outer region is the adrenal cortex and the inner region is the adrenal medulla. The adrenal glands interact with hormones secreted by the pituitary gland and the hypothalamus of the brain. The adrenal cortex produces steroid hormones including cortisol (hydrocortisone) that regulates metabolism of nutrients, corticosterone that suppresses inflammation, aldosterone that regulates sodium and water balance in the body, and a small amount of androgens (male hormones). The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline).

The adrenal glands may become abnormal because of a primary cancer or a metastatic lesion. External hormonal stimulation by the pituitary or other glands may enlarge the adrenals. Adrenal glands may hemorrhage after injury and show signs of traumatic hematoma. Adrenal masses may or may not interfere with the gland's ability to function properly.

Injuries to the kidney region and metabolic problems related to hormones secreted by the adrenal (for example Cushing's syndrome characterized by an overproduction of cortisol) often suggest adrenal abnormalities and call for diagnostic imaging tests. Computed tomography (CT) scans are preferred over ultrasound (sonography) because the adrenals lie deep within in the retroperitoneal cavity, making it difficult to get good ultrasound images. With proper technique, CT scans provide good diagnostic images in almost all patients. Magnetic resonance imaging (MRI) may be used to solve diagnosis problems related to the adrenal glands, but MRI exams are lengthier and more expensive than CT exams. Nuclear medicine techniques such as positron emission tomography (PET) show promise in determining if an adrenal mass is benign or malignant, but PET imaging is more complicated and expensive than CT scanning. It may be reserved for situations where other diagnostic procedures produce inconclusive information.

Adrenal gland CT can detect both malignant and benign tumors, as well as mechanical injury of the gland. When abnormal growth is detected, additional diagnostic tests are usually needed to determine the type of tumor and to define an appropriate treatment.

Since the 1990s, the use of CT in the trauma setting has increased so that abdominal CT scans are routine for most trauma patients. Trauma and mechanical injury to the adrenals may be recognized during initial abdominal trauma exams. Adrenal gland injuries can be severe. Individuals may survive without the adrenal medulla, but the hormones of the adrenal cortex are essential to life.

Precautions

The images produced by CT scans are created by low dose x-ray radiation. Generally the benefit of the scan far outweighs the risk of exposure to this radiation. Women who are or might be pregnant should notify their physician and the radiology technician about the pregnancy before they receive a CT scan. Adrenal CT scans are often enhanced by the injection of a contrast material usually containing iodine into the bloodstream. This allows the radiologist to see the flow of blood through the adrenal gland and surrounding area. The contrast material can cause a severe allergic reaction in individuals who are allergic to iodine. Patients who are allergic to iodine or shellfish should inform the physician and radiology technician before receiving an injection of contrast material.

Description

An adrenal gland CT scan usually takes place in the radiology department of a hospital or in a freestanding imaging facility. Inside the CT scanner is a rotating gantry with an x-ray tube mounted on one side and an arc-shaped detector mounted on the opposite side. The radiology technician places the patient in the appropriate position on the table and then goes to the CT control area, where he or she can manipulate the equipment by computer without being exposed to radiation. The patient remains still while the scanner rotates around the part of the body being examined. The patient may be asked to hold his or her breath during scanning. The scanning procedure is painless.

Modern multi-detector CT scanners can capture many images per second. These images are sent to a computer that either shows cross-sections of the adrenal gland or compiles the images into a three-dimensional picture. Faster scanning helps shorten the time it takes to produce a scan and reduces the time during which the patient must hold his or her breath. Many adrenal gland CT exams can be completed in 10-15 minutes.

Adrenal gland CT often requires use of contrast material to enhance the x-ray images. Most often, the contrast is a solution containing iodine. The solution is injected shortly before the scan begins.

Preparation

The physician may suggest special dietary requirements prior to the exam. Patients should follow all instructions concerning water or food intake before the CT.

Aftercare

Nursing mothers who receive contrast material during an adrenal gland CT should wait 24 hours before resuming breast feeding.

Complications

No complications are expected from this procedure unless an individual reacts to contrast material. Radiology department personnel are trained to deal with contrast reactions.

KEY TERMS

Adenoma— A benign tumor or structure that originates from glandular tissue.

Benign— Mild and non-threatening, not cancerous.

Hematoma— A mass of blood that forms from a broken blood vessel.

Malignant— Unfavorable prognosis, not responding favorably to treatment, generally means cancerous for neoplasms.

Metastatic— Secondary to a cancer that occurred first in another organ in the body and then spread.

Retroperitoneal— Situated behind the peritoneum, the smooth transparent membrane that lines the cavity of the abdomen.

Results

A radiologist interprets the images and reports signs of abnormal pathology such as an enlarged adrenal gland or mass. In Cushing's syndrome, the CT exam may show an adrenal adenoma greater than 2.0 cm in diameter, as well as signs of intra-abdominal fat and evidence of a fatty liver. A larger mass usually indicates malignancy. Changes in size of the lesions from one exam to another help the physician determine if a mass is malignant or benign, since benign adenomas grow more slowly than malignant masses. A mass that is irregular in shape is more likely to be metastasis than an adenoma. Contrast enhancement helps show fat characteristics of benign vs. malignant masses, as does enhancement of the vascular structures. Adrenal gland hematomas and lacerations can be seen on CT scans, as can evidence of associated abdominal trauma injuries and evidence of bleeding.

Health care team roles

A referring physician such as an endocrinologist, oncologist, internal medicine physician, primary care physician or emergency room physician orders the adrenal gland CT. A radiology technician or technologist performs the scan. These are health care professionals specially trained and certified to conduct medical imaging examinations. Many also are certified in computed tomography as a specialty. Radiologists are physicians that interpret the examination and produce a report for the referring physician.