You are in: eMedicine Specialties > Radiology > GENITOURINARY Adrenal MetastasesArticle Last Updated: Mar 12, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Gervais Wansaicheong, MBBS, Registrar, Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore Gervais Wansaicheong is a member of the following medical societies: American Roentgen Ray Society and Royal College of Radiologists Coauthor(s): Jeffrey Goh, MBBS, FRCR, Registrar, Consulting Staff, Department of Diagnostic Radiology, Tan Tock Seng Hospital Editors: Glenn Krinsky, MD, Chief of Abdominal Imaging Section, Associate Professor, Department of Radiology, New York University School of Medicine; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Arnold C Friedman, MD, FACR, Associate Chairman, Department of Radiology, University of Florida Health Science Center; Chief, Department of Radiology, Shands-Jacksonville Hospital; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Consulting Staff, Department of Radiology, Virginia Mason Medical Center Author and Editor Disclosure Synonyms and related keywords: secondaries to the adrenal glands, adrenal gland metastases, adrenal metastasis INTRODUCTIONSection 2 of 12
  BackgroundThe adrenal gland is a common site of metastatic disease. Modern cross-sectional imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI), has revealed that adrenal metastases occur more frequently than previously believed. A diagnosis of adrenal metastasis is important in examining patients with cancer because metastasis indicates stage IV disease. (In this article, references to staging refer to tumor, nodes, and metastases [TNM] staging, unless otherwise stated.) Except in ipsilateral renal cancer, the presence of metastases almost always influences the choice of treatment. PathophysiologyAdrenal metastases may be unilateral or bilateral. The tumors vary in size. Central necrosis and hemorrhage may occur, but calcification is rare. The adrenal gland is the fourth most common site of metastasis, after the lung, liver, and bone. The most common primary sites are the lung,1 breast, skin (melanoma),2 kidney,3 thyroid, and colon. FrequencyInternationalThe reported frequency of adrenal metastases depends on the incidence of the primary tumor; however, for each primary malignancy, the frequency of adrenal metastases is different. Some malignancies are more likely to metastasize to the adrenal glands. About 50% of melanomas, 30-40% of breast and lung cancers, and 10-20% of renal and gastrointestinal tumors metastasize to the adrenal glands. Mortality/MorbidityMost often, the lesions are clinically silent, but cases of hypoadrenalism have occurred. RaceNo specific race-based predilections for adrenal metastases exist. SexNo specific sex-based predilections for adrenal metastases exist. AgeNo specific age-based predilections for adrenal metastases exist. AnatomyThe paired adrenal glands are located at the level between vertebrae T11 and L2, lateral to the body of the L1 vertebra. The gland has an anteromedial ridge and 2 limbs, or “wings.” The maximum width of the body just before the limbs is 0.79 mm on the right side (standard deviation, 0.21 mm) and 0.6 mm on the left side (standard deviation, 0.2 mm). The length of the adrenal limbs varies; they may be as long as 4 cm. The width of the limbs is usually less than 1 cm. The right limbs (0.14-0.49 mm) are usually thinner than the left limbs (0.13-0.52 mm) (see Images 1-2). The adrenal glands are surrounded by fatty areolar tissue with fibrous extensions into the gland; these cause the position of the gland to be relatively fixed. The glands separate from the kidneys during inspiration. The right adrenal gland lies behind the inferior vena cava and above the right kidney. Its medial limb is parallel to the right crus, and its lateral limb is parallel to the liver. The left adrenal gland lies in front of the upper pole of the left kidney. It extends to the renal hilum in 10% of individuals. Its medial limb is related to the aorta and the left crus. The cephalic two thirds of the anterior surface is posterior to the stomach, and the caudal one third of the anterior surface is posterior to the pancreas. Clinical DetailsAdrenal metastases are almost always clinically silent. In the event of extensive bilateral metastatic disease, hypoadrenalism may occur. This is often accompanied by nonspecific symptoms, such as faintness, dizziness, weakness,1 fatigue, and weight loss. At least 50% of patients have vague stomachaches or other gut symptoms, although these symptoms may also result from the malignancy. For these reasons, detailed investigations are not often performed unless proof of adrenal metastases exists. Preferred ExaminationIn adults, CT is the ideal imaging modality for detecting abnormal adrenal glands (see Images 3-4). In patients with primary malignancies that have known predilections for adrenal metastases (especially melanoma, lung cancer, and breast cancer), CT of the abdomen is useful for staging to exclude metastatic disease.4 The usefulness of ultrasonography is limited to detecting large tumors in adults. Children, in whom imaging is less difficult, may be suitable candidates for US. Often, MRI is expensive and not widely available. MRI is useful for further noninvasive characterization of adrenal masses. Radionuclide studies may help demonstrate that a lesion is a functioning adenoma, although false-negative results are known. Positron emission tomography (PET) may be helpful for differentiating incidental adrenal adenomas (the lipid-poor variety) from small metastases. A finding of a focal mass in the adrenal glands does not necessarily indicate metastasis. Percutaneous biopsy often is the next step if CT and MRI findings do not help in conclusively diagnosing benign conditions. Limitations of TechniquesImaging findings can only demonstrate metastasis if an alteration occurs in the outline, the size, or the internal characteristics of the adrenal gland. A normal-appearing gland does not exclude microscopic involvement. One study of patients with small-cell lung cancer showed that as many as 17% of adrenal glands with morphologically normal CT findings had positive results for metastasis on fine-needle aspiration. Small adrenal metastases (<2 cm) are difficult to detect with ultrasonography. Benign adrenal tumors may occur in the general population and in patients with cancer. Noninvasive characterization is important because it prevents unnecessary biopsy. The specificity of noninvasive characterization must be high to prevent attempted curative resection in a patient with metastatic disease. DIFFERENTIALSSection 3 of 12
Adrenal Adenoma Adrenal Carcinoma Adrenal Hemorrhage Other Problems to Be ConsideredUnilateral adrenal mass or enlargement Small masses (<1 cm): Adenoma, ganglioneuroma, hyperplasia, metastasis, and pheochromocytoma Large masses (>4 cm): Carcinoma of adrenal cortex; cyst or pseudocyst; hematoma; infection; inflammation (eg, tuberculosis, histoplasmosis); metastasis (eg, lung or breast related); myelolipoma; neuroblastoma, ganglioneuroblastoma, or ganglioneuroma; pheochromocytoma (eg, multiple endocrine neoplasia) Bilateral adrenal enlargement Common causes: Hemorrhage (eg, in infants, trauma, bleeding disorder), histoplasmosis, hyperplasia, metastasis (eg, lung or breast related), neuroblastoma, and tuberculosis Uncommon causes: RADIOGRAPHSection 4 of 12
FindingsPlain-film imaging of adrenal masses is limited. Large masses are often indistinguishable from renal lesions, and the presence of calcium is not a specific finding (see Image 5). The presence of phleboliths is suggestive of an adrenal hemangioma. Degree of ConfidenceIf the plain-film radiographic findings suggest an adrenal lesion, further evaluation may be performed with CT or MRI (see Image 6). The choice of investigation is determined by availability. The negative predictive value of normal abdominal radiographic findings is low because even images of relatively large adrenal lesions may not demonstrate changes. CT SCANSection 5 of 12
FindingsAdrenal metastases appear as focal masses (see Image 7) or distortion of the contour of the adrenal gland. Larger lesions may have central necrosis or hemorrhage. These lesions are heterogeneous and may have thick enhancing rims. They may also invade contiguous organs, such as the kidneys. Adrenal metastases <3 cm may be homogeneous. Attenuation values of <10 HU on unenhanced CT scans of the adrenal glands are indicative of lipid-containing benign lesions, such as adrenal adenomas (specificity, 100%; sensitivity, 85%); however, lipid-poor adrenal adenomas have attenuation values >10 HU. Attenuation values of 24-37 HU on enhanced CT scans obtained 15 minutes to 1 hour after the administration of contrast material are also indicative of benign lesions (specificity, 96%; sensitivity, 79%). Washout imaging is critical for the characterization of lipid-poor adrenal adenomas. Degree of ConfidenceThe attenuation values of the adrenal glands are more useful than their size for making the diagnosis. The use of the size threshold alone has poor specificity regarding high thresholds (size >2.5 cm: specificity, 79%; sensitivity, 84%) and poor sensitivity regarding low thresholds (size <1.5 cm: specificity, 93%; sensitivity, 16%).4 Bilateral involvement may be seen in a number of benign conditions, such as adrenal adenomas, pheochromocytomas, and tuberculosis. False Positives/NegativesCT findings that may mimic those of left adrenal masses include a mass in the upper pole of the left kidney, gastric diverticulum, splenic lobulation, and a large mass in the tail of the pancreas. MRISection 6 of 12
FindingsAdrenal metastases are usually hypointense on T1-weighted images and relatively hyperintense on T2-weighted images (see Image 8). The exception is metastatic melanoma, which may be bright on T1-weighted images (see Image 9). Occasionally, lesions may remain hyperintense on long–echo-time T2-weighted images, mimicking pheochromocytomas. Degree of ConfidenceChemical-shift imaging with in-phase and out-of-phase imaging techniques is used to exclude metastatic disease by detecting the presence of intracellular lipid within adrenal gland lesions. On out-of-phase images, the lesions have lower signal intensity because the signal from lipid cancels the signal from water by an amount that varies (depending on the quantity of fat present). By comparing out-of-phase images with in-phase images (in which signals from lipid and water are summed), very small amounts of lipid that cannot be demonstrated with other methods can be detected; however, lipid-poor adenomas do not lose signal intensity on out-of-phase images. An adrenal metastasis might not contain lipid (see Image 10). False Positives/NegativesConventional spin-echo MRI and contrast-enhanced MRI findings with benign and malignant conditions have too much overlap to be useful. A small number of malignant tumors, such as metastatic hepatocellular carcinoma, metastatic renal cell carcinoma, metastatic liposarcoma, and adrenocortical carcinoma, may contain enough fat to decrease the signal intensity on out-of-phase images. ULTRASOUNDSection 7 of 12
FindingsAdrenal metastases appear as solid lesions with heterogeneous echogenicity on sonograms (see Image 11). The echogenicity of the lesions is usually less than that of the surrounding fat (hypoechoic). Degree of ConfidenceUltrasonography of the adrenal glands in adults is technically difficult to perform. When it is performed by an experienced operator, ultrasonography can reveal the right adrenal gland in 92% of patients and the left adrenal gland in 71% of patients. Scanning is performed after the patient fasts to reduce bowel gas. In newborns, the adrenal glands are easily imaged. The medulla of the adrenal gland is highly echogenic, and the adrenal cortex is less echogenic. The adrenal glands are more easily visualized in typically sized adults (those with a thin habitus). False Positives/NegativesFalse-positive and false-negative findings may include an adrenal pseudomass, thickened diaphragmatic crus, accessory spleen, gastric fundus, gastric diverticulum, renal vein, splenorenal varices, retrocrural and retroperitoneal adenopathy, upper-pole renal cyst and/or neoplasm, pancreatic mass, hypertrophic caudate lobe, and fluid-filled colon. NUCLEAR MEDICINESection 8 of 12
FindingsNuclear scintigraphy with iodomethylnorcholesterol (NP-59) may be helpful in differentiating benign from malignant lesions. Benign lesions show uptake, although hemorrhage and inflammatory masses are confounding factors. Imaging with fluorodeoxyglucose (FDG) is an alternative technique that is performed with PET. Although initial reports indicate the success of FDG PET,5 this examination is expensive. Degree of ConfidenceNuclear imaging is not widely used. ANGIOGRAPHYSection 9 of 12
FindingsAngiography is not useful for determining the diagnosis. INTERVENTIONSection 10 of 12
If an adrenal lesion cannot be characterized by using CT and MRI images, percutaneous biopsy may be needed to make the diagnosis. The reported accuracy of biopsy is 90-96%. The minor complications of biopsy include abdominal pain, hematuria, nausea, and small pneumothoraces. The major complications of biopsy (2.8-3.6%) include pneumothoraces that require treatment, hemorrhaging, abscesses, pancreatitis, and seeding along the needle track. Medical/Legal Pitfalls
See also the Medscape topic Medical Malpractice and Legal Issues. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
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