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Anatomical and functional imaging in endocrine hypertension.

Chaudhary V, Bano S - Indian J Endocrinol Metab (2012)

Bottom Line: In endocrine hypertension, hormonal excess results in clinically significant hypertension.The functional imaging (such as radionuclide imaging) complements anatomy-based imaging (such as ultrasound, computed tomography, and magnetic resonance imaging) to facilitate diagnostic localization of a lesion causing endocrine hypertension.The aim of this review article is to familiarize general radiologists, endocrinologists, and clinicians with various anatomical and functional imaging techniques used in patients with endocrine hypertension.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiodiagnosis, Employees' State Insurance Corporation (ESIC) Model Hospital, Gurgaon, Haryana, India.

ABSTRACT
In endocrine hypertension, hormonal excess results in clinically significant hypertension. The functional imaging (such as radionuclide imaging) complements anatomy-based imaging (such as ultrasound, computed tomography, and magnetic resonance imaging) to facilitate diagnostic localization of a lesion causing endocrine hypertension. The aim of this review article is to familiarize general radiologists, endocrinologists, and clinicians with various anatomical and functional imaging techniques used in patients with endocrine hypertension.

No MeSH data available.


Related in: MedlinePlus

Atypical adrenal adenoma. A 45-year-old female with primary hyperaldosteronism due to left aldosterone-producing adenoma. Unenhanced CT image (a) shows ~ 4-cm size soft tissue density nodule in left adrenal gland (arrow). Limbs are not enlarged. Contrast-enhanced CT image (b) shows minimal enhancement of the nodule. The diagnosis of adenoma was confirmed on histopathological examination
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Figure 1: Atypical adrenal adenoma. A 45-year-old female with primary hyperaldosteronism due to left aldosterone-producing adenoma. Unenhanced CT image (a) shows ~ 4-cm size soft tissue density nodule in left adrenal gland (arrow). Limbs are not enlarged. Contrast-enhanced CT image (b) shows minimal enhancement of the nodule. The diagnosis of adenoma was confirmed on histopathological examination

Mentions: Computed tomography (CT) is the imaging modality of choice for evaluating adrenal gland morphology and masses associated with it. High-resolution CT of upper abdomen, using 1–3 mm thick slices to reduce volume averaging, is the most accurate technique for identifying adrenal lesions. Contrast-enhanced CT and delayed images help in further characterization of the lesions. The two main causes of primary hyperaldosteronism (Conn's syndrome) are aldosterone-producing adrenal adenoma (APA) and bilateral adrenal hyperplasia (BAH) of the zona glomerulosa that may, at times, be micronodular or macronodular. APAs were previously thought to represent approximately two-third of cases of primary aldosteronism and BAH approximately one-third cases; however, recent evidence suggests that this ratio is reversed.[3] On CT scan, aldosterone-producing adrenal adenomas (APAs) usually appear as small (<4 cm in size), homogenous, well- circumscribed masses with smooth margin. Calcification, necrosis, and hemorrhage are uncommon in benign adenomas. A large amount of intracytoplasmic lipid within the adenoma allows for a quantitative evaluation by measuring the attenuation value of the lesion.[4] An attenuation value of 10 HU (Hounsfield units) or less on unenhanced image is diagnostic of adrenal adenoma [Figure 1], with 79% sensitivity and 96% specificity, and no further investigations are required. However, 30% adenomas are lipid-poor showing the attenuation value greater than 10 HU. A contrast-enhanced CT is required for further characterization of these lesions. A dynamic (at 60 s) and delayed (at 10 min) contrast-enhanced CT scan is obtained, a region of interest is drawn over the adrenal mass, and the attenuation is measured in Hounsfield units at 60 s and at 10 min. Then the percentage of contrast agent washout is calculated using formula [1 - (attenuation at 10 min/attenuation at 60 s)] X 100, where the attenuations are in Hounsfield units. The washout is a measurement of the percentage decrease between the initial enhancement and the delayed enhancement. A washout of greater than 50% is specific for benign adrenal adenoma, and a washout of less than 50% is specific for metastasis or malignancy. Thus, the contrast-agent washout measurement yields 98% sensitivity and 100% specificity and can reliably determine if an adrenal mass is benign or malignant.[56] In addition, we should always remember that nonfunctioning, incidental adrenal adenomas (incidentalomas) are commonly encountered on routine CT scans used for general abdominal imaging. Therefore, the diagnosis of primary hyperaldosteronism cannot be made on imaging result alone but must be correlated with biochemical testing.[7] In general, “a rule of four” has been suggested for incidentalomas, which states that some 4% of CT scan reveals an adrenal incidentaloma (a mean across all ages); some 4% of these are either pheochromocytomas or adrenocortical cancers. A diameter of 4 cm is used to initiate mandatory removal and, finally, the current recommendation of follow-up is four years.[8] Moreover, in primary hyperaldosteronism, discriminating bilateral adrenal hyperplasia (BAH) from an aldosterone-producing adenoma (APA) is important because adrenalectomy, which is usually curative in APA, is seldom effective in BAH. Treatment for BAH is strictly medical. Unfortunately, no single test has been identified to fulfill this need. Moreover, the patients with BAH can have asymmetric adrenal macronodules, whereas some patients with APA may have tumor nodule too small (<5 mm) to be resolved even on high resolution CT scans. Thus, patients with bilateral nodularity or normal-appearing adrenal glands on CT should be referred to for adrenal vein sampling (AVS).[9]


Anatomical and functional imaging in endocrine hypertension.

Chaudhary V, Bano S - Indian J Endocrinol Metab (2012)

Atypical adrenal adenoma. A 45-year-old female with primary hyperaldosteronism due to left aldosterone-producing adenoma. Unenhanced CT image (a) shows ~ 4-cm size soft tissue density nodule in left adrenal gland (arrow). Limbs are not enlarged. Contrast-enhanced CT image (b) shows minimal enhancement of the nodule. The diagnosis of adenoma was confirmed on histopathological examination
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475894&req=5

Figure 1: Atypical adrenal adenoma. A 45-year-old female with primary hyperaldosteronism due to left aldosterone-producing adenoma. Unenhanced CT image (a) shows ~ 4-cm size soft tissue density nodule in left adrenal gland (arrow). Limbs are not enlarged. Contrast-enhanced CT image (b) shows minimal enhancement of the nodule. The diagnosis of adenoma was confirmed on histopathological examination
Mentions: Computed tomography (CT) is the imaging modality of choice for evaluating adrenal gland morphology and masses associated with it. High-resolution CT of upper abdomen, using 1–3 mm thick slices to reduce volume averaging, is the most accurate technique for identifying adrenal lesions. Contrast-enhanced CT and delayed images help in further characterization of the lesions. The two main causes of primary hyperaldosteronism (Conn's syndrome) are aldosterone-producing adrenal adenoma (APA) and bilateral adrenal hyperplasia (BAH) of the zona glomerulosa that may, at times, be micronodular or macronodular. APAs were previously thought to represent approximately two-third of cases of primary aldosteronism and BAH approximately one-third cases; however, recent evidence suggests that this ratio is reversed.[3] On CT scan, aldosterone-producing adrenal adenomas (APAs) usually appear as small (<4 cm in size), homogenous, well- circumscribed masses with smooth margin. Calcification, necrosis, and hemorrhage are uncommon in benign adenomas. A large amount of intracytoplasmic lipid within the adenoma allows for a quantitative evaluation by measuring the attenuation value of the lesion.[4] An attenuation value of 10 HU (Hounsfield units) or less on unenhanced image is diagnostic of adrenal adenoma [Figure 1], with 79% sensitivity and 96% specificity, and no further investigations are required. However, 30% adenomas are lipid-poor showing the attenuation value greater than 10 HU. A contrast-enhanced CT is required for further characterization of these lesions. A dynamic (at 60 s) and delayed (at 10 min) contrast-enhanced CT scan is obtained, a region of interest is drawn over the adrenal mass, and the attenuation is measured in Hounsfield units at 60 s and at 10 min. Then the percentage of contrast agent washout is calculated using formula [1 - (attenuation at 10 min/attenuation at 60 s)] X 100, where the attenuations are in Hounsfield units. The washout is a measurement of the percentage decrease between the initial enhancement and the delayed enhancement. A washout of greater than 50% is specific for benign adrenal adenoma, and a washout of less than 50% is specific for metastasis or malignancy. Thus, the contrast-agent washout measurement yields 98% sensitivity and 100% specificity and can reliably determine if an adrenal mass is benign or malignant.[56] In addition, we should always remember that nonfunctioning, incidental adrenal adenomas (incidentalomas) are commonly encountered on routine CT scans used for general abdominal imaging. Therefore, the diagnosis of primary hyperaldosteronism cannot be made on imaging result alone but must be correlated with biochemical testing.[7] In general, “a rule of four” has been suggested for incidentalomas, which states that some 4% of CT scan reveals an adrenal incidentaloma (a mean across all ages); some 4% of these are either pheochromocytomas or adrenocortical cancers. A diameter of 4 cm is used to initiate mandatory removal and, finally, the current recommendation of follow-up is four years.[8] Moreover, in primary hyperaldosteronism, discriminating bilateral adrenal hyperplasia (BAH) from an aldosterone-producing adenoma (APA) is important because adrenalectomy, which is usually curative in APA, is seldom effective in BAH. Treatment for BAH is strictly medical. Unfortunately, no single test has been identified to fulfill this need. Moreover, the patients with BAH can have asymmetric adrenal macronodules, whereas some patients with APA may have tumor nodule too small (<5 mm) to be resolved even on high resolution CT scans. Thus, patients with bilateral nodularity or normal-appearing adrenal glands on CT should be referred to for adrenal vein sampling (AVS).[9]

Bottom Line: In endocrine hypertension, hormonal excess results in clinically significant hypertension.The functional imaging (such as radionuclide imaging) complements anatomy-based imaging (such as ultrasound, computed tomography, and magnetic resonance imaging) to facilitate diagnostic localization of a lesion causing endocrine hypertension.The aim of this review article is to familiarize general radiologists, endocrinologists, and clinicians with various anatomical and functional imaging techniques used in patients with endocrine hypertension.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiodiagnosis, Employees' State Insurance Corporation (ESIC) Model Hospital, Gurgaon, Haryana, India.

ABSTRACT
In endocrine hypertension, hormonal excess results in clinically significant hypertension. The functional imaging (such as radionuclide imaging) complements anatomy-based imaging (such as ultrasound, computed tomography, and magnetic resonance imaging) to facilitate diagnostic localization of a lesion causing endocrine hypertension. The aim of this review article is to familiarize general radiologists, endocrinologists, and clinicians with various anatomical and functional imaging techniques used in patients with endocrine hypertension.

No MeSH data available.


Related in: MedlinePlus