Imaging in Cushing's syndrome.
Once the diagnosis of Cushing's syndrome (CS) has been established, the main step is to differentiate between ACTH dependent and independent disease. In adults, 80% of CS is due to ACTH-dependent causes and 20% due to adrenal causes. ACTH-secreting neoplasms cause ACTH-dependent CS. These are usually anterior pituitary microadenomas, which result in the classic Cushing's disease. Non-pituitary ectopic sources of ACTH, such as a small-cell lung carcinoma or carcinoid tumours, are the source of the remainder of ACTH-dependent disease. In the majority of patients presenting with clinical and biochemical evidence of CS, modern non-invasive imaging can accurately and efficiently provide the cause and the nature of the underlying pathology. Imaging is essential for determining the source of ACTH in ectopic ACTH production, locating the pituitary tumours and distinguishing adrenal adenomas, carcinomas and hyperplasias. In our chapter we review the adrenal appearances in ACTH-dependent and ACTH-independent CS. We also include a discussion on the use of MRI and CT for the detection and management of pituitary ACTH secreting adenomas. CT of the chest, abdomen and pelvis with intravenous injection of contrast medium is the most sensitive imaging modality for the identification of the ectopic ACTH source and detecting adrenal pathology. MRI is used for characterising adrenal adenomas, problem solving in difficult cases and for detecting ACTH-secreting pituitary adenomas.
Sahdev
Anju
A
Department of Diagnostic Imaging, St. Bartholomew's Hospital, London, UK anju.sahdev@bartsandthelondon.nhs.uk
Reznek
Rodney H
RH
Evanson
Jane
J
Grossman
Ashley B
AB
D000182:ACTH Syndrome, Ectopic / Q000175:diagnosis; D049913:ACTH-Secreting Pituitary Adenoma / Q000175:diagnosis* / Q000000981:diagnostic imaging; D000236:Adenoma / Q000175:diagnosis / Q000000981:diagnostic imaging; D000310:Adrenal Gland Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging; D002277:Carcinoma / Q000175:diagnosis / Q000000981:diagnostic imaging; D003480:Cushing Syndrome / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000209:etiology; D006801:Humans; D006965:Hyperplasia / Q000175:diagnosis / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000175:diagnosis / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D010902:Pituitary Gland / Q000000981:diagnostic imaging / Q000473:pathology*; D010911:Pituitary Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed