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We reviewed 31 patients in whom both bilateral inferior petrosal sinus ampling without CRH stimulation, and a CT scan of the lungs were done. Twenty-five had normal lung CT scans, of whom 23 had a higher inferior petrosal sinus:peripheral ACTH ratio 1.5. After careful follow-up, none was subsequently shown to have ectopic ACTH syndrome. Six had abnormal lung CT scans, of whom two had ratios 1.5. In these two patients, other investigations suggested pituitary disease, and pituitary surgery led to apparent cure. Of the remaining four patients, who had ratios < 1.5, two had incidental lung findings, and pituitary abnormalities were demonstrated at pituitary surgery. The third underwent bilateral adrenalectomy, and no evidence of ectopic ACTH syndrome has emerged as yet after 4 years follow-up. The fourth had a small-cell carcinoma of the lung, confirmed histologically. Our series suggests that whole-lung CT scanning is only necessary in cases of ACTH-dependent Cushing's syndrome where bilateral inferior petrosal sinus sampling has not demonstrated a significant increase in petrosal sinus ACTH levels as compared with the peripheral level. Thus, in our experience the test is now only necessary in those patients (approximately 25%) where the ratio is 1.5

A wide variety of neuroendocrine tumours express somatostatin receptors, and can be visualized by radiolabelled somatostatin analogue scintigraphy. To investigate the value of [^111In]-octreotide scintigraphy (Octreoscan), 48 patients (37 with proven carcinoid, pancreatic endocrine and medullary carcinoma of thyroid tumours, 11 with neuroendocrine syndromes multiple endocrine neoplasia (MEN-1) and Zollinger-Ellison syndrome (ZES) were examined with ¹¹¹In-DTPA-D-Phe¹-octreotide. Scintigrams were obtained at 24 and 48 h, and the results were compared with CT and magnetic resonance imaging (MRI). Thirty-five of 48 patients had positive [¹¹¹In]-octreotide scintigraphy (23/25 (92%) carcinoids, 8/9 (89%) PETs, 4/11 (36%) MEN1 & ZES). Of the 42 lesions located by conventional imaging techniques, 37 (88%) were also identified by Octreoscan. Unexpected lesions (40 sites), not detected by CT or MR imaging were found in 24/48 (50%) patients. [¹¹¹In]-octreotide scintigraphy has a higher sensitivity for tumour detection, and is superior to MR imaging and CT scanning in the identification of previously unsuspected extraliver and lymph node metastases. It may also be helpful for the localization of clinically suspected tumours in patients with MEN-1 and ZES.

We reviewed 31 patients in whom both bilateral inferior petrosal sinus sampling without CRH stimulation, and a CT scan of the lungs were done. Twenty-five had normal lung CT scans, of whom 23 had a higher inferior petrosal sinus : peripheral ACTH ratio ≥1.5. After careful follow-up, none was subsequently shown to have ectopic ACTH syndrome. Six had abnormal lung CT scans, of whom two had ratios ≥1.5. In these two patients, other investigations suggested pituitary disease, and pituitary surgery led to apparent cure. Of the remaining four patients, who had ratios <1.5, two had incidental lung findings, and pituitary abnormalities were demonstrated at pituitary surgery. The third underwent bilateral adrenalectomy, and no evidence of ectopic ACTH syndrome has emerged as yet after 4 years follow-up. The fourth had a small-cell carcinoma of the lung, confirmed histologically. Our series suggests that whole-lung CT scanning is only necessary in cases of ACTH-dependent Cushing's syndrome where bilateral inferior petrosal sinus sampling has not demonstrated a significant increase in petrosal sinus ACTH levels as compared with the peripheral level. Thus, in our experience the test is now only necessary in those patients (approximately 25%) where the ratio is ≤1.5.