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Imaging pancreatic endocrine tumours
Clinical Radiology (1988) 39, 567-569
Abstracts Abstracts of papers presented at the Radiology and Management of Endocrine Disease meeting held on 20-21 January 1988 at Regents College, Regents Park, London NW1 IMAGING PANCREATIC ENDOCRINE TUMOURS
E. BOIJSEN
University Hospital, Lund, Sweden Endocrine tumours of the pancreas are rare, occurring in about one in 200000 inhabitants annually. Most of them produce excess hormones causing characteristic syndromes. The diagnosis is usually made by radioimmunoassay technique and the radiologists commission is to inform about size, site, and number of lesions. Some 20 to 40% of all endocrine tumours do not cause symptoms referable to any polypeptide, but these lesions are nevertheless endocrinologically active. The endocrine tumours usually have a rich vascular supply and therefore pancreatic angiography has become one of the most reliable imaging methods. However, ultrasonography (US), computed tomography (CT), and perhaps magnetic resonance imaging often give quite adequate information. The radiological findings, irrespective of which imaging modality is used, are usually the same, but the detection rate is somewhat different because of different size and localisation. Thus, in patients with insulinoma, both US and CT have rather high sensitivity because the tumour is often single and about 1.5 to 2 cm in diameter. Also, with contrast-enhanced dynamic modern CT equipment, the detection rate of gastrinomas are high (about 80%) but in both types of tumours there will always be undetected lesions. In a number of patients no turnout will be observed with any of the methods mentioned but angiography and the combination of angiography and CT will find tumours down to about 1 cm. Because of improved imaging technique venous sampling is performed only in those patients where an expected tumour has not been found. Glucagonoma, somatostatinoma, vasoactive interstitial polypeptideoma, pancreatic polypeptideoma, and 'non-functioning' endocrine tumours are usually large, have a rich vascular supply and are detected by all the imaging methods. Hepatic metastases are best shown by angiography.
important interactions between approaches to investigation and the influence that diagnosis will have upon management. Functioning pituitary microadenomas present with features of hormone hypersecretion, non-functioning adenomas rarely present until there are secondary effects from the extrasellar expansion. Dilemmas existed before CT scanning and have not yet been resolved even with high resolution CT and MR. Reports in recent years concern high resolution CT of the pituitary gland in normal women, comparisons between CT and the anatomy of normal glands and between CT and operative findings. The normal gland may have a heterogeneous consistency and may show radiological features also held to be associated with a microadenoma. Reports limited to radiological features should not be accepted uncritically, the relevancy of a presumed lesion needs to be assessed against operative and pathological findings. There is agreement that a focal abnormality of less than 5 mm diameter seen on CT is as likely to be a normal part of the gland as a microadenoma. A larger focal abnormality is more likely to be an adenoma but the clinical and biochemical features determine its significance. Similar results are emerging for MR and it is clear that neither CT nor MR can be used in isolation to diagnose or to exclude a pituitary microadenoma. The role of imaging depends upon the endocrine disorder and the method of management which will be carried out. If trans-sphenoidal surgery is intended, imaging can give valuable information about the likely site of the adenoma and also about the condition of the perisellar vessels and the sphenoid sinus; as a result invasive methods are now largely unnecessary. Thus, CT is indicated in patients with acromegaly or Cushing's disease and should be performed prior to trans-sphenoidal operation for a microprolacfinoma. Computed tomography is also useful prior to medical treatment of hyperprolacfinaemia if the prolactin levels are markedly raised as it will exclude unsuspected suprasellar extension. If hyperprolacfinaemia is thought to be 'functional' or if levels are only moderately raised and medical treatment is planned then CT will not influence management. PARATHYROID LOCALISATION: THE LUND EXPERIENCE
THE CUSHING SYNDROMES: CLINICAL ASPECTS
E. BOIJSEN
C. W. B U R K E
University Hospital, Lund, Sweden
The Radcliffe Infirmary, Oxford" The diagnosis of the presence or absence of Cushing's syndrome is best made by paying special attention to objective features that distinguish it from similar syndromes, namely proximal myopathy, skin atrophy, osteoporosis, spontaneous purpura, and in children a combination of growth arrest and obesity. Urinary cortisol excretion and midnight plasma cortisol concentration are the best confirmatory tests. The diagnosis of the cause of Cushing's syndrome requires considerable experience. Adrenal carcinoma can usually be diagnosed on clinical features and CT. The classic ectopic ACTH syndromes are readily diagnosable by hypokalaemia, massive steroid excretion, a short history, and very high levels of cortisol and ACTH. An obvious causative lesion is usually apparent. Adrenal adenomas are clinically indistinguishable from Cushing's disease and though up to 5% may have detectable circulating ACTH, the majority do not and, in combination with the metyrapone test and CT, 100% diagnostic accuracy should be possible. Radiological demonstration of an adrenal mass does not prove that it is the primary cause of Cushing's syndrome, as nodular hyperplasia is an ACTH-dependent lesion. The most difficult diagnosis to confirm is that of Cushing's disease, which may be indistinguishable from benign forms of the ectopic ACTH syndrome. The metyrapone test is 97% accurate in distinguishing pituitary from non-pituitary ACTH but clinical suspicion is vital. The best proof of Cushing's disease is trans-sphenoidal pituitary exploration.
With the development of modern imaging methods the approach to primary hyperparathyroidism (HPT) has changed. Today, attempts are always made to find the enlarged gland before surgery, but in our hospital the surgeon still explores in secondary HPT, because all glands are usually removed. In primary HPT, the first attempt is to find the tumour by ultrasonography. In a collection of 103 adenomas, including 35 of our own, the sensitivity with high resolution ultrasonography (US) was 67%. In our own material the sensitivity was, however, only 57%. The high resolution US (10 MHz) is limited by its low penetratiOn. A dramatic improvement in localisation has been observed when the radionuclide subtraction method with T1-201/99Tc m was introduced. Of a total of 136 adenomas studied with this technique, the sensitivity including our 35 cases was 79% and the specificity almost as high as with US (Table 1). The routine at present is to perform scintigraphy in those cases where US does not give adequate information. The combination of US and scintigraphy gives a sensitivity of about 90%. Even if CT with a high resolution and dynamic scanning has improved in sensitivity it will not add much to the other two imaging methods. However, when the adenoma is situated in the thymus, CT will still be of importance. MRI will add to the information obtained by the other imaging methods. Venous sampling is performed when an adenoma is not shown. Table 1 - Accuracy of imaging methods in recently collected materials including our own 35 cases of p r i m a r y HPT
THE M I C R O A D E N O M A DILEMMA
E. T E A S D A L E
Institute of Neurological Sciences, Glasgow Dilemmas in management of pituitary microadenomas concern both the methods of diagnosis and regimen of treatment. Also there are
US SCINT CT MRI
Sensitivity
Specificity
Accuracy
67 79 66 77
97 96 94 91
89 92 86 87
Abstracts Abstracts of papers presented at the Radiology and Management of Endocrine Disease meeting held on 20-21 January 1988 at Regents College, Regents Park, London NW1 IMAGING PANCREATIC ENDOCRINE TUMOURS
E. BOIJSEN
University Hospital, Lund, Sweden Endocrine tumours of the pancreas are rare, occurring in about one in 200000 inhabitants annually. Most of them produce excess hormones causing characteristic syndromes. The diagnosis is usually made by radioimmunoassay technique and the radiologists commission is to inform about size, site, and number of lesions. Some 20 to 40% of all endocrine tumours do not cause symptoms referable to any polypeptide, but these lesions are nevertheless endocrinologically active. The endocrine tumours usually have a rich vascular supply and therefore pancreatic angiography has become one of the most reliable imaging methods. However, ultrasonography (US), computed tomography (CT), and perhaps magnetic resonance imaging often give quite adequate information. The radiological findings, irrespective of which imaging modality is used, are usually the same, but the detection rate is somewhat different because of different size and localisation. Thus, in patients with insulinoma, both US and CT have rather high sensitivity because the tumour is often single and about 1.5 to 2 cm in diameter. Also, with contrast-enhanced dynamic modern CT equipment, the detection rate of gastrinomas are high (about 80%) but in both types of tumours there will always be undetected lesions. In a number of patients no turnout will be observed with any of the methods mentioned but angiography and the combination of angiography and CT will find tumours down to about 1 cm. Because of improved imaging technique venous sampling is performed only in those patients where an expected tumour has not been found. Glucagonoma, somatostatinoma, vasoactive interstitial polypeptideoma, pancreatic polypeptideoma, and 'non-functioning' endocrine tumours are usually large, have a rich vascular supply and are detected by all the imaging methods. Hepatic metastases are best shown by angiography.
important interactions between approaches to investigation and the influence that diagnosis will have upon management. Functioning pituitary microadenomas present with features of hormone hypersecretion, non-functioning adenomas rarely present until there are secondary effects from the extrasellar expansion. Dilemmas existed before CT scanning and have not yet been resolved even with high resolution CT and MR. Reports in recent years concern high resolution CT of the pituitary gland in normal women, comparisons between CT and the anatomy of normal glands and between CT and operative findings. The normal gland may have a heterogeneous consistency and may show radiological features also held to be associated with a microadenoma. Reports limited to radiological features should not be accepted uncritically, the relevancy of a presumed lesion needs to be assessed against operative and pathological findings. There is agreement that a focal abnormality of less than 5 mm diameter seen on CT is as likely to be a normal part of the gland as a microadenoma. A larger focal abnormality is more likely to be an adenoma but the clinical and biochemical features determine its significance. Similar results are emerging for MR and it is clear that neither CT nor MR can be used in isolation to diagnose or to exclude a pituitary microadenoma. The role of imaging depends upon the endocrine disorder and the method of management which will be carried out. If trans-sphenoidal surgery is intended, imaging can give valuable information about the likely site of the adenoma and also about the condition of the perisellar vessels and the sphenoid sinus; as a result invasive methods are now largely unnecessary. Thus, CT is indicated in patients with acromegaly or Cushing's disease and should be performed prior to trans-sphenoidal operation for a microprolacfinoma. Computed tomography is also useful prior to medical treatment of hyperprolacfinaemia if the prolactin levels are markedly raised as it will exclude unsuspected suprasellar extension. If hyperprolacfinaemia is thought to be 'functional' or if levels are only moderately raised and medical treatment is planned then CT will not influence management. PARATHYROID LOCALISATION: THE LUND EXPERIENCE
THE CUSHING SYNDROMES: CLINICAL ASPECTS
E. BOIJSEN
C. W. B U R K E
University Hospital, Lund, Sweden
The Radcliffe Infirmary, Oxford" The diagnosis of the presence or absence of Cushing's syndrome is best made by paying special attention to objective features that distinguish it from similar syndromes, namely proximal myopathy, skin atrophy, osteoporosis, spontaneous purpura, and in children a combination of growth arrest and obesity. Urinary cortisol excretion and midnight plasma cortisol concentration are the best confirmatory tests. The diagnosis of the cause of Cushing's syndrome requires considerable experience. Adrenal carcinoma can usually be diagnosed on clinical features and CT. The classic ectopic ACTH syndromes are readily diagnosable by hypokalaemia, massive steroid excretion, a short history, and very high levels of cortisol and ACTH. An obvious causative lesion is usually apparent. Adrenal adenomas are clinically indistinguishable from Cushing's disease and though up to 5% may have detectable circulating ACTH, the majority do not and, in combination with the metyrapone test and CT, 100% diagnostic accuracy should be possible. Radiological demonstration of an adrenal mass does not prove that it is the primary cause of Cushing's syndrome, as nodular hyperplasia is an ACTH-dependent lesion. The most difficult diagnosis to confirm is that of Cushing's disease, which may be indistinguishable from benign forms of the ectopic ACTH syndrome. The metyrapone test is 97% accurate in distinguishing pituitary from non-pituitary ACTH but clinical suspicion is vital. The best proof of Cushing's disease is trans-sphenoidal pituitary exploration.
With the development of modern imaging methods the approach to primary hyperparathyroidism (HPT) has changed. Today, attempts are always made to find the enlarged gland before surgery, but in our hospital the surgeon still explores in secondary HPT, because all glands are usually removed. In primary HPT, the first attempt is to find the tumour by ultrasonography. In a collection of 103 adenomas, including 35 of our own, the sensitivity with high resolution ultrasonography (US) was 67%. In our own material the sensitivity was, however, only 57%. The high resolution US (10 MHz) is limited by its low penetratiOn. A dramatic improvement in localisation has been observed when the radionuclide subtraction method with T1-201/99Tc m was introduced. Of a total of 136 adenomas studied with this technique, the sensitivity including our 35 cases was 79% and the specificity almost as high as with US (Table 1). The routine at present is to perform scintigraphy in those cases where US does not give adequate information. The combination of US and scintigraphy gives a sensitivity of about 90%. Even if CT with a high resolution and dynamic scanning has improved in sensitivity it will not add much to the other two imaging methods. However, when the adenoma is situated in the thymus, CT will still be of importance. MRI will add to the information obtained by the other imaging methods. Venous sampling is performed when an adenoma is not shown. Table 1 - Accuracy of imaging methods in recently collected materials including our own 35 cases of p r i m a r y HPT
THE M I C R O A D E N O M A DILEMMA
E. T E A S D A L E
Institute of Neurological Sciences, Glasgow Dilemmas in management of pituitary microadenomas concern both the methods of diagnosis and regimen of treatment. Also there are
US SCINT CT MRI
Sensitivity
Specificity
Accuracy
67 79 66 77
97 96 94 91
89 92 86 87