DrVirgo
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A 49 year old Affrican American woman with hypertension and hyperlipidemia is evaluated in the emergency department with complaints of overwhelming episodes of severe pounding headache, profuse sweating, and palpitations. The patient reports a sense of impending doom during these episodes. She is tachycardic and hypertensive. Which of the following is the best imaging test for diagnosing and localizing the cause of this patient's symptoms?
A. Abdominal aortic angiography
B. CT Scan
C. I-metaiodobenzylguanidine scan
D. Nephrotomography
E. Sonography
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| viket
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B. i would go with CT scan becouse it will (in most cases) detect a tumor.
Among other answers we could use sonography but it will not visualise the tumor if it is very small. I-metaiodbenzylguanidin scan is the method of choice if there is high level of catheholamines and CT, MRI and sonography did not detect tumor.
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| RX 135
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ct/mri not 100% sensitive cause they dont identify extra adrenal tumors...
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| drduck
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under imaging modalities CT scan is the BEST diagnotic tool.
MRI some how is better as T1 and T2 image lets better differentiation between benign adenomas and malignant ones.
but diagnosis of pheochromocytoma is always BIOCHEMICAL....and localisation of the tumor and extent need to be assesed by IMAGING methods.
I-MIBG scan shud be done only if after confirmation of pheochromocytoma by biochemistry assays, imaging doesnot reveal any mass, this is specially useful if the lesion is less than 10 cms in diameter.
if it is >10 cms CT/MRI is the better option as MIBG creats lot more confusion.
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| RX 135
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guess...I-metaiodobenzylguanidine scan..
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| viket
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But to perform I-MIBG we must have biochemistry?!
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| tamerbashir
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CT
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| hero
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interesting article here
http://jnm.snmjournals.org/cgi/content/abstract/2...
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| DrVirgo
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C. I-metaiodobenzylguanidine scan
is the right answer.
There is no mention of this in Kaplan notes 2007, where they say do CT.
And this question is from 2003 Kaplan simulated exam... So i'm wondering if its accurate..
Any thoughts?
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| neurom
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I disagree with the answer. MIBG should be done after biocemically confirmed diagnosis and CT is negative.
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| hero
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emedicine has 2 articles with bit different point of view on imaging studies.
1.
Scintigraphy with radiolabeled 131I-MIBG or 123I-MIBG is indicated.
MIBG scintigraphy allows whole-body exploration. Owing to its high specificity (97%), this morphological study seems to be a valuable adjunct in the detection of extra-adrenal lesions. The main limitation of MIBG scintigraphy is its slightly lower sensitivity (adrenal, 84%; extra-adrenal, 64%) than MRI (adrenal, 97%; extra-adrenal, 88%) or CT scanning (adrenal, 94%; extra-adrenal, 64%). However, despite the lower sensitivity, MIBG scanning offers the greatest specificity, and tumors seen on these images are almost certainly pheochromocytomas. If the MIBG scanning results are positive in a child, consider a diagnosis of neuroblastoma until proven differently.
When a pheochromocytoma is suspected biochemically and is not visualized on standard studies, consider the possibility of an intrathoracic or intracranial tumor. MRI is probably the best study for detecting extra-abdominal tumors, although MIBG scanning may help reveal the general location of the tumor. CT scans or MRI can be focused in that region to localize the tumor.
MIBG may be used to seek extra-adrenal tumors or to provide additional diagnostic information about adrenal masses found with conventional techniques.
2.
A scan with iodine I 131–labeled metaiodobenzylguanidine (MIBG) is reserved for cases in which a pheochromocytoma is confirmed biochemically but CT scanning or MRI do not show a tumor. The molecular structure of iodine I 123 MIBG resembles norepinephrine and concentrates within adrenal or extra-adrenal pheochromocytomas. This isotope has a short half-life and is expensive. It frequently is used in cases of familial pheochromocytoma syndromes, recurrent pheochromocytoma, or malignant pheochromocytoma. In the United States, only 131I-labeled MIBG is available, whereas 123I MIBG is used in Europe and Japan.
Might bcs of it cost it can't be recommended as a first or routine, but q asking about the best imaging test for diagnosing and localizing,which is likely to be this one
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| Ivonne
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I agree with C, very well explained in hero's post and UW. This last one states that CT scan should be done after biochemical dx is confirmed and that normal adrenal glands on CT doesn't rule out the tumor in extra-adrenal location.
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| DrVirgo
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OK, thanks for the sources and discussion... I'm glad you all agree with CT, because that is how I answered the question as well, but was surprised to see otherwise on the explanation... Maybe this was an old question. Again, thanks for confirming my suspicion. 
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| Ivonne
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just wanted to add up to the discussion that IF the patient also would have high blood calcium level and a family h/o hypertension we should rule out MEN type II a by measuring calcitonin level.
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| multifactorial
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CT scan
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| cool doctor
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the question is about the best and its MIBG
but the next step in imaging is CT or MRI
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| DrVirgo
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The explanation to this question said that:
C. I-metaiodobenzylguanidine scan can detect pheos which are adrenal as well as extra adrenal.
I am having this doubt since this was a Kaplan question (simulated exam) but there was NO mention of this scan in the notes... ONLY CT is mentioned...
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| cool doctor
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Thats100% correct dear virgo
if the CT didnt show anything and u still suspect the pheo, this MIBG is the best method to find it especialy if its extramedullary pheo.
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