Incidentaloma CT scan: Difference between revisions
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==CT scan== | ==CT scan== | ||
*[Location] CT scan may be helpful in the diagnosis of [disease name]. Findings on CT scan suggestive of/diagnostic of [disease name] include: | *[Location] CT scan may be helpful in the diagnosis of [disease name]. Findings on CT scan suggestive of/diagnostic of [disease name] include: | ||
* | *the density of the image is attributed to radiograph attenuation. on nonenhanced CT | ||
* | *nonadenomas have higher attenuation in nonenhanced CT. | ||
* | *If an adrenal mass measures <10 HU on unenhanced CT (ie, has the density of fat), the likelihood that it is a benign adenoma is nearly 100 percent. | ||
*However, up to 30 percent of adenomas do not contain large amounts of lipid and may be indistinguishable from nonadenomas on nonenhanced CT scans. A consensus panel noted that a homogeneous adrenal mass with a smooth border and an attenuation value <10 HU on unenhanced CT is very likely to be a benign adenoma [2]. This appears to be a reasonable CT HU cutoff based upon a retrospective analysis of 151 patients with adrenal masses who underwent both a noncontrast CT scan and adrenalectomy [17]. The mean HU (± standard deviation [SD]) for adrenal adenomas/hyperplasia was significantly lower than for adrenal carcinomas, metastases, and pheochromocytomas (16.2±13.6 versus 36.9±4.1, 39.2±15.2, and 38.6±8.2, respectively). The only patients in the nonadenoma groups with a noncontrast CT HU <10 were those with myelolipomas (which were all less than -40 and therefore easily distinguishable). In this series, a noncontrast CT HU ≤10 or a combination of tumor size ≤4 cm and HU ≤20 excluded nonadenomas in 100 percent of cases. On delayed contrast-enhanced CT | |||
* | *adenomas typically exhibit rapid contrast medium washout | ||
**[ | *nonadenomas have delayed contrast material washout [17]. | ||
* | *Ten minutes after administration of contrast, an absolute contrast medium washout of more than 50 percent was reported to be 100 percent sensitive and specific for adenoma when patients with adenomas were compared with carcinomas, pheochromocytomas, and metastases [17-19]. | ||
* | *Surgical resection should be considered in patients with adrenal incidentalomas that have a suspicious imaging phenotype [1]. | ||
*Contrast-enhanced washout CT utilizes the unique perfusion pattern of adenomas. Adenomas take up intravenous CT contrast rapidly, but also have a rapid loss of contrast – a phenomenon termed ‘contrast enhancement washout’. It is assumed that malignant adrenal lesions usually enhance rapidly but demonstrate a slower washout of contrast medium. This washout phenomenon can be quantified by ‘contrast washout values’, which involve lesion attenuation measurements at specific time points acquired in a dedicated adrenal CT: before injection of contrast medium (HU<sub>nativ</sub>), at 60s following injection of contrast medium (HU<sub>max</sub>) and then at 10 or 15min after contrast injection. This allows calculation of the relative contrast enhancement washout (=100×(HU<sub>max</sub>−HU<sub>10/15min</sub>)/HU<sub>max</sub>) and absolute contrast enhancement washout (=100×(HU<sub>max</sub>−HU<sub>10/15min</sub>)/(HU<sub>max</sub>−HU<sub>nativ</sub>)). A relative washout >40% and an absolute washout >60% is assumed to suggest that an adrenal lesion is benign (56, 58, 59, 60). | |||
==References== | ==References== | ||
{{Reflist|2}} | {{Reflist|2}} | ||
Revision as of 19:09, 21 August 2017
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Incidentaloma CT scan On the Web |
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American Roentgen Ray Society Images of Incidentaloma CT scan |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
There are no CT scan findings associated with [disease name].
OR
[Location] CT scan may be helpful in the diagnosis of [disease name]. Findings on CT scan suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].
OR
There are no CT scan findings associated with [disease name]. However, a CT scan may be helpful in the diagnosis of complications of [disease name], which include [complication 1], [complication 2], and [complication 3].
CT scan
- [Location] CT scan may be helpful in the diagnosis of [disease name]. Findings on CT scan suggestive of/diagnostic of [disease name] include:
- the density of the image is attributed to radiograph attenuation. on nonenhanced CT
- nonadenomas have higher attenuation in nonenhanced CT.
- If an adrenal mass measures <10 HU on unenhanced CT (ie, has the density of fat), the likelihood that it is a benign adenoma is nearly 100 percent.
- However, up to 30 percent of adenomas do not contain large amounts of lipid and may be indistinguishable from nonadenomas on nonenhanced CT scans. A consensus panel noted that a homogeneous adrenal mass with a smooth border and an attenuation value <10 HU on unenhanced CT is very likely to be a benign adenoma [2]. This appears to be a reasonable CT HU cutoff based upon a retrospective analysis of 151 patients with adrenal masses who underwent both a noncontrast CT scan and adrenalectomy [17]. The mean HU (± standard deviation [SD]) for adrenal adenomas/hyperplasia was significantly lower than for adrenal carcinomas, metastases, and pheochromocytomas (16.2±13.6 versus 36.9±4.1, 39.2±15.2, and 38.6±8.2, respectively). The only patients in the nonadenoma groups with a noncontrast CT HU <10 were those with myelolipomas (which were all less than -40 and therefore easily distinguishable). In this series, a noncontrast CT HU ≤10 or a combination of tumor size ≤4 cm and HU ≤20 excluded nonadenomas in 100 percent of cases. On delayed contrast-enhanced CT
- adenomas typically exhibit rapid contrast medium washout
- nonadenomas have delayed contrast material washout [17].
- Ten minutes after administration of contrast, an absolute contrast medium washout of more than 50 percent was reported to be 100 percent sensitive and specific for adenoma when patients with adenomas were compared with carcinomas, pheochromocytomas, and metastases [17-19].
- Surgical resection should be considered in patients with adrenal incidentalomas that have a suspicious imaging phenotype [1].
- Contrast-enhanced washout CT utilizes the unique perfusion pattern of adenomas. Adenomas take up intravenous CT contrast rapidly, but also have a rapid loss of contrast – a phenomenon termed ‘contrast enhancement washout’. It is assumed that malignant adrenal lesions usually enhance rapidly but demonstrate a slower washout of contrast medium. This washout phenomenon can be quantified by ‘contrast washout values’, which involve lesion attenuation measurements at specific time points acquired in a dedicated adrenal CT: before injection of contrast medium (HUnativ), at 60s following injection of contrast medium (HUmax) and then at 10 or 15min after contrast injection. This allows calculation of the relative contrast enhancement washout (=100×(HUmax−HU10/15min)/HUmax) and absolute contrast enhancement washout (=100×(HUmax−HU10/15min)/(HUmax−HUnativ)). A relative washout >40% and an absolute washout >60% is assumed to suggest that an adrenal lesion is benign (56, 58, 59, 60).