Adrenal Nodule Calculator

Enter the attenuation values you have; washout and the interpretation update as you type. Absolute washout needs all three phases, relative washout needs portal venous and delayed only.

Disclaimer:

Provided "as is" without warranty of any kind, express or implied, including accuracy, completeness or fitness for a particular purpose. For educational purposes only. The user is solely responsible for verifying results against the source guideline and for all clinical decisions.

CT washout

HU
HU, 60–75 s
HU, 15 min

MRI chemical shift

signal
signal
signal
signal

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Formulas and thresholds

IndexFormulaAdenoma
Unenhanced attenuation—≤ 10 HU: lipid-rich adenoma, no washout needed
Absolute washout(portal − delayed) / (portal − unenhanced) × 100≥ 60%
Relative washout(portal − delayed) / portal × 100≥ 40%
Signal intensity index(in-phase − opposed-phase) / in-phase × 100> 16.5%
Adrenal-to-spleen ratio(adrenal opposed / spleen opposed) ÷ (adrenal in / spleen in) × 100< 71%

Washout is validated for homogeneous nodules 1–4 cm with a true 15-minute delay. Unenhanced > 43 HU is suspicious for malignancy regardless of washout unless the lesion is haemorrhagic or calcified; a lesion that enhances < 10 HU is a cyst or haematoma and has no washout; portal venous ≥ 130 HU is specific for pheochromocytoma, and a third of pheochromocytomas and most hypervascular metastases wash out like adenomas.

References

  1. Boland GW, Lee MJ, Gazelle GS, et al. Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature. AJR Am J Roentgenol. 1998;171(1):201–204. doi:10.2214/ajr.171.1.9648789
  2. Caoili EM, Korobkin M, Francis IR, et al. Adrenal masses: characterization with combined unenhanced and delayed enhanced CT. Radiology. 2002;222(3):629–633. doi:10.1148/radiol.2223010766
  3. Blake MA, Kalra MK, Sweeney AT, et al. Distinguishing benign from malignant adrenal masses: multi-detector row CT protocol with 10-minute delay. Radiology. 2006;238(2):578–585. doi:10.1148/radiol.2382041514
  4. Schieda N, Alrashed A, Flood TA, et al. Comparison of quantitative MRI and CT washout analysis for differentiation of adrenal pheochromocytoma from adrenal adenoma. AJR Am J Roentgenol. 2016;206(6):1141–1148. doi:10.2214/AJR.15.15318
  5. Woo S, Suh CH, Kim SY, Cho JY, Kim SH. Pheochromocytoma as a frequent false-positive in adrenal washout CT: a systematic review and meta-analysis. Eur Radiol. 2018;28(3):1027–1036. doi:10.1007/s00330-017-5076-5
  6. Choi YA, Kim CK, Park BK, Kim B. Evaluation of adrenal metastases from renal cell carcinoma and hepatocellular carcinoma: use of delayed contrast-enhanced CT. Radiology. 2013;266(2):514–520. doi:10.1148/radiol.12120110
  7. Fujiyoshi F, Nakajo M, Fukukura Y, Tsuchimochi S. Characterization of adrenal tumors by chemical shift fast low-angle shot MR imaging: comparison of four methods of quantitative evaluation. AJR Am J Roentgenol. 2003;180(6):1649–1657. doi:10.2214/ajr.180.6.1801649
  8. Israel GM, Korobkin M, Wang C, Hecht EN, Krinsky GA. Comparison of unenhanced CT and chemical shift MRI in evaluating lipid-rich adrenal adenomas. AJR Am J Roentgenol. 2004;183(1):215–219. doi:10.2214/ajr.183.1.1830215
  9. Mayo-Smith WW, Song JH, Boland GL, et al. Management of Incidental Adrenal Masses: A White Paper of the ACR Incidental Findings Committee. J Am Coll Radiol. 2017;14(8):1038–1044. doi:10.1016/j.jacr.2017.05.001