Low attenuation blood in the heart due to anemia

What can you determine about this patient's blood work? • Xray of the Week

Figure 1.

A. Axial CT. B. Coronal CT.

Figure 2. A. Axial CT. Note the prominent interventricular myocardium and septum (red arrow). B. Coronal CT. Note the prominent interventricular myocardium and septum (red arrow).

Figure 3. Axial CT. Note the ROI in the LV is 20 HU.

Figure 4. This patient's blood work indicating severe anemia with Hemoglobin of 3.0 g/dL (N= 12-16 g/dL) and Hematocrit of 8.4% (N=36-46%)

Discussion:

Differences in density on CT of the thorax can be helpful in diagnosis of anemia, especially when complete blood count data is not available. Anemia is thought to be associated with low CT attenuation of blood in the lumen of the left ventricle (Figs. 1-3) (1). The patient in this case has pancytopenia which is a deficiency in red blood cells (anemia), white blood cells, and platelets (Fig. 4) (2). This patient's LV lumen has a measurement of 20 HU (Fig. 3) Studies suggest that CT attenuation of 35 HU corresponding to a hemoglobin level of 10 g/dL can distinguish between anemic and non-anemic patients with a sensitivity of 76% and specificity of 81% (1,3). Foster et al. found that visualization of the hyperdense interventricular septum against the hypodense left ventricular cavity, also known as the interventricular septum sign (Figs. 1-3), on unenhanced CT of the thorax is specific for anemia with a positive predictive value of 100% for males and 89% for females (1,3). Hyperattenuation of the aortic wall against the hypodense aortic blood pool, also known as the aortic ring sign, is more sensitive than the interventricular septum sign (84% vs 72%) in diagnosis of anemia (4,5). However, it has lower specificity because faint calcification in atherosclerotic mural plaques appear dense on unenhanced CT which may occur in other cardiac abnormalities such as Takayasu’s arteritis and intramural aortic hematoma (5). Kamel et al. suggest that the best diagnostic approach to identifying anemia on unenhanced CT of the thorax is a combination of inspection for aortic ring sign, interventricular septum sign, and measurement of aortic CT attenuation values to account for the sensitivity, specificity, and accuracy of these indicators (5).

References:

1. Foster M, Nolan RL, Lam M. Prediction of anemia on unenhanced computed tomography of the thorax. Can Assoc Radiol J. 2003;54(1):26-30. https://pubmed.ncbi.nlm.nih.gov/12625080/

2. Yokuş, Osman, and Habip Gedik. “Etiological Causes of Pancytopenia: A Report of 137 Cases.” Avicenna Journal of Medicine, vol. 6, no. 4, 2016, pp. 109–12. PubMed Central, doi:10.4103/2231-0770.191447

3. MedPix Topic - Assessing Anemia on Thoracic CT. https://medpix.nlm.nih.gov/topic?id=795fffaa-34a2-46bc-87f4-9b77c00e3989 . Accessed 21 Aug. 2020.

4. Collins AJ, Gillespie S, Kelly BE. Can computed tomography identify patients with anaemia?. Ulster Med J. 2001;70(2):116-118. https://pubmed.ncbi.nlm.nih.gov/11795761/

5. Kamel, Ehab M., et al. “Radiological Profile of Anemia on Unenhanced MDCT of the Thorax.” European Radiology, vol. 18, no. 9, Sept. 2008, pp. 1863–68. PubMed, doi:10.1007/s00330-008-0950-9

Amara Ahmed is a medical student at the Florida State University College of Medicine. She serves on the executive board of the American Medical Women’s Association and Humanities and Medicine. She is also an editor of HEAL: Humanism Evolving through Arts and Literature, a creative arts journal at the medical school. Prior to attending medical school, she graduated summa cum laude from the Honors Medical Scholars program at Florida State University where she completed her undergraduate studies in exercise physiology, biology, and chemistry. In her free time, she enjoys reading, writing, and spending time with family and friends.

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Kevin M. Rice, MD is the president of Global Radiology CME

Dr. Rice is a radiologist with Renaissance Imaging Medical Associates and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

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