Anemia Diagnosed by Head Computed Tomography

After several days of generalized weakness, a 79-year-old man presented to the emergency department with a possible head injury due to a fall. He had a cerebral vascular accident several years prior, with residual left-sided weakness. Examination revealed skin pallor but no signs of trauma. Unenhanced head computed tomographic images (UHCT) showed no acute intracranial hemorrhage but demonstrated possible anemia because the dural venous sinus (DVS) had a measurement of 23.6 Hounsfield units (HUs) (image A and image B). His hemoglobin (Hb) level was low (3.1 g/dL). Fecal occult blood was detected, and the patient received a transfusion of 2 units of packed red blood cells.

Attenuation of the DVS on UHCT has been shown to correlate with Hb and hematocrit to predict the degree of anemia.^1-4 Chaudhry et al¹ found that an attenuation of 36.3 HU (AUC, 0.56) in the DVS had moderate sensitivity (80%), high specificity (96.6%), and negative predictive value (99.6%) for diagnosing anemia (Hb <8 g/dL), and less than 42.35 HU (AUC, 0.94) demonstrated a high sensitivity (91.2%), specificity (88.5%), and negative predictive value (98.6%) for an Hb level less than 10 g/dL. Although Hb affects attenuation more than hematocrit, other factors, including age and sex, should be considered when determining the attenuation of the DVS.^3,4 When sex is considered, an increase of 10 HU correlates to a 2.26-g/dL increase in Hb in males and 0.87-g/dL in females.³