ABC/2 is a fast and simple method for estimating the volume of intracerebral hemorrhage (or any other ellipsoid lesion for that matter) which does not require volumetric 3D analysis or software. Intracerebral hemorrhage volume is an important predictor of morbidity and mortality (and thus trial eligibility) which is often under-reported 1. It has been well-validated and correlates highly with volumes calculated by planimetric techniques 2,3.

First described by Kwak et al. 4 and popularized by Kothari et al. 2:

  • A x B x C / 2
    • A = greatest hemorrhage diameter in the axial plane
    • B = hemorrhage diameter at 90º to A in the axial plane
    • C = originally described as the number of CT slices with hemorrhage multiplied by the slice thickness, but can simply be substituted with the craniocaudal diameter of the hemorrhage where there is access to multiplanar reformats 1

If the measurements are made in centimeters (cm), then the volume will be in cubic centimeters (cm3). 

The above formula is a simplified version of the formula for the volume of an ellipsoid, which is:

  • 4/3 π x (A/2) x (B/2) x (C/2)
    • where A, B and C are the three diameters of the ellipsoid

If π is estimated as 3, then the formula can be simplified to ABC/2.

A baseline intracerebral hemorrhage volume of >50-60 mL is a poor prognostic marker 1,5.

There are some pitfalls with the ABC/2 method:

  • assumes an ellipsoid lesion (and thus the more the lesion deviates from this morphology the more inaccurate the calculated volume will be)
  • overestimates oral anticoagulant-related intracerebral hemorrhage volumes (because they are often irregular in shape) 3 
    • an ABC/3 formula has been suggested for these lesions 3 although has not yet been validated
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rID: 50453
Synonyms or Alternate Spellings:
  • ABC/2 method for calculating intracerebral haemorrhage volume
  • intracerebral haemorrhage volume
  • intracerebral hemorrhage volume

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