Evaluating CMR

Measuring Sagittal Diameter

Abdominal sagittal diameter is commonly assessed using a sagittometer (i.e., a sliding beam caliper with a ruler). As with waist circumference, sagittal diameter is typically measured between the top of the iliac crest and the minimal waist. There is no consensus as to optimal landmarking or methodology. Sagittal diameter should be measured at the end of a normal expiration while the individual is relaxed and in a standing or supine position (Figure 2). To measure sagittal diameter, place one of the calipers on the individual’s back at the level of the landmark and close the other caliper until it touches the individual’s abdomen. The calipers should be parallel to the ground if the individual is standing and perpendicular to the ground if the individual is supine. The calipers should be snug without indenting the individual’s skin.

There is no firm evidence to prove whether measuring sagittal diameter in the standing or supine position provides a better indicator of intra-abdominal fat or health risk. Sagittal diameter measures in the standing position will generally be larger than measures in the supine position. The measurement difference will depend on the individual’s degree of obesity and abdominal fat distribution. However, as measures of standing and supine sagittal diameters are related, both may provide comparable estimates of health and intra-abdominal fat.

Sagittal diameter is a good measure of intra-abdominal fat and health risk. Measures of sagittal diameter are not as well studied as waist circumference, and there is no clear evidence to suggest that sagittal diameter provides any advantage over waist circumference in assessing abdominal adiposity or cardiometabolic risk.