Visoiu M, et al. - In this investigation, researchers determined the ultrasound-measured medication spread superiorly and inferiorly after single injection ultrasound-guided rectus sheath blocks and calculated the incidence of cases with spread up to the subcostal margin and below of umbilicus. In addition, they correlated the spread with the volume of medication administered and with the patient's age, weight, height, sex, and body mass index. Findings suggested that incomplete cephalocaudal medication spread could be expected within the posterior rectus sheath after single injection ultrasound-guided rectus sheath blocks. A positive strong correlation was found between total medication spread and age, weight, and height.