The ever-increasing deployment of distributed resources and the opportunities offered to loads for more active roles has changed the previously unidirectional and relatively straight-forward operating profile of distribution systems (DS). DS will be required to be monitored closely for robustness and sufficient power quality. State estimation of transmission systems has consistently served as a monitoring tool, which drives system-wide control actions and, thus, ensures the operational integrity of the electric grid. An update to the classic state estimation for the case of DS is offered in this work, based on a power flow formulation for radial networks that does not require measurements or estimate of the voltage angles.